Spectral linewidth of an external-cavity laser diode stabilized by a fiber-optic ring resonator

Abstract
The spectral linewidth of an external‐cavity single‐mode GaAs/AlGaAs laser diode was stabilized by controlling the phase of the feedback light, where a fiber‐optic ring resonator was used as a linewidth discriminator. The stabilized linewidth is about 500 kHz with a short‐term fluctuation of about 30 kHzpp over a period of 3 h.