Two hollow-cathode He-Cd lasers were frequency locked to gain maxima at 533, 537, and 441 nm while we simultaneously observed the beat between the 533- and 537-nm frequencies. The 100-sec Allan variance of the beat varied from 4.7 to 6.9 MHz over periods up to 50 min.
© 1988 Optical Society of America
B. K. Ward, J. A. Piper, and P. E. Ciddor, "Simultaneous frequency stabilization of three lines in a He-Cd laser," Opt. Lett. 13, 625-627 (1988)