發(fā)布時(shí)間：2018-03-05 18:22

  本文選題：激光器　切入點(diǎn)：腔鏡　出處：《國(guó)防科學(xué)技術(shù)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：本文以高能激光器中常用的正支虛共焦非穩(wěn)腔為研究對(duì)象,討論分析了激光輻照下腔鏡熱變形對(duì)光場(chǎng)模式的影響,研究結(jié)果可以為長(zhǎng)時(shí)間工作條件下高能激光器諧振腔輸出光束特性分析及后續(xù)光束控制提供一定指導(dǎo)意義。論文主要研究?jī)?nèi)容有:基于角譜傳播法的諧振腔光場(chǎng)模式分析,激光輻照下腔鏡熱變形的計(jì)算,腔鏡熱變形對(duì)光場(chǎng)模式的影響研究,不同光束對(duì)發(fā)射系統(tǒng)聚焦距離的影響研究等,主要研究?jī)?nèi)容如下:1.建立了基于角譜傳輸法的諧振腔光場(chǎng)模式的計(jì)算模型,采用腔鏡光闌邊緣“軟化”處理、有源腔內(nèi)增益薄層分布等方法,實(shí)現(xiàn)了光場(chǎng)模式的數(shù)值計(jì)算。完成了基于MATLAB的諧振腔光場(chǎng)模式計(jì)算程序編寫,計(jì)算了正支非穩(wěn)無(wú)源腔的光場(chǎng)模式,將計(jì)算結(jié)果與文獻(xiàn)報(bào)道對(duì)比,驗(yàn)證了計(jì)算程序的正確性。分析計(jì)算了三種有源腔的光場(chǎng)模式,計(jì)算結(jié)果表明,光場(chǎng)振幅分布與腔內(nèi)小信號(hào)增益的分布有關(guān),小信號(hào)增益分布不含相位擾動(dòng)時(shí),相位分布主要由諧振腔結(jié)構(gòu)決定,輸出波面近似平面。2.開展了激光輻照下腔鏡溫升和熱變形的分析研究,在腔鏡熱變形控制方程及有限元分析方程的基礎(chǔ)上,完成了基于ANSYS軟件的命令流控制程序編寫,實(shí)現(xiàn)了溫升和變形的數(shù)值計(jì)算,計(jì)算結(jié)果表明,腔鏡溫升和變形隨激光功率和輻照時(shí)間增加而增加,正支非穩(wěn)高能激光諧振腔中,次鏡溫升與變形大于主鏡,較大的腔鏡熱變形對(duì)激光器輸出光場(chǎng)存在影響。3.采用時(shí)間離散化、光場(chǎng)模式與腔鏡變形序列耦合等方法,研究了出光時(shí)長(zhǎng)較長(zhǎng)時(shí)腔鏡熱變形對(duì)光場(chǎng)模式的影響,計(jì)算了出光4s時(shí)諧振腔輸出光場(chǎng)的振幅分布、相位分布及對(duì)應(yīng)的遠(yuǎn)場(chǎng)光斑。計(jì)算結(jié)果表明,出光過(guò)程中,腔鏡熱變形導(dǎo)致激光器輸出光場(chǎng)發(fā)生變化,波面逐漸發(fā)散,文中計(jì)算條件下,由出光初始時(shí)刻的近似平面變?yōu)槌龉饨Y(jié)束時(shí)刻的近似發(fā)散球面,其遠(yuǎn)場(chǎng)光斑在y方向分裂為上下兩個(gè)光斑。試驗(yàn)驗(yàn)證了腔鏡熱變形對(duì)激光器輸出光場(chǎng)的影響,討論分析了采取腔鏡背面冷卻措施時(shí)的溫升、變形及對(duì)光場(chǎng)的影響。4.解析推導(dǎo)了激光發(fā)射光學(xué)系統(tǒng)發(fā)射平面波、球面波、高斯光束時(shí)的聚焦距離與調(diào)焦量的關(guān)系,計(jì)算了激光發(fā)射光學(xué)系統(tǒng)發(fā)射平面波、球面波、高斯光束時(shí)的聚焦距離。結(jié)果表明:望遠(yuǎn)鏡相同的調(diào)焦量下,球面波的聚焦位置、平面波的聚焦位置與高斯光束的束腰位置存在偏差,可通過(guò)增加高斯光束的束腰寬度、增大發(fā)射系統(tǒng)的擴(kuò)束比等方法,減小高斯光束與平面波的聚焦距離差,可通過(guò)增大球面波的曲率半徑,減小球面波與平面波的聚焦距離差;當(dāng)要求聚焦距離一致時(shí),需根據(jù)發(fā)射光束特征,對(duì)望遠(yuǎn)鏡的調(diào)焦量進(jìn)行調(diào)整,如果按照平面波的方法對(duì)球面波進(jìn)行聚焦發(fā)射,聚焦位置必定偏離預(yù)定位置。
[Abstract]:In this paper, the influence of the thermal deformation of the mirror on the mode of optical field is discussed and analyzed, which is commonly used in high energy laser, and the positive branch and virtual confocal unstable resonator is used as the research object. The results can provide some guidance for the analysis of the output beam characteristics of the high energy laser resonator and the subsequent beam control under the condition of long time operation. The main contents of this paper are as follows: the optical field mode analysis of the resonator based on the angular spectrum propagation method. The calculation of the thermal deformation of the mirror under laser irradiation, the study of the influence of the thermal deformation of the mirror on the mode of the light field, the study of the influence of different beams on the focusing distance of the emission system, etc. The main research contents are as follows: 1. The calculation model of optical field model of resonant cavity based on angular spectrum transmission method is established. The method of "softening" the edge of the mirror diaphragm and the distribution of gain thin layer in the active cavity are adopted. The numerical calculation of the optical field mode is realized, and the calculation program of the optical field mode of the resonator cavity based on MATLAB is completed, and the optical field mode of the positively supported unstable passive cavity is calculated. The calculated results are compared with those reported in the literature. The calculation results show that the amplitude distribution of the optical field is related to the distribution of the small signal gain in the cavity, and the small signal gain distribution does not contain phase perturbation. The phase distribution is mainly determined by the structure of the resonator, and the output wave surface is approximately plane. 2. The temperature rise and thermal deformation of the mirror under laser irradiation are analyzed and studied. Based on the governing equation of the thermal deformation of the mirror and the finite element analysis equation, The command flow control program based on ANSYS software is completed, and the numerical calculation of temperature rise and deformation is realized. The results show that the temperature rise and deformation increase with the increase of laser power and irradiation time. The temperature rise and deformation of the secondary mirror are larger than that of the primary mirror, and the larger thermal deformation of the mirror affects the output light field of the laser. 3. The method of time discretization and coupling of the light field mode with the mirror deformation sequence is adopted. The influence of the thermal deformation of the mirror on the mode of the light field is studied when the time is long. The amplitude distribution, the phase distribution and the corresponding far field spot of the output light field of the resonator are calculated when the output light is 4 s. The calculation results show that, in the process of light output, the distribution of the amplitude, the phase distribution and the corresponding far field spot are calculated. The thermal deformation of the mirror causes the laser output light field to change, and the wave surface gradually diverges. In this paper, the approximate plane at the initial time of the light is changed into the approximate divergent sphere at the end of the light. The far-field spot splits into two spots in the y direction. The effect of the thermal deformation of the mirror on the output light field of the laser is verified by experiments, and the temperature rise is discussed and analyzed when the cooling measures on the back of the mirror are taken. The relationship between the focusing distance of laser emitting optical system and the focusing quantity of Gao Si beam is derived analytically, and the plane wave and spherical wave emitted by laser emitting optical system are calculated. The results show that the focusing position of spherical wave and plane wave are different from those of Gao Si beam under the same focusing range of telescope, which can be increased by increasing the waist width of Gao Si beam. By increasing the beam expansion ratio and decreasing the focusing distance difference between Gao Si beam and plane wave, the focusing distance difference between spherical wave and plane wave can be reduced by increasing the curvature radius of spherical wave, and when the focusing distance is the same, The focusing quantity of the telescope should be adjusted according to the characteristics of the emitting beam. If the spherical wave is focused according to the plane wave method, the focusing position must deviate from the predetermined position.
【學(xué)位授予單位】：國(guó)防科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN248

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