Compact phase-conjugate mirror utilizing four-wave mixing in a loop configuration

摘要

A compact loop four-wave mixing phase conjugator that can be used in practical optical applications comprises a reflective nonlinear cell, relay optics, an optical gain medium, and an optical diode that together form a unidirectional ring laser resonator. In operation, a signal beam . epsilon..sub.1 is directed to the nonlinear cell, where it passes through a nonlinear medium contained within the cell and is reflected out of the cell as loop beam &egr;.sub.2. The relay optics direct loop beam . epsilon..sub.2 through the optical diode, optical gain medium, and back to the nonlinear cell, where it intersects and optically interferes with the signal beam &egr;.sub.1 to form a refractive index grating in the nonlinear medium. The optical diode and gain medium are positioned in the loop so that an oscillation beam &egr;.sub.3 builds up from optical noise in the resonator and oscillates in a direction counter to the propagation direction of loop beam &egr;.sub.2. A portion of oscillation beam &egr;.sub.3 is transmitted by the refractive index grating, reflects off the reflective portion of the nonlinear cell and emerges from the cell as phase conjugate output beam &egr;.sub.4.