GALLIUM-ARSENIDE METAL-SEMICONDUCTOR-METAL PHOTODIODES AS OPTOELECTRONIC MIXERS FOR MICROWAVE SINGLE-SIDE-BAND MODULATION

Gallium arsenide (GaAs) metal-semiconductar-metal (MSM) photodetectors have unique propel-ties including high-bandwidth, linearity, and biph ase response that make them suitable as mixers and programmable weight s for microwave and communications applications. An optical technique for microwave single-sideband modulation that uses GaAs MSM photodiode s as mixers is reported. It uses MSM Schottky photodiodes formed in a GaAs/Al0.3Ga0.7As materials system to detect microwave in-phase and qu adrature signals on optical carriers. Modulation of the photodetector bias voltages results in a single-sideband modulation of the microwave signal. Radio frequency and undesired-sideband suppression of 36 and 27 dB, respectively, were achieved. The optical wavelength was 850 nm, and the bandwidth of the photodetectors was greater than or equal to 29 GHz.