A PHOTODETECTOR ARRAY FOR ACOUSTOOPTIC SIGNAL PROCESSORS

Acousto-optic (AO) signal processors are of interest for processing wide bandwidth signals in real-time. A recently developed photodetector structure has important potential advantages for this application. It uses the exponential current to voltage relationship obtainable with a profile channel metal oxide semiconductor field-effect transistor to provide a steady state logarithmic relationship between incident light intensity and output voltage and a dynamic range exceeding 70 dB. This paper discusses the design considerations associated with the use of the new photodetector structure in the context of a 128 element photodetector array being developed for real-time processing of wide bandwidth signals. This design uses a series-parallel architecture to provide a minimum exposure time of 1 μs. The photodetector and readout electronics are optimized to provide high sensitivity and response speed for transient signals. Simulation results suggest that the dynamic range exceeds 50 dB for pulses less than 1 μs in duration.