Alternative approach to stable lasers: the optically pumped NH(3) laser.
A beat-note stability of 500 Hz over 1 sec has been observed between two free-running optically pumped NH(3) lasers. The 12-microm laser frequency is strongly isolated from cavity-mirror motion and is relatively insensitive to perturbations in the pump lasers.
Siemsen
K J
KJ
Williams
E
E
Reid
J
J