Ultraviolet-Induced Transient and Stable Color Centers in Self-Q-Switching Laser Glass

The optical absorption spectrum of ultraviolet‐ (uv‐) induced room‐temperature stable color centers and the uv spectrum for their generation in a laser self‐Q‐switching glass were obtained. The optical absorption spectrum is similar to that for x‐ray‐irradiated silicate glasses of simpler composition. The uv generation spectrum was found to consist of a narrow Gaussian line of width 2250 cm⁻¹ with peak at 45 800 cm⁻¹. The optical absorption spectrum of the uv‐induced transient color centers was also obtained and appears to consist of the superposition of a broad asymmetric absorption band peaked near 740 nm and a Gaussian‐shaped annihilation band peaked near 674 nm. The lifetime of the 740‐nm band was found to be about 200 msec and that of the 674‐nm band about 400 msec. The 740‐nm transient absorption band is identified with the $E_{\text{1,2}}^{-}$ band which Mackey, Smith, and Halperin attribute to a trapped electron polaron. The line shape of this transient absorption is interpreted in terms of a large‐polaron strong‐coupling model from which various properties are inferred. The transient annihilation band at 674 nm is identified with the temporary bleaching of a room‐temperature stable trapped‐hole center. A model is suggested for the production of both stable and transient color centers.