Hydrogen Raman laser for efficient coherent summation of nanosecond optical pulses

An efficient Raman laser utilizing stimulated Raman scattering by rotational levels in gaseous hydrogen was built and investigated. Coherent summation of 50 neodymium laser beams into a single spatially coherent optical beam at the frequency of the first Stokes component ν_s = 8856 cm^–1 was achieved with an efficiency of 70% under conditions of saturated amplification of an external signal in the Raman amplifier.