Integrated Detectors for Embedded Optical Interconnections on Electrical Boards, Modules, and Integrated Circuits

Significant opportunities exist for optical interconnections at the board, module, and chip level if compact, low-loss, high-data-rate optical interconnections can be integrated into these electrical interconnection systems. To create such an integrated optoelectronic/electronic microsystem, mask-based alignment of the optical interconnection waveguide, optoelectronic active devices, and interface circuits is attractive from a packaging alignment standpoint. This paper describes an integration process for creating optical interconnections which can be integrated in a postprocessing format onto standard boards, modules, and integrated circuits. These optical interconnections utilize active thin-film optoelectronic components embedded in the waveguide/interconnection substrate, thus eliminating the need for optical beam turning elements and their alignment, and providing an electrical output on the substrate from an optical interconnection. These embedded optical interconnections are reported herein using BCB polymer optical waveguides with embedded InGaAs-based thin-film inverted metal–semiconductor–metal (I-MSM) photodetectors on an Si substrate. These interconnections have been fabricated and tested, and the coupled optical signal from the waveguide to the embedded photodetector was theoretically modeled at 56.4%, which was supported by an experimental estimate of 47.8%. The measured full-width at half maximum of the electrical pulse from the MSM photodetector embedded in the waveguide was 16.73 ps for an input 500-fs optical laser pulse.