Variation of the absorption spectra of forsterite laser crystals with active Cr ~(3+) and Cr ~(4+) ions under the action of a beam of high-energy electrons

摘要

This paper discusses the variation of the absorption spectra of single crystals of forsterite Mg _2SiO _4 as a result of irradiation with an beam of electrons with energy 21 MeV. The irradiation causes additional absorption to appear in the crystals in the form of a broad band in the 350-800-nm region, with its maximum in the 430-nm region (Ekc). The additional absorption intensity is usually substantially higher in crystals grown in an oxidizing atmosphere than in crystals grown in a neutral atmosphere, with the exception of crystals strongly doped with chromium, for which the value of the additional absorption is virtually independent of the oxidative potential of the growth atmosphere. When crystals of chromium-containing forsterite grown in an oxidizing atmosphere are codoped with lithium, one additional intense polarized band appears in the absorption spectrum, with a polarization-dependent maximum close to 375 nm (Eb) or 400 nm (Ec).