Integrated waveguides for optical interconnects

Purpose To detail results of research into optical waveguides fabricated from silicon on insulator (SOI) for on-chip high speed applications and from polymer for more general applications. Design/methodology/approach This paper shows the processes for wet etch fabrication of SOI single mode rib waveguides including compact crystal plane turning mirrors. Losses for the mirror facets are determined by difference measurements. Multimode polymer strip waveguides are fabricated on glass substrates by conventional photolithography using SU8 polymer and tested for attenuation. Findings Fabrication of compact turning mirrors for silicon waveguides requires precise alignment of masks and controlled etching of the corner facets in order to obtain correct alignment of the mirror face with the incoming and outgoing waveguides. Measurements of losses per mirror facet show typical losses of 1-2 dB/facet. Suggestions for improvements are made. Preliminary results for polymer waveguides show the necessity for high quality lithography. Originality/value Optical interconnects for high speed communication on board and on chip are part of the ITRS Road Map for advanced interconnects. Design of optical elements to enable this, including reduction of on-chip area by turning mirrors, is necessary for on-chip optical technology to be successful. Compact etched mirrors described here extend previous designs and enable fabrication at any position on-chip. New etch mask techniques for silicon waveguide fabrication are also described.