Abstract

Many researchers have studied the noise properties of optical amplifiers and have shown theoretically that all nonlinear optical amplifiers introduce noise into the amplified beam.¹ For example, a phase- conjugate mirror (PCM) generates light that exhibits excess quantum noise that is inherent to the phase-conjugation process.² Additional noise may result from fluctuations (e.g., collisions) in the nonlinear medium.³ The total noise generated during the phase-conjugation process determines the minimum signal that can be phase conjugated for a specified value of the signal-to-noise ratio. The only previous experimental work that has addressed the issue of phase conjugation of weak beams is that of Andreev et al.⁴ who demonstrated that it is possible to perform phase conjugation with a pulsed beam containing 30 photons. Their system is based on Brillouin-enhanced four- wave mixing with an optical preamplifier.

© 1996 Optical Society of America