We present a study of frequency locking two diode-pumped Nd:YAG non-pl
anar ring oscillator lasers to a Fabry-Perot cavity with 215 000 fines
se. Measurements of the beat frequency between the two lasers, locked
to adjacent TEM(11) modes, show a root Allan variance of 0.25 Hz for 1
s integration time and a minimum of 0.12 Hz for 50 s integration time
.