Integration of optoelectronic switch matrices using metal-semiconductor-metal photodetectors and polyimide waveguide circuitry

Abstract

The integration of metal-semiconductor-metal (MSM) photodetector arrays with multimode polyimide waveguides has been demonstrated. MSM detectors were fabricated using transparent indium tin oxide (ITO) interdigitated electrodes on semi-insulating GaAs substrates. Light at 830 nm was coupled efficiently from the waveguides into the underlying photodetectors through gaps in the SiO2 buffer layer. Absolute responsivities of the integrated MSM detectors were around 0.5 A/W, and 3-dB bandwidths of 4 to 6 GHz were measured. Division of the input optical signal between four detectors of increasing length integrated along a single waveguide was achieved. Four 1 x4 arrays were used to assemble a prototype hybrid 4x4 optoelectronic switch. Band- widths of around 1.2 GHz, limited by the electronic circuitry, were measured. The isolation was better than 35 dB, and the crosstalk was approximately ?35 dB. The advantages of polyimide waveguides for on- chip interconnection in switch matrices are discussed.