The technology of volume Bragg gratings (VBGs) recorded in photo-thermo-refractive glass allows considerable narrowing of the linewidth of laser diodes from a couple of nanometers to tens of picometeres. Such narrowband systems with GHz-wide emission spectra found broad applications for Diode Pumped Alkali vapor Lasers, optically pumped rare gas metastable lasers, Spin Exchange Optical Pumping, atom cooling, wide area Raman spectroscopy, etc.
In addition to high lasing power, these applications require a very precise emission wavelength with extremely narrow linewidth, and the wavelength tunability to match an absorption line width of a particular alkali metal. For example, for Rb (794.7 nm) the linewidth dependence on pressure caused by interaction with 3He and N2 gases in the cell is on the order of 20 GHz/atm. Thus, the requirements for the pump laser systems become stricter since it requires not only narrow line but also the ability to tune the linewidth to match an absorption linewidth.
In this paper, we present the results of development of a new generation of narrowband laser systems. The compact design, capability of simultaneous emission of several narrowband emission lines (e.g. for Rb/Cs or Rb/K gas systems), wavelength and linewidth tunability, high signal to noise ratio (>30 dB) makes the new system suitable for SEOP and other ultra-narrow linewidth demanding applications.