Optical Manipulation Based On Novel Chiral Microstructures

The society that we are living in nowadays has an intensive demand for faster infor-mation transmission and processing capabilities.We have witnessed a rapid progress in the development of electronic devices in the past few decades.However,the thermal effect as well as the signal delay between devices set limit to the miniaturization of the electronic devices.Optical devices which possess high speed processing ability for optical signal are particularly attractive for applications,but the integration of conventional photonic component on the electric devices is hindered by the size mismatch between them,since the size of dielectric photonic devices can not be scaled down furtherly by the diffraction limit.Fortunately a recent emerged subject,plasmonics,enables the integration of opto-electronics devices on the chip-scale.Surface plasmon polaritons(SPPs)is one of the fundamental conceptions of plasmonics,which are surface waves propagating along in-terfaces and can be used to manipulate light at the subwavelength scale.The development and utilization of new types of plasmonic devices have two trends:using novel media as constituting materials to conventional materials and engineering innovative structures.So far,both the research of using chiral media with dielectric chirality as optional constitut-ing materials and engineering functional chiral structures with structural chirality in the optical regime are still open issues.To this end,this thesis attempts to study the influence of chirality on electromagnetic waves in chiral interfaces with dielectric chirality and in metamaterials with structural chirality in this thesis.For the dielectrically chiral materi-als,we mainly study numerically the characteristics of SPPs in chiral waveguides whereas for the structurally chiral materials we design a nano-chiral metamaterial numerically and experimentally use electric field to control its mechanical property and thus realize the dynamic mamipulation of light.The main research contents are as follows:We demonstrate theoretically the characteristics of SPPs with chiral-metal-chiral(CMC)and metal-chiral-metal(MCM)waveguiding structures and derive special dis-persion relations,which are universal:they can be degenarated to the cases for nonchiral insulator-metal-insulator(IMI),metal-insulator-metal(MIM)and single-interface SPPs.By showing dispersion curves,we investigate the existence of cutoff effect in different modes for these structures and find that the introduction of chirality will change the cutoff frequencies.By calculating the SPPs propagation length,we find that the introduction of chirality will enhance its propagation ability.We study the impact of chirality on the quantum spin Hall effect of SPPs and the lateral optical force arising from this phenomenon.The excitation conditions of SPPs are affected by the small changes of the environment's chirality.Furthermore,we reveal how the the lateral optical force and optical torques interact with the chirality of nano-particles loacated or adsorbed in the vicinity of the surface.Introducing strong or weak chirality to the background medium would benefit the discrimination of chiral enantiomers of the SPPs.We present the study of dispersion characteristics of the SPPs in a waveguiding struc-ture constructed by anisotropic birefringent crystal-metal-chiral medium.We reveal that the chiral-anisotropic SPPs have sensitivity to the magnitude and sign of both the real and imaginary part of the chirality parameter.We also show that the anisotropy plays a key role in such performance and shows tunable ability in enantiomeric discrimination.The phenomena are due to extrinsic chirality,which arises from the mutual orientation of the SPPs and the optical axis.This planar waveguiding structure does not rely on complicated fabrication but provides the opportunity of on-chip surface-sensitive biosensing.Finally,we demonstrate the design and fabrication of a reconfigurable chiral meta-material,and realize experimentally the dynamic manipulation of the polarization of light in the near infrared spectral range.We observe a giant quadratic electrogyration:both circular birefringence and circular dichroism are quadratically dependent on the presence of a static electric field.Under an application of only 0-18V voltage,we experimentally observe a 160 range of polarization azimuth rotation and a 9° range of ellipticity angle upon transmission of a normally incident linearly polarized light.The electromechanical metamaterial exhibits quadratic electrogyration more than 7 orders of magnitude stronger than quartz crystals.