Abstract

A linewidth of 80 kHz and a frequency jitter of 900 kHz of a free-running single-mode Ti:Al₂O₃ ring laser was measured by using optical homodyne and heterodyne measurement methods. A single-mode 1km optical fiber was used for a 5-μs optical phase delay at 780 nm. Single-mode output of the home-made Ti:Al₂O₃ ring laser could be tuned between 730-820 nm and the average output power was 300 mW. In the homodyne optical spectrum a oscillation with period of 1/τ (=190 kHz), where τ is the delay time by the optical fiber, was observed on the beat spectrum like the result in the laser diode experiment with subcoherence delay time.¹ We have obtained the 80-kHz linewidth by comparing the homodyne beat spectrum with theoretical calculations. A 80-MHz acoustooptic modulator was employed in one arm of the homodyne setup to shift the optical frequency for heterodyne measurement. A 900-kHz frequency jitter from the time varying heterodyne beat signal on the rf spectrum analyzer was obtained, which is about two times better than the Schulz’s result of 2MHz.²

© 1991 Optical Society of America