發(fā)布時間：2018-06-02 19:34

  本文選題：8微米 + OPO��； 參考：《哈爾濱工業(yè)大學》2015年碩士論文

【摘要】：8-12μm長波紅外波段位于大氣窗口且對人眼安全,該波段光源在光電對抗、激光醫(yī)療、激光雷達和有毒氣體探測等方面具有重要的應(yīng)用價值。目前,8-12μm波段激光的主要獲取手段是光學參量振蕩和光學參量放大,利用非線性轉(zhuǎn)換將低波長的激光向高波長轉(zhuǎn)換。在常用的非線性頻率轉(zhuǎn)換晶體中,Zn Ge P2晶體憑借極高的有效非線性系數(shù)和良好的機械強度、高熱導率等優(yōu)點,成為獲得8-10μm波段激光首選晶體。由于ZGP晶體光學性質(zhì)的限制,泵浦光的波長需要在2μm以上,而且獲得較高功率的8-10μm波段激光比較困難。本論文的目的是探索級聯(lián)式OPA方法對8μm功率的放大效果以及這種方法是否具有應(yīng)用價值。級聯(lián)光學參量放大(OPA)技術(shù)是通過ZGP光學參量振蕩(OPO)產(chǎn)生的2.8μm信號光對8μm閑頻光進行OPA,根據(jù)泵浦光和種子光偏振方向,OPO和OPA中ZGP晶體的匹配方式只能為一類+二類或二類+一類,本文中采用的是前者。由于這種方法文獻中沒有人報道,所以我們開始需要驗證級聯(lián)OPA方法的可行性。我們利用脈沖能量較大的泵浦光驗證方法的可行性,利用平均功率較高的泵浦光探索影響OPA放大效果的因素。為此,我們搭建了兩套泵浦源系統(tǒng),第一套通過最高輸出重頻1k Hz能量30m J的Ho:YAG激光器泵浦ZGP OPO,獲得了1.23W的8μm和4.34W的2.8μm激光;第二套通過最高輸出重頻16k Hz平均功率110W的Ho:YAG激光器泵浦ZGP OPO,獲得了平均功率3.05W的2.8μm和12.3W的8μm激光。光學參量放大是三波混頻的一種,我們通過求解三波混頻耦合方程組得到了OPA光學參量放大系數(shù)公式,放大系數(shù)和初始泵浦光光強以及ZGP晶體長度有關(guān)。在大能量OPA實驗中,通過分光合束裝置將泵浦光和種子光調(diào)節(jié)重合后,8μm功率由1.23W增益到1.41W,確定了級聯(lián)OPA方法是可行的;在高功率OPA實驗中,驗證了光斑重合程度、光斑大小和泵浦光初始光強因素對OPA放大效果的影響。最后,通過對光學參量振蕩器和分光合束裝置結(jié)構(gòu)進行優(yōu)化,級聯(lián)OPA將8μm平均功率由3.52W放大到4.7W,總放大倍數(shù)為1.34,考慮到分光合束裝置帶來的損耗,OPA放大倍數(shù)為1.42,具備了一定的應(yīng)用價值。
[Abstract]:The 8-12 渭 m long wave infrared band is located in the atmospheric window and is safe to the human eye. The light source in this band has important application value in optoelectronic countermeasure, laser medical treatment, lidar and toxic gas detection and so on. At present, optical parametric oscillation and optical parametric amplification are the main methods of obtaining 8-12 渭 m wavelength laser. The low wavelength laser is converted to high wavelength by nonlinear conversion. In common nonlinear frequency conversion crystals, Zn-Ge-P2 crystal has become the preferred crystal for obtaining 8-10 渭 m laser due to its high effective nonlinear coefficient, good mechanical strength and high thermal conductivity. Due to the limitation of optical properties of ZGP crystal, the wavelength of pump light needs to be more than 2 渭 m, and it is difficult to obtain 8-10 渭 m wavelength laser with high power. The purpose of this thesis is to explore the amplification effect of cascade OPA method for 8 渭 m power and whether this method has application value. The cascade optical parametric amplification (OPA) technique is a 2.8 渭 m signal light generated by ZGP optical parametric oscillation. According to the polarization direction of pump light and seed light, the matching mode of ZGP crystals in OPA can only be a second or a second class. The former is used in this paper. Since this method has not been reported in the literature, we need to verify the feasibility of cascaded OPA method. We use the pump light with high pulse energy to verify the feasibility of the method, and use the pump light with higher average power to explore the factors that affect the amplification of OPA. For this reason, we have set up two pump source systems. The first one is pumped by the Ho:YAG laser with the highest output repetition frequency of 1kHz energy 30mJ, and the 1.23W 8 渭 m and 4.34W 2.8 渭 m laser are obtained. The second set is pumped by a Ho:YAG laser with a maximum output repetition rate of 16 kHz and an average power of 110 W. The average power of the ZGP laser is 2.8 渭 m and 12.3 W, respectively, and the average power is 2.8 渭 m and 12.3 W, respectively. Optical parametric amplification is a kind of three-wave mixing. By solving the coupling equations of three-wave mixing, we obtain the formula of OPA optical parametric magnification factor, which is related to the initial pump light intensity and the length of ZGP crystal. In the OPA experiment of large energy, it is determined that the cascade OPA method is feasible after the pump light and seed light are adjusted and coincident by a photosynthetic beam splitter from 1.23W to 1.41W, and the degree of spot coincidence is verified in the high-power OPA experiment. The effect of spot size and initial intensity of pump light on the amplification of OPA. Finally, by optimizing the structure of optical parametric oscillator and photosynthetic beam splitting device, The average power of 8 渭 m was amplified from 3.52 W to 4.7 W, and the total magnification was 1.34 by cascaded OPA.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN212

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本文編號：1969933