Degenerate intracavity parametric processes with injected signal

Abstract

A common way of increasing the efficiency of optical frequency conversion processes is by the injection of a coherent signal at the desired frequency. We study the efficiency of this method and its effect on the quantum statistics of the fields by performing theoretical analyses of the intracavity parametric χ (2) processes of second harmonic generation and degenerate optical parametric oscillation with injected signal fields. We find that the threshold behaviour of the optical parametric oscillator with an injected signal field gives further insight into the normal threshold behaviour, considered as a limiting case as the signal field goes to zero. An injected signal is also shown to change the critical points of the systems, which define the region where the maximum of noise suppression and other quantum effects may be expected. We also investigate the self-pulsing behaviour of second harmonic generation, showing how an injected signal can affect the oscillations. We show the process of second harmonic generation can be blocked by an injected signal of the appropriate intensity, effectively removing the crystal from the cavity.