diode-laser-pumped nonplanar ring oscillator to less than 3 Hz of relative linewidth

We present results on the frequency stabilization of two diode-laser-pumped ring lasers that are independently locked to the same high-finesse interferometer. We measure the relative frequency stability by locking the lasers one free spectral range apart and observing the heterodyne beat note. The resultant beat note width of 2.9 Hz is consistent with the theoretical system noise-limited linewidth and is appoximately 20 times that expected for shot-noise-limited performance. Frequency-stable lasers are required as master oscilla-tors in a variety of applications, including coherent communication, high-resolution spectroscopy, and gravity-wave detection. Helium-neon, dye, and ar-gon-ion lasers have been successfully stabilized for potential use in these fields. 1-3 These lasers are typi-cally discrete-element systems that have wideband frequency noise and require complex locking servos. Diode-laser-pumped Nd:YAG lasers have also been stabilized to reference interferometers.4 However