ABSOLUTE FREQUENCY MEASUREMENTS WITH A SET OF TRANSPORTABLE HE-NE/CH4 OPTICAL FREQUENCY STANDARDS AND PROSPECTS FOR FUTURE DESIGN AND APPLICATIONS

Abstract

The accumulated results of absolute frequency measurements (AFM) carried out in 1997-2000 with transportable double-mode He-Ne/CH4 optical frequency standards ( =3.39µm) in a collaboration of several laboratories are presented. The performance of this secondary optical frequency standard is estimated on a level of 10 -13 (in repeatability), and 1 x 10 -14/S (in stability). The next steps towards He-Ne/CH4 standards with one order of magnitude better performance, including devices based on monolithic zerodur resonators, are discussed. Important applications of transportable He-Ne/CH4 optical frequency standards have appeared now due to dramatic progress in the field of optical frequency measurements. Used to stabilze the repetition rate of a Ti:Sa fs laser, these compact secondary standards can transfer their performance into a whole optical range covered by a fs comb. Thus they can play the role of a narrow spectrum interrogative oscillator for super-accurate optical or microwave frequency standards substituting in some tasks a H-maser or oscilliators based on cryogenic sapphire resonators.