Development of Phase-lock System between Two Single-Mode Lasers for Optical-Optical Double Resonance Spectroscopy

Abstract

The difference frequency between two single-mode CW lasers was stabilized to a microwave (MW) frequency reference by using an optical phase-lock loop (PLL). The long-term frequency jittering of the beat spectrum was much suppressed by this method. The difference frequency was able to be continuously scanned from 0.1 to 18 GHz by changing the microwave reference frequency. It was also possible to scan the two lasers synchronously keeping the difference frequency constant. This stable and flexible light source would be an ideal light source for optical-optical double resonance (OODR) spectroscopy and resonance laser Raman experiments. For the demonstration, this new system was applied to an OODR experiment using a Rubidium atom. The hyperfine structures in the D2 line were observed in the sub-Doppler condition.