Laser receiver with a quantum detection limit in the near-IR range

A laser receiver (LR) with an active quantum filter (AQF) (λ  = 1.315 μm) based on an iodine photodissociation laser is studied. It is shown that the LR sensitivity can be brought up to the quantum detection limit by increasing the AQF gain. Taking into account the space-time statistics of spontaneous emission of the AQF, the LR sensitivity is determined as a function of the reception solid angle and the recorder response time. Under the conditions of the experiments performed, the LR sensitivity is, to a good approximation, proportional to the square root of the product of the reception solid angle and the recorder time constant. The above dependence is confirmed experimentally upon more than a hundred-fold variation of the response time. For the reception angle that was three times greater than the diffraction-limited angle, the quantum detection limit was achieved, which amounts to approximately three photons for a 40-ns pulse for the unit signal-to-noise ratio.