Crystal thermal characteristic is a key factor to affect output laser property. In some applications, the facets of crystal will be contaminated by dust in the air, which will enhance the heat absorption of laser and cause local thermal unbalance. Therefore a novel crystal heat dissipation method is proposed in this paper. Crystal is mounted in a specially designed heat sink, heat conducts between the contacting surfaces of crystal and heat sink. Pump incident laser irradiates from the end facet of crystal. The end facet of crystal is cooling by convection heat transfer with flowing protect gas. The experiment device is established, the pump laser is Hydrogen Fluoride laser with the wavelength of 2.8μm, pulse energy of 600mJ, and repetition rate of 50Hz. The crystal is Fe: ZnSe with the dimension of 20mm× 20mm× 6mm. The beam quality is measured in the condition with and without heat sink for comparison, the results indicate that the heat dissipation method proposed in this paper is benefit for improving the beam quality.
An experimental setup of mid-infrared Fe:ZnSe laser operating at room temperature has been established, which was end-pumped by a non-chain pulsed HF laser. The temperature has significant influence on the level lifetime of Fe:ZnSe laser. As the crystal temperature changes from 85 to 295 K, the level lifetime of Fe ions changes from 57 to 0.35 μs, it is important for matching the pump pulse width and the level lifetime. Electronic excitation HF laser with short pulsed width is a good pump source for Fe2+:ZnSe laser at room temperature. For the Fe2+:ZnSe crystal with size of 20×20mm, when the pumping spot diameters is lower than 9.2mm, the phenomenon of transversal parasitic oscillation could been suppressed effectively. At room temperature, the output energy of Fe2+:ZnSe reaches 294mJ, the slope efficiency is about 36%, and the optical to optical efficiency respecting to the pump energy is 34%.
The working mechanism of the non-chain pulsed DF laser is analyzed in this paper, then the glow discharge with the method of UV-preionized discharge is displayed, and finally the experimental investigation on the output characteristics of non-chain pulsed DF laser is done. With SF6, which is non-toxic and non-corrosive, and D2 as the active medium, the dependence of the output characteristics of pulsed DF laser on the gas mixture ratio and the total pressure are investigated. In the experiment, the optimal gas mixture ratio of SF6-D2 and total pressure are 10:1 and 10.5kPa, respectively. At the same time, by making a measurement on the output spectrum of DF laser with a DF laser spectrum analyzer, 17 P-branch transition lines are achieved and the majority of output energy is concentrated on several lines near the 3.876μm line. The laser beam divergence angles in horizontal and vertical directions are 1mrad by using the laser spot ablation method. At the charging voltage of 39kV, under the best working condition(SF6: D2 = 10:1, Ptotal= 10.5kPa), the maximum single pulse output energy of 3.58J, pulse duration of 215ns, peak power of 16.65 MW, and electro-optical conversion efficiency of 2.08%, are obtained.