-
本文提出了一种亚波长聚焦的表面等离激元透镜, 该透镜由二氧化硅填充金膜纳米狭缝阵列组成, 金膜的出射表面为二次柱面. 表面等离激元在狭缝入口处激发并沿狭缝传输, 在狭缝出口转变为带有一定相位延迟的自由空间传播的光波. 通过对透镜结构参数的控制, 可以调节来自各狭缝的光波间的相对相位, 使它们在设定的焦点处进行相长干涉, 从而实现聚焦效果. 本文用时域有限差分法数值计算了二次柱面等离激元透镜的聚焦特性. 数值模拟结果表明, 所设计的孔径为2 m的透镜, 能够实现微米级焦距和焦深、且焦斑半高宽低至0.4倍波长的亚 波长聚焦. 该表面等离激元透镜结构简单紧凑、尺寸小, 有利于光子器件的集成, 在集成光学、光学微操纵、超分辩率成像、光存储、生化传感等相关领域有潜在的应用价值.A novel plasmonic lens (PL) with simple nano-structure is proposed to realize the subwavelength focusing. The proposed PL is composed of the gold film with only five dielectric-filled nanoslits. The exit surface of the gold film is processed into quadric shape that can be parabolic, elliptical or hyperbolic cylinders. The film is fabricated to form five uniformly spaced nanoslits with different widths and depths. All five slits are symmetrically arranged with respect to the center of lens and filled with a dielectric medium (i.e., SiO2). Under the illumination of TM polarized beams, the surface plasmon polaritons (SPPs) are excited at the entrance surface of the PL, then pass through the SiO2-filled slits while acquiring specific phase retardations, and are finally coupled to the light waves in the free space. Each light wave originating from the slit can be regarded as an individual point source, and the constructive interference of light waves from slits gives rise to the beam focusing at the focal plane of the PL. We investigate the phase modulation mechanism of the PL and find that the focusing performance relies on the shape of exit surface, filling medium and geometric parameters of the slits. A suitable phase modulation can be achieved by adjusting the structure parameters of the PL with a specific exit surface shape. Three kinds of quadratic cylindrical PLs, i.e., parabolic, elliptical and hyperbolic cylindrical ones with continuous or stepped exit surface are designed to realize the focusing of TM polarized subwavelength beams in visible spectrum. The finite difference time domain (FDTD) method is employed to compute the light field and to investigate the focusing characteristics of the proposed PL. The performance measurements include the focal length, depth of focus (DOF) and full-width half-maximum (FWHM). The simulation results confirm that the proposed PL with a 2-m-diameter aperture can achieve the subwavelength focusing at a focal length of micron scale. The attainable smallest FWHM of the focal spot is 0.4050 (0 denoting the wavelength of the incident light) which is well beyond the diffraction limit. It is also worth mentioning that the step-like cylindrical PL can yield a sharper focal spot than the continuous cylindrical PL. For example, the FWHM of focal spot produced by the stepped elliptical cylindrical PL is about 92% of that produced by the continuous elliptical cylindrical PL. The proposed PL has the advantages of simple and compact structure with much smaller lateral dimension and easy integration with other photonic devices. Our study helps design the easy-to-fabricate PLs and facilitates applications of plasmonic devices in the fields such as optical micro manipulation, super-resolution imaging, optical storage and biochemical sensing.
[1] Kawata S 2001 Near-Field Optics and Surface Plasmon Polaritons (Vol.81) (Berlin Heidelberg: Springer) p19
[2] Juan M L, Righini M Quidant R 2011 Nat Photonics 5 349
[3] MAIER S A 2006 Plasmonics:Fundamentals and Applications (New York: Springer) p21
[4] Chen J, Wang C, Lu G, Li W, Xiao J, Gong Q 2012 Opt. Express 20 17734
[5] Takeda1 M, Kimura1 N, Inoue T, Aizawa K 2015 Jpn. J. Appl. Phys. 54 09MG02
[6] Zhao X N, Zhang X P, Cao P F, Cheng L, Duan J X, Cheng L B, Kong W J, Yang L L 2013 Optik 124 6740
[7] Lan L, Jiang W, Ma Y 2013 Appl. Phys.Lett. 102 231119
[8] Venugopalan P, Zhang Q M, Li X P, Kuipers L, Gu M 2014 Opt. Lett. 39 5744
[9] Wang J, Zhou W 2010 Plasmonics 5 325
[10] Guo K, Liu J L, Liu S T 2014 Opt Commun 331 124
[11] Liu Y, Fu Y Q, Zhou X L 2010 Plasmonics 5 117
[12] Hao F H, Wang R Wang J 2010 Plasmonics 5 45
[13] Okuda S, Kimur N, Takeda M, Inoue T, Aizawa K 2014 Opt. Rev. 21 560
[14] Liu Y X, Xu Hua, Stief F, Zhitenev N, Yu M 2011 Opt. Express 19 20233
[15] Wu G, Chen J J Zhang R, Xiao J H, Gong Q H 2013 Opt. Lett. 38 3776
[16] Duan X F Zhou G R, Huang Y Q, Shang Y F, Ren X M 2015 Opt. Express 23 2639
[17] Cheng L, Cao P F, Li Y, Kong W J, Zhao X N, Zhang X P 2012 Plasmonics 7 175
[18] Sun Z J, Kim H K 2004 Appl. Phys. Lett. 85 642
[19] Yu Y T, Zappe H 2011 Opt. Express 19 9434
[20] Xu T, Wang C T, Du C L, Luo X G 2008 Opt. Express 16 4753
[21] Johnson R B, Christy R W 1972 Phys. Rev. B 6 4370
[22] Palik E D 1985 Handbook of optical constants of solids (New York: Academic Press) pp723-729
[23] Barnes W L 2006 J. Opt. A-Pure Appl. Opt. 8 S87
[24] Chen J N, Xu Q F, Wang G 2011 Chinese. Phys. B 20 114211
[25] Zhan Q, Leger J 2002 Opt. Express 10 324
[26] Li Y, Wolf E 1981 Opt. Commun. 39 211
[27] Feng D 2014 J. Opt. Soc. Am. A 31 2071
[28] Shi H F, Du C L, Luo X G 2007 Appl. Phys. Lett. 91 093111
-
[1] Kawata S 2001 Near-Field Optics and Surface Plasmon Polaritons (Vol.81) (Berlin Heidelberg: Springer) p19
[2] Juan M L, Righini M Quidant R 2011 Nat Photonics 5 349
[3] MAIER S A 2006 Plasmonics:Fundamentals and Applications (New York: Springer) p21
[4] Chen J, Wang C, Lu G, Li W, Xiao J, Gong Q 2012 Opt. Express 20 17734
[5] Takeda1 M, Kimura1 N, Inoue T, Aizawa K 2015 Jpn. J. Appl. Phys. 54 09MG02
[6] Zhao X N, Zhang X P, Cao P F, Cheng L, Duan J X, Cheng L B, Kong W J, Yang L L 2013 Optik 124 6740
[7] Lan L, Jiang W, Ma Y 2013 Appl. Phys.Lett. 102 231119
[8] Venugopalan P, Zhang Q M, Li X P, Kuipers L, Gu M 2014 Opt. Lett. 39 5744
[9] Wang J, Zhou W 2010 Plasmonics 5 325
[10] Guo K, Liu J L, Liu S T 2014 Opt Commun 331 124
[11] Liu Y, Fu Y Q, Zhou X L 2010 Plasmonics 5 117
[12] Hao F H, Wang R Wang J 2010 Plasmonics 5 45
[13] Okuda S, Kimur N, Takeda M, Inoue T, Aizawa K 2014 Opt. Rev. 21 560
[14] Liu Y X, Xu Hua, Stief F, Zhitenev N, Yu M 2011 Opt. Express 19 20233
[15] Wu G, Chen J J Zhang R, Xiao J H, Gong Q H 2013 Opt. Lett. 38 3776
[16] Duan X F Zhou G R, Huang Y Q, Shang Y F, Ren X M 2015 Opt. Express 23 2639
[17] Cheng L, Cao P F, Li Y, Kong W J, Zhao X N, Zhang X P 2012 Plasmonics 7 175
[18] Sun Z J, Kim H K 2004 Appl. Phys. Lett. 85 642
[19] Yu Y T, Zappe H 2011 Opt. Express 19 9434
[20] Xu T, Wang C T, Du C L, Luo X G 2008 Opt. Express 16 4753
[21] Johnson R B, Christy R W 1972 Phys. Rev. B 6 4370
[22] Palik E D 1985 Handbook of optical constants of solids (New York: Academic Press) pp723-729
[23] Barnes W L 2006 J. Opt. A-Pure Appl. Opt. 8 S87
[24] Chen J N, Xu Q F, Wang G 2011 Chinese. Phys. B 20 114211
[25] Zhan Q, Leger J 2002 Opt. Express 10 324
[26] Li Y, Wolf E 1981 Opt. Commun. 39 211
[27] Feng D 2014 J. Opt. Soc. Am. A 31 2071
[28] Shi H F, Du C L, Luo X G 2007 Appl. Phys. Lett. 91 093111
计量
- 文章访问数: 6217
- PDF下载量: 219
- 被引次数: 0