Spectroscopic data on the absorption and the fluorescence spectra and fluorescence lifetimes are presented for Cr<sup>4+</sup>:Y<sub>2</sub>SiO<sub>5</sub>, the newest Cr<sup>4+</sup>-doped laser crystal. The fluorescence measurements were conducted at temperatures ranging from 10 to 310 K, and the absorption spectra were measured at room temperature and 77 K. Spectroscopic analysis of the absorption and the emission spectra is performed on the basis of a distorted tetra-hedral symmetry for the Cr<sup>4+</sup> site, namely <i>C</i><sub>3<i>v</i></sub>. The tetravalent chromium substitutes for Si<sub>4+</sub> in this crystal, and there is no evidence for the presence of chromium in any other valence state. The Cr<sup>4+</sup> site is characterized by strong crystal field parameters. We have tentatively assigned the sharp line at 1146 nm in the low-temperature fluorescence spectrum (excited by 1064-nm radiation) to the spin-forbidden singlet-to-triplet transition <sup>1</sup>E-<sup>3</sup>A<sub>2</sub>, and the broad band with the peak at 1225 nm to the spin-allowed <sup>3</sup><i>T</i><sub>2</sub>-<sup>3</sup><i>A</i><sub>2</sub> transition. Excitation at 532 nm results in an additional type of emission in the near infrared. A similar dependence of the lasing wavelength on the pump wavelength was observed in the laser operation of the crystal at 77 K [Chai <i>et al.</i>, in <i>Advanced Solid-State Lasers</i>, L. L. Chase and A. A. Pinto, eds., Vol. 13 of OSA Proceedings Series (Optical Society of America, Washington, D.C., 1992), pp. 28–30].
© 1993 Optical Society of America
C. Deka, M. Bass, B. H. T. Chai, and Y. Shimony, "Optical spectroscopy of Cr4+:Y2SiO5," J. Opt. Soc. Am. B 10, 1499-1507 (1993)