圓二色光譜的靈敏度由於波長與分子尺寸的不匹配所以通常很弱。在這個工作中我們利用時域有限差分法模擬計算以確認奈米天線可以增強圓二色及光學掌性。我們證實當使用線偏振光激發時，不對稱的奈米結構可以視為奈米四分一波片且而可以在間隙中產生高強度圓偏振態的近場。相較於單一結構，週期性的奈米結構可以增加有效區域，因此我們設計出一系列週期性的結構。最後為了製作方便，我們使用菱形天線並製作出實際的結構。另一方面由於反相結構具有方便分子進入有效增強區域的優勢，於是我們將之與不對稱結構結合設計出奈米橢圓洞，使奈米橢圓洞不僅具有光學力來捕捉小粒子也可以產生圓偏振近場來增強圓二色光譜的訊號。
實驗部份我們改裝商業化的圓二色光譜，但是由於光學元件對不同偏振光反射率不同的問題，目前無法得到可信的結果。未來我們希望在聚苯乙烯球上修飾掌性分子，用線偏振光激發奈米橢圓洞時可以捕捉聚苯乙烯球得到分子的圓二色光譜或是螢光偵測圓二色光譜。

The sensitivity of circular dichroism is usually low due to the mismatch between wavelength and molecule size. In this work we use finite-difference time-domain method to calculate and to make sure if the nanoantenna can enhance circular dichroism and optical chirality. It shows that upon linearly polarized excitation, an asymmetry cross antenna serves as a nanosized quarter waveplate and creates circularly polarized near field with highly enhanced intensity inside the gap. Compared with solitary cross antennas, periodic structures are able to enlarge the effective area. Therefore, we design a series of periodic structures. To easily fabricate the antennas, we use diamond shape antennas and fabricate it. On the other hand, the advantage of inverse structure is to make molecules enter the effective enhanced area. We combine the advantage of inverse structure with asymmetry nanostructures to design elliptical nanoholes. Our elliptical nanoholes not only provide plasmonic optical force for trapping small particles but also generate circularly polarized near fields to enhance the signal of circular dichroism.
We modify commercial circular dichroism spectrometer for experiment. However, we still haven’t got the reliable result due to the fact that optical elements respond differently to different reflectance of polarized light. In the future, we plan to modify chiral molecules on polystyrene spheres. When exciting elliptical nanoholes by linearly polarized light, we can trap the polystyrene spheres to get the molecular circular dichroism or fluorescence-detected circular dichroism.

(1) Berova, N.; Polavarapu, P. L.; Nakanishi, K.; Woody, R. W.: Comprehensive chiroptical spectroscopy; John Wiley & Sons, Inc., Hoboken, New Jersey: Hoboken, New Jersey, 2012.
(2) Barron, L. D.: Molecular Light Scattering and Optical Activity; 2 ed.; Cambridge University Press: New York, 2004.
(3) Michl, J.; Thulstrup, E. W.: Spectroscopy with Polarized Light: Solute Alignment by Photoselection, Liquid Crystal, Polymers, and Membranes Corrected Software Edition; Wiley-VCH; 1 edition 1995.
(4) Hartland, G. V. Optical studies of dynamics in noble metal nanostructures. Chemical reviews 2011, 111, 3858-3887.
(5) Ozbay, E. Plasmonics: Merging Photonics and Electronics at Nanoscale Dimensions. Science 2006, 311, 189-193.
(6) Zayats, A. V.; Smolyaninov, I. I.; Maradudin, A. A. Nano-optics of surface plasmon polaritons. Physics Reports 2005, 408, 131-314.
(7) Zorić, I.; Zäch, M.; Kasemo, B.; Langhammer, C. Gold, Platinum, and Aluminum Nanodisk Plasmons: Material Independence, Subradiance, and Damping Mechanisms. Acs Nano 2011, 5, 2535-2546.
(8) Barnes, W. L.; Dereux, A.; Ebbesen, T. W. Surface plasmon subwavelength optics. Nature 2003, 424, 824-830.
(9) Mayer, K. M.; Hafner, J. H. Localized surface plasmon resonance sensors. Chemical reviews 2011, 111, 3828-3857.
(10) Flory, F. Optical properties of nanostructured materials: a review. Journal of Nanophotonics 2011, 5, 052502.
(11) Maier, S. A.; Kik, P. G.; Atwater, H. A.; Meltzer, S.; Harel, E.; Koel, B. E.; Requicha, A. A. Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides. Nature materials 2003, 2, 229-232.
(12) Maier, S. A.; Atwater, H. A. Plasmonics: Localization and guiding of electromagnetic energy in metal/dielectric structures. Journal of Applied Physics 2005, 98, 011101.
(13) Oulton, R. F.; Sorger, V. J.; Genov, D. A.; Pile, D. F. P.; Zhang, X. A hybrid plasmonic waveguide for subwavelength confinement and long-range propagation. Nature Photonics 2008, 2, 496-500.
(14) Dai, W. H.; Lin, F. C.; Huang, C. B.; Huang, J. S. Mode conversion in high-definition plasmonic optical nanocircuits. Nano letters 2014, 14, 3881-3886.
(15) Danckwerts, M.; Novotny, L. Optical Frequency Mixing at Coupled Gold Nanoparticles. Physical Review Letters 2007, 98.
(16) Kim, S.; Jin, J.; Kim, Y. J.; Park, I. Y.; Kim, Y.; Kim, S. W. High-harmonic generation by resonant plasmon field enhancement. Nature 2008, 453, 757-760.
(17) Hanke, T.; Krauss, G.; Träutlein, D.; Wild, B.; Bratschitsch, R.; Leitenstorfer, A. Efficient Nonlinear Light Emission of Single Gold Optical Antennas Driven by Few-Cycle Near-Infrared Pulses. Physical Review Letters 2009, 103.
(18) Zhang, S.; Genov, D. A.; Wang, Y.; Liu, M.; Zhang, X. Plasmon-Induced Transparency in Metamaterials. Physical Review Letters 2008, 101.
(19) Singh, R.; Al-Naib, I. A. I.; Yang, Y.; Roy Chowdhury, D.; Cao, W.; Rockstuhl, C.; Ozaki, T.; Morandotti, R.; Zhang, W. Observing metamaterial induced transparency in individual Fano resonators with broken symmetry. Applied Physics Letters 2011, 99, 201107.
(20) Pryce, I. M.; Kelaita, Y. A.; Aydin, K.; Atwater, H. A. Compliant metamaterials for resonantly enhanced infrared absorption spectroscopy and refractive index sensing. Acs Nano 2011, 5, 8167-8174.
(21) Lapine, M.; Shadrivov, I. V.; Powell, D. A.; Kivshar, Y. S. Magnetoelastic metamaterials. Nature materials 2012, 11, 30-33.
(22) Khodasevych, I. E.; Shah, C. M.; Sriram, S.; Bhaskaran, M.; Withayachumnankul, W.; Ung, B. S. Y.; Lin, H.; Rowe, W. S. T.; Abbott, D.; Mitchell, A. Elastomeric silicone substrates for terahertz fishnet metamaterials. Applied Physics Letters 2012, 100, 061101.
(23) Wu, C.; Khanikaev, A. B.; Adato, R.; Arju, N.; Yanik, A. A.; Altug, H.; Shvets, G. Fano-resonant asymmetric metamaterials for ultrasensitive spectroscopy and identification of molecular monolayers. Nature materials 2012, 11, 69-75.
(24) Tang, Y.; Cook, T. A.; Cohen, A. E. Limits on Fluorescence Detected Circular Dichroism of Single Helicene Molecules. J Phys Chem A 2009, 113, 6213-6216.
(25) Biagioni, P.; Savoini, M.; Huang, J. S.; Duo, L.; Finazzi, M.; Hecht, B. Near-field polarization shaping by a near-resonant plasmonic cross antenna. Physical Review B 2009, 80.
(26) Collett, E.: Field guide to polarized light; SPIE Publications, 2005; Vol. FG05.
(27) Hecht, E.: Optics; Addison-Wesley; 4 edition, 2001.
(28) Lipkin, D. M. Existence of a New Conservation Law in Electromagnetic Theory. Journal of Mathematical Physics 1964, 5, 696-700.
(29) Tang, Y.; Cohen, A. E. Optical Chirality and Its Interaction with Matter. Physical Review Letters 2010, 104.
(30) Tang, Y.; Cohen, A. E. Enhanced enantioselectivity in excitation of chiral molecules by superchiral light. Science 2011, 332, 333-336.
(31) Hendry, E.; Carpy, T.; Johnston, J.; Popland, M.; Mikhaylovskiy, R. V.; Lapthorn, A. J.; Kelly, S. M.; Barron, L. D.; Gadegaard, N.; Kadodwala, M. Ultrasensitive detection and characterization of biomolecules using superchiral fields. Nature nanotechnology 2010, 5, 783-787.
(32) Zhao, Y.; Belkin, M. A.; Alu, A. Twisted optical metamaterials for planarized ultrathin broadband circular polarizers. Nature communications 2012, 3, 870.
(33) He, Y.; Larsen, G. K.; Ingram, W.; Zhao, Y. Tunable three-dimensional helically stacked plasmonic layers on nanosphere monolayers. Nano letters 2014, 14, 1976-1981.
(34) Hentschel, M.; Schaferling, M.; Weiss, T.; Liu, N.; Giessen, H. Three-dimensional chiral plasmonic oligomers. Nano letters 2012, 12, 2542-2547.
(35) Hentschel, M.; Schaferling, M.; Metzger, B.; Giessen, H. Plasmonic diastereomers: adding up chiral centers. Nano letters 2013, 13, 600-606.
(36) Gansel, J. K.; Thiel, M.; Rill, M. S.; Decker, M.; Bade, K.; Saile, V.; von Freymann, G.; Linden, S.; Wegener, M. Gold helix photonic metamaterial as broadband circular polarizer. Science 2009, 325, 1513-1515.
(37) Lan, X.; Chen, Z.; Dai, G.; Lu, X.; Ni, W.; Wang, Q. Bifacial DNA origami-directed discrete, three-dimensional, anisotropic plasmonic nanoarchitectures with tailored optical chirality. Journal of the American Chemical Society 2013, 135, 11441-11444.
(38) Ma, W.; Kuang, H.; Xu, L.; Ding, L.; Xu, C.; Wang, L.; Kotov, N. A. Attomolar DNA detection with chiral nanorod assemblies. Nature communications 2013, 4, 2689.
(39) Ma, W.; Kuang, H.; Wang, L.; Xu, L.; Chang, W. S.; Zhang, H.; Sun, M.; Zhu, Y.; Zhao, Y.; Liu, L.; Xu, C.; Link, S.; Kotov, N. A. Chiral plasmonics of self-assembled nanorod dimers. Scientific reports 2013, 3, 1934.
(40) Kuzyk, A.; Schreiber, R.; Zhang, H.; Govorov, A. O.; Liedl, T.; Liu, N. Reconfigurable 3D plasmonic metamolecules. Nature materials 2014, 13, 862-866.
(41) Mastroianni, A. J.; Claridge, S. A.; Alivisatos, A. P. Pyramidal and Chiral Groupings of Gold Nanocrystals Assembled Using DNA Scaffolds. Journal of the American Chemical Society 2009, 131, 8455-8459.
(42) Schäferling, M.; Dregely, D.; Hentschel, M.; Giessen, H. Tailoring Enhanced Optical Chirality: Design Principles for Chiral Plasmonic Nanostructures. Physical Review X 2012, 2.
(43) Schäferling, M.; Yin, X.; Engheta, N.; Giessen, H. Helical Plasmonic Nanostructures as Prototypical Chiral Near-Field Sources. ACS Photonics 2014, 1, 530-537.
(44) Hendry, E.; Mikhaylovskiy, R. V.; Barron, L. D.; Kadodwala, M.; Davis, T. J. Chiral electromagnetic fields generated by arrays of nanoslits. Nano letters 2012, 12, 3640-3644.
(45) Meinzer, N.; Hendry, E.; Barnes, W. L. Probing the chiral nature of electromagnetic fields surrounding plasmonic nanostructures. Physical Review B 2013, 88.
(46) Martin Schäferling; Xinghui Yin; Giessen, H. Formation of chiral fields in a symmetric environment. Opt. Express 2012, 20, 26326-26336.
(47) García-Etxarri, A.; Dionne, J. A. Surface-enhanced circular dichroism spectroscopy mediated by nonchiral nanoantennas. Physical Review B 2013, 87.
(48) Davis, T.; Hendry, E. Superchiral electromagnetic fields created by surface plasmons in nonchiral metallic nanostructures. Physical Review B 2013, 87.
(49) Schaferling, M.; Yin, X.; Giessen, H. Formation of chiral fields in a symmetric environment. Opt. Express 2012, 20, 26326-26336.
(50) 邱國斌、蔡定平. 金屬表面電漿簡介. 物理雙月刊 2006, 28, 472-485.
(51) 吳民耀、劉威志. 表面電漿子理論與模擬. 物理雙月刊 2006, 28, 486-496.
(52) Maier, S. A.: Plasmonics: Fundamentals and Applications; Springer; Softcover reprint of hardcover 1st ed. 2007 edition 2010.
(53) Endriz, J. G. Surface waves and grating-tuned photocathodes. Applied Physics Letters 1974, 25, 261.
(54) Salerno, M.; Felidj, N.; Krenn, J. R.; Leitner, A.; Aussenegg, F. R.; Weeber, J. C. Near-field optical response of a two-dimensional grating of gold nanoparticles. Physical Review B 2001, 63.
(55) Dostálek, J.; Homola, J.; Miler, M. Rich information format surface plasmon resonance biosensor based on array of diffraction gratings. Sensors and Actuators B: Chemical 2005, 107, 154-161.
(56) Hu, C.; Liu, D. High-performance Grating Coupled Surface Plasmon Resonance Sensor Based on Al-Au Bimetallic Layer. Modern Applied Science 2010, 4, 8-13.
(57) Munday, J. N.; Atwater, H. A. Large integrated absorption enhancement in plasmonic solar cells by combining metallic gratings and antireflection coatings. Nano letters 2011, 11, 2195-2201.
(58) Gramotnev, D. K.; Bozhevolnyi, S. I. Plasmonics beyond the diffraction limit. Nature Photonics 2010, 4, 83-91.
(59) Giannini, V.; Fernandez-Dominguez, A. I.; Heck, S. C.; Maier, S. A. Plasmonic nanoantennas: fundamentals and their use in controlling the radiative properties of nanoemitters. Chemical reviews 2011, 111, 3888-3912.
(60) Schuck, P. J.; Fromm, D. P.; Sundaramurthy, A.; Kino, G. S.; Moerner, W. E. Improving the Mismatch between Light and Nanoscale Objects with Gold Bowtie Nanoantennas. Physical Review Letters 2005, 94.
(61) Biagioni, P.; Huang, J. S.; Duò, L.; Finazzi, M.; Hecht, B. Cross Resonant Optical Antenna. Physical Review Letters 2009, 102.
(62) Bharadwaj, P.; Deutsch, B.; Novotny, L. Optical Antennas. Advances in Optics and Photonics 2009, 1, 438.
(63) Novotny, L.; Hulst, N. v. Antennas for light. Nature Photonics 2011, 5, 83-90.
(64) Paolo Biagioni, J.-S. H. a. B. H. Nanoantennas for visible and infrared radiation. Reports on Progress in Physics 2012, 75, 024402.
(65) Agio, M. Optical antennas as nanoscale resonators. Nanoscale 2012, 4, 692-706.
(66) Righini, M.; Zelenina, A. S.; Girard, C.; Quidant, R. Parallel and selective trapping in a patterned plasmonic landscape. Nature Physics 2007, 3, 477-480.
(67) Righini, M.; Volpe, G.; Girard, C.; Petrov, D.; Quidant, R. Surface plasmon optical tweezers: tunable optical manipulation in the femtonewton range. Physical Review Letters 2008, 100.
(68) Juan, M. L.; Gordon, R.; Pang, Y.; Eftekhari, F.; Quidant, R. Self-induced back-action optical trapping of dielectric nanoparticles. Nature Physics 2009, 5, 915-919.
(69) Zhang, W.; Huang, L.; Santschi, C.; Martin, O. J. Trapping and sensing 10 nm metal nanoparticles using plasmonic dipole antennas. Nano letters 2010, 10, 1006-1011.
(70) Zhao, R.; Tassin, P.; Koschny, T.; Soukoulis, C. M. Optical forces in nanowire pairs and metamaterials. Opt. Express 2010, 18, 25665-25676.
(71) Huang, L.; Maerkl, S. J.; Martin, O. J. F. Integration of plasmonic trapping in a microfluidic environment. Opt. Express 2009, 17, 6018-6024.
(72) Juan, M. L.; Righini, M.; Quidant, R. Plasmon nano-optical tweezers. Nature Photonics 2011, 5, 349-356.
(73) Kneipp, K.; Wang, Y.; Kneipp, H.; Perelman, L. T.; Itzkan, I.; Dasari, R.; Feld, M. S. Single molecule detection using surface-enhanced Raman scattering (SERS). Physical Review Letters 1997, 78, 1667-1670.
(74) Xu, H. X.; Aizpurua, J.; Kall, M.; Apell, P. Electromagnetic contributions to single-molecule sensitivity in surface-enhanced Raman scattering. Physical Review E 2000, 62, 4318-4324.
(75) Maier, S. A. Plasmonic field enhancement and SERS in the effective mode volume picture. Opt. Express 2006, 14, 1957-1964.
(76) Wei, H.; Hao, F.; Huang, Y. Z.; Wang, W. Z.; Nordlander, P.; Xu, H. X. Polarization dependence of surface-enhanced Raman scattering in gold nanoparticle-nanowire systems. Nano letters 2008, 8, 2497-2502.
(77) Anderson, N.; Anger, P.; Hartschuh, A.; Novotny, L. Subsurface Raman imaging with nanoscale resolution. Nano letters 2006, 6, 744-749.
(78) Anger, P.; Bharadwaj, P.; Novotny, L. Enhancement and Quenching of Single-Molecule Fluorescence. Physical Review Letters 2006, 96.
(79) Kühn, S.; Håkanson, U.; Rogobete, L.; Sandoghdar, V. Enhancement of Single-Molecule Fluorescence Using a Gold Nanoparticle as an Optical Nanoantenna. Physical Review Letters 2006, 97.
(80) Kinkhabwala, A.; Yu, Z.; Fan, S.; Avlasevich, Y.; Müllen, K.; Moerner, W. E. Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna. Nature Photonics 2009, 3, 654-657.
(81) Kravets, V. G.; Zoriniants, G.; Burrows, C. P.; Schedin, F.; Geim, A. K.; Barnes, W. L.; Grigorenko, A. N. Composite au nanostructures for fluorescence studies in visible light. Nano letters 2010, 10, 874-879.
(82) Anker, J. N.; Hall, W. P.; Lyandres, O.; Shah, N. C.; Zhao, J.; Van Duyne, R. P. Biosensing with plasmonic nanosensors. Nature materials 2008, 7, 442-453.
(83) Chen, S.; Svedendahl, M.; Duyne, R. P.; Kall, M. Plasmon-enhanced colorimetric ELISA with single molecule sensitivity. Nano letters 2011, 11, 1826-1830.
(84) Cattoni, A.; Ghenuche, P.; Haghiri-Gosnet, A. M.; Decanini, D.; Chen, J.; Pelouard, J. L.; Collin, S. λ3/1000 plasmonic nanocavities for biosensing fabricated by soft UV nanoimprint lithography. Nano letters 2011, 11, 3557-3563.
(85) Liu, N.; Tang, M. L.; Hentschel, M.; Giessen, H.; Alivisatos, A. P. Nanoantenna-enhanced gas sensing in a single tailored nanofocus. Nature materials 2011, 10, 631-636.
(86) Kuznetsov, A. I.; Evlyukhin, A. B.; Goncalves, M. R.; Reinhardt, C.; Koroleva, A.; Arnedillo, M. L.; Kiyan, R.; Marti, O.; Chichkov, B. N. Laser Fabrication of Large-Scale Nanoparticle Arrays for Sensing Applications. Acs Nano 2011, 5, 4843-4849.
(87) Birgit Päivänranta; Hannes Merbold; Reto Giannini; Luca Büchi; Sergey Gorelick; Christian David; Jörg F. Löffler; Thomas Feurer; Ekinci, Y. High Aspect Ratio Plasmonic Nanostructures for Sensing Applications. Nano letters 2011, 5, 6374-6382.
(88) Yanik, A. A.; Cetin, A. E.; Huang, M.; Artar, A.; Mousavi, S. H.; Khanikaev, A.; Connor, J. H.; Shvets, G.; Altug, H. Seeing protein monolayers with naked eye through plasmonic Fano resonances. Proceedings of the National Academy of Sciences of the United States of America 2011, 108, 11784-11789.
(89) McGraw, R. Description of Aerosol Dynamics by the Quadrature Method of Moments. Aerosol Science and Technology 1997, 27, 255-265.
(90) Taflove, A.; Hagness, S. C.: Computational Electrodynamics: The Finite-Difference Time-Domain Method, Third Edition; Artech House; 3 edition, 2005.
(91) Yee, K. S. Numerical Solution of Initial Value Problems of Maxwells Equations Yee. IEEE Transactions on Antennas and Propagation 1966, 14, 302-307.
(92) Ciarlet, P. G.: The Finite Element Method for Elliptic Problems SIAM: Society for Industrial and Applied Mathematics; 2nd edition, 2002.
(93) Inan, U. S.; Marshall, R. A.: Numerical Electromagnetics: The FDTD Method; Cambridge University Press; 1 edition, 2011.
(94) Zentgraf, T.; Meyrath, T.; Seidel, A.; Kaiser, S.; Giessen, H.; Rockstuhl, C.; Lederer, F. Babinet’s principle for optical frequency metamaterials and nanoantennas. Physical Review B 2007, 76.
(95) Hentschel, M.; Weiss, T.; Bagheri, S.; Giessen, H. Babinet to the Half: Coupling of Solid and Inverse Plasmonic Structures. Nano letters 2013, 13, 4428-4433.
(96) Yang, H. U.; Olmon, R. L.; Deryckx, K. S.; Xu, X. G.; Bechtel, H. A.; Xu, Y.; Lail, B. A.; Raschke, M. B. Accessing the Optical Magnetic Near-Field through Babinet’s Principle. ACS Photonics 2014, 1, 894-899.
(97) Chen, K. Y.; Lee, A. T.; Hung, C. C.; Huang, J. S.; Yang, Y. T. Transport and trapping in two-dimensional nanoscale plasmonic optical lattice. Nano letters 2013, 13, 4118-4122.
(98) Huang, J. S.; Callegari, V.; Geisler, P.; Bruning, C.; Kern, J.; Prangsma, J. C.; Wu, X.; Feichtner, T.; Ziegler, J.; Weinmann, P.; Kamp, M.; Forchel, A.; Biagioni, P.; Sennhauser, U.; Hecht, B. Atomically flat single-crystalline gold nanostructures for plasmonic nanocircuitry. Nature communications 2010, 1, 150.
(99) Chen, W.-L.; Lin, F.-C.; Lee, Y.-Y.; Li, F.-C.; Chang, Y.-M.; Huang, J.-S. The Modulation Effect of Transverse, Antibonding, and Higher-Order Longitudinal Modes on the Two-Photon Photoluminescence of Gold Plasmonic Nanoantennas. Acs Nano 2014, 8, 9053-9062.
(100) Haupts, U.; Tittor, J.; Oesterhelt, D. Closing in on bacteriorhodopsin: progress in understanding the molecule. Annual review of biophysics and biomolecular structure 1999, 28, 367-399.
(101) Furumaki, S.; Yabiku, Y.; Habuchi, S.; Tsukatani, Y.; Bryant, D. A.; Vacha, M. Circular Dichroism Measured on Single Chlorosomal Light-Harvesting Complexes of Green Photosynthetic Bacteria. The Journal of Physical Chemistry Letters 2012, 3, 3545-3549.
(102) Nina P. M. Huck; Wolter F. Jager; Ben de Lange; Feringa, B. L. Dynamic Control and Amplification of Molecular Chirality by Circular Polarized Light. Science 1996, 273, 1686-1688
(103) Temnov, V. V.; Armelles, G.; Woggon, U.; Guzatov, D.; Cebollada, A.; Garcia-Martin, A.; Garcia-Martin, J.-M.; Thomay, T.; Leitenstorfer, A.; Bratschitsch, R. Active magneto-plasmonics in hybrid metal–ferromagnet structures. Nature Photonics 2010, 4, 107-111.