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The temperature and pressure dependence of the photoluminescence from ZnS:Mn 2ϩ , ZnS:Cu 2ϩ , and ZnS:Eu 2ϩ nanocrystals were investigated in the temperature range from 10 to 300 K and under hydrostatic pressure up to 6 GPa at room temperature. The orange emission ͑590 nm͒ from the 4 T 1-6 A 1 transition of Mn 2ϩ ions, the green emission ͑518 nm͒ from the 4 f 6 5d 1-4 f 7 transition of Eu 2ϩ ions and the blue emission ͑460 nm͒ related to the transition from the conduction band of ZnS to the t 2 level of Cu 2ϩ ions were observed in the Mn-, Eu-, and Cu-doped samples, respectively. It was found that all of these emission bands decrease in intensity with increasing temperature. Among them the intensity of the Mn-orange emission dropped faster. The activation energies were estimated to be 58, 16, and 42 meV for the Mn-orange, Eu-green, and Cu-blue emissions, respectively. A negative pressure coefficient of Ϫ26 meV/GPa was obtained for the Mn-orange emission, which agrees with the value calculated from the crystal field theory. The pressure coefficient of the Cu-blue emission was found to be 62 meV/GPa, which is almost same as the value of the band gap of bulk ZnS. However, the pressure coefficient of the Eu-green emission is 23 meV/GPa, which is contrary to the predication by the crystal field theory. The strong interaction between the 4 f 6 5d 1 state of the Eu 2ϩ ions and the conduction band of ZnS may be the origin for the positive pressure coefficient and the small thermal activation energy of Eu-green emission.

We demonstrate a 966 nm laser diode (LD) side-pumped Er,Pr:GYSGG laser crystal operated at 2.79 μm under a high repetition rate. The lifetimes of the upper level I4 and lower level I4 are 0.66 and 0.85 ms, respectively. The laser performance under different repetition rates and pulse widths is experimentally studied with the optimal cavity structure. A maximum output power of 8.86 W is achieved at 125 Hz and 200 μs pulse widths, corresponding to the slope efficiency of 14.8% and electrical-to-optical efficiency of 7.7%. With increasing frequency from 50 to 200 Hz, the slope efficiency varies from 24.7% to 11.7% operated at a 125 μs pulse width. Moreover, the Mx2/My2 factors of 7.52/7.59 and Θ/Θ far-field divergences of 16.1/16.5 mrad are also measured. The results indicate that a high-performance 2.79 μm laser could be realized on the Er,Pr:GYSGG radiation resistant crystal by deactivation and LD side-pumping.

We demonstrate the growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level (4)I(11/2) and lower laser level (4)I(13/2) are 0.59 and 0.84 ms, respectively, which are due to the doping of the Pr(3+) ions. A maximum pulse energy of 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with a flash lamp, which corresponds to the electrical-to-optical efficiency of 0.6% and a slope efficiency of 0.7%. A maximum average power of 2.9 W at 60 Hz is achieved, which corresponds to the electrical-to-optical efficiency of 0.4% and slope efficiency of 0.8%. Compared with a Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at a higher pulse repetition rate. These results suggest that doping deactivator Pr(3+) ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation resistance and high repetition frequency.