A REFLECTION-TYPE SUBSTRATE-MODE GRATING STRUCTURE FOR WAVELENGTH-DIVISION-MULTI-DEMULTIPLEXING

Abstract

We describe a technique to design and implement a wavelength-division-multi/demultiplexing device with a reflection substrate-mode grating pair in dichromated gelatin. This device is based on a diffraction volume grating pair, which provides and angularly dispersive function, to separate optical signals at different wavelengths through the dielectric substrate with total internal reflection. In this structure, the channel separation is enhanced by multiple reflections at substrate-air interfaces with a shorter longitudinal distance. Normally incident coupling and on-axis output imaging with this structure provide easier alignment with coupled optical fibers. The device with a polarization-insensitive high efficiency ( > 80 %) for 76-nm bandwidth has been fabricated.