Polymer-Based Volume Holograms for a Surface-Normal 3×3 Non-Blocking Wavelength-Selective Crossbar

Abstract

In this paper, we present a 3x3 non-blocking crossbar for network applications. This device is pivotal for the realization for a computer-to-computer interconnect network where both wavelength division multiplexing and space division multiplexing are employed to enhance the transmission bandwidth. We report the formation of a surface -normal wavelength selective non-blocking crossbar using photopolymer-based volume holograms in conjugation with graded index (GRIN) lenses. The elimination of edge-coupling significantly enhances the packaging reliability. Furthermore, such a configuration is compatible with the implementation of vertical cavity surface-emitting lasers where the characteristic of azimuthal symmetry is maintained in the waveguiding substrate. The prototype polymer-based volume hologram for a multiple-wavelength 3x3 crossbar is experimentally demonstrated at 755, 765, and 775 nm. The unique beam routing property of GRIN lens reduced nine wavelengths to three wavelengths while maintaining the required nine (3x3) individual interconnects. Realizing the fact that the wavelength-switching speed of semiconductor lasers is as fast as 1 nsec, we expect to build a fully packaged system with much less system latency.