Masafumi Seki

Optimization of phase-only computer-generated holograms using an ion-exchange process

A highly efficient phase-only hologram has been produced using an ion-exchange method. An optimum condition for the phase profile of the hologram is described. The ion density and the phase profile generated by the ion exchange were calculated by computer simulations. The diffraction patterns of different gratings are calculated based on these data, and an optimum phase distribution is estimated. The optimum condition has been verified experimentally.

Phase-only computer-generated hologram produced by an ion-exchange technique

We have produced a highly efficient phase-only hologram, in which the refractive index of the substrate is modified by using an ion-exchange method. This binary phase-only hologram is produced using a conventional binary hologram as a mask for the ion exchange. A simplified theory of the phase-only hologram is presented along with a description of the fabrication method and the experimental test results.

Optimization of gradient-index computer-generated hologram

We have produced a high efficient phase-only hologram, of which refractive index distribution is modified by using an ion exchange method. This paper describes an optimum condition of the phase profile of the hologram. In computer simulation, ion density and phase profile generated by ion exchanging is calculated. The diffractiion patterns of the gratings are calculated based on phase distribution data of the gratings. An optimum phase distribution is estimated. The optimum condition is verified experimentally.

Novel design for a high-performance guided-wave multi/demultiplexer in glass

Abstract A guided-wave multimode multi/demultiplexer which comprises interference filters and gradient-index waveguides was investigated both theoretically and experimentally. Effective design considerations concerning filter configuration and waveguide geometry led to a high-performance multi/demultiplexer in a glass substrate. Original filter configurations suitable for operation in a waveguide were devised through theoretical analysis. The transmission band-widths for two channels with 100 nm separation were as wide as 66 nm. Waveguide parameters were optimized to obtain low transmission loss (propagation loss plus slot loss) and also to realize efficient coupling to input/output fibres. The insertion losses were around 1 dB for demultiplexing and less than 2 db for multiplexing.

High-precision refractive index distribution measurement of optical waveguides

Abstract Phase shift interferometry is applied to the measurement of 2-D refractive index distributions of optical waveguides, where the cross sections are generally very small. The problems about magnification and spatial resolution are discussed. Experimental results show that the measuring accuracy of refractive index for an asymmetric optical waveguide achieved the order of 10-5. The high precision results are very useful for numerical analyses of the optical waveguides.

New approaches to practical guided-wave passive devices based on ion-exchange technologies in glass

For the use in cost-effective optical communication systems, two types of guided-wave devices have been studied using ion exchange in glass: (1) A microlens-loaded coupler module composed of a polarization-maintaining fiber array, a directional coupler and a twin-microlens array for coherent balanced receivers has been proposed and fabricated with an excess loss of 1.0 dB and an extinction ratio of _> 20 dB for 0-60 degC operation. (2) An optimum mask pattern for splitters has been devised theoretically and verified experimentally, which has reduced the scattering loss to < .0.1 dB and also suppressed their possible bimodal behavior in the branching region.