Abstract

An declination in efficiency of Cr:Mg2SiO4 laser was observed as chromium concentration increased, which was explained by the presence of inefficient absorption in lasing wavelength range. This absorption obviously appeared in the crystals grown under oxygen partial pressure less than 10⁻⁸ atm. was attributed to divalent chromium ion substituted in Mg site. Divalent chromium ions, which have two absorption peaks at 860nm and 1800 nm that corresponds to 5E-5T2 and 5E-3T1 transition respectively, are easily oxidized to trivalent state by annealing in the atmosphere of high oxygen partial pressure. By annealing, divalent chromium ions decreased and tetravalent chromium ions in Si site increased. At the same time, figure of merit increased as much as two times than that of non-annealed crystals.

© 1991 Optical Society of America