CHAPS: A new precision laser-spectroscopic technique

We present a new technique for high-resolution pulsed spectroscopy that employs optical heterodyne detection to determine the instantaneous frequency of individual optical pulses, together with a frequency-binning method to generate high-precision spectra. We further demonstrate that active tuning of the light source is not necessary if the inherent frequency jitter of the source spans the spectral region of interest. This heterodyne-assisted approach to coherent pulsed spectroscopy (CHAPS) is applied in real time by using output from a pulsed, injection-seeded optical parametric oscillator-amplifier (OPO-OPA) system, the optical bandwidth of which is characterized via two-photon excitation of the 6S-8S transition in cesium. The resulting sub-Doppler measurements demonstrate the utility of CHAPS as a high-resolution spectroscopic technique and confirm that the pulsed OPO-OPA system operates very close to the Fourier-transform limit.