Ultra-stable optical frequency reference at 1.064 /spl mu/m using a C/sub 2/HD molecular overtone transition

Recently we have developed a new frequency modulation technique for detection of weak resonances of molecules located inside a high finesse cavity. We match the FM sideband frequency to the exact splitting of the cavity free spectral range. With this method we are now detecting saturated molecular overtone transitions with very high sensitivities. The resulting excellent signal-noise ratio for these weak but narrow overtone lines has opened the door for realizing high quality optical frequency references in many spectral regions in the visible and near infrared. Here we demonstrate its potential by presenting our recent frequency stabilization result of locking a diode-laser-pumped Nd:YAG laser to the P(5) line of the HCCD (/spl nu//sub 2/+3/spl nu//sub 3/) band at 1064 nm.