Optical frequency comb at NIM

Absolute measurement of stabilized lasers´ optical frequency is an important subject in metrology. The traditional tool for establishing the llnk between Cs atomic frequency standard and an optical frequency is harmonic frequency chain [´I. But, such a harmonic frequency chain is very expensive to built and complicated to operate. Only few national metrology institutes have built these systems. For a country without such facility, such a5 in China, the international comparison of stabilized lasers is the only method to realize this link indirectly. The introduction of optical fkequency comb technique greatly simplifies this work, and a frequency comb system can be used for the routine frequency measurement of many stabilized lasers ranging from visible to infrared r2J [31. Therefore, optical frequency comb system will become an indispensable metrological tool.