Theoretical Research on Optimization of Signal-Noise Ratio Based on Cascaded Four-Wave Mixing System

Theoretical research on the optimization of the signal-noise ratio (SNR) based on the cascaded four-wave mixing process is performed. This cascaded four-wave mixing process includes the phase-sensitive and phase-insensitive two cascaded methods. In the phase-insensitive cascaded system, the intensity of the probe beam is always amplified and the SNR of the probe beam is always reduced. However, in the phase-sensitive cascaded system, the intensity of the probe beam can be either amplified or reduced which depends on the total phase modulation of the light field in two Rb pools. Under the same intensity gain condition, the efficient gain in the phase-sensitive cascaded four-wave mixing system is greater than that in the phase-insensitive cascaded four-wave mixing system. In addition, when the total phase of the light field in two Rb pools is equal to 0 or 2π, both the intensity of the probe beam shows an amplification with the maximal amplitude, and the SNR is increased to the maximal value in the phase-sensitive cascaded four-wave mixing system.