The National Metrology Institute of Japan (NMIJ) at the National Institute of Advanced Industrial Science and Technology (AIST) is investigating a continuous-wave optical frequency synthesizer by using a femtosecond mode-locked laser and a continuous-wave optical parametric oscillator (OPO). The frequency of the optical output is synthesized from an accurate microwave frequency generated by an atomic clock.

We succeeded in phase locking an OPO to an optical frequency comb generated by a femtosecond mode-locked laser in the 830nm region. We expect this synthesizer to become an important tool for optical frequency measurement, accurate spectroscopy, high-density wavelength division multiplexing and optical frequency standardization.