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

Abstract

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