Compressing photodetectors for long optical pulses using a lateral blooming drain structure

A compressing photodetector structure suitable for detecting continuous wave and long pulsewidth optical signals for applications such as acoustooptical signal processing and machine vision is described. Subthreshold injection of carriers over a photodetector blooming gate is used to generate a compressing transfer characteristic. The photodetector transfer characteristic is integrating at low light levels and logarithmically compressing at higher light levels. The output voltage at which logarithmic compression becomes dominant may be adjusted in a range extending below 5-nW incident optical power by varying the bias voltage difference between the photodetector blooming and imaging gates. The predictions of simulation models that were developed correlate well with the experimental measurements