本文選題：橢圓偏振 + 高斯脈沖�。� 參考：《西安工業(yè)大學(xué)》2015年碩士論文

【摘要】：激光在大氣環(huán)境中的傳輸特性問題對于激光測距、激光雷達(dá)、激光武器、衛(wèi)星遙感等實際應(yīng)用領(lǐng)域的研究工作具有重要意義。受湍流的影響,大氣折射率的隨機擾動引起光束波前畸變,從而產(chǎn)生閃爍、光斑漂移和光束擴展等湍流效應(yīng),這些現(xiàn)象將會嚴(yán)重影響外場光電系統(tǒng)的正常工作。偏振激光在波束控制上與其它波束相比具有更高的自由度,應(yīng)用范圍廣,目標(biāo)識別能力和抗干擾能力較強以及較低的誤碼率等優(yōu)點。本文以偏振激光脈沖波束為例,研究了激光波束在湍流大氣中傳輸時,波束的脈沖展寬、光束擴展和退偏特性。論文的研究成果如下：第一,以橢圓偏振高斯脈沖波束為例,研究了該波束在斜程湍流大氣中的脈沖展寬特性。基于廣義的Huygens-Fresnel原理,結(jié)合雙頻互相干函數(shù)以及Rytov微擾法,推導(dǎo)出橢圓偏振高斯脈沖波束通過斜程湍流大氣時接收機處的平均光強和脈沖展寬的表達(dá)式,數(shù)值計算結(jié)果表明：橢圓偏振高斯脈沖波束在斜程湍流大氣中的脈沖展寬取決于天頂角η和接收機高度H,內(nèi)尺度因子β對脈沖展寬的影響不大。第二,以橢圓偏振高斯脈沖波束為例,推導(dǎo)出該波束通過斜程湍流大氣時在接收機處波束有效擴展半徑的表達(dá)式,研究了該波束的光束擴展特性。數(shù)值計算結(jié)果表明：橢圓偏振高斯脈沖波束在斜程湍流大氣中的光束擴展主要與脈沖激光的初始束腰半徑W0、激光波長λ和偏振角φ有關(guān),隨著傳輸距離L的增大波束的有效擴展半徑w(L)隨著w0的增大而減小,隨著λ的增大而增大,而且φ越大波束的w(L)也越大。第三,以橢圓偏振部分空間相干部分光譜相干電磁高斯-謝爾模型脈沖波束(EGSMP)為例,基于隨機電磁波束的相干偏振理論和廣義Huygens-Fresnel原理,結(jié)合Rytov' s相位結(jié)構(gòu)函數(shù)的二次近似和廣義斯托克斯(Stokes)參量,推導(dǎo)出斜程湍流大氣中傳輸時橢圓偏振部分空間相干部分光譜相干EGSMP波束在接收平面處的電磁交叉譜密度函數(shù)(CSDF)矩陣元和交叉偏振度的表達(dá)式。最后對比分析了湍流強度、波束的初始脈沖寬度、波束束寬、波束的空間相干長度和時間相干長度等對橢圓偏振波束和部分偏振波束的退偏特性影響。結(jié)果表明：湍流強度、波束的初始脈沖寬度、波束束寬、波束的空間相干長度和時間相干長度等對橢圓偏振波束的退偏特性影響較大,而對部分偏振波束的退偏特性影響較小。本文的研究結(jié)果將對改善激光工作系統(tǒng)在湍流大氣中傳輸時的使用性能奠定了堅實的理論基礎(chǔ)。
[Abstract]:The problem of laser propagation characteristics in atmospheric environment is of great significance to the research of laser ranging, laser radar, laser weapons, satellite remote sensing and other practical applications. Under the influence of turbulence, the random perturbation of atmospheric refractive index causes beam wavefront distortion, resulting in turbulence effects such as scintillation, spot drift and beam propagation. These phenomena will seriously affect the normal operation of the external field optoelectronic system. Polarization laser has higher degree of freedom, wider application range, stronger ability of target recognition and anti-jamming and lower bit error rate than other beams in beam control. Taking the polarized laser pulse beam as an example, the pulse broadening, beam propagation and depolarization characteristics of the laser beam propagating in turbulent atmosphere are studied in this paper. The research results are as follows: firstly, the pulse broadening characteristics of the elliptically polarized Gao Si pulse beam in sloping turbulent atmosphere are studied. Based on the generalized Huygens-Fresnel principle, the expressions of the average light intensity and pulse broadening at the receiver when the elliptical polarized Gao Si pulse beam passes through the oblique turbulent atmosphere are derived by combining the dual frequency cross-correlation function and the Rytov perturbation method. The numerical results show that the pulse broadening of elliptically polarized Gao Si pulse beam in slanted turbulent atmosphere depends on the zenith angle 畏 and receiver height H, and the internal scale factor 尾 has little effect on the pulse broadening. Secondly, taking the elliptically polarized Gao Si pulse beam as an example, the effective propagation radius of the beam at the receiver is derived, and the beam propagation characteristics of the beam are studied. The numerical results show that the beam propagation of elliptically polarized Gao Si pulse beam in oblique turbulent atmosphere is mainly related to the initial beam waist radius W0, the wavelength 位 and the polarization angle 蠁 of the pulsed laser. With the increase of the transmission distance L, the effective spreading radius (WL) of the beam decreases with the increase of w0 and increases with the increase of 位, and the larger the beam is, the larger the WL) of the beam is. Thirdly, taking the elliptically polarized partially spatially coherent partially coherent electromagnetic Gaussian Schell model as an example, the coherent polarization theory of random electromagnetic beam and the generalized Huygens-Fresnel principle are used as an example. Combined with the quadratic approximation of Rytovs phase structure function and the generalized Stokes Stokes parameter, The expressions of electromagnetic cross-spectral density function (EGSMP) matrix elements and degree of cross-polarization of elliptical partially coherent partially spectral coherent EGSMP beams at the receiving plane during propagation in slanted turbulent atmosphere are derived. Finally, the effects of turbulence intensity, the initial pulse width of the beam, the beam width, the spatial coherence length and the time coherent length of the beam on the depolarization characteristics of elliptical and partially polarized beams are compared and analyzed. The results show that the turbulence intensity, the initial pulse width of the beam, the beam width, the spatial coherence length of the beam and the time coherent length of the beam have great influence on the depolarization characteristics of elliptical polarization beam, but have little effect on the depolarization characteristic of partially polarized beam. The results of this paper will lay a solid theoretical foundation for improving the performance of laser operating system in turbulent atmosphere.
【學(xué)位授予單位】：西安工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN24

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