Studies Of The Optical Devices Based On Liquid Crystal And Surface Plasma

Studies of the optical devices, based on surface plasmon (SP) and liquid crystal (LC) respectively are presented in this thesis. Generally following items are included: twisted nematic liquid crystal(TNLC) broad-band waveplates, tunable Fabry-Perot(FP) filter based on TNLC, FP cavity based on SP waveguide cavity, metal super lens, dielectric gratings on metal slab.Achromatic waveplate composed of two TNLC cells is designed out based on the theory that LC is anisotropic like solid crystal. Parameters of TNLC cells, such as cell thicknesses, azimuthal angles and twisted angles are mathematically optimized during design process. The numerical results suggest the proposed waveplate has broad band and large fabrication tolerance. In addition, compared with other types of achromatic waveplates, the proposed type can be fabricated with larger aperture.LC is electrically and optically tunable. Tunable LC FP filter which takes advantage of this characteristic can be used in optical communication C-band. Analytical formula calculating the reflection phase of one-quarter dielectric film stack is derived out. This reflection phase leads to the shift of working wavelength and applied voltage. Performance of LC FP filter is analyzed by calculating LC director distribution under applied voltage. Simulation results indicate that even when LC FP filter has long cavity length (e. g. several microns), the reflector phase is considerable and can not be neglected in design process.Compared with LC FP filter, FP waveguide cavity based on SP is more compact and integrated. Three-slab waveguide (i. e. metal-insulator-metal, MIM) is considered here to develop SP cavity. With two metal mirrors inserted in the dielectric slab, FP cavity can be formed. The influence of mirror thickness on the performance of the cavity is analyzed with finite difference time domain method (FDTD). The thickness of metal mirror will change not only the reflection phase but also the cavity length and quality factor at the same resonant wavelength. Multi-cavity configuration is proposed to remove rest resonant peaks while high quality factor is guaranteed.Super lens composed of metal slabs is also operated on SP. One novel multi-layer super lens with non-uniform slab thicknesses is presented to improve the resolution deteriorated by metal loss. The physical thickness of each slab is optimized. Compared with single-layer or periodic structure super lens, the proposed structurecan excite more SP modes and the resolution can be improved as well.For enhanced transmission based on SP, the configuration with dielectric-grating on metal slab is considered and the influence of dielectric grating parameters on transmission efficiency is discussed. The enhanced transmission is directly related to excitation of symmetric and anti-symmetric modes of SP. An optimum configuration can be achieved with maximum transmission efficiencies at different diffraction orders. A novel refractive index sensor with high sensitivity is introduced, which works in transmission mode. This configuration is more flexible and easier for an arrayed-integration than metal gratings.The super resolution of super lens is verified experimentally. At first, lithography mask with sub-micron configuration is fabricated by e-beam lithography. Some parameters, such as thickness of PMMA film, dose of electrons and exposure time, are experimentally studied. Experimental results suggest that the thickness of PMMA film should be comparable with line-width to be done and smaller dose will produce narrower line-width on PMMA film. Then the sub-micron structure on PMMA is transferred to Cr film by wet-etching. Secondly, the lithography mask is used as object in silver super lens experiment. Super resolution of silver super lens is verified at first sight by comparing images under two conditions (with and without silver super lens). The influence of the peak transmission of silver in UV band and the broadband source used in experiment is discussed. The enhanced intensity of SP on silver surface is helpful for sub-wavelength resolution.