Internal Noise and Signal-to-Noise Ratio of a Tuned Laser Amplifier

If a laser preamplifier could be developed to have sufficiently low internal noise it would be possible to achieve nearly 100% quantum efficiency in optical receivers now limited, especially in the near IR region, by the low efficiency of available photo-emissive detectors. It is shown that under proper conditions such a low level of internal noise could be achieved in a tuned laser amplifier. These conditions are related to the design parameters of the amplifier and the resulting requirements on bandwidth and beamwidth are discussed.