| The DF laser radiation is concentrated in the spectral range3.5～4.1μm(“transparency window” of atmosphere), which is a useful medium waves infraredlaser badly needed in laser radar, laser spectroscopy, laser interaction with matter,etc. Arounding repetitive frequency DF laser, the study was focused on keytechnologies of massive uniform discharge, optical resonator, repetition ratesoperation, tail gas treatment, etc. On this basises, the measurement of gaincoefficient, analysis of spectral character and optimizing experiments of outputperformance had been done, which could lay a foundation for practical design ofnon-chain DF laser.The circuit parameters of spark pin UV pre-ionization discharge non-chainpulsed DF laser (LC reverse circuit) were researched to realize the massive uniformglow discharge. Mathematical model had been established to describe its dischargeparameters using continuity-equations of electrons and Kirchhoff equations. Thenthe corresponding experiments were carried out to verify the results of this modeland the optimal circuit parameters of DF laser were obtained on theory. To obtain abigger gap glow discharge, the self-initiated volume discharge (SIVD) was imported,which realized the massive uniform glow discharge without preionization by using a voltage-doubling circuit and roughened cathode. A mathematical model wasestablished to describe the discharge parameters of this circuit. Both the experimentand calculation showed that it was easy to realize massive uniform glow dischargewith SIVD.The parameters of resonator have marked influences on output performancesand anti-misalignment of mirrors.The dependence of some parameters on curvatureradius of rear mirror had been analyzed, such as beam width, beam divergence angle,misalignment sensitivity, effective mode volume, and then the optimum curvatureradius of rear mirror was obtained. Three groups of unstable confocal cavityparameters had been designed and their characteristics of misalignment wereanalyzed. The laser spots of stable and unstable cavities had been measured usingthe method of laser ablation, the beam divergence angle of which were6mrad and1.2mrad respectively.When DF laser works at closed cycle, its working life of single gas-filled wasvery short. Consumptions of working gas and deexcite collisions of dischargingproducts were major factors for output energy lowers of DF laser. A technicalscheme which could realize real-time refresh of working gas had been introducedand feasibility study for chemical scrubber adsorbing DF molecular, which deexciteeffect was the most significant in the discharging products, had been done. Using therefresh equipment of working gas and chemical scrubber could increase workingstabilization of DF laser. Through analyzing the chemical processes which wereoccured in discharge area of DF laser, we found that the harmful ingredient in tailgas were DF and SF4. The principle of alkaline solution removing DF and SF4wasanalyzed, and miniaturized tail gas processing equipment was designed. The tail gascould meet national safety effluent standard after treating.Based on the influence of spectral lines broadening on gain coefficient, thealgorithm which was used to calculate gain coefficient of DF laser had been deducedusing the variable output coupling method. Gain distribution on the cross-section ofgain medium was researched on experimentally using this algorithm. The DF laser spectrum analyzer was used to measure the output spectrum of DF laser, and22lines were obtained in the spectial range:3.5～4.1μm. Working gas parameters wereoptimized for non-chain DF laser. The total pressure and optimum ratio of themixture gas (SF6-D2)，are8.1kPa and8:1，respectively. The maximum single pulseenergy of3.6J, pulse width of135ns, peak power of26.67MW and electro-opticalconversion efficiency of3.1%are achieved. The maximum average power of150Wand electro-optical conversion efficiency of2.58%are achieved at50Hz, whoseamplitude difference of laser pulses is less than8%. |
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