A method for fabricating microlens arrays that uses the contraction effect of UV-curable photopolymers is presented. Lenses with diameters ranging from 0.2 to 2 mm that were made under different conditions are optically evaluated. The optimum conditions for producing low f-number lenses are discussed.

We experimentally investigate random laser (RL) emission from dye-doped polymer random media with inhomogeneously distributed scatterers. A random structure, which we call a bubble structure (BS), is realized by using nonscattering spacer particles randomly distributed in a gain medium. The experimental results show that the bubble-structured RL that incorporates an appropriate amount of spacer particles exhibits a higher spectral peak and a larger slope efficiency than conventional RLs. The highest peak intensity is observed when the size variation of spacer particles is maximized. Furthermore, an analysis of laser modes reveals that an increase in the spectral peak intensity can be partly attributed to the mode selection properties of the BS.

The feasibility and the properties of shift-multiplexed self-referential holographic data storage (SR-HDS) were investigated. Although SR-HDS has attractive features as typified by referenceless holographic recording, its multiplexing properties, which are consummately important for holographic data storage, have not been clarified until now. The results of numerical and experimental evaluations of medium shift dependence in SR-HDS clarified that the shift selectivity is almost the same as in collinear holography. Furthermore, 25 datapages were successfully shift-multiplexed with the shift pitch of 8.3 μm by the numerical simulation.

Dynamic properties of doubly-scattered laser speckles produced by a cascade of two moving diffusers are investigated theoretically and experimentally. Space-time correlation functions for both single and double scattering cases are derived in terms of the roughness and the moving velocities of the diffusers, the spacing between them, the spot size and the wavefront-curvature radius of an illuminating laser beam, and the position of a detecting plane. Time-correlation length τ_c defined by the 1/e correlation time is then evaluated to measure the velocities of moving diffusers. It is found that, if both the diffusers move simultaneously, the reciprocal 1/τ_c of the time-correlation length is no longer proportional to the velocity of each diffuser. Nevertheless, the relative velocity of the two diffusers is shown to be proportional to 1/τ_c when they are illuminated at the beam waist with a suitable spot size and when the speckle fluctuations are detected in the far field. The root-mean-square velocity shows linear dependence on 1/τ_c under broad-beam illumination and near-field detection. An experimental study has been conducted to verify the theoretical results. Good agreement is obtained between theoretical and experimental results.