基于相位调制的部分相干光特性分析与实验研究

发布时间：2018-04-09 02:13

本文选题：部分相干光　切入点：相位调制　出处：《西安电子科技大学》2014年硕士论文

【摘要】：相干光在传输过程中受大气的影响退化为部分相干光;同时部分相干光的大气传输特性可以有效抑制湍流带来的光强闪烁、相位起伏等影响。近几年激光雷达研究的热点之一的新体制激光符合成像雷达,正是要用具有部分相干光特性的激光作为发射光源。因此,研究部分相干光的产生方法是很必要的。采用激光照射到旋转毛玻璃形成的动态散斑作为部分相干光源是如今最常用的产生方法,可行性高且系统成本较低,但毛玻璃的存在会大大降低激光输出功率;激光器谐振腔内调制产生部分相干光的系统较为复杂,且成本相对较高;基于液晶空间光调制器的部分相干光方案也受限于输出功率和调制速度等因素。因此开展可产生高功率输出、相干性可控和可快速预置光场的部分相干光的研究,具有重要的学术意义和应用价值。本文基于阵列光束合成和部分相干光理论,从理论和实验的角度分别对光纤阵列产生部分相干光系统的方案进行验证。首先介绍了光的相干性理论,然后分别阐述了光的时间相干性,空间相干性和部分相干性。介绍了一种典型部分相干光的数学模型,并从关联性角度来描述其光场的相干性,简单描述了光场的高阶相关理论,并通过光的强度关联系数来为后续测试部分相干光相干长度做出理论铺垫。基于光束合成理论,研究了不同模型,不同间距,不同附加随机相位抖动方差下的光场强度分布的数值仿真,为后续实验系统改进和实验测试提供理论依据。利用铌酸锂相位型调制器、平面波导(PLC)光纤分路器和光纤阵列基板(FA)设计和改进了实验室搭建的部分相干光的方案。采用实验室开发的基于FPGA的相位调制器驱动电路可为相位调制器提供最高10MHz,±5V的模拟电压输出。利用光纤阵列部分相干光产生系统对部分相干合成后的光强分布与空间相干性进行了实验测试,通过驱动电路系统加载不同范围均匀随机电压,可使强度关联系数在1~1.48范围内可控。通过实验结果测试与理论仿真对比,验证了方案可行性。
[Abstract]:The atmospheric effect of coherent light is reduced to partially coherent light, and the atmospheric propagation characteristics of partially coherent light can effectively suppress the effects of turbulence, such as intensity scintillation and phase fluctuation.In recent years, one of the hotspots of lidar, laser coincidence imaging radar, is to use laser with partial coherent light as the emitting light source.Therefore, it is necessary to study the generation method of partially coherent light.The dynamic speckle produced by laser irradiation to the rotating glass is the most commonly used generation method nowadays, which has high feasibility and low system cost, but the laser output power will be greatly reduced by the existence of the ground glass.The system of laser resonator modulation to produce partially coherent light is complex and the cost is relatively high. The partially coherent light scheme based on liquid crystal spatial light modulator is also limited by the output power and modulation speed.Therefore, the research of partially coherent light which can produce high power output, coherence controllable and fast preset light field has important academic significance and application value.Based on the theory of array beam synthesis and partially coherent light, the scheme of optical fiber array generating partially coherent optical system is verified theoretically and experimentally in this paper.Firstly, the coherence theory of light is introduced, and then the temporal coherence, spatial coherence and partial coherence of light are described respectively.In this paper, a mathematical model of a typical partially coherent light is introduced, and the coherence of the light field is described from the angle of correlation, and the high order correlation theory of the light field is briefly described.The correlation coefficient of light intensity is used to lay a theoretical foundation for the subsequent measurement of coherent length of partially coherent light.Based on the theory of beam synthesis, the numerical simulation of intensity distribution of light field with different models, different spacing and different variance of additional random phase jitter is studied, which provides a theoretical basis for the improvement of the experimental system and the experimental test.Using lithium niobate phase modulator, planar waveguide PLC fiber splitter and fiber array substrate FAA), the scheme of partially coherent light in laboratory is designed and improved.The phase modulator drive circuit based on FPGA developed in laboratory can provide the analog voltage output of up to 10 MHz and 卤5 V for the phase modulator.The optical intensity distribution and spatial coherence after partial coherent combination are experimentally tested using partially coherent optical fiber array optical generation system. The uniform random voltages with different ranges are loaded through the drive circuit system.The strength correlation coefficient can be controlled in the range of 1 ~ 1.48.The feasibility of the scheme is verified by comparing the experimental results with the theoretical simulation.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN958.98

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