We propose and perform two-dimensional angular filtering on the basis of volume Bragg gratings (VBGs) in a series connection for cleaning up a laser beam. The dependence between angular selectivity and VBG parameters is analyzed with the coupled wave theory. Near-field modulation, contrast ratio, and power spectral density were used to evaluate the effect of filtering in both the spatial and frequency domain. The results from our initial experiments showed that the near-field modulation and contrast ratio of laser beam were remarkably improved.

A very large radial graded-index (GRIN) polymer was successfully prepared for the first time, to the best of our knowledge, by two methods: the curved mold method and the diffusion copolymerization method. Both methods gave a radial GRIN polymer with a diameter of 70 mm and a ∆n value greater than 0.02. Ray tracing through these radial GRIN polymers was used to predict that such a GRIN polymer could be a promising candidate for thinner ophthalmic lenses with no spherical aberration or multifocusing characteristics.

A gradient-index (GRIN) contact lens (CL) is proposed to decrease spherical aberration and to increase the diopter. A plastic radial GRIN rod was successfully obtained by using the vapor-phase diffusion copolymerization technique. The resulting index distribution of the GRIN rod was almost parabolic against the distance from the center axis, and the Δn value was -0.030. The GRIN CL was prepared by grinding and polishing the rod. It is theoretically and experimentally concluded that using the radial GRIN material can significantly improve the optical properties of CL's.

We propose and perform broadband angular filtering with the combination of a volume Bragg grating and a surface grating pair. The condition for broadband operation is discussed. Near-field modulation, contrast ratio, and power spectral density are used to evaluate the filtering performances in the spatial and frequency domain. Experimental results show that the bandwidth of the output beam through the grating combination is remarkably increased, and the medium and high frequencies are effectively eliminated.

ABSTRACT:A new method for preparing very large radial-GRIN (graded index) polymer plates is proposed. The resulting radial-GRIN plate has a diameter of 70 mm of the GRIN region and Lin of 0.02. The optical characteristics of the large radial-GRIN lens were estimated by calculating the trajectory ofa ray through GRIN lens which was based on Maxwell's ray equation. It was confirmed that such large GRIN polymers are promising for eye glasses with no spherical aberration or multifocus properties.