Efficient tunable LiF:$F_2^-$ crystal lasers

Optimization of the technology of preparation of active elements made of LiF crystals containing $F_2^-$ color centers ensured high values of the parameters of wide-band generation of light by the $F_2^-$ color centers in a nonselective resonator pumped with YAG:Nd$^{3+}$ laser radiation ($\lambda$ = 1.064 $\mu$). The efficiency measured relative to the incident pump energy was 25%, the efficiency of energy absorption was 32%, and the differential efficiency was 50%. The lasing band had a maximum at $\lambda$ =1.17 $\mu$ and the half-width was $\Delta\lambda>1000$ cm$^{-1}$. Stimulated emission of radiation by the $F_2^-$ centers was observed when the pump laser was operated under free-running conditions (smooth pulses) and the efficiency measured relative to the incident pump energy was then 0.5%. An efficient LiF:$F_2^-$ laser with a spectrally narrow ($<0.05$ nm) and continuously tunable (within the 1.09–1.23 $\mu$ range) emission line was constructed. The efficiency at the maximum of the tuning curve ($\lambda$ = 1.17 $\mu$) was 10% measured relative to the incident energy and 12% measured relative to the absorbed energy; the differential efficiency was 23%. The operating temperature of the active elements of the laser was the room value and the repetition frequency of the output pulses was up to 100 Hz.