Atomic and molecular spectroscopy with a phase-locked, continuous-wave optical parametric oscillator

We demonstrated the phase-locking and continuous tuning capabilities of a continuous-wave, monolithic optical parametric oscillator (cw-OPO). At first, the cw-OPO was phase-locked to an optical frequency comb in the 830 nm region. The residual phase noise under phase-locking was 220 mrad in rms and the energy concentration to the carrier was 95%. Next, the signal light from the cw-OPO was phase-modulated by an external electrooptic modulator (EOM) in the microwave frequency. The single sideband was extracted by using a diffraction grating and a spatial filter. We could observe the Doppler broadened absorption and fluorescence profile of the Cs-D₂ line by tuning the signal wavelength to 852 nm and by scanning the microwave modulation frequency. We are trying the sub-Doppler spectroscopy of several atoms and molecules with the phase-locked cw-OPO and these results will also be presented.