-
极化激元作为光与物质的混合激发可以实现纳米光场的精确调控, 为未来纳米光电器件的小型化和集成化提供了有效的途径. 近年来, 借助散射型扫描近场光学显微镜对多类型极化激元的观测, 多种光学现象背后的物理机制被揭示, 进一步加深了对极化激元物理和相互作用的理解, 也极大地推动了极化激元调控及其应用的研究. 基于此, 本文总结了最新的极化激元近场研究进展. 不同于前期关于二维材料极化激元的综述, 本文不仅涵盖了三维至一维的极化激元材料体系, 还在极化激元纳米光学特性方面增添了各向异性极化激元的最新研究工作, 并且系统总结了极化激元调控的最新进展以及在亚衍射成像和聚焦、纳米结构识别、光调制器和分子检测等方面的相关应用. 最后, 对极化激元未来的研究方向进行了展望.Polaritons, as hybrid excitations of light and matter, are important for miniaturizing the integrated nano-optoelectronic devices due to their capability of manipulating nanolight. Recently, the state-of-the-art nano-imaging technique (e.g. scattering-type scanning near-field optical microscope) has visualized various types of polaritons and revealed the physical mechanism behind them. The nanometer-resolution imaging not only deepens our understanding of fundamentals of polaritons but also promotes the studies of polariton manipulation and applications. In this review paper, we systematically summarize the recent near-field study of polaritons. Rather than other previous reviews focusing on polaritons in two-dimensional materials, our review extends the polaritonic systems to multiple dimensions (3D/2D/1D), at the same time we also collect the latest progress of polaritons in anisotropic systems. Moreover, we show the recent study of polariton manipulation and their corresponding applications, e.g. sub-diffractional imaging, focusing, optical modulator, nanostructure diagnosis and molecular sensing. Our review also look forward to future opportunities of polaritonics and its nanophotonic applications.
-
Keywords:
- near-field imaging /
- polaritons /
- anisotropy /
- manipulation and application
1. 引 言
极化激元是一种由光子与其他(准)粒子耦合产生的特殊电磁模式, 具有半光-半物质属性, 可以将自由空间光聚焦压缩至纳米尺度, 显著增强光与物质相互作用, 实现亚波长下对自由空间光的操控. 极化激元的概念是由著名物理学家黄昆先生[1]于1951年首次提出, 描述了离子晶体中辐射场和晶格振动的杂化模式. 最初的极化激元体系是传统贵金属中的等离极化激元, 由光子与金属中自由电子集体振荡形成, 可将自由空间光局域至亚波长尺度, 但其中的电子散射导致等离极化激元较高的传播损耗且光场局域能力较弱(<λ0/10)[2,3]. 此后, 随着二维材料的兴起, 得益于其大比表面积和天然的晶格对称性(异质结无需晶格匹配), 相比于传统贵金属, 不仅提升了等离极化激元的性质(例如石墨烯等离极化激元的强光场局域和电学可调), 还将极化激元体系拓展至多种类型[4,5], 包括极性晶体(支持光子-声子耦合的声子极化激元)[6]、半导体(支持光子-激子耦合的激子极化激元)[7]、高温超导体(支持光子-库珀对耦合的库珀对极化激元)[8]、磁性材料(支持光子-磁振子耦合的磁振子极化激元)[9]等. 除了库珀对极化激元和磁振子极化激元未被实空间成像证实, 其他类型的极化激元都拥有各自的优势和劣势: 等离极化激元拥有强的光场局域(<λ0/100)和色散电学可调, 但具有较高的光学损耗(传播寿命为飞秒量级); 声子极化激元拥有强的光场局域(<λ0/100), 可有效避免电子散射而具有较低的光学损耗(传播寿命为皮秒量级), 但极性晶体因其本征的晶格属性使其性质很难被调控且共振频率范围窄; 激子极化激元有低的光学损耗(传播寿命为纳秒量级), 但光场局域能力弱(~λ0/2)且性质难以被调控.
光学显微术因具有适用性广、快速、无损的探测优势, 成为广泛应用于材料性质研究的表征技术. 物体被光照射后向外辐射的电磁波总是包含辐射波和倏逝波[10]. 传统光学显微镜由于受到阿贝衍射极限的限制, 空间分辨率不能超过入射光波长的一半, 仅能收集和探测辐射波, 即“远场”光学信息, 而携带物体表面高频精细信息的倏逝波, 即“近场”光学信息, 则无法被探测和收集. 极化激元是局域并沿着物体表面传播, 在垂直物体表面方向场强呈指数衰减的倏逝波, 因此研究极化激元的相关物理特性需要能突破衍射极限的光学显微成像技术. 基于探针的扫描近场光学显微术(SNOM)是近场光学和扫描探针显微镜的结合, 探针可同时对光进行纳米尺度的局域、增强和散射, 利用探针与样品相互作用实现倏逝波的探测, 能同时获得样品的振幅和相位信息, 并且具有纳米级空间分辨率(约10 nm)和宽范围的适用波段(可见光到太赫兹)[11–17]. 其中散射型SNOM(s-SNOM)是将入射光聚焦在探针针尖产生高度局域的近场增强, 再通过针尖散射被探测器接收, 对入射光偏振和衬底均无要求, 并且通过合适的调制解调方法可以显著抑制因针尖散射引入的大量背景信号, 获得高信噪比的近场光学图像[18,19]. 因此, s-SNOM被广泛应用于极化激元学的研究, 揭示了许多传统光学无法测量的新奇物理现象.
相比于之前关于二维材料极化激元的综述[20], 本文涵盖了多种极化激元材料体系, 包括三维至一维, 不仅增添了各向异性极化激元的最新研究工作, 还系统总结了极化激元调控的最新进展以及相关应用. 本文首先简要介绍s-SNOM的基本原理及其激发与探测极化激元的方式; 其次, 分类阐述了通过s-SNOM探测的不同类型极化激元在纳米尺度上的新奇光学现象; 再次, 系统总结极化激元调控方式, 探索了这些技术背后的物理, 并列举了极化激元的相关潜在应用; 最后, 讨论了极化激元学未来潜在的发展方向.
2. 近场光学成像技术和极化激元探测
2.1 s-SNOM工作原理
s-SNOM是基于原子力显微镜(AFM)技术, 利用外部光路将光聚焦在置于样品表面几十纳米处的AFM探针尖端并使其极化, 从而在针尖曲率半径的范围内产生极大的局域近场增强. 针尖与样品相互作用, 被针尖散射的光将包含针尖下方样品的光学信息, 转换为远场被探测器接收, 通过探针逐点扫描则可获得近场光学图像. 然而, 针尖与样品相互作用是一个复杂的过程, 致使正确解释针尖收集到的光学信息主要面临两个困难: 1)针尖作为光学天线, 利用“避雷针效应”实现针尖与样品间的高度光场局域, 导致针尖柄的具体形状会显著影响散射光的信号强度[17,21]; 2)针尖尺寸远小于入射光的聚焦光斑, 因此针尖散射光中除了近场光学信号, 还包含由针尖柄、悬臂以及样品表面等散射的远场背景信号且强度远大于近场信号. 因此, s-SNOM的关键是实验中提取纯净的近场信号和理论上选取合适的针尖-样品耦合模型.
实验上, s-SNOM通常采用调制-解调方法进行背景信号抑制, 基本原理是基于AFM探针轻敲模式, 针尖以频率$ \varOmega $ (200—300 kHz)垂直振动, 周期性地改变针尖-样品间的距离, 并且振荡振幅远小于入射光波长, 从而使近场信号和背景信号被调制. 由于近场信号随针尖-样品间距呈非线性变化而背景信号呈线性变化, 因此利用锁相放大器在针尖轻敲频率的高次谐波($ n\varOmega , n\geqslant 2 $)处解调散射信号可大幅抑制背景信号[22,23]. 再结合伪外差干涉法(基于参考波的正弦相位调制), 则能得到纯净的近场信号并同时测量近场信号的振幅和相位[24,25].
理论上, 目前常用的是基于点偶极子模型发展而来的偶极子模型. 由于针尖与样品间的强耦合作用, 正确理解针尖散射信号需要将针尖与样品看作整体, 并且针尖的形状和长度会直接影响散射效率.
2.1.1 点偶极子模型
点偶极子模型是最简单的理论模型[26–28], 忽略了探针的具体形状, 用半径r、介电常数$ {\varepsilon }_{{\mathrm{t}}} $的球表示, 被置于距离样品表面z处. 样品被视为各向同性的半无限大平面, 介电常数为$ {\varepsilon }_{{\mathrm{s}}} $. 当垂直于样品表面的电场$ {E}_{0} $入射时, 针尖将被极化, 极化率 $ \alpha =4{\mathrm{\pi }}{r}^{3}\left({\varepsilon }_{{\mathrm{t}}}-1\right)/\left({\varepsilon }_{{\mathrm{t}}}+2\right) $ , 偶极矩$ p=\alpha {E}_{0} $, 为了简化计算, 极化球被进一步近似为位于球体中心的具有相同强度的偶极子, 所产生的电场为
$$ {E}_{{\mathrm{d}}{\mathrm{i}}{\mathrm{p}}{\mathrm{o}}{\mathrm{l}}{\mathrm{e}}}=\frac{p}{2{\mathrm{\pi }}{\left(r+z\right)}^{3}}. $$ (1) 该电场会作用于样品, 在其内部产生电荷形成新的电场, 被一个距离探针偶极子$ 2(r+z) $的镜像偶极子描述, 偶极矩$ {p}'=\beta p $, 其中$ \beta ={(\varepsilon }_{{\mathrm{s}}}-1)/{(\varepsilon }_{{\mathrm{s}}}+ 1) $为样品的介电响应函数. 镜像偶极子产生的电场又会作用于探针偶极子产生场增强, 因此在静电极限下(两个偶极子传播相位被忽略), 实际的探针偶极矩变为
$$ p = \alpha \left({E}_{0}+\frac{{p}'}{2{\mathrm{\pi }}{\left[2\left(r+z\right)\right]}^{3}}\right) = \frac{\alpha {E}_{0}}{1-\dfrac{\alpha \beta }{16{\mathrm{\pi }}{(r+z)}^{3}}}. $$ (2) 针尖-样品耦合系统的电场是探针和镜像偶极子场多次相互作用的叠加, 因此耦合系统的有效极化率为
$$ {\alpha }_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}}=\frac{\alpha (1+\beta )}{1-\dfrac{\alpha \beta }{16{\mathrm{\pi }}{(r+z)}^{3}}} . $$ (3) 耦合系统的散射场是与有效极化率成正比, 即$ {E}_{{\mathrm{s}}{\mathrm{c}}{\mathrm{a}}}\propto {\alpha }_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}}{E}_{0} $, 其中$ {\alpha }_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}}=s{{\mathrm{e}}}^{{\mathrm{i}}\varphi } $, 对应于实验中应用伪外差干涉法测量得到的振幅和相位, 因此可从散射场反推样品的介电性质. 由于实验过程中探针的介电常数和针尖-样品间距保持不变, 近场光学图像的对比度仅受样品局部介电常数的影响.
2.1.2 有限偶极子模型
对于更复杂的系统, 过于简化探针形状的点偶极子模型不再适用, 随后发展出了考虑探针具体形状的有限偶极子模型[29]. 由于模型中考虑了探针的具体形状, 更加还原了探针作为纳米天线的功能, 与实验数据具有更好的一致性[30]. 该模型中探针被假设成为一个细长的球体, 运用相同的镜像偶极子方法, 细长球体的有效极化率为[31]
$$ {\alpha }_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}}={R}^{2}L\dfrac{\dfrac{2L}{R}+{\mathrm{l}}{\mathrm{n}}\dfrac{R}{4eL}}{{\mathrm{l}}{\mathrm{n}}\dfrac{4L}{{e}^{2}}}\left(2+\dfrac{\beta \left(g-\dfrac{R+H}{L}\right){\mathrm{l}}{\mathrm{n}}\dfrac{4L}{4H+3R}}{{\mathrm{l}}{\mathrm{n}}\dfrac{4L}{R}-\beta \left(g-\dfrac{3R+4H}{4L}\right){\mathrm{l}}{\mathrm{n}}\dfrac{2L}{2H+R}}\right), $$ (4) 其中R是细长球体尖端的半径, L是细长球体的长度, H是细长球体与样品的间距, g是细长球体尖端局域电荷和总诱导电荷的比值, 当接近0.7时将趋于恒定, $ \beta $是样品的介电响应函数, 与点偶极子模型中相同.
2.2 s-SNOM 激发和探测极化激元
极化激元是一种局域在样品表面的倏逝波, 面外波矢仅有虚部, 面内动量与自由空间光存在动量失配. 当s-SNOM探针靠近一个极化激元系统时, 探针散射的倏逝波具有大的动量范围, 在1/a (针尖半径的倒数)的量级, 因此能提供足够的动量激发极化激元[32,33], 并将其转换为远场信号而被探测. s-SNOM是通过实空间成像方式研究极化激元, 需要极化激元驻波模式的形成, 主要有两种方式: 1) 探针激发极化激元, 当极化激元传播至样品边界时会被反射, 再与探针新激发的极化激元相干涉形成驻波模式, 以干涉条纹的形式被记录, 相邻条纹的间距为极化激元波长的一半[6,34]; 2) 样品边界/金属纳米天线激发极化激元[35], 沿着样品表面传播与入射光相干涉形成条纹, 相邻条纹间距为极化激元波长, 此时探针仅具有探测功能.
2.3 s-SNOM 技术的发展
除具有纳米级空间分辨率, s-SNOM还与其他光谱技术相结合实现了化学分辨率和时间分辨率. 将远场傅里叶变换红外光谱(FTIR)与s-SNOM结合发展出的纳米傅里叶变换红外光谱(nano-FTIR), 解决了传统FTIR在纳米材料光谱测量中分辨率受衍射极限限制的问题, 可在较宽的频率范围内实现纳米级空间分辨率的近场红外光谱测量. 此外, 通过nano-FTIR对纳米材料进行线扫描可以得到物质的二维红外光谱图像, 即高光谱成像图. 与此同时, s-SNOM还可与传统超快光谱技术结合, 发展出超快近场成像(ultrafast s-SNOM)技术, 可在飞秒或纳秒级时间尺度下研究纳米局域极化激元的动力学演化过程.
3. s-SNOM在极化激元中的近场研究
3.1 等离极化激元
石墨烯是一种半金属, 因同时具有电学可调控性和宽的操作频率(可见光到太赫兹)成为继传统贵金属后被广泛研究的等离极化激元材料. 石墨烯等离极化激元的首次实验观测是Chen等[34]和Fei等[36]通过s-SNOM实空间成像实现的. 他们利用金属针尖产生的强局域场增强(提供足够的动量补偿)分别在碳化硅(图1(a))和二氧化硅衬底上成功激发石墨烯等离极化激元, 观察到以柱面波形式向外传播的等离极化激元到达石墨烯边界后被反射形成的驻波条纹, 条纹间距为等离极化激元波长的一半, 验证了其强的光场局域性($ {\lambda }_{0}/{\lambda }_{{\mathrm{s}}{\mathrm{p}}}\approx 40 $), 并且通过背栅电压实现了对等离极化激元波长的调控. 除了针尖激发, Alonso-González等[37]利用金属天线共振激发石墨烯等离极化激元, 直接观测到等离极化激元波前形状(图1(b)), 并通过改变空间电导分布实现了对其传播方向的调控. 将两个单层石墨烯进行Bernal堆叠, 基于层间的电子隧穿效应, Fei等[38]观察到堆叠形成的bilayer石墨烯(层间强耦合)等离极化激元比单层和随机堆叠的double-layer石墨烯(层间弱耦合)具有更高的光场局域能力. 此外, Dong等[39]和Zhao等[40]分别通过近场光学成像技术观测到石墨烯等离极化激元与电流的相互作用, 即当电流方向与等离极化激元传播方向相同(反)时, 等离极化激元波长变大(小)(图1(c)), 可称为等离极化激元的多普勒效应. 最近, Kim等[41]通过将覆盖在石墨烯上的过渡金属硫化物氧化为过渡金属氧化物, 成功激活了过渡金属氧化物与石墨烯之间不同功函数的电荷转移. 如图1(d)所示, 他们利用s-SNOM在氧化钨与石墨烯界面处观察到双极性低损耗的石墨烯等离极化激元. 由于仅有最上层的二硒化钨会被氧化为氧化钨, 因此通过覆盖不同层数的二硒化钨, 即在氧化钨与石墨烯之间插入不同厚度的介电范德瓦耳斯间隔层, 可精确控制氧化激活电荷转移程度, 进而实现对等离极化激元的调控.
![图 1 石墨烯等离极化激元的实空间成像 (a)碳化硅衬底上石墨烯等离极化激元的近场光学成像[34]; (b)金属天线激发石墨烯等离极化激元波前成像[37]; (c)不同电流下石墨烯等离极化激元近场光学图像(上)及其相应的线轮廓(下)[40]; (d)不同数量二硒化钨间隔层分离的氧化钨/石墨烯异质结纳米红外光学图像[41]\r\nFig. 1. Real-space imaging of graphene plasmons: (a) Near-field imaging of graphene plasmons on SiC substrate[34]; (b) wavefront mapping of graphene plasmons launched by metal antenna[37]; (c) near-field images of the propagating graphene plasmons under different driving currents (top panel) and the corresponding line profiles (bottom panel) [40]; (d) nano-infrared images of WOx/graphene heterostructures with a varied number of tungsten diselenide (WSe2) spacer layers[41].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-1.png)
图 1 石墨烯等离极化激元的实空间成像 (a)碳化硅衬底上石墨烯等离极化激元的近场光学成像[34]; (b)金属天线激发石墨烯等离极化激元波前成像[37]; (c)不同电流下石墨烯等离极化激元近场光学图像(上)及其相应的线轮廓(下)[40]; (d)不同数量二硒化钨间隔层分离的氧化钨/石墨烯异质结纳米红外光学图像[41]Fig. 1. Real-space imaging of graphene plasmons: (a) Near-field imaging of graphene plasmons on SiC substrate[34]; (b) wavefront mapping of graphene plasmons launched by metal antenna[37]; (c) near-field images of the propagating graphene plasmons under different driving currents (top panel) and the corresponding line profiles (bottom panel) [40]; (d) nano-infrared images of WOx/graphene heterostructures with a varied number of tungsten diselenide (WSe2) spacer layers[41].除了常见的二维石墨烯, 其他一些一维材料中等离极化激元也展现了优异的特性. 砷化铟是一种窄带隙III-V族半导体, 在表面具有电荷积累层, 是理想的等离极化激元材料. Chen研究组[42]首次在纳米尺度通过近场成像技术观察到一维砷化铟纳米线表面等离极化激元的驻波干涉模式, 并通过改变纳米线直径和周围介电环境对等离极化激元性质(波长、色散、传播损耗等)进行调控(图2(a)), 并且在具有孪晶超晶格结构的砷化铟纳米线中观察到$ {\mathrm{\varGamma }}-{{L}} $带间子带跃迁(图2(c))[43]. 此外, 他们还研究了锑化铟纳米线等离极化激元超快动力学过程(图2(b))[44]. 当一维体系中由于量子限制, 电子间产生强关联效应时, 电子行为表现为拉廷格液体[45,46], 其集体电荷激发是一维量子等离极化激元. 一维碳纳米管因具备强量子局域性可支持拉廷格等离极化激元, 其首次实验观测是由Wang研究组[47,48]通过近场成像实现. 他们分别对金属碳纳米管和半导体碳纳米管进行研究, 发现截然不同的拉廷格等离极化激元现象. 金属碳纳米管中拉廷格等离极化激元不同于经典等离极化激元, 传播速度表现为量子化, 不依赖载流子浓度和激发波长, 而是由导电通道的量子化数量决定. 与之相反, 半导体碳纳米管拉廷格等离极化激元的特性(例如波长、振幅、传播速度等)则可被门电压连续调控(图2(d)). 这种差别来源于两者不同的能带结构, 其中金属碳纳米管具有线性的能带结构, 而半导体碳纳米管则是双曲型能带结构, 分别对应于线性和非线性拉廷格体系. Wang 等[49]通过远场红外吸收光谱首次探测到二碲化钨薄膜中双曲等离极化激元共振模式, 并发现各向异性特征和等离极化激元共振频率有明显的温度依赖性. 近期, Chen等[50]首次在实空间观测到低对称单斜晶系银碲纳米薄片中面内各向异性太赫兹等离极化激元, 其对光场的压缩能力高达65倍.
![图 2 一维纳米结构中的等离极化激元 (a)砷化铟纳米线的原子力显微镜图像(上)和对应的红外纳米光学成像图(下)[42], 入射光频率为901 cm–1, 标尺为1; (b)锑化铟纳米线的超快近场光学图像, 泵浦光和探测光的延迟从0—10 ps[44], 标尺为500 nm; (c)不同时间延迟下砷化铟孪晶超晶格纳米线的红外光谱测量结果[43]; (d)金属型(M1和M2)和半导体型(S1和S2)碳纳米管的近场光学图像, 背栅电压数值分别为–20 V (上)和0 V (下)[48]\r\nFig. 2. Plasmon polaritons in one-dimensional nanostructures: (a) AFM topography image of an indium arsenide nanowire (top) and corresponding nano-infrared image (bottom) [42], the incident frequency is 901 cm–1, scale bar, 1 μm; (b) ultrafast near-field images of the indium antimonide nanowire with pump-probe delays from 0—10 ps[44], scale bar, 500 nm; (c) infrared amplitude spectra of the indium arsenide twinning superlattice nanowire at different pump-probe delay times[43]; (d) near-field images of metallic (M1 and M2) and semiconducting (S1 and S2) carbon nanotubes at different gate volrages –20 V (top panel) and 0 V (bottom panel)[48].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-2.png)
图 2 一维纳米结构中的等离极化激元 (a)砷化铟纳米线的原子力显微镜图像(上)和对应的红外纳米光学成像图(下)[42], 入射光频率为901 cm–1, 标尺为1; (b)锑化铟纳米线的超快近场光学图像, 泵浦光和探测光的延迟从0—10 ps[44], 标尺为500 nm; (c)不同时间延迟下砷化铟孪晶超晶格纳米线的红外光谱测量结果[43]; (d)金属型(M1和M2)和半导体型(S1和S2)碳纳米管的近场光学图像, 背栅电压数值分别为–20 V (上)和0 V (下)[48]Fig. 2. Plasmon polaritons in one-dimensional nanostructures: (a) AFM topography image of an indium arsenide nanowire (top) and corresponding nano-infrared image (bottom) [42], the incident frequency is 901 cm–1, scale bar, 1 μm; (b) ultrafast near-field images of the indium antimonide nanowire with pump-probe delays from 0—10 ps[44], scale bar, 500 nm; (c) infrared amplitude spectra of the indium arsenide twinning superlattice nanowire at different pump-probe delay times[43]; (d) near-field images of metallic (M1 and M2) and semiconducting (S1 and S2) carbon nanotubes at different gate volrages –20 V (top panel) and 0 V (bottom panel)[48].3.2 声子极化激元
极性材料中声子极化激元没有电子损耗, 而是由本征的光学声子散射寿命决定(通常为皮秒量级), 因此比等离极化激元具有更高的品质因子. 光在介质中的传播特性源于动量空间中的等频面, 由介电张量($ {\boldsymbol{\varepsilon}} ={\mathrm{d}}{\mathrm{i}}{\mathrm{a}}{\mathrm{g}}\left[{\varepsilon }_{x}, {\varepsilon }_{y}, {\varepsilon }_{z}\right] $)的符号决定(面内分量$ {\varepsilon }_{\perp }={\varepsilon }_{x}, {\varepsilon }_{y} $; 面外分量$ {\varepsilon }_{/ /}={\varepsilon }_{z} $). 在传统各向同性介质中, 介电张量沿各个方向数值相等且同号, 极化激元等频线(某一特定频率下色散曲面的截面)为圆形(各个方向波矢大小相等). 与之相反, 各向异性介质中, 介电张量沿各个方向不再相等, 主要分为两种情况: 1) 介电张量沿各个方向同号但数值不等, 极化激元等频线为椭圆形(各个方向波矢大小不相等); 2) 介电张量沿各个方向数值不等且异号, 极化激元等频线为双曲形(波矢方向受限但大小不限), 此时在等频线渐近线附近极化激元理论上具有无限大的波矢分量和极大的波矢态密度, 意味着极强的光场局域能力和增强的光与物质相互作用. 最初, 研究者们是在人工超构材料中实现双曲光学色散, 但由于复杂的制备过程引入较高的光学损耗, 以及受限的人造单元尺寸对双曲极化激元波矢大小的限制, 使其无法被广泛应用.
Dai等[6]发现六角氮化硼介电张量的面内和面外分量在中红外波段为异号, 即天然的双曲材料, 并首次对氮化硼薄层双曲声子极化激元进行近场光学成像(图3(a)), 发现其具有与石墨烯等离极化激元相似的光场局域能力($ {\lambda }_{0}/{\lambda }_{{\mathrm{s}}{\mathrm{p}}}\approx 25 $)和更长的传播寿命(皮秒量级), 并且声子极化激元波长与氮化硼薄层厚度呈线性依赖关系, 这来源于氮化硼薄片层间上、下表面的声子极化激元的耦合[55]. 当氮化硼的厚度减小至单个原子层时, 不再具有层间耦合作用, 线性厚度依赖关系消失, 声子极化激元能将自由空间光波长缩小60倍[56]. Xu等[51]还在一维氮化硼纳米管中观察到声子极化激元, 图3(b)中展示了声子极化激元的驻波干涉模式. 氮化硼通常是由机械剥离得到, 光轴垂直于晶体表面而呈面外双曲特性, 支持体局域型双曲声子极化激元, 但当光轴旋转90°, 则会变为面内双曲特性, 支持表面局域型双曲声子极化激元[52,57]. 图3(c)中, Li等[52]通过金属针尖在氮化硼边界处成功激发表面局域型双曲声子极化激元, 它们拥有与体局域型双曲声子极化激元相似的寿命, 但更强的光场局域和更小的群速度. 为了直接观察面内各向异性, 他们制备了氮化硼纳米光栅作为超表面, 观察到声子极化激元内陷波前(代表面内双曲色散特征)以及从双曲色散到椭圆色散的光学拓扑转变(图3(d), (e))[53,54].
![图 3 氮化硼中双曲声子极化激元的近场光学研究 (a)氮化硼薄层(厚度为256 nm)中声子极化激元的近场光学图像, 入射光频率为1560 cm–1, 标尺为800 nm(左); 声子极化激元波长随氮化硼薄层厚度的变化趋势[6], 入射光频率为1560 cm–1(右); (b)氮化硼纳米管(厚度为40 nm)中声子极化激元的近场光学图像[51], 入射光频率为1400 cm–1; (c)氮化硼薄层中声子极化激元体局域(M0)和表面局域(SM0)模式的近场光学图像[52], 黑色和白色箭头表示薄片及其边缘上的近场振荡周期, 分别对应于M0和SM0模式波长的一半, 入射光频率为1420 cm–1, 标尺为2 μm; (d)氮化硼超构表面中声子极化激元的渠道化传播现象[53]; (e)氮化硼超构表面中声子极化激元的光学拓扑转变, 内陷型波前(上)和外扩型波前(下)[54]\r\nFig. 3. Near-field optical study of hyperbolic phonon polaritons in boron nitride (hBN): (a) Near-field image of phonon polaritoins in hBN (thickness 256 nm), the incident frequency is 1560 cm–1. Scale bar, 800 nm (left); wavelength of phonon polaritons probed at 1560 cm–1 for hBN with different thicknesses (right)[6]; (b) near-field image of phonon polaritons in hBN nanotubes[51], the incident frequency is 1400 cm–1; (c) near-field image of volume-confined (M0) and surface (SM0) phonon polaritons of a 40 nm-thick hBN flake at 1420 cm–1[52], the black and white arrows indicate the periods of near-field oscillations on the flake and its edge, corresponding to half the wavelength of M0 and SM0 modes, respectively, scale bar, 2 μm; (d) phonon polariton canalization in a hBN metasurface[53]; (e) optical topological transition of phonon polaritons in a hBN metasurface: concave wavefronts (top panel) and convex wavefronts (bottom panel)[54].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-3.png)
图 3 氮化硼中双曲声子极化激元的近场光学研究 (a)氮化硼薄层(厚度为256 nm)中声子极化激元的近场光学图像, 入射光频率为1560 cm–1, 标尺为800 nm(左); 声子极化激元波长随氮化硼薄层厚度的变化趋势[6], 入射光频率为1560 cm–1(右); (b)氮化硼纳米管(厚度为40 nm)中声子极化激元的近场光学图像[51], 入射光频率为1400 cm–1; (c)氮化硼薄层中声子极化激元体局域(M0)和表面局域(SM0)模式的近场光学图像[52], 黑色和白色箭头表示薄片及其边缘上的近场振荡周期, 分别对应于M0和SM0模式波长的一半, 入射光频率为1420 cm–1, 标尺为2 μm; (d)氮化硼超构表面中声子极化激元的渠道化传播现象[53]; (e)氮化硼超构表面中声子极化激元的光学拓扑转变, 内陷型波前(上)和外扩型波前(下)[54]Fig. 3. Near-field optical study of hyperbolic phonon polaritons in boron nitride (hBN): (a) Near-field image of phonon polaritoins in hBN (thickness 256 nm), the incident frequency is 1560 cm–1. Scale bar, 800 nm (left); wavelength of phonon polaritons probed at 1560 cm–1 for hBN with different thicknesses (right)[6]; (b) near-field image of phonon polaritons in hBN nanotubes[51], the incident frequency is 1400 cm–1; (c) near-field image of volume-confined (M0) and surface (SM0) phonon polaritons of a 40 nm-thick hBN flake at 1420 cm–1[52], the black and white arrows indicate the periods of near-field oscillations on the flake and its edge, corresponding to half the wavelength of M0 and SM0 modes, respectively, scale bar, 2 μm; (d) phonon polariton canalization in a hBN metasurface[53]; (e) optical topological transition of phonon polaritons in a hBN metasurface: concave wavefronts (top panel) and convex wavefronts (bottom panel)[54].近年来, 氧化钼作为一种具有3种不同晶格常数的双轴晶体, 被证实是一种天然的面内双曲材料. Ma等[58]首次通过实验在氧化钼晶体中观察到低损耗的天然面内双曲声子极化激元(图4(a)). 通过近场成像和纳米傅里叶变换红外光谱技术, 他们在实空间证明了具有面内双曲色散的声子极化激元不仅能将自由空间光局域至1/60, 且传播寿命可达8 ps, 远超迄今为止报道的同位素掺杂氮化硼声子极化激元和低温下的石墨烯等离极化激元. 用银天线激发时, 不同于各向同性极化激元的同心圆形波前, 氧化钼面内双曲极化激元呈现出内陷型波前(图4(b))[59]. 基于其独特的双曲色散特性, Alonso-González研究组在纳米尺度上观察到一系列反常的光学现象, 例如反常折射(折射后极化激元波矢和传播方向非共线且折射波矢远大于入射波矢)(图4(c))[60]、负反射(极化激元入射波与反射波在法线同侧且反射角与入射角不同)(图4(d))[61]、复杂干涉(极化激元高动量组分间的干涉使其发生纳米聚焦)[63]等. 此外, Zheng等[64]和Qu等[65]分别针对双曲极化激元的反常传播行为, 优化设计了金属纳米天线, 实现了中红外光场的纳米聚焦. 当对氧化钼进行一维线性光栅图案化时, 周期性光栅和面内各向异性的相互作用会打破极化激元光栅衍射的动量匹配对称性, 从而使声子极化激元不对称甚至单向衍射, 即只在光栅一侧传播(图4(e))[62].
![图 4 氧化钼中各向异性声子极化激元的近场光学成像 (a)氧化钼中椭圆型(上)和双曲型(下)声子极化激元的近场光学图像[58], 入射光频率分别为为990 cm–1 (上)和900 cm–1 (下), 标尺为2 μm ; (b)氧化钼中银天线激发的双曲型声子极化激元, 表现为内陷型波前[59], 入射光频率为944 cm–1; (c)双曲极化激元的反常折射现象, 白色虚线内部衬底为空气, 外部为氧化硅[60], 入射光波长为11.3 μm; (d)双曲极化激元的负反射现象[61], 入射光频率为881 cm–1; (e)氧化钼光栅结构中声子极化激元的单向传播[62], 入射光频率为904 cm–1 [62]\r\nFig. 4. Near-field imaging of anisotropic polaritons in molybdenum trioxide ($ \alpha $-MoO3): (a) Near-field images of elliptical and hyperbolic phonon polaritons in $ \alpha $-MoO3 at incident frequencies at 990 cm–1 (top panel) and 900 cm–1 (bottom panel) [58], Scale bars, 2 μm; (b) silver antenna-launched hyperbolic phonon polaritons in a $ \alpha $-MoO3 flake recorded at 944 cm–1, revealing concave wavefronts[59]; (c) anomalous refraction of hyperbolic polaritons at $ {\lambda }_{0}=11.3\;{\text{μm}}$, the substrates inside and outside of the white dashed lines are air and silicon dioxide, respectively[60]; (d) negative reflection of heperbolic poalritons[61], the incident frequency is 881 cm–1; (e) unidirectional propagation of phonon polaritons in grating $ \alpha $-MoO3 crystal at frequency 904 cm–1 [62].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-4.png)
图 4 氧化钼中各向异性声子极化激元的近场光学成像 (a)氧化钼中椭圆型(上)和双曲型(下)声子极化激元的近场光学图像[58], 入射光频率分别为为990 cm–1 (上)和900 cm–1 (下), 标尺为2 μm ; (b)氧化钼中银天线激发的双曲型声子极化激元, 表现为内陷型波前[59], 入射光频率为944 cm–1; (c)双曲极化激元的反常折射现象, 白色虚线内部衬底为空气, 外部为氧化硅[60], 入射光波长为11.3 μm; (d)双曲极化激元的负反射现象[61], 入射光频率为881 cm–1; (e)氧化钼光栅结构中声子极化激元的单向传播[62], 入射光频率为904 cm–1 [62]Fig. 4. Near-field imaging of anisotropic polaritons in molybdenum trioxide ($ \alpha $ 
$ \alpha $ 
$ \alpha $ 
$ {\lambda }_{0}=11.3\;{\text{μm}}$ 
$ \alpha $ 
除了体局域型(在材料内部传播, 垂直界面方向波矢为纯实数)和表面局域型(沿界面传播, 垂直界面方向波矢为纯虚数)声子极化激元, Ma等[66]通过近场成像实验证明了在方解石晶体(晶面与光轴夹角为23.3°)中存在第三种极化激元模式, 即“幽灵”双曲声子极化激元, 不仅在晶体表面以面内双曲色散远距离定向传播(20 μm), 还在垂直界面方向呈振荡衰减(图5(a)). 他们通过对麦克斯韦方程严格求解, 证明了该极化激元沿着垂直表面方向的传播常数为复数(同时具有实部和虚部). 晶体的晶格对称性是决定其物理性质的关键因素, Hu等[67]发现在低对称的单斜晶体钨酸镉中三阶介电张量不能对角化(即非对角量不为零), 会打破极化激元传播的镜面对称性, 导致其非对称传播, 但仍保留了旋转对称性, 他们将这类极化激元称为双曲剪切极化激元(图5(b)). 除了以上中红外波段的声子极化激元, 近期钛酸锶被实验证明在中红外到远红外宽光谱范围内支持表面声子极化激元(图5(c))[68], 为基于钙钛矿的宽带远红外和太赫兹纳米光子学建立了新的平台.
![图 5 体材料中声子极化激元的近场光学成像 (a)方解石中声子极化激元“幽灵”模式的近场光学图像, 可以实现20 μm的无衍射传播[66], 入射光频率为1460 cm–1; (b)钨酸镉晶体中声子极化激元剪切模式的实空间成像, 其镜像对称性被打破[67], 入射光频率为875 cm–1; (c)钛酸锶晶体中声子极化激元的纳米红外光谱测量结果, 工作频率为远红外频段[68]\r\nFig. 5. Near-field imaging of phonon polaritons in bulk materials: (a) Near-field image of antenna-launched ghost hepebolic phonon polaritons at the surface of bulk calcite at the illuminating frequency 1460 cm–1, generating diffraction-free propagation with a distance up to 20 μm[66]; (b) real-space imaging of symmetry-broken hyperbolic shear phonon polaritons in monoclinic cadmium tungstate (CdWO4) at frequemcy 875 cm–1 [67] ; (c) hyperspectral far-infrared imaging of surface phonon polaritons in strontium titanate[68].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-5.png)
图 5 体材料中声子极化激元的近场光学成像 (a)方解石中声子极化激元“幽灵”模式的近场光学图像, 可以实现20 μm的无衍射传播[66], 入射光频率为1460 cm–1; (b)钨酸镉晶体中声子极化激元剪切模式的实空间成像, 其镜像对称性被打破[67], 入射光频率为875 cm–1; (c)钛酸锶晶体中声子极化激元的纳米红外光谱测量结果, 工作频率为远红外频段[68]Fig. 5. Near-field imaging of phonon polaritons in bulk materials: (a) Near-field image of antenna-launched ghost hepebolic phonon polaritons at the surface of bulk calcite at the illuminating frequency 1460 cm–1, generating diffraction-free propagation with a distance up to 20 μm[66]; (b) real-space imaging of symmetry-broken hyperbolic shear phonon polaritons in monoclinic cadmium tungstate (CdWO4) at frequemcy 875 cm–1 [67] ; (c) hyperspectral far-infrared imaging of surface phonon polaritons in strontium titanate[68].3.3 激子极化激元
由于二维材料的激子结合能相比于体半导体中高出约1个数量级[69], 激子极化激元通常存在于二维半导体材料中, 典型的代表为过渡金属硫化物. 因其在可见至近红外波段具有大的能隙和强的激子结合能, 被认为可在常温下支持非常稳定的激子极化激元. 首次对激子极化激元的实空间观测是在厚度为260 nm的二硒化钨薄片中(图6(a))[70]. 除了稳定态, Mrejen等[71]进一步研究了二硒化钨激子极化激元的动力学过程, 对激子极化激元的形成和传播进行了实时的实空间成像(图6(b)), 发现其在常温下具有超慢的群速度($ {V}_{{\mathrm{g}}}\sim0.017 c $, c为真空中的光速). Sternbach等[72]则利用光激发在二硒化钨中注入电子-空穴对, 通过瞬态纳米成像显示了沿二硒化钨晶体内部锥形轨迹转播的双曲射线. 图6(c)所示为光激发后不同时间延迟下, 二硒化钨双曲激子极化激元波前成像图. 当二硒化钨薄片的厚度减小至几个原子层时, 不同于体波导中极化激元的横磁模式, Hu等[73]观察到激子极化激元的横电模式, 并进行了近场成像, 发现可以通过调整激发光的偏振态对其进行开关效应(图6(d)), 并且其性质(如波长、传播长度等)可被激发光能量、样品厚度显著调控. 此外, 他们还在二硒化钼中观察到了激子极化激元, 其传播距离可达12 μm (图6(e))[7].
![图 6 二维半导体材料中激子极化激元的近场光学研究 (a)二硒化钨晶体中激子极化激元的近场光学图像[70], 入射光波长为900 nm, 标尺为1 μm; (b)二硒化钨晶体中激子极化激元的超快近场光学成像[71], 入射光波长为$ (760\pm 5)\;{\mathrm{n}}{\mathrm{m}} $, 标尺为2 μm; (c)不用时间延迟下二硒化钨瞬态双曲激子极化激元近场相位图[72], 激发波数为910 cm–1; (d)不同入射偏振下二硒化钨晶体(厚度为9 nm)中激子极化激元的近场光学成像[73], 激发能量为1.44 eV, 标尺为1 μm; (e)二硒化钼晶体中激子极化激元的近场光学图像[7], 激发能量为1.35 eV\r\nFig. 6. Near-field optical study of exciton polaritons in two-dimensional semiconductors: (a) Near-field image of exciton polaritons in a WSe2 flake taken at $ {\lambda }_{0}=900\;{\mathrm{n}}{\mathrm{m}} $[70], scale bar, 1 μm; (b) ultrafast near-field imaging of exciton polaritons in WSe2[71], $ {\lambda }_{0}=(760\pm 5)\;{\mathrm{n}}{\mathrm{m}}, $ scale bars, 2 μm; (c) near-field phase images of transient hyperbolic exciton polaritons for a series of time delays taken at 910 cm–1 [72]; (d) polarization-dependent near-field images of exciton polaritons in a 9-nm-thick WSe2 sample taken at an excitation energy of 1.44 eV[73], scale bar, 1 μm; (e) near-field image of exciton polaritons in molybdenum selenide (MoSe2) taken at excitation energy of 1.35 eV[7].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-6.png)
图 6 二维半导体材料中激子极化激元的近场光学研究 (a)二硒化钨晶体中激子极化激元的近场光学图像[70], 入射光波长为900 nm, 标尺为1 μm; (b)二硒化钨晶体中激子极化激元的超快近场光学成像[71], 入射光波长为$ (760\pm 5)\;{\mathrm{n}}{\mathrm{m}} $ 
Fig. 6. Near-field optical study of exciton polaritons in two-dimensional semiconductors: (a) Near-field image of exciton polaritons in a WSe2 flake taken at$ {\lambda }_{0}=900\;{\mathrm{n}}{\mathrm{m}} $ 
$ {\lambda }_{0}=(760\pm 5)\;{\mathrm{n}}{\mathrm{m}}, $ 
3.4 杂化极化激元
极化激元是以倏逝波的形式延伸到上下介质中, 因此当两个或多个不同类型的极化激元同时满足动量(相似的波矢)和共振频率(光谱重叠)匹配时, 它们的耦合将形成杂化极化激元, 从而提供单个极化激元无法获得的新奇特性. 常见的为制备石墨烯/氮化硼异质结, 由于各自的等离极化激元和声子极化激元具有频率重叠, 耦合形成的杂化极化激元可同时结合等离极化激元的电学可调性和声子极化激元的低损耗优势. 一方面, 氮化硼可以为石墨烯提供原子级光滑和干净的保护层作用, 显著减小衬底的介电损耗, 将等离极化激元寿命提高至500 fs (图7(a))[74]; 另一方面, 通过与石墨烯等离极化激元杂化, 原本因固有晶格属性不易被原位调控的氮化硼声子极化激元可获得电学可调性(图7(b)), 并且杂化极化激元的传播长度是氮化硼声子极化激元的1.5—2.0倍[75,76]. 如图7(c)所示, Hu等[77]通过化学改变石墨烯掺杂水平, 调控了石墨烯/氧化钼异质结中杂化极化激元的等频色散曲线, 即实现从开口形状至闭合形状的拓扑转变. 当石墨烯费米能级较低时, 氧化钼厚度还可作为另一个调节维度实现杂化极化激元的波前改变[78]. Duan等[79]和Zhang等[80]研究了同时包含各向同性(碳化硅)和各向异性(氧化钼)介质复杂体系中的光学色散, 并成功在纳米尺度上发现了一种新的光学拓扑转变: 双曲型光学色散开口方向旋转90°(图7(d)). 转变发生时, 罕见的线性交叉光学色散导致了光子的射线化传播, 其具有极高的光场局域能力和极大的光学态密度[79]. 基于黑磷暴露在空气中极易降解的特殊性质, Huber等[81]设计了一种二氧化硅/黑磷/二氧化硅异质结, 并利用基于s-SNOM的泵浦-探测技术对黑磷电子-空穴对进行带间激发, 引起二氧化硅表面声子模式与黑磷表面等离极化激元模式杂化, 最终实现了杂化极化激元的开关效应. 如图7(e)所示, 由于黑磷中电子-空穴对的复合, 杂化极化激元在50 fs内被激发, 直至5 ps消失.
![图 7 异质结中极化激元的近场光学研究 (a)氮化硼/石墨烯/氮化硼夹层结构中超低损耗石墨烯等离极化激元的近场光学成像, 其传播寿命高达500 fs[74], 入射光子能量为116 meV; (b)石墨烯/氮化硼结构中杂化极化激元(等离极化激元-声子极化激元耦合)波长随背栅电压的变化趋势, 氮化硼声子极化激元波长不随电压变化[76]; (c)石墨烯/氧化钼结构中杂化极化激元波前随费米能级的变化趋势[77]; (d)石墨烯/碳化硅结构中双曲声子极化激元光场分布随入射光频率的变化趋势[79]; (e)氧化硅/黑磷/氧化硅夹层结构中极化激元的超快近场光学成像[81], 标尺为1 μm\r\nFig. 7. Near-field optical study of polaritons in heterostructures: (a) Near-field imaging of ultra low-loss graphene plasmons in hBN/graphene/hBN heterostructures with a propagation lifetime of up to 500 fs at a photon energy of $ \hslash \omega =116\;{\mathrm{m}}{\mathrm{e}}{\mathrm{V}} $[74]; (b) gate-dependence of the hybrid polariton (coupling between plasmons and phonon polaritons) wavelength in a graphene/hBN heterostructure while the wavelength of hBN phonon polaritons is nearly independent with gate voltage[76]; (c) the hybrid polariton wavefronts in graphene/$ \alpha $-MoO3 heterostructures at different graphene Fermi energies[77]; (d) near-field amplitude images of hyperbolic phonon polaritons in graphene/4H-SiC heterostructures at different illuminating frequencies[79]; (e) ultrafast near-field imaging of polaritons in a SiO2/black phosphorus/SiO2 heterostructure at different delay times between the pump and probe pulses[81], scale bar, 1 μm.](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-7.png)
图 7 异质结中极化激元的近场光学研究 (a)氮化硼/石墨烯/氮化硼夹层结构中超低损耗石墨烯等离极化激元的近场光学成像, 其传播寿命高达500 fs[74], 入射光子能量为116 meV; (b)石墨烯/氮化硼结构中杂化极化激元(等离极化激元-声子极化激元耦合)波长随背栅电压的变化趋势, 氮化硼声子极化激元波长不随电压变化[76]; (c)石墨烯/氧化钼结构中杂化极化激元波前随费米能级的变化趋势[77]; (d)石墨烯/碳化硅结构中双曲声子极化激元光场分布随入射光频率的变化趋势[79]; (e)氧化硅/黑磷/氧化硅夹层结构中极化激元的超快近场光学成像[81], 标尺为1 μmFig. 7. Near-field optical study of polaritons in heterostructures: (a) Near-field imaging of ultra low-loss graphene plasmons in hBN/graphene/hBN heterostructures with a propagation lifetime of up to 500 fs at a photon energy of$ \hslash \omega =116\;{\mathrm{m}}{\mathrm{e}}{\mathrm{V}} $ 
$ \alpha $ 
4. 极化激元调控
综上所述, 极化激元具有一系列优异的光学性质, 包括极强的光场局域能力、增强的光物相互作用和极大的光学态密度等, 故在光电探测、光学成像、信息传输等多个领域有巨大的应用潜力. 然而, 极化激元的实际应用强烈依赖于对其传播行为的精确调控, 例如波长、传播损耗、波前形状、传播方向等. 本节中系统总结了近几年关于极化激元调控的最新研究进展, 概括了多种不同类型的调控手段.
4.1 介电环境
杂质散射和介电损耗在极化激元中普遍存在, 因此周围介电环境是影响极化激元传播的重要因素. 将氮化硼放在不同衬底(悬空、介电性、金属性)上, Fali等[82]发现当衬底从介电性变为金属性时, 厚度归一化的氮化硼声子极化激元波矢随着衬底介电常数实部绝对值的增大而增大. 除了改变不同衬底, 衬底本身的性质也为极化激元的调控提供了一条新的途径. 尤其是相变材料(如Ge3Sb2Te6或二氧化钒等), 在外界(激光脉冲、电压或温度等)刺激下, 会发生晶相至非晶相或金属至绝缘体的可逆转变, 因在不同相中拥有完全不同的介电特性而为极化激元提供了可调控的介电环境. 二氧化钒在不同温度下会发生金属至绝缘体的转变, Folland等[83]将其作为氮化硼衬底, 实现了温度依赖的声子极化激元色散调控(图8(a)). 由于二氧化钒两个相无法在相同温度下共存的限制, Chaudhary等[84]选取了另一种相变材料Ge3Sb2Te6 (GST)作为氮化硼衬底, 借助GST在激光脉冲下可进行非挥发性的非晶相(a-GST)至晶相(c-GST)的可逆转变, 通过激光直写不同元件结构, 实现了可重写的极化激元超构透镜(图8(b))、对极化激元波前调控和亚波长聚焦. 若衬底具有各向异性也会使极化激元具有新的特性, 例如将氮化硼放置在黑磷上时, 声子极化激元将展现面内椭圆色散, 具有增强且可调的光学各向异性, 最高可达1.25, 高于黑磷固有的各向异性(1.13)(图8(c))[85]. 将极化激元材料悬空置于空气中是另一种特殊的介电调控方式, 不仅能有效避免不平整衬底对极化激元的散射, 还为极化激元调控增添了一种新的方式(悬空高度). Hu等[86]发现悬空石墨烯中等离极化激元波长和传播长度相比于有衬底的情况显著增加(图8(d)), 并且增加悬空高度能减弱衬底声子对等离极化激元的影响, 进一步提高品质因子和传播长度. Dai等[87]和Zheng等[88]也分别在悬空的氮化硼和氧化钼中声子极化激元观察到类似的现象.
![图 8 基于介电环境对极化激元的调控研究 (a)氮化硼声子极化激元在介质性和金属性二氧化钒界面处折射现象的实空间成像, 其波长分别为550 nm和362 nm[83]; (b)基于相变材料Ge3Sb2Te6图案化对氮化硼声子极化激元传播的精确调控[84], 入射光频率为1455 cm–1, 标尺为5 μm; (c)各向异性衬底(黑磷)对氮化硼声子极化激元的调控, 原本各向同性传播的极化激元沿不同方向具有不同波长, 在入射光频率为1420 cm–1时最大各向异性值为1.25[85], 标尺为2 μm; (d)空气衬底(悬空)对石墨烯等离极化激元传播损耗的调控, 即减小其传播损耗[86]\r\nFig. 8. Manipulation of polaritons based on dielectric environment: (a) Real-space imaging of refraction of hBN phonon polaritons at the dielectric-metallic vanadium dioxide domain boundary with polariton wavelengths of 550 nm and 362 nm[83], respectively; (b) manipulation of hBN phonon polariton propagation based on patterning of the phase change material Ge3Sb2Te6 at an incident frequency of 1455 cm–1[84], scale bars, 5 μm; (c) manipulation of hBN phonon polaritons by an anisotropic substrate (black phosphorus) with a maximum value of anisotropy ($ \alpha =b/a $) $ {\alpha }_{{\mathrm{m}}{\mathrm{a}}{\mathrm{x}}}=1.25 $ at 1420 cm–1, i.e., originally isotropically propagating poalritons have different wavelengths along different direcitons[85], scale bar, 2 μm; (d) manipulation of graphene plasmon propagation loss by air substrate (suspension), i.e., reduction of the propagation loss[86].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-8.png)
图 8 基于介电环境对极化激元的调控研究 (a)氮化硼声子极化激元在介质性和金属性二氧化钒界面处折射现象的实空间成像, 其波长分别为550 nm和362 nm[83]; (b)基于相变材料Ge3Sb2Te6图案化对氮化硼声子极化激元传播的精确调控[84], 入射光频率为1455 cm–1, 标尺为5 μm; (c)各向异性衬底(黑磷)对氮化硼声子极化激元的调控, 原本各向同性传播的极化激元沿不同方向具有不同波长, 在入射光频率为1420 cm–1时最大各向异性值为1.25[85], 标尺为2 μm; (d)空气衬底(悬空)对石墨烯等离极化激元传播损耗的调控, 即减小其传播损耗[86]Fig. 8. Manipulation of polaritons based on dielectric environment: (a) Real-space imaging of refraction of hBN phonon polaritons at the dielectric-metallic vanadium dioxide domain boundary with polariton wavelengths of 550 nm and 362 nm[83], respectively; (b) manipulation of hBN phonon polariton propagation based on patterning of the phase change material Ge3Sb2Te6 at an incident frequency of 1455 cm–1[84], scale bars, 5 μm; (c) manipulation of hBN phonon polaritons by an anisotropic substrate (black phosphorus) with a maximum value of anisotropy ($ \alpha =b/a $ 
$ {\alpha }_{{\mathrm{m}}{\mathrm{a}}{\mathrm{x}}}=1.25 $ 
4.2 物理场调控
极化激元在室温下通常具有很高的损耗, 降低温度是一条有效途径. Ni等[89,90]对石墨烯等离极化激元和氮化硼声子极化激元进行低温近场测量(图9(a), (b)), 发现接近液氮温度(60 K)时, 两类极化激元都比常温时具有更长的传播寿命, 分别可达1.6 ps和5 ps. 这是因为有效避免了石墨烯中的声学声子散射、谷间电子-声子散射和电子-电子散射, 以及氮化硼中的声子散射. 利用铝酸镧/钛酸锶异质结界面处产生的二维电子气中电子-声子相互作用, Zhou等[91]通过改变温度(300—12 K)实现了对钛酸锶表面声子极化激元起始频率的调控(蓝移$ \sim14\;{{\mathrm{c}}{\mathrm{m}}}^{-1} $)(图9(c)).
![图 9 基于物理场对极化激元的调控研究 (a)低温(60 K)下石墨烯等离极化激元的低损耗传播, 其传播寿命高达皮秒量级(1.6 ps)[89]; (b)不同温度下氮化硼声子极化激元的传播损耗测量, 接近液化氮温度时寿命超过5 ps [90]; (c)不同温度下钛酸锶和铝酸镧/钛酸锶异质结中声子极化激元的起始频率测量[91]; (d)不同背栅电压下极化激元在氧化钼和石墨烯/氧化钼界面处的折射现象[92], 标尺为1 μm; (e)碳化硅晶体中纳米压痕周边应力分布的近场光学测量[94], 地形图像(左), s-SNOM图像(右); (f)不同磁场强度下石墨烯狄拉克磁致激子极化激元的近场光学分布[95]\r\nFig. 9. Study on the manipulation of polaritons based on physical field: (a) Low-loss propagation of graphene plasmons at liquid-nitrogen temperature (T = 60 K) with propagation lifetime up to 1.6 ps[89]; (b) temperature dependence of hBN phonon polariton propagation loss, with lifetimes exceeding 5 ps when closing to liquild-nitrogen temperatures[90]; (c) the onset frequency of phonon polaritons as a function of temperature in strontium titanate (STO) and lanthanum aluminate/strontium titanate (LAO/STO) heterostructures[91]; (d) refraction phenomenon of gate-tunable negative refraction of polaritons from hyperbolic $ \alpha $-MoO3 to elliptic graphene/$ \alpha $-MoO3[92], scale bar, 1 μm; (e) near-field optical measurments of the residual strain field around the nanoindent in a silicon carbide crystal[94], topography image (left panel), s-SNOM image (right panel); (f) near-field images of magenetic field-dependent Dirac magnetoexcitons in graphene[95].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-9.png)
图 9 基于物理场对极化激元的调控研究 (a)低温(60 K)下石墨烯等离极化激元的低损耗传播, 其传播寿命高达皮秒量级(1.6 ps)[89]; (b)不同温度下氮化硼声子极化激元的传播损耗测量, 接近液化氮温度时寿命超过5 ps [90]; (c)不同温度下钛酸锶和铝酸镧/钛酸锶异质结中声子极化激元的起始频率测量[91]; (d)不同背栅电压下极化激元在氧化钼和石墨烯/氧化钼界面处的折射现象[92], 标尺为1 μm; (e)碳化硅晶体中纳米压痕周边应力分布的近场光学测量[94], 地形图像(左), s-SNOM图像(右); (f)不同磁场强度下石墨烯狄拉克磁致激子极化激元的近场光学分布[95]Fig. 9. Study on the manipulation of polaritons based on physical field: (a) Low-loss propagation of graphene plasmons at liquid-nitrogen temperature (T = 60 K) with propagation lifetime up to 1.6 ps[89]; (b) temperature dependence of hBN phonon polariton propagation loss, with lifetimes exceeding 5 ps when closing to liquild-nitrogen temperatures[90]; (c) the onset frequency of phonon polaritons as a function of temperature in strontium titanate (STO) and lanthanum aluminate/strontium titanate (LAO/STO) heterostructures[91]; (d) refraction phenomenon of gate-tunable negative refraction of polaritons from hyperbolic$ \alpha $ 
$ \alpha $ 
基于石墨烯电导率会随着费米能级移动而改变的独特性质, 电学调控成为石墨烯等离极化激元的一种主动调控方式. 无论施加的背栅电压与狄拉克点电压的差值为正(电子掺杂)或是负(空穴掺杂), 都能实现石墨烯等离极化激元的波长调控和开关效应(例如双层石墨烯)[38]. 并且电学调控还可用于几乎所有包含石墨烯等离极化激元的极化激元系统. 例如Hu等[92]在石墨烯/氧化钼异质结中, 利用两类不同拓扑态极化激元坡印廷矢量方向的差异, 在双曲介质和各向同性介质界面处实现了电学可调的双曲极化激元负折射(图9(d)). 此外, 对双层转角氧化钼/石墨烯异质结施加电压可有效调控杂化极化激元的波长、振幅、耗散率等参数, 这些参数随电压的不同变化趋势来源于杂化极化激元复动量面内和面外分量的复杂相互作用[93].
应变导致的晶格畸变会强烈改变材料的内在特性(力、光、电学性质), 甚至引起结构相变. 通过对碳化硅纳米压痕近场成像可以识别小至50 nm尺度下的应变特征和纳米裂纹随不同程度应变的演变过程(图9(e)), 以及掺杂碳化硅中应变引起的局域载流子特性的变化[94]. 同样地, 氮化硼中面内化学键的均匀拉伸与压缩也会使(横向光学)声子频率移动, 进而调控声子极化激元的光谱范围[96].
对具有自由电荷载流子的材料施加磁场时, 由于量子化朗道能级的形成会显著影响电荷载流子的轨道运动. 相邻朗道能级间的光学跃迁会产生独特的集体模式, 即磁致激子(也被称为磁致等离激元). Dapolito等[95]通过对近电中性的石墨烯施加磁场, 首次在实空间观测到了传播的狄拉克磁致激子极化激元并从中得到磁场调控的色散(图9(f)).
4.3 材料组分调控
对于组成元素具有多种同位素的极化激元材料, 例如氮化硼和氧化钼中的硼元素和钼元素, 其同位素变化会增加光学声子散射造成极化激元显著的光学损耗, 因此同位素富集是增加声子寿命、减小光学损耗的有效方法. Giles等[97]和Zhao等[98]分别通过制备硼同位素富集的氮化硼晶体和钼同位素富集的氧化钼晶体, 结合近场成像实验, 观察到超低损耗的声子极化激元(图10(a)和图10(b)), 相比于天然晶体, 寿命分别提高3倍和1.7倍. 与之相反, 对极性晶体材料进行原子插层会干扰晶格振动而改变光学介电响应. Javier等[99]和Wu等[100]分别通过钠原子插层五氧化二钒和氢原子插层氧化钼实现了声子极化激元光谱范围的调控(剩余射线带频移(图10(c))和可逆的开关效应(图10(d)).
![图 10 基于材料组分对极化激元的调控研究 (a)同位素富集氮化硼(上)和天然氮化硼(下)中声子极化激元的近场光学图像, 入射光频率分别为1510 cm–1和1480 cm–1 [97]; (b)天然氧化钼(左)和同位素富集氧化钼(右)中声子极化激元的近场光学图像, 入射光频率分别为994 cm–1和990 cm–1 [98]; (c)五氧化二钒($ \alpha $-V2O5)晶体中钠原子插层对声子极化激元工作频率(剩余射线带)的调制作用, 实心水平线标记了$ \alpha $-V2O5中的近似横向光学(TO)声子模式(TO1, 975 cm–1; TO2, 770 cm–1)和 $ {\alpha }'$-(Na)V2O5 (TO, 950 cm–1)[99]; (d)氢原子插层对氧化钼中声子极化激元的调制作用, 入射光频率为890 cm–1 [100]\r\nFig. 10. Study on the manipulation of polaritons based on material components: (a) Near-field images of phonon polaritons in isotopically enriched hBN (top panel) and natural hBN (bottom panel) at incident frequencies of 1510 cm–1 and 1480 cm–1 [97], respectively; (b) near-field images of phonon polaritons in natural $ \alpha $-MoO3 (left panel) and isotopically enriched $ \alpha $-MoO3 (right panel) at incident frequencies of 994 cm–1 and 990 cm–1 [98], respectively; (c) nano-spectroscopy of vanadium pentoxide ($ \alpha $-V2O5) (left panel) and Na-intercalated $ \alpha $-V2O5 ($ {\alpha }'$-(Na)V2O5) (right panel) flakes[99], solid horizontal lines mark the approximate transversal optic (TO) phonon modes in $ \alpha $-V2O5 (TO1, 975 cm–1; TO2, 770 cm–1) and $ {\alpha }'$-(Na)V2O5 (TO, 950 cm–1); (d) optical micrographs and near-field images of a MoO3 flake at 890 cm–1 before intercaltion, after intercalation (10 s) and after deintercalation[100].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-10.png)
图 10 基于材料组分对极化激元的调控研究 (a)同位素富集氮化硼(上)和天然氮化硼(下)中声子极化激元的近场光学图像, 入射光频率分别为1510 cm–1和1480 cm–1 [97]; (b)天然氧化钼(左)和同位素富集氧化钼(右)中声子极化激元的近场光学图像, 入射光频率分别为994 cm–1和990 cm–1 [98]; (c)五氧化二钒($ \alpha $ 
$ \alpha $ 
$ {\alpha }'$ 
Fig. 10. Study on the manipulation of polaritons based on material components: (a) Near-field images of phonon polaritons in isotopically enriched hBN (top panel) and natural hBN (bottom panel) at incident frequencies of 1510 cm–1 and 1480 cm–1 [97], respectively; (b) near-field images of phonon polaritons in natural$ \alpha $ 
$ \alpha $ 
$ \alpha $ 
$ \alpha $ 
$ {\alpha }'$ 
$ \alpha $ 
$ {\alpha }'$ 
4.4 转角调控
双层转角二维材料不仅具有新奇的电学特性, 还可以支持杂化极化激元, 转角也成为调控极化激元的一个新自由度. 将bilayer石墨烯的层间进行小角度旋转, 两层石墨烯的晶格周期性将发生几何干涉引起原子堆积的长程变化, 形成莫尔超晶格. 如图11(a)所示, Sunku等[101]通过转角bilayer石墨烯(TBG)中形成的周期性接近等离极化激元波长的孤子超晶格网络, 设计实现了电学可调的等离极化激元纳米光子晶体, 其中畴壁区域光导响应的增强来源于光孤子的拓扑保护边界态. Hesp等[102]在TBG中观察到了带间等离极化激元, 来源于莫尔超晶格微带间的光学跃迁, 不同于单层石墨烯中的带内等离极化激元, 其等离极化激元色散直接与莫尔超晶格中的电子运动相关. 对于最小转角bilayer石墨烯 (mTBG, 转角小于0.1°) 晶格的重构会产生由窄畴壁网格分隔的AB/BA堆叠相间排列呈三角形域的莫尔超晶格(图11(b)), 在光响应方面引起光电性质的重整化, 例如在纳米尺度畴壁处发生的光电流模式[103,104].
![图 11 二维转角体系中极化激元的调控 (a)转角双层石墨烯等离极化激元光子晶体的近场光学成像(左)和暗场TEM可视化图像[101]; (b)最小转角石墨烯的光电流探测, 存在电子和空穴分布[104], 标尺为500 nm; (c)转角双层氧化钼中声子极化激元的光学拓扑转变, 当转角为光学魔角($ {\theta =54}^{\circ} $)时, 极化激元沿某一方向高度定向传播[105]; (d)转角三层氧化钼晶体中可以实现极化激元无衍射传播的面内全角度调控[106]\r\nFig. 11. Manipulation of polaritons in two-dimensional twist systems: (a) Near-field imaging (left) and dark-field TEM visualization (right) of twist bilayer graphene nano-light photonic crystal[101]; (b) photocurrent map of minimally twisted bilayer graphene in the presence of electron and hole distributions[104], scale bar, 500 nm; (c) near-field amplitude images of twisted $ \alpha $-MoO3 at an incident wavelength of 11 μm for different rotation angles, a clear optical topological transition is observed, where polaritons propagate highly oriented along a certain direction at the critical angle of $ {\theta =54}^{\circ} $[105]; (d) near-field amplitude images of trilayer $ \alpha $-MoO3 at an illuminating wavelength of 10.9 μm for different rotation angles[106], demonstrating that in-plane full-angle manipulation of polariton diffraction-free propagation can be achieved.](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-11.png)
图 11 二维转角体系中极化激元的调控 (a)转角双层石墨烯等离极化激元光子晶体的近场光学成像(左)和暗场TEM可视化图像[101]; (b)最小转角石墨烯的光电流探测, 存在电子和空穴分布[104], 标尺为500 nm; (c)转角双层氧化钼中声子极化激元的光学拓扑转变, 当转角为光学魔角($ {\theta =54}^{\circ} $ 
Fig. 11. Manipulation of polaritons in two-dimensional twist systems: (a) Near-field imaging (left) and dark-field TEM visualization (right) of twist bilayer graphene nano-light photonic crystal[101]; (b) photocurrent map of minimally twisted bilayer graphene in the presence of electron and hole distributions[104], scale bar, 500 nm; (c) near-field amplitude images of twisted$ \alpha $ 
$ {\theta =54}^{\circ} $ 
$ \alpha $ 
由于各向异性, 改变转角时, 双层氧化钼中声子极化激元的等频线会发生从面内开口双曲型到闭合椭圆的拓扑转变 [105,107–109]. 在此期间当转角为一个特定值(光学魔角)时, 等频线变为两条平行直线(光学平带), 声子极化激元沿着特定方向且无衍射传播(图11(c)). 然而, 双层转角系统仅在特定频率下存在一个光学魔角, 无法对无衍射传播进行调控(光场能量仅沿一个固定方向传播). Duan等[106]在三层转角氧化钼晶体中, 通过转角重构克服这一限制, 实现了宽光谱频率范围内极化激元面内无衍射传播的全角度调控(图11(d)).
4.5 源调控
极化激元的传播特性与材料对称性密切相关, 在高对称性晶体中, 尤其是双曲极化激元, 其波前的镜像对称性不利于定向传播. 最近, Hu等[110]提出一种源调控方式, 即控制激发源极化特性直接在高对称晶体中激发对称性破缺的双曲极化激元. 他们在方解石晶体表面制备金圆盘纳米天线, 通过施加不同线偏振方向平面波调控金圆盘面内电偶极矩极化方向, 实现了宽频率范围内双曲极化激元非对称性传播的调控以及对称与非对称之间的自由切换(图12). 相比于对称状态, 对称破缺的双曲极化激元具有更高的能量定向传输效率.
5. 极化激元的应用
极化激元优异的光学特性(例如高光场局域性、动态可调谐性、增强的光-物相互作用、双曲色散特性等)为一系列纳米光子学应用提供了巨大的潜力, 下文将列出几个有代表性的应用方向.
5.1 亚衍射成像和聚焦
传统的光学元件(如棱镜、透镜、凹面镜等)由于受到衍射极限的限制, 无法实现低于自由空间光波长的一半的光学聚焦. Li等[111]和Dai等[116] 利用氮化硼声子极化激元的低损耗和双曲色散特性, 通过改变入射光频率调控极化激元面外传播方向, 实现了突破衍射极限的超分辨成像(图13(a))和纳米聚焦. 此外, Duan等[60]基于实验中发现的氧化钼双曲声子极化激元反常折射行为(即从低到高折射率介质, 折射角大于入射角), 设计了纳米光学棱镜和目前已知最高焦点分辨率($ {\lambda }_{0}/50 $)的面内双曲透镜(图13(b)).
![图 13 极化激元的相关应用 (a) 基于氮化硼声子极化激元的超分辨成像[111], 上图为实验装置示意图, 中图为hBN薄片的AFM形貌, 下图为用宽带激光器拍摄的hBN下方金纳米盘的近场图像, 标尺为0.5 μm; (b) 基于氧化钼声子极化激元的亚衍射聚焦, 入射光波长为11.16 μm[60]; (c) 石墨烯/二硫化钼异质结中基于二硫化钼光生载流子掺杂对石墨烯等离极化激元的光调制[112]; (d) 基于氮化硼声子极化激元干涉对内部缺陷识别的近场成像图, 激发波数为1541 cm–1 [113]; (e) 包含分子的氮化硼高光谱成像图[114]; (f) 基于氮化硼声子极化激元的分子探测, hBN带和被分子覆盖的hBN带, 采用hBN中的声子极性子进行分子检测[115]\r\nFig. 13. Applications of polaritons: (a) Super-resolution imaging via phonon polaritons in hBN[111], upper panel is the sketch of the experimental setup, middle panel is the AFM topography of the hBN flake, bottom panel is the near-field images of gold nanodisks beneath hBN taken with the broadband laser. Scale bars, 0.5 μm; (b) sub-diffractional focusing based on refraction of phonon polaritons in $ \alpha $-MoO3 at an illuminating wavelength of 11.16 μm[60]; (c) optical switching of graphene plasmons based on the photogenerated carrier doping in a graphene/MoS2 heterostructure. Dashed lines indicate the graphene edge[112]; (d) near-field image of the hBN slab revealing concealed inner defects at an incident frequency of 1541 cm–1 [113]; (e) hyperspectral line scan map of hBN containg organic molecules[114]; (f) infrared transmission spectra of bare molecular layer, hBN ribbons and hBN ribbons covered with molecules, demonstrating molecular detection using phonon polaritons in hBN[115].](/fileWLXB/journal/article/wlxb/2024/8/PIC/8-20232001-13.png)
图 13 极化激元的相关应用 (a) 基于氮化硼声子极化激元的超分辨成像[111], 上图为实验装置示意图, 中图为hBN薄片的AFM形貌, 下图为用宽带激光器拍摄的hBN下方金纳米盘的近场图像, 标尺为0.5 μm; (b) 基于氧化钼声子极化激元的亚衍射聚焦, 入射光波长为11.16 μm[60]; (c) 石墨烯/二硫化钼异质结中基于二硫化钼光生载流子掺杂对石墨烯等离极化激元的光调制[112]; (d) 基于氮化硼声子极化激元干涉对内部缺陷识别的近场成像图, 激发波数为1541 cm–1 [113]; (e) 包含分子的氮化硼高光谱成像图[114]; (f) 基于氮化硼声子极化激元的分子探测, hBN带和被分子覆盖的hBN带, 采用hBN中的声子极性子进行分子检测[115]Fig. 13. Applications of polaritons: (a) Super-resolution imaging via phonon polaritons in hBN[111], upper panel is the sketch of the experimental setup, middle panel is the AFM topography of the hBN flake, bottom panel is the near-field images of gold nanodisks beneath hBN taken with the broadband laser. Scale bars, 0.5 μm; (b) sub-diffractional focusing based on refraction of phonon polaritons in$ \alpha $ 
5.2 光调制器
日益增长的数据处理数量和传输速度急需兼具小型化和高速度的设备[117,118]. 调制器是将信息信号转换为光信号进行传输并用于光通信. 全光调制器虽具有高速、低损耗和宽带的优异特性, 但总是很难避免因衍射极限和微弱的光子间相互作用造成的高功耗和大尺寸[119,120]. 有效的全光等离激元调制器在原子薄度的石墨烯/二硫化钼异质结中被实现[112]. 基于二硫化钼中的光生载流子对石墨烯的掺杂, 石墨烯等离极化激元频率可被弱LED光(光强低至$ 0.15\;{\mathrm{m}}{\mathrm{W}}/{{\mathrm{c}}{\mathrm{m}}}^{2} $)调制约43 cm–1(图13(c)), 比主流石墨烯非线性全光调制器($ \sim{10}^{3}\;{\mathrm{m}}{\mathrm{W}}/{{\mathrm{c}}{\mathrm{m}}}^{2} $)小4个数量级, 且调制深度还可通过缩短激光波长和增大激光功率被进一步提高.
5.3 纳米结构识别
除了晶体边界, 晶体内部缺陷也会反射传播的极化激元. 通过对极化激元与内部缺陷相互作用形成的干涉驻波条纹进行分析可以定位和识别缺陷结构. 由于光场的倏逝波特性, 通常只能在样品表面以下有限的深度($ < 50\;{\mathrm{n}}{\mathrm{m}} $)内获取有效信息. 氮化硼声子极化激元独特的体局域传播特性使其对晶体内部结构非常敏感且不受有限深度的限制. Dai等[113]利用被氮化硼内部空气间隙反射后形成的声子极化激元干涉对空气间隙进行了识别(图13(d)). 由于极化激元特性与空气间隙的厚度和垂直位置密切相关, 因此对极化激元波长、反射、色散等详细分析可以精确获得隐藏在氮化硼内部的空气间隙的形状、位置和尺寸.
5.4 光学传感
得益于等离极化激元对光的亚波长局域和周围环境的敏感性, 金属等离极化激元已被广泛应用于传感技术(包括单分子检测). 相比于等离极化激元, 低损耗的氮化硼声子极化激元可以提供更强的光场增强, 并且其天然的双曲特性(即大的光学密度态)可显著增强对分子的红外吸收. Autore等[115]通过制备氮化硼纳米带阵列, 实现了少量有机分子的探测, 其中声子极化激元与分子振动在实验上达到了强耦合的开始状态. 如图13(f)所示, 对于没有覆盖在氮化硼纳米带上的有机分子, 其厚度只有超过100 nm时才能看到光谱特征, 而对于覆盖在氮化硼上的有机分子, 厚度仅需10 nm就能看到明显的光谱凹陷, 代表对分子吸收的显著增强. Bylinkin等[114]在此基础上进一步优化, 通过近场成像实验证明无需结构化的氮化硼声子极化激元也可以与分子振动进行强耦合(图13(e)), 并且这种耦合会导致声子极化激元传播长度的急剧减小和负群速度的反常色散.
6. 总结与展望
本文在介绍多种极化激元体系近场光学性质研究最新进展的基础上, 系统总结了各类极化激元的调控方式及其潜在的应用场景. 值得指出的是, 具有各向异性光学色散的极化激元体系为实现纳米尺度下光与物质相互作用的精确调控提供了许多新思路和新优势, 例如理论上无限大的光学态密度、显著的光场局域和电磁场增强、动态可逆的调控手段等. 虽然该领域已经取得了丰硕的研究成果, 但仍有许多前景广阔的研究方向和未解决的科学问题, 概述如下.
1)探索新型极化激元体系
目前对极化激元的近场光学研究主要集中在等离极化激元、声子极化激元和激子极化激元三类. 然而从理论上来讲, 只要动量和能量合适, 光子可以与其他多种粒子(准粒子)的集体振荡产生强相互作用, 得到更多类型的极化激元, 例如超导体中的库珀对极化激元、铁磁体中的磁振子极化激元、非平衡态下的Mott局域电子极化激元等. 这些极化激元的实空间观测尚未实现, 其光电物性研究才刚刚开始, 对多个领域的发展具有极大的推动作用, 其中一个显著的例子是库珀对极化激元能否突破传统极化激元的传播损耗边界, 获得像超导态一样的无损耗极化激元模式.
此外, 目前已经研究的极化激元体系尚未完善, 例如低对称性传播的剪切式极化激元模式在单斜晶体中发现, 但更复杂的三斜晶体中是否存在更多极化激元模式还是一个悬而未决的问题. 而不同类型极化激元具有各自的缺点, 例如等离极化激元的高损耗、声子极化激元的难调控等, 是否可以通过构建复杂的极化激元体系(即范德瓦尔斯异质结结构)综合多种极化激元的优点, 剔除其缺点, 也是另一个值得研究的课题.
2)增加极化激元更多维度调控方式
如上文所述, 在等离极化激元和声子极化激元方面已开发出多种调控方法. 实际情况中, 为了拓展极化激元在不同物理条件下的多面适用性, 不同调控方法通常会同时使用, 例如选择同位素富集的氮化硼与石墨烯制备异质结, 既能显著减少极化激元损耗, 还能增添电学可调性. 然而, 除了近期对电中性石墨烯施加磁场调控磁激子极化激元色散外, 应用于激子极化激元的其他调控方法还未被有效地研究, 并且新的调控方法也仍需被探索. 例如, 调控极化激元对称性, 包括色散拓扑对称和时间反演对称, 有助于研究非厄米态和非平衡态中表面电磁波特性.
3)构建更多类型极化激元材料异质结
范德瓦耳斯体系的优势之一是存在丰富多样的异质结. 基于石墨烯的多种异质结构(例如氮化硼/石墨烯、氧化钼/石墨烯等)已经取得许多近场方面的重要研究结果, 但是基于各向异性材料的异质结研究才刚起步, 而与相变材料的结合也主要是报道了基于氮化硼. 若是能推广至更多其他极化激元材料或是不同类型各向异性材料相结合(例如氧化钼/五氧化二钒等), 利用激光、温度、原子平面组装、转角等技术, 有望实现更多新奇的物理特性, 例如拓扑保护、超导转变等.
[1] Huang K U N 1951 Nature 167 779
[2] Barnes W L, Dereux A, Ebbesen T W 2003 Nature 424 824
Google Scholar
[3] Ditlbacher H, Hohenau A, Wagner D, Kreibig U, Rogers M, Hofer F, Aussenegg F R, Krenn J R 2005 Phys. Rev. Lett. 95 257403
Google Scholar
[4] Basov D N, Fogler M M, García de Abajo F J 2016 Science 354 aag1992
Google Scholar
[5] Low T, Chaves A, Caldwell J D, Kumar A, Fang N X, Avouris P, Heinz T F, Guinea F, Martin-Moreno L, Koppens F 2017 Nat. Mater. 16 182
Google Scholar
[6] Dai S, Fei Z, Ma Q, Rodin A S, Wagner M, McLeod A S, Liu M K, Gannett W, Regan W, Watanabe K, Taniguchi T, Thiemens M, Dominguez G, Neto A H C, Zettl A, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2014 Science 343 1125
Google Scholar
[7] Hu F, Luan Y, Scott M E, Yan J, Mandrus D G, Xu X, Fei Z 2017 Nat. Photon. 11 356
Google Scholar
[8] Berkowitz M E, Kim B S Y, Ni G, McLeod A S, Lo C F B, Sun Z, Gu G, Watanabe K, Taniguchi T, Millis A J, Hone J C, Fogler M M, Averitt R D, Basov D N 2021 Nano Lett. 21 308
Google Scholar
[9] Costa A T, Vasilevskiy M I, Fernández-Rossier J, Peres N M R 2023 Nano Lett. 23 4510
Google Scholar
[10] Wolf E, Nieto-Vesperinas M 1985 J. Opt. Soc. Am. A 2 886
[11] Hillenbrand R, Keilmann F, Hanarp P, Sutherland D S, Aizpurua J 2003 Appl. Phys. Lett. 83 368
Google Scholar
[12] Cvitkovic A, Ocelic N, Hillenbrand R 2007 Nano Lett. 7 3177
Google Scholar
[13] Hillenbrand R, Keilmann F 2000 Phys. Rev. Lett. 85 3029
Google Scholar
[14] Hillenbrand R, Taubner T, Keilmann F 2002 Nature 418 159
Google Scholar
[15] Andryieuski A, Zenin V A, Malureanu R, Volkov V S, Bozhevolnyi S I, Lavrinenko A V 2014 Nano Lett. 14 3925
Google Scholar
[16] Huth F, Chuvilin A, Schnell M, Amenabar I, Krutokhvostov R, Lopatin S, Hillenbrand R 2013 Nano Lett. 13 1065
Google Scholar
[17] Mastel S, Lundeberg M B, Alonso-González P, Gao Y, Watanabe K, Taniguchi T, Hone J, Koppens F H L, Nikitin A Y, Hillenbrand R 2017 Nano Lett. 17 6526
Google Scholar
[18] Deutsch B M, Hillenbrand R, Novotny L 2008 Opt. Express 16 2 494
[19] Taubner T, Hillenbrand R, Keilmann F 2003 J. Micro. 210 311
Google Scholar
[20] 段嘉华, 陈佳宁 2019 物理学报 68 110701
Google Scholar
Duan J H, Chen J N 2019 Acta Phys. Sin. 68 110701
Google Scholar
[21] Gramotnev D K, Bozhevolnyi S I 2014 Nat. Photon. 8 13
Google Scholar
[22] Gucciardi P G, Bachelier G, Allegrini M 2006 J. Appl. Phys. 99 124309
Google Scholar
[23] Knoll B, Keilmann F 2000 Opt. Commun. 182 321
Google Scholar
[24] Ocelic N, Huber A, Hillenbrand R 2006 Appl. Phys. Lett. 89 101124
Google Scholar
[25] Moreno C, Alda J, Kinzel E, Boreman G 2017 Appl. Opt. 56 1037
Google Scholar
[26] HillenbRand R, Knoll B, Keilmann F 2001 J. Micro. 202 77
Google Scholar
[27] Zenhausern F, Martin Y, Wickramasinghe H K 1995 Science 269 1083
Google Scholar
[28] Richards D, Zayats A, Keilmann F, Hillenbrand R 2004 Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 362 787
[29] Cvitkovic A, Ocelic N, Hillenbrand R 2007 Opt. Express 15 8550
Google Scholar
[30] Amarie S, Keilmann F 2011 Phys. Rev. B 83 045404
Google Scholar
[31] Chen X Z, Hu D B, Mescall R, You G J, Basov D N, Dai Q, Liu M K 2019 Adv. Mater. 31 1804774
Google Scholar
[32] Jiang B Y, Zhang L M, Castro Neto A H, Basov D N, Fogler M M 2016 J. Appl. Phys. 119 054305
Google Scholar
[33] Fei Z, Andreev G O, Bao W, Zhang L M, McLeod A S, Wang C, Stewart M K, Zhao Z, Dominguez G, Thiemens M, Fogler M M, Tauber M J, Castro-Neto A H, Lau C N, Keilmann F, Basov D N 2011 Nano Lett. 11 4701
Google Scholar
[34] Chen J, Badioli M, Alonso-González P, Thongrattanasiri S, Huth F, Osmond J, Spasenović M, Centeno A, Pesquera A, Godignon P, Zurutuza Elorza A, Camara N, de Abajo F J G, Hillenbrand R, Koppens F H L 2012 Nature 487 77
Google Scholar
[35] Dai S, Ma Q, Yang Y, Rosenfeld J, Goldflam M D, McLeod A, Sun Z, Andersen T I, Fei Z, Liu M, Shao Y, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2017 Nano Lett. 17 5285
Google Scholar
[36] Fei Z, Rodin A S, Andreev G O, Bao W, McLeod A S, Wagner M, Zhang L M, Zhao Z, Thiemens M, Dominguez G, Fogler M M, Neto A H C, Lau C N, Keilmann F, Basov D N 2012 Nature 487 82
Google Scholar
[37] Alonso-González P, Nikitin A Y, Golmar F, Centeno A, Pesquera A, Vélez S, Chen J, Navickaite G, Koppens F, Zurutuza A, Casanova F, Hueso L E, Hillenbrand R 2014 Science 344 1369
Google Scholar
[38] Fei Z, Iwinski E G, Ni G X, Zhang L M, Bao W, Rodin A S, Lee Y, Wagner M, Liu M K, Dai S, Goldflam M D, Thiemens M, Keilmann F, Lau C N, Castro-Neto A H, Fogler M M, Basov D N 2015 Nano Lett. 15 4973
Google Scholar
[39] Dong Y, Xiong L, Phinney I Y, Sun Z, Jing R, McLeod A S, Zhang S, Liu S, Ruta F L, Gao H, Dong Z, Pan R, Edgar J H, Jarillo-Herrero P, Levitov L S, Millis A J, Fogler M M, Bandurin D A, Basov D N 2021 Nature 594 513
Google Scholar
[40] Zhao W, Zhao S, Li H, Wang S, Wang S, Utama M I B, Kahn S, Jiang Y, Xiao X, Yoo S, Watanabe K, Taniguchi T, Zettl A, Wang F 2021 Nature 594 517
Google Scholar
[41] Kim B S Y, Sternbach A J, Choi M S, Sun Z, Ruta F L, Shao Y, McLeod A S, Xiong L, Dong Y, Chung T S, Rajendran A, Liu S, Nipane A, Chae S H, Zangiabadi A, Xu X, Millis A J, Schuck P J, Dean C R, Hone J C, Basov D N 2023 Nat. Mater. 22 838
Google Scholar
[42] Zhou Y X, Chen R K, Wang J Y, Huang Y S, Li M, Xing Y J, Duan J H, Chen J J, Farrell J D, Xu H Q, Chen J N 2018 Adv. Mater. 30 1802551
Google Scholar
[43] Xue M F, Li M, Huang Y S, Chen R K, Li YL, Wang J Y, Xing Y J, Chen J J, Yan H Q, Xu H Q, Chen J N 2020 Adv. Mater. 32 2004120
Google Scholar
[44] Xue M F, Pan D, Zhao J H, Chen J N 2023 Adv. Mater. 35 2208952
Google Scholar
[45] Luttinger J M 2004 J. Math. Phys 4 1154
[46] Voit J 1995 Rep. Pro. Phys. 58 977
Google Scholar
[47] Shi Z W, Hong X P, Bechtel H A, Zeng B, Martin M C, Watanabe K, Taniguchi T, Shen Y R, Wang F 2015 Nat. Photon. 9 515
Google Scholar
[48] Wang S, Zhao S H, Shi Z W, Wu F Q, Zhao Z Y, Jiang L L, Watanabe K, Taniguchi T, Zettl A, Zhou C W, Wang F 2020 Nat. Mater. 19 986
Google Scholar
[49] Wang C, Huang S Y, Xing Q X, Xie Y G, Song C Y, Wang F J, Yan H G 2020 Nat. Commun. 11 1158
Google Scholar
[50] Chen S, Leng P L, Konečná A, et al. 2023 Nat. Mater. 22 860
Google Scholar
[51] Xu X G, Ghamsari B G, Jiang J H, Gilburd L, Andreev G O, Zhi C, Bando Y, Golberg D, Berini P, Walker G C 2014 Nat. Commun. 5 4782
Google Scholar
[52] Li P, Dolado I, Alfaro-Mozaz F J, Nikitin A Y, Casanova F, Hueso L E, Vélez S, Hillenbrand R 2017 Nano Lett. 17 228
Google Scholar
[53] Li P, Hu G, Dolado I, Tymchenko M, Qiu C-W, Alfaro-Mozaz F J, Casanova F, Hueso L E, Liu S, Edgar J H, Vélez S, Alu A, Hillenbrand R 2020 Nat. Commun. 11 3663
Google Scholar
[54] Li P, Dolado I, Alfaro-Mozaz F J, Casanova F, Hueso L E, Liu S, Edgar J H, Nikitin A Y, Vélez S, Hillenbrand R 2018 Science 359 892
Google Scholar
[55] Shi Z W, Bechtel H A, Berweger S, Sun Y, Zeng B, Jin C, Chang H, Martin M C, Raschke M B, Wang F 2015 ACS Photon. 2 790
Google Scholar
[56] Dai S, Fang W, Rivera N, Stehle Y, Jiang B-Y, Shen J, Tay R Y, Ciccarino C J, Ma Q, Rodan-Legrain D, Jarillo-Herrero P, Teo E H T, Fogler M M, Narang P, Kong J, Basov D N 2019 Adv. Mater. 31 1806603
Google Scholar
[57] Dai S, Tymchenko M, Yang Y, Ma Q, Pita-Vidal M, Watanabe K, Taniguchi T, Jarillo-Herrero P, Fogler M M, Alù A, Basov D N 2018 Adv. Mater. 30 1706358
Google Scholar
[58] Ma W, Alonso-González P, Li S, Nikitin A Y, Yuan J, Martín-Sánchez J, Taboada-Gutiérrez J, Amenabar I, Li P, Vélez S, Tollan C, Dai Z, Zhang Y, Sriram S, Kalantar-Zadeh K, Lee S T, Hillenbrand R, Bao Q 2018 Nature 562 557
Google Scholar
[59] Zheng Z, Xu N, Oscurato S L, Tamagnone M, Sun F, Jiang Y, Ke Y, Chen J, Huang W, Wilson W L, Ambrosio A, Deng S, Chen H 2019 Sci. Adv. 5 eaav8690
Google Scholar
[60] Duan J H, Álvarez-Pérez G, Tresguerres-Mata A I F, Taboada-Gutiérrez J, Voronin K V, Bylinkin A, Chang B, Xiao S, Liu S, Edgar J H, Martín J I, Volkov V S, Hillenbrand R, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2021 Nat. Commun. 12 4325
Google Scholar
[61] Álvarez-Pérez G, Duan J H, Taboada-Gutiérrez J, Ou Q, Nikulina E, Liu S, Edgar J H, Bao Q, Giannini V, Hillenbrand R, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2022 Sci. Adv. 8 eabp8486
Google Scholar
[62] Zhang Q, Ou Q, Si G, Hu G, Dong S, Chen Y, Ni J, Zhao C, Fuhrer M S, Yang Y, Alù A, Hillenbrand R, Qiu C-W 2022 Sci. Adv. 8 eabn9774
Google Scholar
[63] Martín-Sánchez J, Duan J H, Taboada-Gutiérrez J, Álvarez-Pérez G, Voronin K V, Prieto I, Ma W, Bao Q, Volkov V S, Hillenbrand R, Nikitin A Y, Alonso-González P 2021 Sci. Adv. 7 eabj0127
Google Scholar
[64] Zheng Z B, Jiang J Y, Xu N S, Wang X M, Huang W C, Ke Y L, Zhang S R, Chen H J, Deng S Z 2022 Adv. Mater. 34 2104164
Google Scholar
[65] Qu Y P, Chen N, Teng H C, Hu H, Sun J Z, Yu R W, Hu D B, Xue M F, Li C, Wu B, Chen J N, Sun Z P, Liu M K, Liu Y Q, García de Abajo F J, Dai Q 2022 Adv. Mater. 34 2105590
Google Scholar
[66] Ma W L, Hu G W, Hu D B, Chen R K, Sun T, Zhang X L, Dai Q, Zeng Y, Alù A, Qiu C W, Li P N 2021 Nature 596 362
Google Scholar
[67] Hu G W, Ma W L, Hu D B, Wu J, Zheng C Q, Liu K P, Zhang X D, Ni X, Chen J N, Zhang X L, Dai Q, Caldwell J D, Paarmann A, Alù A, Li P N, Qiu C W 2023 Nat. Nanotechnol. 18 64
Google Scholar
[68] Lahneman D J, Qazilbash M M 2021 Phys. Rev. B 104 235433
Google Scholar
[69] Koch S W, Kira M, Khitrova G, Gibbs H M 2006 Nat. Mater. 5 523
Google Scholar
[70] Fei Z, Scott M E, Gosztola D J, Foley J J, Yan J, Mandrus D G, Wen H, Zhou P, Zhang D W, Sun Y, Guest J R, Gray S K, Bao W, Wiederrecht G P, Xu X 2016 Phys. Rev. B 94 081402
Google Scholar
[71] Mrejen M, Yadgarov L, Levanon A, Suchowski H 2019 Sci. Adv. 5 eaat9618
Google Scholar
[72] Sternbach A J, Chae S H, Latini S, Rikhter A A, Shao Y, Li B, Rhodes D, Kim B, Schuck P J, Xu X, Zhu X Y, Averitt R D, Hone J, Fogler M M, Rubio A, Basov D N 2021 Science 371 617
Google Scholar
[73] Hu F, Luan Y, Speltz J, Zhong D, Liu C H, Yan J, Mandrus D G, Xu X, Fei Z 2019 Phys. Rev. B 100 121301
Google Scholar
[74] Woessner A, Lundeberg M B, Gao Y, Principi A, Alonso-González P, Carrega M, Watanabe K, Taniguchi T, Vignale G, Polini M, Hone J, Hillenbrand R, Koppens F H L 2015 Nat. Mater. 14 421
Google Scholar
[75] Dai S, Ma Q, Liu M K, Andersen T, Fei Z, Goldflam M D, Wagner M, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Janssen G C A M, Zhu S E, Jarillo-Herrero P, Fogler M M, Basov D N 2015 Nat. Nanotechnol. 10 682
Google Scholar
[76] Hu G W, Shen J L, Qiu C W, Alù A, Dai S Y 2020 Adv. Opt. Mater. 8 1901393
Google Scholar
[77] Hu H, Chen N, Teng H, Yu R W, Qu Y P, Sun J, Xue M F, Hu D, Wu B, Li C, Chen J, Liu M, Sun Z, Liu Y, Li P, Fan S, García de Abajo F J, Dai Q 2022 Nat. Nanotechnol. 17 940
Google Scholar
[78] Zeng Y, Ou Q, Liu L, Zheng C, Wang Z, Gong Y, Liang X, Zhang Y, Hu G, Yang Z, Qiu C W, Bao Q, Chen H, Dai Z 2022 Nano Lett. 22 4260
Google Scholar
[79] Duan J H, Álvarez-Pérez G, Voronin K V, Prieto I, Taboada-Gutiérrez J, Volkov V S, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2021 Sci. Adv. 7 eabf2690
Google Scholar
[80] Zhang Q, Ou Q D, Hu G W, Liu J Y, Dai Z G, Fuhrer M S, Bao Q L, Qiu C W 2021 Nano Lett. 21 3112
Google Scholar
[81] Huber M A, Mooshammer F, Plankl M, Viti L, Sandner F, Kastner L Z, Frank T, Fabian J, Vitiello M S, Cocker T L, Huber R 2017 Nat. Nanotechnol. 12 207
Google Scholar
[82] Fali A, White S T, Folland T G, He M, Aghamiri N A, Liu S, Edgar J H, Caldwell J D, Haglund R F, Abate Y 2019 Nano Lett. 19 7725
Google Scholar
[83] Folland T G, Fali A, White S T, Matson J R, Liu S, Aghamiri N A, Edgar J H, Haglund R F, Abate Y, Caldwell J D 2018 Nat. Commun. 9 4371
Google Scholar
[84] Chaudhary K, Tamagnone M, Yin X, Spägele C M, Oscurato S L, Li J, Persch C, Li R, Rubin N A, Jauregui L A, Watanabe K, Taniguchi T, Kim P, Wuttig M, Edgar J H, Ambrosio A, Capasso F 2019 Nat. Commun. 10 4487
Google Scholar
[85] Chaudhary K, Tamagnone M, Rezaee M, Bediako D K, Ambrosio A, Kim P, Capasso F 2019 Sci. Adv. 5 eaau7171
Google Scholar
[86] Hu H, Yu R W, Teng H C, Hu D B, Chen N, Qu Y P, Yang X X, Chen X Z, McLeod A S, Alonso-González P, Guo X D, Li C, Yao Z H, Li Z J, Chen J N, Sun Z P, Liu M K, García de Abajo F J, Dai Q 2022 Nat. Commun. 13 1465
Google Scholar
[87] Dai S Y, Quan J M, Hu G W, Qiu C W, Tao T H, Li X Q, Alù A 2018 Nano Lett. 19 1009
[88] Zheng Z B, Sun F S, Xu N S, Huang W C, Chen X X, Ke Y L, Zhan R Z, Chen H J, Deng S Z 2022 Adv. Opt. Mater. 10 2102057
Google Scholar
[89] Ni G X, McLeod D A, Sun Z Y, Wang L, Xiong L, Post K W, Sunku S S, Jiang B Y, Hone J, Dean C R, Fogler M M, Basov D N 2018 Nature 557 530
Google Scholar
[90] Ni G X, McLeod A S, Sun Z Y, Matson J R, Lo C F B, Rhodes D A, Ruta F L, Moore S L, Vitalone R A, Cusco R, Artús L, Xiong L, Dean C R, Hone J C, Millis A J, Fogler M M, Edgar J H, Caldwell J D, Basov D N 2021 Nano Lett. 21 5767
Google Scholar
[91] Zhou Y X, Waelchli A, Boselli M, Crassee I, Bercher A, Luo W W, Duan J H, van Mechelen J, van der Marel D, Teyssier J, Willem Rischau C, Korosec L, Gariglio S, Triscone J M, Kuzmenko A B 2023 Nat. Commun. 14 7686
Google Scholar
[92] Hu H, Chen N, Teng H, Yu R W, Xue M F, Chen K, Xiao Y, Qu Y P, Hu D, Chen J 2023 Science 379 558
Google Scholar
[93] Zhou Z, Song R K, Xu J B, Ni X, Dang Z J, Zhao Z C, Quan J M, Dong S Y, Hu W D, Huang D, Chen K, Wang Z S, Cheng X B, Raschke M B, Alù A, Jiang T 2023 Nano Lett. 23 11252
Google Scholar
[94] Huber A J, Ziegler A, Köck T, Hillenbrand R 2009 Nat. Nanotechnol. 4 153
Google Scholar
[95] Dapolito M, Tsuneto M, Zheng W, Wehmeier L, Xu S, Chen X, Sun J, Du Z, Shao Y, Jing R, Zhang S, Bercher A, Dong Y, Halbertal D, Ravindran V, Zhou Z, Petrovic M, Gozar A, Carr G L, Li Q, Kuzmenko A B, Fogler M M, Basov D N, Du X, Liu M 2023 Nat. Nanotechnol. 18 1409
Google Scholar
[96] Lyu B S, Li H Y, Jiang L L, Shan W F, Hu C, Deng A L, Ying Z, Wang L L, Zhang Y R, Bechtel H A, Martin M C, Taniguchi T, Watanabe K, Luo W D, Wang F, Shi Z W 2019 Nano Lett. 19 1982
Google Scholar
[97] Giles A J, Dai S, Vurgaftman I, Hoffman T, Liu S, Lindsay L, Ellis C T, Assefa N, Chatzakis I, Reinecke T L 2018 Nat. Mater. 17 134
Google Scholar
[98] Zhao Y Q, Chen J C, Xue M F, Chen R K, Jia S T, Chen J J, Bao L H, Gao H J, Chen J N 2022 Nano Lett. 22 10208
Google Scholar
[99] Taboada-Gutiérrez J, Álvarez-Pérez G, Duan J H, Ma W, Crowley K, Prieto I, Bylinkin A, Autore M, Volkova H, Kimura K 2020 Nat. Mater. 19 964
Google Scholar
[100] Wu Y J, Ou Q D, Yin Y F, Li Y, Ma W L, Yu W Z, Liu G Y, Cui X Q, Bao X Z, Duan J H, Álvarez-Pérez G, Dai Z G, Shabbir B, Medhekar N, Li X P, Li C M, Alonso-González P, Bao Q L 2020 Nat. Commun. 11 2646
Google Scholar
[101] Sunku S, Ni G, Jiang B-Y, Yoo H, Sternbach A, McLeod A, Stauber T, Xiong L, Taniguchi T, Watanabe K 2018 Science 362 1153
Google Scholar
[102] Hesp N C, Torre I, Rodan-Legrain D, Novelli P, Cao Y, Carr S, Fang S, Stepanov P, Barcons-Ruiz D, Herzig Sheinfux H 2021 Nat. Phys. 17 1162
Google Scholar
[103] Sunku S S, Halbertal D, Stauber T, Chen S, McLeod A S, Rikhter A, Berkowitz M E, Lo C F B, Gonzalez-Acevedo D E, Hone J C, Dean C R, Fogler M M, Basov D N 2021 Nat. Commun. 12 1641
Google Scholar
[104] Hesp N C, Torre I, Barcons-Ruiz D, Herzig Sheinfux H, Watanabe K, Taniguchi T, Krishna Kumar R, Koppens F H 2021 Nat. Commun. 12 1640
Google Scholar
[105] Duan J H, Capote-Robayna N, Taboada-Gutiérrez J, Álvarez-Pérez G, Prieto I, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2020 Nano Lett. 20 5323
Google Scholar
[106] Duan J H, Álvarez-Pérez G, Lanza C, Voronin K, Tresguerres-Mata A, Capote-Robayna N, Álvarez-Cuervo J, Tarazaga Martín-Luengo A, Martín-Sánchez J, Volkov V, Nikitin A, Alonso-González P 2023 Nat. Mater. 22 867
Google Scholar
[107] Hu G W, Ou Q D, Si G Y, Wu Y J, Wu J, Dai Z G, Krasnok A, Mazor Y, Zhang Q, Bao Q L, Qiu C W, Alù A 2020 Nature 582 209
Google Scholar
[108] Chen M Y, Lin X, Dinh T H, Zheng Z R, Shen J L, Ma Q, Chen H S, Jarillo-Herrero P, Dai S Y 2020 Nat. Mater. 19 1307
Google Scholar
[109] Zheng Z B, Sun F S, Huang W C, Jiang J Y, Zhan R Z, Ke Y L, Chen H J, Deng S Z 2020 Nano Lett. 20 5301
Google Scholar
[110] Hu C X, Sun T, Zeng Y, Ma W L, Dai Z G, Yang X S, Zhang X L, Li P N 2023 eLight 3 14
Google Scholar
[111] Li P N, Lewin M, Kretinin A V, Caldwell J D, Novoselov K S, Taniguchi T, Watanabe K, Gaussmann F, Taubner T 2015 Nat. Commun. 6 7507
Google Scholar
[112] Guo X D, Liu R N, Hu D B, Hu H, Wei Z, Wang R, Dai Y Y, Cheng Y, Chen K, Liu K H, Zhang G Y, Zhu X, Sun Z P, Yang X X, Dai Q 2020 Adv. Mater. 32 1907105
Google Scholar
[113] Dai S Y, Tymchenko M, Xu Z Q, Tran T T, Yang Y F, Ma Q, Watanabe K, Taniguchi T, Jarillo-Herrero P, Aharonovich I, Basov D N, Tao T H, Alù A 2018 Nano Lett. 18 5205
Google Scholar
[114] Bylinkin A, Schnell M, Autore M, Calavalle F, Li P, Taboada-Gutièrrez J, Liu S, Edgar J H, Casanova F, Hueso L E, Alonso-Gonzalez P, Nikitin A Y, Hillenbrand R 2021 Nat. Photon. 15 197
Google Scholar
[115] Autore M, Li P, Dolado I, Alfaro-Mozaz F J, Esteban R, Atxabal A, Casanova F, Hueso L E, Alonso-González P, Aizpurua J, Nikitin A Y, Vélez S, Hillenbrand R 2018 Light Sci. Appl. 7 17172
[116] Dai S, Ma Q, Andersen T, Mcleod A S, Fei Z, Liu M K, Wagner M, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2015 Nat. Commun. 6 6963
Google Scholar
[117] Nozaki K, Tanabe T, Shinya A, Matsuo S, Sato T, Taniyama H, Notomi M 2010 Nat. Photon. 4 477
Google Scholar
[118] Almeida V R, Barrios C A, Panepucci R R, Lipson M 2004 Nature 431 1081
Google Scholar
[119] Nozaki K, Matsuo S, Fujii T, Takeda K, Shinya A, Kuramochi E, Notomi M 2019 Nat. Photon. 13 454
Google Scholar
[120] Jahani S, Kim S, Atkinson J, Wirth J C, Kalhor F, Noman A A, Newman W D, Shekhar P, Han K, Van V, DeCorby R G, Chrostowski L, Qi M, Jacob Z 2018 Nat. Commun. 9 1893
Google Scholar
期刊类型引用(0)
其他类型引用(1)
-
图 1 石墨烯等离极化激元的实空间成像 (a)碳化硅衬底上石墨烯等离极化激元的近场光学成像[34]; (b)金属天线激发石墨烯等离极化激元波前成像[37]; (c)不同电流下石墨烯等离极化激元近场光学图像(上)及其相应的线轮廓(下)[40]; (d)不同数量二硒化钨间隔层分离的氧化钨/石墨烯异质结纳米红外光学图像[41]
Fig. 1. Real-space imaging of graphene plasmons: (a) Near-field imaging of graphene plasmons on SiC substrate[34]; (b) wavefront mapping of graphene plasmons launched by metal antenna[37]; (c) near-field images of the propagating graphene plasmons under different driving currents (top panel) and the corresponding line profiles (bottom panel) [40]; (d) nano-infrared images of WOx/graphene heterostructures with a varied number of tungsten diselenide (WSe2) spacer layers[41].
图 2 一维纳米结构中的等离极化激元 (a)砷化铟纳米线的原子力显微镜图像(上)和对应的红外纳米光学成像图(下)[42], 入射光频率为901 cm–1, 标尺为1; (b)锑化铟纳米线的超快近场光学图像, 泵浦光和探测光的延迟从0—10 ps[44], 标尺为500 nm; (c)不同时间延迟下砷化铟孪晶超晶格纳米线的红外光谱测量结果[43]; (d)金属型(M1和M2)和半导体型(S1和S2)碳纳米管的近场光学图像, 背栅电压数值分别为–20 V (上)和0 V (下)[48]
Fig. 2. Plasmon polaritons in one-dimensional nanostructures: (a) AFM topography image of an indium arsenide nanowire (top) and corresponding nano-infrared image (bottom) [42], the incident frequency is 901 cm–1, scale bar, 1 μm; (b) ultrafast near-field images of the indium antimonide nanowire with pump-probe delays from 0—10 ps[44], scale bar, 500 nm; (c) infrared amplitude spectra of the indium arsenide twinning superlattice nanowire at different pump-probe delay times[43]; (d) near-field images of metallic (M1 and M2) and semiconducting (S1 and S2) carbon nanotubes at different gate volrages –20 V (top panel) and 0 V (bottom panel)[48].
图 3 氮化硼中双曲声子极化激元的近场光学研究 (a)氮化硼薄层(厚度为256 nm)中声子极化激元的近场光学图像, 入射光频率为1560 cm–1, 标尺为800 nm(左); 声子极化激元波长随氮化硼薄层厚度的变化趋势[6], 入射光频率为1560 cm–1(右); (b)氮化硼纳米管(厚度为40 nm)中声子极化激元的近场光学图像[51], 入射光频率为1400 cm–1; (c)氮化硼薄层中声子极化激元体局域(M0)和表面局域(SM0)模式的近场光学图像[52], 黑色和白色箭头表示薄片及其边缘上的近场振荡周期, 分别对应于M0和SM0模式波长的一半, 入射光频率为1420 cm–1, 标尺为2 μm; (d)氮化硼超构表面中声子极化激元的渠道化传播现象[53]; (e)氮化硼超构表面中声子极化激元的光学拓扑转变, 内陷型波前(上)和外扩型波前(下)[54]
Fig. 3. Near-field optical study of hyperbolic phonon polaritons in boron nitride (hBN): (a) Near-field image of phonon polaritoins in hBN (thickness 256 nm), the incident frequency is 1560 cm–1. Scale bar, 800 nm (left); wavelength of phonon polaritons probed at 1560 cm–1 for hBN with different thicknesses (right)[6]; (b) near-field image of phonon polaritons in hBN nanotubes[51], the incident frequency is 1400 cm–1; (c) near-field image of volume-confined (M0) and surface (SM0) phonon polaritons of a 40 nm-thick hBN flake at 1420 cm–1[52], the black and white arrows indicate the periods of near-field oscillations on the flake and its edge, corresponding to half the wavelength of M0 and SM0 modes, respectively, scale bar, 2 μm; (d) phonon polariton canalization in a hBN metasurface[53]; (e) optical topological transition of phonon polaritons in a hBN metasurface: concave wavefronts (top panel) and convex wavefronts (bottom panel)[54].
图 4 氧化钼中各向异性声子极化激元的近场光学成像 (a)氧化钼中椭圆型(上)和双曲型(下)声子极化激元的近场光学图像[58], 入射光频率分别为为990 cm–1 (上)和900 cm–1 (下), 标尺为2 μm ; (b)氧化钼中银天线激发的双曲型声子极化激元, 表现为内陷型波前[59], 入射光频率为944 cm–1; (c)双曲极化激元的反常折射现象, 白色虚线内部衬底为空气, 外部为氧化硅[60], 入射光波长为11.3 μm; (d)双曲极化激元的负反射现象[61], 入射光频率为881 cm–1; (e)氧化钼光栅结构中声子极化激元的单向传播[62], 入射光频率为904 cm–1 [62]
Fig. 4. Near-field imaging of anisotropic polaritons in molybdenum trioxide ($ \alpha $-MoO3): (a) Near-field images of elliptical and hyperbolic phonon polaritons in $ \alpha $-MoO3 at incident frequencies at 990 cm–1 (top panel) and 900 cm–1 (bottom panel) [58], Scale bars, 2 μm; (b) silver antenna-launched hyperbolic phonon polaritons in a $ \alpha $-MoO3 flake recorded at 944 cm–1, revealing concave wavefronts[59]; (c) anomalous refraction of hyperbolic polaritons at $ {\lambda }_{0}=11.3\;{\text{μm}}$, the substrates inside and outside of the white dashed lines are air and silicon dioxide, respectively[60]; (d) negative reflection of heperbolic poalritons[61], the incident frequency is 881 cm–1; (e) unidirectional propagation of phonon polaritons in grating $ \alpha $-MoO3 crystal at frequency 904 cm–1 [62].
图 5 体材料中声子极化激元的近场光学成像 (a)方解石中声子极化激元“幽灵”模式的近场光学图像, 可以实现20 μm的无衍射传播[66], 入射光频率为1460 cm–1; (b)钨酸镉晶体中声子极化激元剪切模式的实空间成像, 其镜像对称性被打破[67], 入射光频率为875 cm–1; (c)钛酸锶晶体中声子极化激元的纳米红外光谱测量结果, 工作频率为远红外频段[68]
Fig. 5. Near-field imaging of phonon polaritons in bulk materials: (a) Near-field image of antenna-launched ghost hepebolic phonon polaritons at the surface of bulk calcite at the illuminating frequency 1460 cm–1, generating diffraction-free propagation with a distance up to 20 μm[66]; (b) real-space imaging of symmetry-broken hyperbolic shear phonon polaritons in monoclinic cadmium tungstate (CdWO4) at frequemcy 875 cm–1 [67] ; (c) hyperspectral far-infrared imaging of surface phonon polaritons in strontium titanate[68].
图 6 二维半导体材料中激子极化激元的近场光学研究 (a)二硒化钨晶体中激子极化激元的近场光学图像[70], 入射光波长为900 nm, 标尺为1 μm; (b)二硒化钨晶体中激子极化激元的超快近场光学成像[71], 入射光波长为$ (760\pm 5)\;{\mathrm{n}}{\mathrm{m}} $, 标尺为2 μm; (c)不用时间延迟下二硒化钨瞬态双曲激子极化激元近场相位图[72], 激发波数为910 cm–1; (d)不同入射偏振下二硒化钨晶体(厚度为9 nm)中激子极化激元的近场光学成像[73], 激发能量为1.44 eV, 标尺为1 μm; (e)二硒化钼晶体中激子极化激元的近场光学图像[7], 激发能量为1.35 eV
Fig. 6. Near-field optical study of exciton polaritons in two-dimensional semiconductors: (a) Near-field image of exciton polaritons in a WSe2 flake taken at $ {\lambda }_{0}=900\;{\mathrm{n}}{\mathrm{m}} $[70], scale bar, 1 μm; (b) ultrafast near-field imaging of exciton polaritons in WSe2[71], $ {\lambda }_{0}=(760\pm 5)\;{\mathrm{n}}{\mathrm{m}}, $ scale bars, 2 μm; (c) near-field phase images of transient hyperbolic exciton polaritons for a series of time delays taken at 910 cm–1 [72]; (d) polarization-dependent near-field images of exciton polaritons in a 9-nm-thick WSe2 sample taken at an excitation energy of 1.44 eV[73], scale bar, 1 μm; (e) near-field image of exciton polaritons in molybdenum selenide (MoSe2) taken at excitation energy of 1.35 eV[7].
图 7 异质结中极化激元的近场光学研究 (a)氮化硼/石墨烯/氮化硼夹层结构中超低损耗石墨烯等离极化激元的近场光学成像, 其传播寿命高达500 fs[74], 入射光子能量为116 meV; (b)石墨烯/氮化硼结构中杂化极化激元(等离极化激元-声子极化激元耦合)波长随背栅电压的变化趋势, 氮化硼声子极化激元波长不随电压变化[76]; (c)石墨烯/氧化钼结构中杂化极化激元波前随费米能级的变化趋势[77]; (d)石墨烯/碳化硅结构中双曲声子极化激元光场分布随入射光频率的变化趋势[79]; (e)氧化硅/黑磷/氧化硅夹层结构中极化激元的超快近场光学成像[81], 标尺为1 μm
Fig. 7. Near-field optical study of polaritons in heterostructures: (a) Near-field imaging of ultra low-loss graphene plasmons in hBN/graphene/hBN heterostructures with a propagation lifetime of up to 500 fs at a photon energy of $ \hslash \omega =116\;{\mathrm{m}}{\mathrm{e}}{\mathrm{V}} $[74]; (b) gate-dependence of the hybrid polariton (coupling between plasmons and phonon polaritons) wavelength in a graphene/hBN heterostructure while the wavelength of hBN phonon polaritons is nearly independent with gate voltage[76]; (c) the hybrid polariton wavefronts in graphene/$ \alpha $-MoO3 heterostructures at different graphene Fermi energies[77]; (d) near-field amplitude images of hyperbolic phonon polaritons in graphene/4H-SiC heterostructures at different illuminating frequencies[79]; (e) ultrafast near-field imaging of polaritons in a SiO2/black phosphorus/SiO2 heterostructure at different delay times between the pump and probe pulses[81], scale bar, 1 μm.
图 8 基于介电环境对极化激元的调控研究 (a)氮化硼声子极化激元在介质性和金属性二氧化钒界面处折射现象的实空间成像, 其波长分别为550 nm和362 nm[83]; (b)基于相变材料Ge3Sb2Te6图案化对氮化硼声子极化激元传播的精确调控[84], 入射光频率为1455 cm–1, 标尺为5 μm; (c)各向异性衬底(黑磷)对氮化硼声子极化激元的调控, 原本各向同性传播的极化激元沿不同方向具有不同波长, 在入射光频率为1420 cm–1时最大各向异性值为1.25[85], 标尺为2 μm; (d)空气衬底(悬空)对石墨烯等离极化激元传播损耗的调控, 即减小其传播损耗[86]
Fig. 8. Manipulation of polaritons based on dielectric environment: (a) Real-space imaging of refraction of hBN phonon polaritons at the dielectric-metallic vanadium dioxide domain boundary with polariton wavelengths of 550 nm and 362 nm[83], respectively; (b) manipulation of hBN phonon polariton propagation based on patterning of the phase change material Ge3Sb2Te6 at an incident frequency of 1455 cm–1[84], scale bars, 5 μm; (c) manipulation of hBN phonon polaritons by an anisotropic substrate (black phosphorus) with a maximum value of anisotropy ($ \alpha =b/a $) $ {\alpha }_{{\mathrm{m}}{\mathrm{a}}{\mathrm{x}}}=1.25 $ at 1420 cm–1, i.e., originally isotropically propagating poalritons have different wavelengths along different direcitons[85], scale bar, 2 μm; (d) manipulation of graphene plasmon propagation loss by air substrate (suspension), i.e., reduction of the propagation loss[86].
图 9 基于物理场对极化激元的调控研究 (a)低温(60 K)下石墨烯等离极化激元的低损耗传播, 其传播寿命高达皮秒量级(1.6 ps)[89]; (b)不同温度下氮化硼声子极化激元的传播损耗测量, 接近液化氮温度时寿命超过5 ps [90]; (c)不同温度下钛酸锶和铝酸镧/钛酸锶异质结中声子极化激元的起始频率测量[91]; (d)不同背栅电压下极化激元在氧化钼和石墨烯/氧化钼界面处的折射现象[92], 标尺为1 μm; (e)碳化硅晶体中纳米压痕周边应力分布的近场光学测量[94], 地形图像(左), s-SNOM图像(右); (f)不同磁场强度下石墨烯狄拉克磁致激子极化激元的近场光学分布[95]
Fig. 9. Study on the manipulation of polaritons based on physical field: (a) Low-loss propagation of graphene plasmons at liquid-nitrogen temperature (T = 60 K) with propagation lifetime up to 1.6 ps[89]; (b) temperature dependence of hBN phonon polariton propagation loss, with lifetimes exceeding 5 ps when closing to liquild-nitrogen temperatures[90]; (c) the onset frequency of phonon polaritons as a function of temperature in strontium titanate (STO) and lanthanum aluminate/strontium titanate (LAO/STO) heterostructures[91]; (d) refraction phenomenon of gate-tunable negative refraction of polaritons from hyperbolic $ \alpha $-MoO3 to elliptic graphene/$ \alpha $-MoO3[92], scale bar, 1 μm; (e) near-field optical measurments of the residual strain field around the nanoindent in a silicon carbide crystal[94], topography image (left panel), s-SNOM image (right panel); (f) near-field images of magenetic field-dependent Dirac magnetoexcitons in graphene[95].
图 10 基于材料组分对极化激元的调控研究 (a)同位素富集氮化硼(上)和天然氮化硼(下)中声子极化激元的近场光学图像, 入射光频率分别为1510 cm–1和1480 cm–1 [97]; (b)天然氧化钼(左)和同位素富集氧化钼(右)中声子极化激元的近场光学图像, 入射光频率分别为994 cm–1和990 cm–1 [98]; (c)五氧化二钒($ \alpha $-V2O5)晶体中钠原子插层对声子极化激元工作频率(剩余射线带)的调制作用, 实心水平线标记了$ \alpha $-V2O5中的近似横向光学(TO)声子模式(TO1, 975 cm–1; TO2, 770 cm–1)和 $ {\alpha }'$-(Na)V2O5 (TO, 950 cm–1)[99]; (d)氢原子插层对氧化钼中声子极化激元的调制作用, 入射光频率为890 cm–1 [100]
Fig. 10. Study on the manipulation of polaritons based on material components: (a) Near-field images of phonon polaritons in isotopically enriched hBN (top panel) and natural hBN (bottom panel) at incident frequencies of 1510 cm–1 and 1480 cm–1 [97], respectively; (b) near-field images of phonon polaritons in natural $ \alpha $-MoO3 (left panel) and isotopically enriched $ \alpha $-MoO3 (right panel) at incident frequencies of 994 cm–1 and 990 cm–1 [98], respectively; (c) nano-spectroscopy of vanadium pentoxide ($ \alpha $-V2O5) (left panel) and Na-intercalated $ \alpha $-V2O5 ($ {\alpha }'$-(Na)V2O5) (right panel) flakes[99], solid horizontal lines mark the approximate transversal optic (TO) phonon modes in $ \alpha $-V2O5 (TO1, 975 cm–1; TO2, 770 cm–1) and $ {\alpha }'$-(Na)V2O5 (TO, 950 cm–1); (d) optical micrographs and near-field images of a MoO3 flake at 890 cm–1 before intercaltion, after intercalation (10 s) and after deintercalation[100].
图 11 二维转角体系中极化激元的调控 (a)转角双层石墨烯等离极化激元光子晶体的近场光学成像(左)和暗场TEM可视化图像[101]; (b)最小转角石墨烯的光电流探测, 存在电子和空穴分布[104], 标尺为500 nm; (c)转角双层氧化钼中声子极化激元的光学拓扑转变, 当转角为光学魔角($ {\theta =54}^{\circ} $)时, 极化激元沿某一方向高度定向传播[105]; (d)转角三层氧化钼晶体中可以实现极化激元无衍射传播的面内全角度调控[106]
Fig. 11. Manipulation of polaritons in two-dimensional twist systems: (a) Near-field imaging (left) and dark-field TEM visualization (right) of twist bilayer graphene nano-light photonic crystal[101]; (b) photocurrent map of minimally twisted bilayer graphene in the presence of electron and hole distributions[104], scale bar, 500 nm; (c) near-field amplitude images of twisted $ \alpha $-MoO3 at an incident wavelength of 11 μm for different rotation angles, a clear optical topological transition is observed, where polaritons propagate highly oriented along a certain direction at the critical angle of $ {\theta =54}^{\circ} $[105]; (d) near-field amplitude images of trilayer $ \alpha $-MoO3 at an illuminating wavelength of 10.9 μm for different rotation angles[106], demonstrating that in-plane full-angle manipulation of polariton diffraction-free propagation can be achieved.
图 12 基于激发源对方解石中声子极化激元的调控 (a)不同入射光偏振态下, 方解石声子极化激元的近场光学成像[110], 入射光频率为1470 cm–1; (b)沿图(a)黑色虚线方向的近场光场分布, 可以看出当入射光偏振改变时, 天线激发的声子极化激元近场分布不同[110]
Fig. 12. Excitation source-based manipulation of phonon polaritons in calcite: (a) Infrared nano-imaging of phonon polaritons in calcite at different polarization angles at an incident frequency of 1470 cm–1 [110]; (b) near-field amplitude profiles extracted along dashed line in Fig.(a)[110].
图 13 极化激元的相关应用 (a) 基于氮化硼声子极化激元的超分辨成像[111], 上图为实验装置示意图, 中图为hBN薄片的AFM形貌, 下图为用宽带激光器拍摄的hBN下方金纳米盘的近场图像, 标尺为0.5 μm; (b) 基于氧化钼声子极化激元的亚衍射聚焦, 入射光波长为11.16 μm[60]; (c) 石墨烯/二硫化钼异质结中基于二硫化钼光生载流子掺杂对石墨烯等离极化激元的光调制[112]; (d) 基于氮化硼声子极化激元干涉对内部缺陷识别的近场成像图, 激发波数为1541 cm–1 [113]; (e) 包含分子的氮化硼高光谱成像图[114]; (f) 基于氮化硼声子极化激元的分子探测, hBN带和被分子覆盖的hBN带, 采用hBN中的声子极性子进行分子检测[115]
Fig. 13. Applications of polaritons: (a) Super-resolution imaging via phonon polaritons in hBN[111], upper panel is the sketch of the experimental setup, middle panel is the AFM topography of the hBN flake, bottom panel is the near-field images of gold nanodisks beneath hBN taken with the broadband laser. Scale bars, 0.5 μm; (b) sub-diffractional focusing based on refraction of phonon polaritons in $ \alpha $-MoO3 at an illuminating wavelength of 11.16 μm[60]; (c) optical switching of graphene plasmons based on the photogenerated carrier doping in a graphene/MoS2 heterostructure. Dashed lines indicate the graphene edge[112]; (d) near-field image of the hBN slab revealing concealed inner defects at an incident frequency of 1541 cm–1 [113]; (e) hyperspectral line scan map of hBN containg organic molecules[114]; (f) infrared transmission spectra of bare molecular layer, hBN ribbons and hBN ribbons covered with molecules, demonstrating molecular detection using phonon polaritons in hBN[115].
-
[1] Huang K U N 1951 Nature 167 779
[2] Barnes W L, Dereux A, Ebbesen T W 2003 Nature 424 824
Google Scholar
[3] Ditlbacher H, Hohenau A, Wagner D, Kreibig U, Rogers M, Hofer F, Aussenegg F R, Krenn J R 2005 Phys. Rev. Lett. 95 257403
Google Scholar
[4] Basov D N, Fogler M M, García de Abajo F J 2016 Science 354 aag1992
Google Scholar
[5] Low T, Chaves A, Caldwell J D, Kumar A, Fang N X, Avouris P, Heinz T F, Guinea F, Martin-Moreno L, Koppens F 2017 Nat. Mater. 16 182
Google Scholar
[6] Dai S, Fei Z, Ma Q, Rodin A S, Wagner M, McLeod A S, Liu M K, Gannett W, Regan W, Watanabe K, Taniguchi T, Thiemens M, Dominguez G, Neto A H C, Zettl A, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2014 Science 343 1125
Google Scholar
[7] Hu F, Luan Y, Scott M E, Yan J, Mandrus D G, Xu X, Fei Z 2017 Nat. Photon. 11 356
Google Scholar
[8] Berkowitz M E, Kim B S Y, Ni G, McLeod A S, Lo C F B, Sun Z, Gu G, Watanabe K, Taniguchi T, Millis A J, Hone J C, Fogler M M, Averitt R D, Basov D N 2021 Nano Lett. 21 308
Google Scholar
[9] Costa A T, Vasilevskiy M I, Fernández-Rossier J, Peres N M R 2023 Nano Lett. 23 4510
Google Scholar
[10] Wolf E, Nieto-Vesperinas M 1985 J. Opt. Soc. Am. A 2 886
[11] Hillenbrand R, Keilmann F, Hanarp P, Sutherland D S, Aizpurua J 2003 Appl. Phys. Lett. 83 368
Google Scholar
[12] Cvitkovic A, Ocelic N, Hillenbrand R 2007 Nano Lett. 7 3177
Google Scholar
[13] Hillenbrand R, Keilmann F 2000 Phys. Rev. Lett. 85 3029
Google Scholar
[14] Hillenbrand R, Taubner T, Keilmann F 2002 Nature 418 159
Google Scholar
[15] Andryieuski A, Zenin V A, Malureanu R, Volkov V S, Bozhevolnyi S I, Lavrinenko A V 2014 Nano Lett. 14 3925
Google Scholar
[16] Huth F, Chuvilin A, Schnell M, Amenabar I, Krutokhvostov R, Lopatin S, Hillenbrand R 2013 Nano Lett. 13 1065
Google Scholar
[17] Mastel S, Lundeberg M B, Alonso-González P, Gao Y, Watanabe K, Taniguchi T, Hone J, Koppens F H L, Nikitin A Y, Hillenbrand R 2017 Nano Lett. 17 6526
Google Scholar
[18] Deutsch B M, Hillenbrand R, Novotny L 2008 Opt. Express 16 2 494
[19] Taubner T, Hillenbrand R, Keilmann F 2003 J. Micro. 210 311
Google Scholar
[20] 段嘉华, 陈佳宁 2019 物理学报 68 110701
Google Scholar
Duan J H, Chen J N 2019 Acta Phys. Sin. 68 110701
Google Scholar
[21] Gramotnev D K, Bozhevolnyi S I 2014 Nat. Photon. 8 13
Google Scholar
[22] Gucciardi P G, Bachelier G, Allegrini M 2006 J. Appl. Phys. 99 124309
Google Scholar
[23] Knoll B, Keilmann F 2000 Opt. Commun. 182 321
Google Scholar
[24] Ocelic N, Huber A, Hillenbrand R 2006 Appl. Phys. Lett. 89 101124
Google Scholar
[25] Moreno C, Alda J, Kinzel E, Boreman G 2017 Appl. Opt. 56 1037
Google Scholar
[26] HillenbRand R, Knoll B, Keilmann F 2001 J. Micro. 202 77
Google Scholar
[27] Zenhausern F, Martin Y, Wickramasinghe H K 1995 Science 269 1083
Google Scholar
[28] Richards D, Zayats A, Keilmann F, Hillenbrand R 2004 Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 362 787
[29] Cvitkovic A, Ocelic N, Hillenbrand R 2007 Opt. Express 15 8550
Google Scholar
[30] Amarie S, Keilmann F 2011 Phys. Rev. B 83 045404
Google Scholar
[31] Chen X Z, Hu D B, Mescall R, You G J, Basov D N, Dai Q, Liu M K 2019 Adv. Mater. 31 1804774
Google Scholar
[32] Jiang B Y, Zhang L M, Castro Neto A H, Basov D N, Fogler M M 2016 J. Appl. Phys. 119 054305
Google Scholar
[33] Fei Z, Andreev G O, Bao W, Zhang L M, McLeod A S, Wang C, Stewart M K, Zhao Z, Dominguez G, Thiemens M, Fogler M M, Tauber M J, Castro-Neto A H, Lau C N, Keilmann F, Basov D N 2011 Nano Lett. 11 4701
Google Scholar
[34] Chen J, Badioli M, Alonso-González P, Thongrattanasiri S, Huth F, Osmond J, Spasenović M, Centeno A, Pesquera A, Godignon P, Zurutuza Elorza A, Camara N, de Abajo F J G, Hillenbrand R, Koppens F H L 2012 Nature 487 77
Google Scholar
[35] Dai S, Ma Q, Yang Y, Rosenfeld J, Goldflam M D, McLeod A, Sun Z, Andersen T I, Fei Z, Liu M, Shao Y, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2017 Nano Lett. 17 5285
Google Scholar
[36] Fei Z, Rodin A S, Andreev G O, Bao W, McLeod A S, Wagner M, Zhang L M, Zhao Z, Thiemens M, Dominguez G, Fogler M M, Neto A H C, Lau C N, Keilmann F, Basov D N 2012 Nature 487 82
Google Scholar
[37] Alonso-González P, Nikitin A Y, Golmar F, Centeno A, Pesquera A, Vélez S, Chen J, Navickaite G, Koppens F, Zurutuza A, Casanova F, Hueso L E, Hillenbrand R 2014 Science 344 1369
Google Scholar
[38] Fei Z, Iwinski E G, Ni G X, Zhang L M, Bao W, Rodin A S, Lee Y, Wagner M, Liu M K, Dai S, Goldflam M D, Thiemens M, Keilmann F, Lau C N, Castro-Neto A H, Fogler M M, Basov D N 2015 Nano Lett. 15 4973
Google Scholar
[39] Dong Y, Xiong L, Phinney I Y, Sun Z, Jing R, McLeod A S, Zhang S, Liu S, Ruta F L, Gao H, Dong Z, Pan R, Edgar J H, Jarillo-Herrero P, Levitov L S, Millis A J, Fogler M M, Bandurin D A, Basov D N 2021 Nature 594 513
Google Scholar
[40] Zhao W, Zhao S, Li H, Wang S, Wang S, Utama M I B, Kahn S, Jiang Y, Xiao X, Yoo S, Watanabe K, Taniguchi T, Zettl A, Wang F 2021 Nature 594 517
Google Scholar
[41] Kim B S Y, Sternbach A J, Choi M S, Sun Z, Ruta F L, Shao Y, McLeod A S, Xiong L, Dong Y, Chung T S, Rajendran A, Liu S, Nipane A, Chae S H, Zangiabadi A, Xu X, Millis A J, Schuck P J, Dean C R, Hone J C, Basov D N 2023 Nat. Mater. 22 838
Google Scholar
[42] Zhou Y X, Chen R K, Wang J Y, Huang Y S, Li M, Xing Y J, Duan J H, Chen J J, Farrell J D, Xu H Q, Chen J N 2018 Adv. Mater. 30 1802551
Google Scholar
[43] Xue M F, Li M, Huang Y S, Chen R K, Li YL, Wang J Y, Xing Y J, Chen J J, Yan H Q, Xu H Q, Chen J N 2020 Adv. Mater. 32 2004120
Google Scholar
[44] Xue M F, Pan D, Zhao J H, Chen J N 2023 Adv. Mater. 35 2208952
Google Scholar
[45] Luttinger J M 2004 J. Math. Phys 4 1154
[46] Voit J 1995 Rep. Pro. Phys. 58 977
Google Scholar
[47] Shi Z W, Hong X P, Bechtel H A, Zeng B, Martin M C, Watanabe K, Taniguchi T, Shen Y R, Wang F 2015 Nat. Photon. 9 515
Google Scholar
[48] Wang S, Zhao S H, Shi Z W, Wu F Q, Zhao Z Y, Jiang L L, Watanabe K, Taniguchi T, Zettl A, Zhou C W, Wang F 2020 Nat. Mater. 19 986
Google Scholar
[49] Wang C, Huang S Y, Xing Q X, Xie Y G, Song C Y, Wang F J, Yan H G 2020 Nat. Commun. 11 1158
Google Scholar
[50] Chen S, Leng P L, Konečná A, et al. 2023 Nat. Mater. 22 860
Google Scholar
[51] Xu X G, Ghamsari B G, Jiang J H, Gilburd L, Andreev G O, Zhi C, Bando Y, Golberg D, Berini P, Walker G C 2014 Nat. Commun. 5 4782
Google Scholar
[52] Li P, Dolado I, Alfaro-Mozaz F J, Nikitin A Y, Casanova F, Hueso L E, Vélez S, Hillenbrand R 2017 Nano Lett. 17 228
Google Scholar
[53] Li P, Hu G, Dolado I, Tymchenko M, Qiu C-W, Alfaro-Mozaz F J, Casanova F, Hueso L E, Liu S, Edgar J H, Vélez S, Alu A, Hillenbrand R 2020 Nat. Commun. 11 3663
Google Scholar
[54] Li P, Dolado I, Alfaro-Mozaz F J, Casanova F, Hueso L E, Liu S, Edgar J H, Nikitin A Y, Vélez S, Hillenbrand R 2018 Science 359 892
Google Scholar
[55] Shi Z W, Bechtel H A, Berweger S, Sun Y, Zeng B, Jin C, Chang H, Martin M C, Raschke M B, Wang F 2015 ACS Photon. 2 790
Google Scholar
[56] Dai S, Fang W, Rivera N, Stehle Y, Jiang B-Y, Shen J, Tay R Y, Ciccarino C J, Ma Q, Rodan-Legrain D, Jarillo-Herrero P, Teo E H T, Fogler M M, Narang P, Kong J, Basov D N 2019 Adv. Mater. 31 1806603
Google Scholar
[57] Dai S, Tymchenko M, Yang Y, Ma Q, Pita-Vidal M, Watanabe K, Taniguchi T, Jarillo-Herrero P, Fogler M M, Alù A, Basov D N 2018 Adv. Mater. 30 1706358
Google Scholar
[58] Ma W, Alonso-González P, Li S, Nikitin A Y, Yuan J, Martín-Sánchez J, Taboada-Gutiérrez J, Amenabar I, Li P, Vélez S, Tollan C, Dai Z, Zhang Y, Sriram S, Kalantar-Zadeh K, Lee S T, Hillenbrand R, Bao Q 2018 Nature 562 557
Google Scholar
[59] Zheng Z, Xu N, Oscurato S L, Tamagnone M, Sun F, Jiang Y, Ke Y, Chen J, Huang W, Wilson W L, Ambrosio A, Deng S, Chen H 2019 Sci. Adv. 5 eaav8690
Google Scholar
[60] Duan J H, Álvarez-Pérez G, Tresguerres-Mata A I F, Taboada-Gutiérrez J, Voronin K V, Bylinkin A, Chang B, Xiao S, Liu S, Edgar J H, Martín J I, Volkov V S, Hillenbrand R, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2021 Nat. Commun. 12 4325
Google Scholar
[61] Álvarez-Pérez G, Duan J H, Taboada-Gutiérrez J, Ou Q, Nikulina E, Liu S, Edgar J H, Bao Q, Giannini V, Hillenbrand R, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2022 Sci. Adv. 8 eabp8486
Google Scholar
[62] Zhang Q, Ou Q, Si G, Hu G, Dong S, Chen Y, Ni J, Zhao C, Fuhrer M S, Yang Y, Alù A, Hillenbrand R, Qiu C-W 2022 Sci. Adv. 8 eabn9774
Google Scholar
[63] Martín-Sánchez J, Duan J H, Taboada-Gutiérrez J, Álvarez-Pérez G, Voronin K V, Prieto I, Ma W, Bao Q, Volkov V S, Hillenbrand R, Nikitin A Y, Alonso-González P 2021 Sci. Adv. 7 eabj0127
Google Scholar
[64] Zheng Z B, Jiang J Y, Xu N S, Wang X M, Huang W C, Ke Y L, Zhang S R, Chen H J, Deng S Z 2022 Adv. Mater. 34 2104164
Google Scholar
[65] Qu Y P, Chen N, Teng H C, Hu H, Sun J Z, Yu R W, Hu D B, Xue M F, Li C, Wu B, Chen J N, Sun Z P, Liu M K, Liu Y Q, García de Abajo F J, Dai Q 2022 Adv. Mater. 34 2105590
Google Scholar
[66] Ma W L, Hu G W, Hu D B, Chen R K, Sun T, Zhang X L, Dai Q, Zeng Y, Alù A, Qiu C W, Li P N 2021 Nature 596 362
Google Scholar
[67] Hu G W, Ma W L, Hu D B, Wu J, Zheng C Q, Liu K P, Zhang X D, Ni X, Chen J N, Zhang X L, Dai Q, Caldwell J D, Paarmann A, Alù A, Li P N, Qiu C W 2023 Nat. Nanotechnol. 18 64
Google Scholar
[68] Lahneman D J, Qazilbash M M 2021 Phys. Rev. B 104 235433
Google Scholar
[69] Koch S W, Kira M, Khitrova G, Gibbs H M 2006 Nat. Mater. 5 523
Google Scholar
[70] Fei Z, Scott M E, Gosztola D J, Foley J J, Yan J, Mandrus D G, Wen H, Zhou P, Zhang D W, Sun Y, Guest J R, Gray S K, Bao W, Wiederrecht G P, Xu X 2016 Phys. Rev. B 94 081402
Google Scholar
[71] Mrejen M, Yadgarov L, Levanon A, Suchowski H 2019 Sci. Adv. 5 eaat9618
Google Scholar
[72] Sternbach A J, Chae S H, Latini S, Rikhter A A, Shao Y, Li B, Rhodes D, Kim B, Schuck P J, Xu X, Zhu X Y, Averitt R D, Hone J, Fogler M M, Rubio A, Basov D N 2021 Science 371 617
Google Scholar
[73] Hu F, Luan Y, Speltz J, Zhong D, Liu C H, Yan J, Mandrus D G, Xu X, Fei Z 2019 Phys. Rev. B 100 121301
Google Scholar
[74] Woessner A, Lundeberg M B, Gao Y, Principi A, Alonso-González P, Carrega M, Watanabe K, Taniguchi T, Vignale G, Polini M, Hone J, Hillenbrand R, Koppens F H L 2015 Nat. Mater. 14 421
Google Scholar
[75] Dai S, Ma Q, Liu M K, Andersen T, Fei Z, Goldflam M D, Wagner M, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Janssen G C A M, Zhu S E, Jarillo-Herrero P, Fogler M M, Basov D N 2015 Nat. Nanotechnol. 10 682
Google Scholar
[76] Hu G W, Shen J L, Qiu C W, Alù A, Dai S Y 2020 Adv. Opt. Mater. 8 1901393
Google Scholar
[77] Hu H, Chen N, Teng H, Yu R W, Qu Y P, Sun J, Xue M F, Hu D, Wu B, Li C, Chen J, Liu M, Sun Z, Liu Y, Li P, Fan S, García de Abajo F J, Dai Q 2022 Nat. Nanotechnol. 17 940
Google Scholar
[78] Zeng Y, Ou Q, Liu L, Zheng C, Wang Z, Gong Y, Liang X, Zhang Y, Hu G, Yang Z, Qiu C W, Bao Q, Chen H, Dai Z 2022 Nano Lett. 22 4260
Google Scholar
[79] Duan J H, Álvarez-Pérez G, Voronin K V, Prieto I, Taboada-Gutiérrez J, Volkov V S, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2021 Sci. Adv. 7 eabf2690
Google Scholar
[80] Zhang Q, Ou Q D, Hu G W, Liu J Y, Dai Z G, Fuhrer M S, Bao Q L, Qiu C W 2021 Nano Lett. 21 3112
Google Scholar
[81] Huber M A, Mooshammer F, Plankl M, Viti L, Sandner F, Kastner L Z, Frank T, Fabian J, Vitiello M S, Cocker T L, Huber R 2017 Nat. Nanotechnol. 12 207
Google Scholar
[82] Fali A, White S T, Folland T G, He M, Aghamiri N A, Liu S, Edgar J H, Caldwell J D, Haglund R F, Abate Y 2019 Nano Lett. 19 7725
Google Scholar
[83] Folland T G, Fali A, White S T, Matson J R, Liu S, Aghamiri N A, Edgar J H, Haglund R F, Abate Y, Caldwell J D 2018 Nat. Commun. 9 4371
Google Scholar
[84] Chaudhary K, Tamagnone M, Yin X, Spägele C M, Oscurato S L, Li J, Persch C, Li R, Rubin N A, Jauregui L A, Watanabe K, Taniguchi T, Kim P, Wuttig M, Edgar J H, Ambrosio A, Capasso F 2019 Nat. Commun. 10 4487
Google Scholar
[85] Chaudhary K, Tamagnone M, Rezaee M, Bediako D K, Ambrosio A, Kim P, Capasso F 2019 Sci. Adv. 5 eaau7171
Google Scholar
[86] Hu H, Yu R W, Teng H C, Hu D B, Chen N, Qu Y P, Yang X X, Chen X Z, McLeod A S, Alonso-González P, Guo X D, Li C, Yao Z H, Li Z J, Chen J N, Sun Z P, Liu M K, García de Abajo F J, Dai Q 2022 Nat. Commun. 13 1465
Google Scholar
[87] Dai S Y, Quan J M, Hu G W, Qiu C W, Tao T H, Li X Q, Alù A 2018 Nano Lett. 19 1009
[88] Zheng Z B, Sun F S, Xu N S, Huang W C, Chen X X, Ke Y L, Zhan R Z, Chen H J, Deng S Z 2022 Adv. Opt. Mater. 10 2102057
Google Scholar
[89] Ni G X, McLeod D A, Sun Z Y, Wang L, Xiong L, Post K W, Sunku S S, Jiang B Y, Hone J, Dean C R, Fogler M M, Basov D N 2018 Nature 557 530
Google Scholar
[90] Ni G X, McLeod A S, Sun Z Y, Matson J R, Lo C F B, Rhodes D A, Ruta F L, Moore S L, Vitalone R A, Cusco R, Artús L, Xiong L, Dean C R, Hone J C, Millis A J, Fogler M M, Edgar J H, Caldwell J D, Basov D N 2021 Nano Lett. 21 5767
Google Scholar
[91] Zhou Y X, Waelchli A, Boselli M, Crassee I, Bercher A, Luo W W, Duan J H, van Mechelen J, van der Marel D, Teyssier J, Willem Rischau C, Korosec L, Gariglio S, Triscone J M, Kuzmenko A B 2023 Nat. Commun. 14 7686
Google Scholar
[92] Hu H, Chen N, Teng H, Yu R W, Xue M F, Chen K, Xiao Y, Qu Y P, Hu D, Chen J 2023 Science 379 558
Google Scholar
[93] Zhou Z, Song R K, Xu J B, Ni X, Dang Z J, Zhao Z C, Quan J M, Dong S Y, Hu W D, Huang D, Chen K, Wang Z S, Cheng X B, Raschke M B, Alù A, Jiang T 2023 Nano Lett. 23 11252
Google Scholar
[94] Huber A J, Ziegler A, Köck T, Hillenbrand R 2009 Nat. Nanotechnol. 4 153
Google Scholar
[95] Dapolito M, Tsuneto M, Zheng W, Wehmeier L, Xu S, Chen X, Sun J, Du Z, Shao Y, Jing R, Zhang S, Bercher A, Dong Y, Halbertal D, Ravindran V, Zhou Z, Petrovic M, Gozar A, Carr G L, Li Q, Kuzmenko A B, Fogler M M, Basov D N, Du X, Liu M 2023 Nat. Nanotechnol. 18 1409
Google Scholar
[96] Lyu B S, Li H Y, Jiang L L, Shan W F, Hu C, Deng A L, Ying Z, Wang L L, Zhang Y R, Bechtel H A, Martin M C, Taniguchi T, Watanabe K, Luo W D, Wang F, Shi Z W 2019 Nano Lett. 19 1982
Google Scholar
[97] Giles A J, Dai S, Vurgaftman I, Hoffman T, Liu S, Lindsay L, Ellis C T, Assefa N, Chatzakis I, Reinecke T L 2018 Nat. Mater. 17 134
Google Scholar
[98] Zhao Y Q, Chen J C, Xue M F, Chen R K, Jia S T, Chen J J, Bao L H, Gao H J, Chen J N 2022 Nano Lett. 22 10208
Google Scholar
[99] Taboada-Gutiérrez J, Álvarez-Pérez G, Duan J H, Ma W, Crowley K, Prieto I, Bylinkin A, Autore M, Volkova H, Kimura K 2020 Nat. Mater. 19 964
Google Scholar
[100] Wu Y J, Ou Q D, Yin Y F, Li Y, Ma W L, Yu W Z, Liu G Y, Cui X Q, Bao X Z, Duan J H, Álvarez-Pérez G, Dai Z G, Shabbir B, Medhekar N, Li X P, Li C M, Alonso-González P, Bao Q L 2020 Nat. Commun. 11 2646
Google Scholar
[101] Sunku S, Ni G, Jiang B-Y, Yoo H, Sternbach A, McLeod A, Stauber T, Xiong L, Taniguchi T, Watanabe K 2018 Science 362 1153
Google Scholar
[102] Hesp N C, Torre I, Rodan-Legrain D, Novelli P, Cao Y, Carr S, Fang S, Stepanov P, Barcons-Ruiz D, Herzig Sheinfux H 2021 Nat. Phys. 17 1162
Google Scholar
[103] Sunku S S, Halbertal D, Stauber T, Chen S, McLeod A S, Rikhter A, Berkowitz M E, Lo C F B, Gonzalez-Acevedo D E, Hone J C, Dean C R, Fogler M M, Basov D N 2021 Nat. Commun. 12 1641
Google Scholar
[104] Hesp N C, Torre I, Barcons-Ruiz D, Herzig Sheinfux H, Watanabe K, Taniguchi T, Krishna Kumar R, Koppens F H 2021 Nat. Commun. 12 1640
Google Scholar
[105] Duan J H, Capote-Robayna N, Taboada-Gutiérrez J, Álvarez-Pérez G, Prieto I, Martín-Sánchez J, Nikitin A Y, Alonso-González P 2020 Nano Lett. 20 5323
Google Scholar
[106] Duan J H, Álvarez-Pérez G, Lanza C, Voronin K, Tresguerres-Mata A, Capote-Robayna N, Álvarez-Cuervo J, Tarazaga Martín-Luengo A, Martín-Sánchez J, Volkov V, Nikitin A, Alonso-González P 2023 Nat. Mater. 22 867
Google Scholar
[107] Hu G W, Ou Q D, Si G Y, Wu Y J, Wu J, Dai Z G, Krasnok A, Mazor Y, Zhang Q, Bao Q L, Qiu C W, Alù A 2020 Nature 582 209
Google Scholar
[108] Chen M Y, Lin X, Dinh T H, Zheng Z R, Shen J L, Ma Q, Chen H S, Jarillo-Herrero P, Dai S Y 2020 Nat. Mater. 19 1307
Google Scholar
[109] Zheng Z B, Sun F S, Huang W C, Jiang J Y, Zhan R Z, Ke Y L, Chen H J, Deng S Z 2020 Nano Lett. 20 5301
Google Scholar
[110] Hu C X, Sun T, Zeng Y, Ma W L, Dai Z G, Yang X S, Zhang X L, Li P N 2023 eLight 3 14
Google Scholar
[111] Li P N, Lewin M, Kretinin A V, Caldwell J D, Novoselov K S, Taniguchi T, Watanabe K, Gaussmann F, Taubner T 2015 Nat. Commun. 6 7507
Google Scholar
[112] Guo X D, Liu R N, Hu D B, Hu H, Wei Z, Wang R, Dai Y Y, Cheng Y, Chen K, Liu K H, Zhang G Y, Zhu X, Sun Z P, Yang X X, Dai Q 2020 Adv. Mater. 32 1907105
Google Scholar
[113] Dai S Y, Tymchenko M, Xu Z Q, Tran T T, Yang Y F, Ma Q, Watanabe K, Taniguchi T, Jarillo-Herrero P, Aharonovich I, Basov D N, Tao T H, Alù A 2018 Nano Lett. 18 5205
Google Scholar
[114] Bylinkin A, Schnell M, Autore M, Calavalle F, Li P, Taboada-Gutièrrez J, Liu S, Edgar J H, Casanova F, Hueso L E, Alonso-Gonzalez P, Nikitin A Y, Hillenbrand R 2021 Nat. Photon. 15 197
Google Scholar
[115] Autore M, Li P, Dolado I, Alfaro-Mozaz F J, Esteban R, Atxabal A, Casanova F, Hueso L E, Alonso-González P, Aizpurua J, Nikitin A Y, Vélez S, Hillenbrand R 2018 Light Sci. Appl. 7 17172
[116] Dai S, Ma Q, Andersen T, Mcleod A S, Fei Z, Liu M K, Wagner M, Watanabe K, Taniguchi T, Thiemens M, Keilmann F, Jarillo-Herrero P, Fogler M M, Basov D N 2015 Nat. Commun. 6 6963
Google Scholar
[117] Nozaki K, Tanabe T, Shinya A, Matsuo S, Sato T, Taniyama H, Notomi M 2010 Nat. Photon. 4 477
Google Scholar
[118] Almeida V R, Barrios C A, Panepucci R R, Lipson M 2004 Nature 431 1081
Google Scholar
[119] Nozaki K, Matsuo S, Fujii T, Takeda K, Shinya A, Kuramochi E, Notomi M 2019 Nat. Photon. 13 454
Google Scholar
[120] Jahani S, Kim S, Atkinson J, Wirth J C, Kalhor F, Noman A A, Newman W D, Shekhar P, Han K, Van V, DeCorby R G, Chrostowski L, Qi M, Jacob Z 2018 Nat. Commun. 9 1893
Google Scholar
期刊类型引用(0)
其他类型引用(1)
下载:
下载:
计量
- 文章访问数: 4483
- PDF下载量: 294
- 被引次数: 1
