| With the request of high-power coherent light source in middle-infrared wavebands in the area of photoelectric confrontation, DF lasers have been paid more andmore attentions. DF lasers, which have an output wave bands ranging from3.5-4.2μmand the central wave length of3.8μm, locate in the middle-infrared wave bands thatare in an urgent need for military aspect. Generally, DF lasers can be divided into twoworking categories: chained and unchained. The chained DF lasers are with a largestructure, simple explosion of working gas and difficult maintenance, though a highpower output. However, unchained pulsed DF lasers, available to avoid thedisadvantages of explosion and decay during continuous wave operations, have asmall volume and are manipulated simply, with high average power and peak power.The research work in this dissertation is about developing a novel kind of pulsedDF laser mainframe and then analyzing the properties of output laser by the developedmainframe. The pulsed DF laser mainly consists of a vacuum system, a gas cycliccooling system, an optical resonator system, and a main support. The gas cycliccooling system has the components of fans, heat exchanger, flow passage, andmolecular sieve. After changing the structures and positions of the pipelines, theoff-centric fans which are special for fast axial flow lasers are successfully applied onDF transverse flow laser. The two units of fans provide the driving force for the gas cyclic flowing by parallel-connected way. In this paper, the flat-concave stable cavityis applied to the optical resonator. Total-reflecting mirror is a spherical mirror whileoutput mirror is a flat mirror. The resonator modulates the directions of optical axesthrough a multi-orientation structural adjustment. The molecular sieve has thefunction of absorbing excited species extinctions generated by working process tomaintain the stable output of lasers.In order to ensure the steady operation of laser, the finite element method is usedto study the static properties of the whole mechanism and then optimize themechanism to obtain an improvement. After optimized, the mechanism whosemaximum deformation is reduced from2.34mm to1.67mm has a smaller entiredeformation than before. The maximum stress is reduced from296MPa to193MPa todecrease the stress concentration phenomena. It can conclude that the strength andstiffness of the whole mechanism meet working requirements. Then, in order toensure the uniformity of gas discharge in discharge chamber and achieve the steadyoutput of laser, the principle of computational fluid dynamics is employed tonumerically analyze the motion states of gas in flow field. The analyses include thepressure loss in gas flowing process, flowing velocities of discharged areas, anduniform distribution, and so on. Furthermore, the flow passage is optimized as to animprovement in accordance with its influential factors. After optimized, by pitot tubes,the measured flowing velocity of discharged areas is up to16.3m/s. The maximumnon-uniformity of longitudinal flowing velocity distribution is up to7.1%while thelateral4.3%. Both of the tested results can satisfy the working requirements for lasersteady output.Experiments of single pulse and repetition discharging are carried out with thedeveloped pulsed DF laser mainframe. From experimental results, in the workingpressure of8.1KPa, when the proportion between gases is SF6:D2=8:1, output energyof single pulsed laser reaches to3.6J. Also, when the repeat frequency is50Hz, theaverage power reaches to150W. |
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