Color-switching in an optical parametric oscillator using a phase-conjugate mirror

TL;DR

This paper demonstrates a novel optical parametric oscillator using a phase-conjugate mirror based on four-wave mixing in rubidium vapor, enabling stable, passively mode-locked pulses with potential quantum applications.

Contribution

Introduces a phase-conjugate resonator with a glancing-angle mirror that allows stable pulsing and tunability without circulating light, advancing optical parametric oscillator technology.

Findings

Achieved stable, passively mode-locked pulses.

Demonstrated tuning of resonant modes via pump control.

Suppressed thermal and acoustic instabilities.

Abstract

We construct a phase-conjugate resonator which passively produces stable pulses that alternate between the probe and the conjugate colors. The requisite phase-conjugate mirror inside the resonator is constructed using non-degenerate four-wave mixing (4WM) in rubidium vapor. The glancing-angle phase-conjugate mirror is a 100\% output coupler, and therefore this resonator is unusual in that no light circulates the cavity more than once. Without the gain of the phase-conjugate mirror, the cavity boundary conditions, and thus resonant modes, are not defined and therefore can be tuned by the pump. The output of the optical parametric oscillator that is formed above threshold can passively mode-lock. The phase-conjugate mirror removes thermal or acoustic instabilities that are on a MHz or slower timescale. This work provides a new method for stable pulsing using phase-conjugate optics, and suggests a platform for producing mode-locked pulses with squeezed light, as the 4WM process has already demonstrated quantum correlations.