Theory of spontaneous emission factor and noise figure of optical
parametric amplifiers
Abstract
This study develops a theory of noise in optical parametric amplifiers
(OPAs) based on the quantum-mechanical Langevin equations. We derive
theoretical expressions for the spontaneous emission factor of OPAs for
the first time. This enables analyzing the effect of internal loss on
the noise characteristics. In addition, we analyze the noise figures of
the laser amplifier, phase-insensitive OPA, and phase-sensitive
OPA.