Frequency-stable, narrow linewidth oscillation of red diode laser with phase-conjugate feedback using stimulated photorefractive backscattering

Abstract

Frequency-stable, narrow linewidth oscillation of a 638 nm AlGaInP diode laser has been achieved with an external photorefractive BaTiO3 phase conjugator in a novel configuration. The mechanism of the phase conjugation in this configuration is the stimulated photorefractive backscattering process with the measured phase-conjugate reflectivity of <1.8×10−3%. With this new phase-conjugate feedback method, the laser linewidth was reduced to ∼0.1 nm (within the resolution limit of the spectrum analyzer used) and the oscillation frequency was highly stabilized, while it was impossible with a conventional cat conjugator.