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## All-optical mass sensing based on ultra-strong coupling quantum dot-nanomechanical resonator system

Yang Jian-Yong, Chen Hua-Jun
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• #### 摘要

提出一种复合量子点-纳米机械振子系统, 该系统以半导体芯片为基底, 量子点嵌入倒置半导体圆锥纳米线的底端, 通过光学抽运-探测技术来驱动量子点-纳米机械振子系统, 研究该系统中的相干光学特性. 通过探测吸收谱给出确定机械振子频率和量子点-纳米机械振子耦合强度的全光学方法. 此外, 基于该系统理论上提出一种在室温下的全光学质量传感方案. 通过测量吸收谱中附着在机械振子上纳米颗粒的质量引起的共振频移, 可间接测出额外纳米颗粒的质量. 与先前的复合纳米机械振子系统相比, 系统中的激子-声子耦合强度的数值可与振子频率比拟, 可实现超强耦合, 有利于相干光学特性的观测, 在超高精度及高分辨率质量传感器件方面有着潜在应用.

#### Abstract

Nanomechanical oscillators have not only the advantages of extremely small mass and volume, but also high vibration frequency and quality factor, so they are widely used in the field of sensors. In recent years, nanomechanical oscillators comprised of graphene nanoribbons, carbon nanotubes, molybdenum disulfide and other materials have been used to make mass sensors. Great progress has been made in the application of mass sensing, but the measurement environment is limited to ultra-low temperature. Presented in this paper is a hybrid quantum dot-nanomechanical resonator (QD-NR) system which is based on semiconductor chips with quantum dots embedded at the bottom of inverted semiconductor conical nanowires. The system has the advantages of high integration level, full optical interface and low temperature compatibility. In addition, it has a coupling strength, a frequency as large as the vibration frequency of the mechanical oscillator, and a long spin life, which provides the possibility of realizing the quantum unassembled readout of a single spin at room temperature. We investigate the coherent optical properties with the optical pump-probe scheme, and an all-optical mean for determining the resonator frequency and the coupling strength of the QD and NR is presented with the absorption spectrum under different parameter regimes. We set the frequency of the pump light to be equal to the exciton frequency and scan the frequency range of the detection light, and then two sharp peaks will appear in the absorption spectrum of the probe light, and the sharp peak is for the frequency of the mechanical oscillator. Moreover, the coupling strength can be obtained from the linear relationship between the peak splitting width and the coupling strength in the absorption spectrum. Further, we put forward a room temperature mass sensing based on the hybrid QD-NR system, and the frequency shift caused by additional nanoparticles can be directly measured with the absorption spectrum, and then the mass of extra nanoparticles can be determined. Comparing with the previous nanomechanical oscillator, the exciton-phonon coupling strength is very strong in the system and can reach the ultra-strong coupling, which is advantageous for observing the coherent optical properties and reaching high precision and resolution mass sensing. In this system, the mass responsivity can reach. The scheme is expected to be applied to mass measurement of some biomolecules, isotopes and other materials, and also be widely used in other fields at a nanogram level.

#### 作者及机构信息

###### 通信作者: 陈华俊, chenphysics@126.com
• 基金项目: 国家自然科学基金(批准号: 11804004, 11647001)和安徽省自然科学基金(批准号: 1708085QA11)资助的课题

#### Authors and contacts

###### Corresponding author: Chen Hua-Jun, chenphysics@126.com
• Funds: Project supported by the National Natural Science Foundation of China (Grant No. 11647001, 11804004) and the Anhui Provincial Natural Science Foundation of China (Grant No. 1708085QA11)

#### 施引文献

• 图 1  基于超强耦合量子点-纳米机械振子的系统示意图

Fig. 1.  Schematic diagram of the system based on super-strong coupling quantum dot-nanometer mechanical oscillator.

图 2  (a)不同温度下探测吸收与探测光-激子失谐量${\varDelta _{\rm{s}}}$的函数关系; (b)室温(300 K)和低温(5 K)下, 不同的振子频率时探测吸收与探测光-激子失谐量${\varDelta _{\rm{s}}}$的函数关系; 图中参数为${\varGamma _1} =0.1\;{\rm{ MHz}}$, ${\varGamma _2} =0.05\;{\rm{ MHz}}$, ${\varOmega _0^2} =0.01\;{\rm{ (MHz}}{{\rm{)}}^2}$, ${\varDelta _0} = 0$, ${g_0} = 0.5{\omega _{\rm{n}}}$

Fig. 2.  (a) Function relationship between detection absorption and detection light-exciton detuning ${\varDelta _{\rm{s}}}$ at different temperatures; (b) the functional relationship between the detected absorption and the detector-exciton detuning ${\varDelta _{\rm{s}}}$under different oscillator frequencies at room temperature and low temperature. ${\varGamma _1} =0.1\;{\rm{ MHz}}$, ${\varGamma _2} =0.05\;{\rm{ MHz}}$, ${\varOmega _0^2} =0.01\;{\rm{ (MHz}}{{\rm{)}}^2}$, ${\varDelta _0} \!=\! 0$, ${g_0} \!=\! 0.5{\omega _{\rm{n}}}$

图 3  (a) ${\varDelta _0} = {\omega _{\rm{n}}}$时不同耦合强度得到的探测吸收谱; (b)吸收光谱中两峰的劈裂宽度与耦合强度的关系; 两图中参数均为${\varGamma _1} =0.2\;{\rm{ MHz}}$, ${\varGamma _2} =0.1\;{\rm{ MHz}}$, ${\omega _{\rm{n}}} =0.52\;{\rm{ MHz}}$, ${\varOmega _0} =0.15\;{\rm{ MHz}}$, $Q = 1000$

Fig. 3.  (a) Detection absorption spectra obtained at different coupling intensities with ${\varDelta _0} = {\omega _{\rm{n}}}$; (b) the relationship between the splitting width of the two peaks in the absorption spectrum and the coupling strength. The parameters in both figures are ${\varGamma _1} =0.2\;{\rm{ MHz}}$, ${\varGamma _2} =0.1\;{\rm{ MHz}}$, ${\omega _{\rm{n}}} =0.52\;{\rm{ MHz}}$, ${\varOmega _0} =0.15\;{\rm{ MHz}}$, $Q = 1000$.

图 4  (a)振子上外加纳米颗粒时的吸收谱, 图中${\varGamma _1} =0.1\;{\rm{ MHz}}$, ${\varGamma _2} =0.05\;{\rm{ MHz}}$, $\varOmega _0^2 =0.01\;{\rm{ (MHz}}{{\rm{)}}^2}$, ${\varDelta _0} = 0$, ${\omega _{\rm{n}}} =0.52\;{\rm{ MHz}}$, ${g_0} = 0.5{\omega _{\rm{n}}}$, $Q = 1000$; (b)外加纳米颗粒个数与振子频移的关系

Fig. 4.  (a) Absorption spectra when nanoparticles are added to the oscillator, where ${\varGamma _1} =0.1\;{\rm{ MHz}}$, ${\varGamma _2} =0.05\;{\rm{ MHz}}$, $\varOmega _0^2 =0.01\;{\rm{ (MHz}}{{\rm{)}}^2}$, ${\varDelta _0} = 0$, ${\omega _{\rm{n}}} =0.52 \;{\rm{MHz}}$, ${g_0} = 0.5{\omega _{\rm{n}}}$, $Q = 1000$; (b) the relationship between the number of added nanoparticles and the oscillator frequency shift.

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##### 出版历程
• 收稿日期:  2019-04-24
• 修回日期:  2019-10-15
• 上网日期:  2019-11-27
• 刊出日期:  2019-12-01

## 基于超强耦合量子点-纳米机械振子系统的全光学质量传感

• 安徽理工大学力学与光电物理学院, 淮南　232001
• ###### 通信作者: 陈华俊, chenphysics@126.com
基金项目: 国家自然科学基金(批准号: 11804004, 11647001)和安徽省自然科学基金(批准号: 1708085QA11)资助的课题

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