Comparison of photomultipliers and avalanche photodiodes for laser applications

Photomultipliers and avalanche photodiodes are compared as detectors of short light pulses such as might be encountered in laser ranging or laser PCM communication systems. Expressions are derived for the optimum spectral response of the amplifier-filter combination which maximizes the signal-to-noise ratio for the two detectors. Assuming that this optimized filter is used, the minimum detectable energy of a laser pulse is then calculated for the two detectors as a function of detector quantum efficiency, laser pulse length, and background light level. As an example, the detectors are compared for laser pulses of lengths 100 ns, 10 ns, and 1 ns at 1.06 µm.