湍流大气中偏振激光脉冲波束传输特性

发布时间：2018-04-27 09:17

本文选题：椭圆偏振 + 高斯脉冲　；参考：《西安工业大学》2015年硕士论文

【摘要】：激光在大气环境中的传输特性问题对于激光测距、激光雷达、激光武器、卫星遥感等实际应用领域的研究工作具有重要意义。受湍流的影响,大气折射率的随机扰动引起光束波前畸变,从而产生闪烁、光斑漂移和光束扩展等湍流效应,这些现象将会严重影响外场光电系统的正常工作。偏振激光在波束控制上与其它波束相比具有更高的自由度,应用范围广,目标识别能力和抗干扰能力较强以及较低的误码率等优点。本文以偏振激光脉冲波束为例,研究了激光波束在湍流大气中传输时,波束的脉冲展宽、光束扩展和退偏特性。论文的研究成果如下：第一,以椭圆偏振高斯脉冲波束为例,研究了该波束在斜程湍流大气中的脉冲展宽特性。基于广义的Huygens-Fresnel原理,结合双频互相干函数以及Rytov微扰法,推导出椭圆偏振高斯脉冲波束通过斜程湍流大气时接收机处的平均光强和脉冲展宽的表达式,数值计算结果表明：椭圆偏振高斯脉冲波束在斜程湍流大气中的脉冲展宽取决于天顶角η和接收机高度H,内尺度因子β对脉冲展宽的影响不大。第二,以椭圆偏振高斯脉冲波束为例,推导出该波束通过斜程湍流大气时在接收机处波束有效扩展半径的表达式,研究了该波束的光束扩展特性。数值计算结果表明：椭圆偏振高斯脉冲波束在斜程湍流大气中的光束扩展主要与脉冲激光的初始束腰半径W0、激光波长λ和偏振角φ有关,随着传输距离L的增大波束的有效扩展半径w(L)随着w0的增大而减小,随着λ的增大而增大,而且φ越大波束的w(L)也越大。第三,以椭圆偏振部分空间相干部分光谱相干电磁高斯-谢尔模型脉冲波束(EGSMP)为例,基于随机电磁波束的相干偏振理论和广义Huygens-Fresnel原理,结合Rytov' s相位结构函数的二次近似和广义斯托克斯(Stokes)参量,推导出斜程湍流大气中传输时椭圆偏振部分空间相干部分光谱相干EGSMP波束在接收平面处的电磁交叉谱密度函数(CSDF)矩阵元和交叉偏振度的表达式。最后对比分析了湍流强度、波束的初始脉冲宽度、波束束宽、波束的空间相干长度和时间相干长度等对椭圆偏振波束和部分偏振波束的退偏特性影响。结果表明：湍流强度、波束的初始脉冲宽度、波束束宽、波束的空间相干长度和时间相干长度等对椭圆偏振波束的退偏特性影响较大,而对部分偏振波束的退偏特性影响较小。本文的研究结果将对改善激光工作系统在湍流大气中传输时的使用性能奠定了坚实的理论基础。
[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.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24

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