Physical and technological aspects of compact He-Ne/CH4 optical frequency standards of highest performance

The new generation of transportable He-Ne/CH 4 ((lambda) equals 3.39 micrometer) optical frequency standards (TOFS) stabilized over resolved magnetic hyperfine structure (MHFS) and recoil doublet of F 2 (2 ) methane line is considered. The main limitations of the performance of present devices are caused by the residual first order Doppler effect manifestation. Several physical and technological improvements are in progress for reaching the level of 10 -13 - 10 -14 in frequency reproducibility/repeatability, while a relative frequency stability may exceed the stability of H-maser at averaging times (10 -3 - 10 4 ) s. In combination with 'fs-comb generators' the compact and precise He-Ne/CH 4 standards will be able to transfer their excellent short and middle term stability (10 -14 per sec now, 10 -15 per sec in near future) to the desired range of spectrum. In such a way they can play a role of narrow spectrum interrogative oscillators for super accurate frequency standards based on laser cooled atoms/ions or can be used as one of the optical references for fs-comb optical synthesizers.