When light encounters molecules in the air, the predominant mode of scattering is elastic scattering, called Rayleigh scattering. This scattering is responsible for the blue color of the sky; it increases with the fourth power of the frequency and is more effective at short wavelengths. It is also possible for the incident photons to interact with the molecules in such a way that energy is either gained or lost so that the scattered photons are shifted in frequency. Such inelastic scattering is called Raman scattering.
      New reliable preferably all solid-state sources of laser radiation in up-to-now uncovered spectral regions are highly desirable due to the growing number of applications of suchdevices in medicine, spectroscopy, defense, and research in general. Stimulated Raman scattering (SRS) in solid state crystals has been recently more widely employed for laser radiation frequency conversion. Use of solid state SRS converters is advantageous due tohigh conversion efficiency, no phase matching necessity, and easier handling comparing togaseous and liquid Raman cells. Among the most efficient known Raman crystals belong Ba(NO3)2 and KGd(WO4)2. New Raman-active crystal - BaWO4 - was recently predicted to be a promising Raman material suitable for a wide range of pumping pulse durationfrom picoseconds to nanoseconds.

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