FEL太赫兹源低损耗光腔与传输系统研究

发布时间：2018-03-07 15:11

本文选题：太赫兹波　切入点：自由电子激光　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：基于自由电子激光技术的太赫兹源,具有输出功率高、波长大范围内连续可调、光束品质好等优点,是实现可调谐、高功率太赫兹源的最佳途径之一。光学谐振腔是自由电子激光装置中的重要组成部分,为实现太赫兹波在光学谐振腔内的振荡放大,最终达到高功率的饱和输出,必须使得光学谐振腔内的单程增益大于光学谐振腔内的损耗,因此设计低损耗的光学谐振腔是获得太赫兹高功率输出的关键。针对太赫兹波段的特点,为了提高增益、减小损耗,在传统开放式光学谐振腔基础上全程加入了波导约束结构。论文重点研究了波导约束结构下光学谐振腔内存在的传播模式、波导内的传输损耗以及波导与自由空间的耦合损耗问题;同时针对太赫兹波在大气环境中传播时衰减严重的问题,分析设计了低损耗的高功率太赫兹光束传输系统。首先,论文针对实际项目中所设计的波导约束光学谐振腔结构,分别详细计算分析了波导的欧姆损耗和渐变波导部分的反射损耗,并结合HFSS仿真软件进行对比验证,结果表明所设计的波导约束结构在太赫兹波段的波导传输损耗可以近似忽略。然后,论文采用模式分解法分析了波导端口与反射镜之间的耦合损耗问题,研究了最小耦合损耗与最佳反射镜曲率半径之间的关系,并结合实际空间尺寸的限制设计了一个在50μm-100μm范围内耦合损耗都足够小的反射镜。通过对波导约束下光学谐振腔结构的耦合损耗的相关计算与分析,使得光学谐振腔的损耗符合低损耗要求,同时为设计影响增益的电子束、波荡器等参数提供了参考依据。最后,论文针对所产生的太赫兹波需要远距离、低损耗传输问题,基于高斯光束传播的相关性质,设计了一个低真空、低损耗的高功率太赫兹光束传输系统,仿真分析了50μm-100μm范围内的太赫兹光束经过该系统的束斑半径变化,确认其光束品质可不受影响。
[Abstract]:Terahertz free electron laser source based on the technology, with high output power, wavelength range can be adjusted continuously, the advantages of good beam quality, is one of the best ways to realize tunable, high power terahertz source. Optical resonator is an important group of free electron laser in part for amplifying oscillations and realize THz wave in the optical resonant cavity, eventually reaching saturation high output power, the gain loss must be greater than the optical resonant cavity optical resonant cavity, so the design of low loss optical resonator is the key to obtain high power terahertz output. According to the characteristics of the terahertz band, in order to improve the gain and loss, in the traditional open optical on the basis of the whole resonator joined the waveguide structure. The paper focuses on the constraints of existing waveguide structure constrained optical resonant cavity propagation modes in the waveguide, transmission The problem of coupling loss and loss of waveguide and free space; at the same time for terahertz wave propagation in atmosphere attenuation is a serious problem, analysis and design of high power terahertz beam transmission system of low loss waveguides. First, designed in this paper according to the actual project in the beam optical cavity structure were analyzed in detail on the basis of the ohmic loss and part of the tapered waveguide reflection loss waveguide, and validated by HFSS simulation software. The results show that the designed waveguide constraint in terahertz waveguide transmission loss can be neglected. Then, using the mode decomposition method to analyze the problem of coupling loss between the waveguide port and the reflector, study the relationship between the minimum coupling the loss and the best mirror radius of curvature, and a design of the 50 M-100 m range is combined with the actual space size limit Mirror and loss are small enough. Through the calculation of coupling loss of optical waveguide resonant cavity structure constraints and analysis, the loss of optical resonator with low loss requirements, at the same time as the electron beam gain design, undulator parameters provide the basis. Finally, aiming at the terahertz generated the waves need to distance, low loss transmission problems, related properties of Gauss beam propagation based on the design of a low vacuum, high power terahertz beam transmission system with low loss, the simulation analysis of 50 mu M-100 mu in the range of M Hz beam through the beam spot radius is the changes of the system, the beam quality can not confirm affected.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4

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