High-Frequency Optically Heterodyned Saturation Spectroscopy Via Resonant Degenerate Four-Wave Mixing

Abstract

Resonant degenerate four-wave mixing with two close optical frequencies ($\omega , \omega +\delta$) is used to perform high-frequency optically heterodyned saturation spectroscopy. Doppler-free spectra of ${\mathrm{I}}_2$ ($\lambda =514.5\mathrm{}$ nm) are obtained in this way for $20 \mathrm{kHz}<\delta <20\mathrm{} \mathrm{MHz}$. Lock-in detection for $\delta <1\mathrm{}$ MHz allows relaxation studies and line assignments. At higher frequencies, rf-power detection yields Doppler-free doublets split by $\frac{3\delta }{2}$.