Continuous-wave laser utilizing $F_2^-$ centers in an LiF crystal

Continuous lasing in $F_2^-$ centers in a crystal of LiF was observed in the 1.14–1.2 $\mu$ range. At room temperature the output power was 70 mW when the crystal was pumped with a cw YAG:Nd$^{3+}$ laser ($\lambda$ = 1.06 $\mu$) of 9 W power. The possibility of increasing the efficiency of the color-center laser was analyzed. At a high pulse repetition frequency the average output power was 120 mW. In this case a $Q$-switched YAG:Nd$^{3+}$ laser was employed (the pulse repetition frequency was 50 kHz, the pulse duration was 1 $\mu$ sec, and the pump pulse power was 70 W). The $Q$ factor was modulated by a passive switch whose operation also depended on $F_2^-$ centers in an LiF crystal.