Abstract

Integrated free space optical interconnect has the potential to provide a large number of high speed connections between electronic integrated circuits. The overall optical arrangement is briefly described. We intend to use a single laser or a pair of lasers to power an interchip connection with several hundred communications channels. Differential optical encoding will be used to provide higher speed and eliminate referencing problems. We propose using reflective GaAs quantum well modulators as output ports. Energy requirements of such modulators are very low and their fabrication on silicon substrates has been demonstrated. We have tested arrays of differential modulators with 5-µm diam windows fabricated on GaAs substrates at frequencies up to 1 GHz with no high frequency roll-off. As optical input ports we propose using silicon photodetectors which are fully compatible with the standard CMOS silicon integrated circuit process. We have fabricated a test chip with a variety of differential amplifier circuits and photodiodes using a production facility. The photodiodes have sizes of 5 × 5 µm and 10×10 µm. The circuits have been tested and shown to run at 140 MHz with 100 µW of optical input power.

© 1989 Optical Society of America