Enhanced Kerr nonlinearity in a left-handed atomic system consisting of three levels driven by a bichromatic field is presented in this paper.Based on bichromatic field coherence,the real parts of the permittivity and permeability can obtain negative values simultaneously in the same detuning frequency region.By adjusting the frequency difference and the Rabi frequencies of the bichromatic field,the multi-band left-handed behavior of the presented atomic metamaterial is exhibited.Meanwhile,the enhanced Kerr nonlinearity can be realized in this multi-band left-handed three-level atomic system.It is shown that the third-order susceptibility possesses focusing or defocusing properties in the same frequency band.
We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.
冀志超张心正张玉娇王振华Irena Drevensek-OlenikRomano Rupp李威吴强许京军The MOE Key Laboratory of Weak-Light Nonlinear Photonicsand TEDA Institute of Applied Physics and School of PhysicsNankai University
By utilizing a Fabry-Perot (FP) nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry-Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.
The characteristics of whispering gallery modes(WGM) in silver-coated inverted-wedge silica microdisks are theoretically investigated by using finite element method. Dielectric TE mode always exists in silver-coated inverted-wedge resonators; dielectric TM mode tends to couple with SPP modes; only pure interior surface plasmonic polariton(SPP) mode but not pure exterior SPP mode is observed in contrast to the metal-coated cylindrical and toroidal resonators. The dependence of quality factor of different kinds of WGMs on the radius of the resonator and the thickness of the coated silver layer are systematically analyzed. We find that the quality factors of the hybrid WGMs associated with SPP mode can reach 104. The maximum light intensity enhancement in ambient for a hybrid mode consisting of a dielectric TM mode and an exterior SPP mode can be obtained when a silver film of thickness ~40 nm is deposited. The silver-coated inverted-wedge silica resonators may be widely applied in sensing and surface enhanced Raman scattering.
BO FangWANG XiaoOuLI YingGAO FengZHANG GuoQuanXU JingJun
Plasmonic metasurfaces have recently attracted much attention because of their novel characteristics with respect to light polarization and wave front control on deep-subwavelength scales.The development of metasurfaces with reconfigurable optical responses is opening new opportunities in high-capacity communications,real-time holograms and adaptive optics.Such tunable devices have been developed in the mid-infrared spectral range and operated in light intensity modulation schemes.Here we present a novel optically reconfigurable hybrid metasurface that enables polarization tuning at optical frequencies.The functionality of tuning is realized by switching the coupling conditions between the plasmonic modes and the binary isomeric states of an ethyl red switching layer upon light stimulation.We achieved more than 20°nonlinear changes in the transmitted polarization azimuth using just 4 mW of switching light power.Such design schemes and principles could be easily applied to dynamically adjust the functionalities of other metasurfaces.
