Optical frequency fork based on stimulated Raman scattering

In this paper, we reported novel dual-wavelength lasers based on the stimulated Raman scattering (SRS) of multiple crystals. We called them “optical frequency forks” (OFFs) because the frequency interval was fixed and much smaller than the traditional frequency shifting of SRS. Using GdVO4 and BaWO4 crystals as the Raman mediums, and the frequency doubling (532 nm) of a pico-second Nd:YAG laser as the pump source, we obtained four groups of OFFs with the same frequency interval of 42 cm−1 successively, including 558.4 and 559.7 nm, 587.4 and 590.2 nm, 619.5 and 624.4, as well as 508.2 and 507.2 nm. Different with previous dual-wavelength solid-state lasers, here each frequency component (or to say “fork head”) comes from different optical path, so the composed OFFs possess many advantages, including stable, high efficiency, controllable energy ratio of fork heads, and adjustable frequency interval by replacing Raman laser medium. Such OFF is hopeful to find important applications in domains where high quality dual-wavelength lasers are needed, such as generating coherent THz radiation by difference frequency, optical beating, differential absorption, fine spectrum, etc.