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This work proposes a simple method, based on the crystal rotation technique and heterodyne interferometry, to simultaneously determine the pretilt angle and cell gap of nematic liquid crystal cells. When heterodyne light passes through a nematic liquid crystal cell, the phase retardation given by the characteristic parameters of the cell can be measured accurately by heterodyne interferometry. This phase retardation relates to the pretilt angle, cell gap, and angle of incidence on the cell. By using the measured phase retardations at two incident angles, the pretilt angle and cell gap of the nematic liquid crystal cell can be estimated by numerical analysis. This method is feasible, requiring only two incident angles and prior knowledge of two characteristic parameters--extraordinary and ordinary refractive indices of the liquid crystal. It is characterized by the advantages of simplicity of installation, ease of operation, high stability, high accuracy, and high resolution.

Based on the coupled-wave theory, a holographic spatial walk-off polarizer (HSWP) is designed. This HSWP is a transmission-type phase volume holographic grating on a substrate and its optical recording geometry can be derived from Chen's corrected methodology with a desired reconstruction condition. A pair of fabricated HSWPs with the splitting angle of 60 degrees is applied to assemble a new type of 4-port polarizationindependent optical circulator. The operating principles and the characteristics of the proposed HSWP and the prototype optical circulator are discussed.

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The Bragg mismatching condition for volume holograms occurs because of the changes in the thickness and the refractive index of holographic recording materials during the recording and reconstruction procedures. We propose an improved compensation method to physically correct these effects in the fabrications of volume holograms for optical interconnects. In order to show the validity of this method, Slavich photographic plate VRP-M is used to fabricate optical interconnects. The correction of the Bragg diffraction angle shift of about 2.10°, which is induced by 6.14% film shrinkage and 0.06 refractive index shift, is successfully demonstrated with the surface-normal configuration. A shrinkage- and refractive-index shift-corrected volume hologram with 23% diffraction efficiency is experimentally confirmed. The methodology proposed is applicable to other phase media when the associated film shrinkage and refractive-index shift data are experimentally determined.