Two stage laser stabilization using external cavities: Application to a 10 μm CO 2 laser locked to an OsO 4 transition

A cw carbon dioxide laser, operating on the 10 μm R(0) transition (28.832 THz), was stabilized by locking its frequency to an evacuated Fabry–Pérot cavity. The Fabry–Pérot cavity was in turn stabilized to the saturated absorption resonance of the Q(15) line of 188 OsO 4 , contained in a second Fabry–Pérot cavity. Cesium-clock referenced, frequency chain measurements of the resultant line frequency are presented together with detailed studies of the line shift sensitivities to various operating parameters.