The signal-to-noise ratio of a regenerative optical quantum amplifier

Nicolai G. Basov, Arkadii Z Grasyuk, Iosif G. Zubarev

Jacques Arnaud

The amplification before detection of the carrier of a modulated optical signal by a narrow-band quantum amplifier enhances the signal-to-noise ratio, particularly when the signal wave-front is distorted. A further improvement is obtained by using a combination of wide-band and narrow-band quantum amplifiers. The practical application of these schemes requires a degenerate regenerative ring-type amplifier capable of amplifying arbitrary transverse field configurations. Experiments show that such an amplifier with a gain of 24 dB and a bandwidth of 1 MHz is feasible. The incident beam axis can be displaced by as much as ten times the beam-waist radius without losing more than 4 dB in gain. Frequency modulation may be converted into amplitude modulation by the phase shift introduced in the carrier.

Anatoly Viktorovich Masalov, A. A. Putilin

Gautam Vemuri, Rajarshi Roy

In super-regenerative detection, a weak external signal is amplified in an oscillator that is periodically switched on and then quenched. It is shown that very weak optical signals, slightly above the noise level, can be detected effectively by a laser used as a super-regenerative receiver. The detector output for different signal levels and its operating characteristics are determined by numerical integration of stochastic differential equations that represent the growth of laser radiation from a background consisting of signal and noise.

S. B. Wang, Wei Liu, Xuyin Niu +2 more

In this paper, two models for simulating the shot noise and electronic noise performances of resonant photodetectors designed for homodyne measurements are presented. One is based on a combination of a buffer and a low-noise amplifier, and the other is based on an operational amplifier. Through the comparisons between the numerical simulation results and the experimentally obtained data, excellent agreements are achieved, which show that the models provide a highly efficient guide for the development of a high signal-to-noise ratio (SNR) resonant photodetector. Furthermore, we demonstrate a high SNR resonant photodetector for homodyne measurements at the 147 MHz optical sideband, achieving a 20.8 dB SNR of the shot noise to the electronic noise with a 2 mW optical signal input, utilizing a combination of a buffer and a low-noise amplifier. Concurrently, we have obtained another resonant photodetector at the 1.14 GHz optical sideband, which exhibits a 13 dB SNR based on an operational amplifier.

M. I. Dzhibladze, R. R. Erikashvili, E. Sh. Teplitskii +2 more