Abstract

This paper reports experimental results on a self-starting unidirectional ring resonator using a photorefractive undoped GaAs crystal as the amplification medium. Two types of ring configurations, triangular and rectangular, were investigated. The oscillation occurred only in the small portion of the crystal near the cathode under a dc voltage, which can provide a uniform, amplified phase-conjugate beam in a four-wave mixing in the same GaAs crystal. The cross-section of the resonating beam in the rectangular configuration was considerably larger than that in the triangular one. The coupling efficiency in the resonator as a function of external-pump beam intensity under different applied dc voltages was measured. The maximum observed value was about 40% of the external-pump beam intensity, which was about twice of that in Cr-doped GaAs reported by Rajbenbach et al.¹ The oscillation can occur with the external-pump beam intensity as low as 1 mW/cm². The coupling efficiency became saturated at high intensities.

© 1990 Optical Society of America