Doppler-free continuous-wave phase-conjugate spectrum of SF_6 by resonant degenerate four-wave mixing at 106 μm

A phase-conjugate signal has been obtained in SF(6) with a peak reflectivity of 1.2 x 10(-3) by using a cw CO(2) laser operating on the P(16) line. The degenerate four-wave mixing spectrum exhibits a Doppler-free structure with 2-MHz resolution. When the reflectivity spectrum is compared with the saturated-absorption spectrum, matching peaks in the reflectivity spectrum are found over an 80-MHz bandwidth.