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基于铌酸锂晶体参量过程产生与探测太赫兹波

Generation and Detection of Terahertz Wave Using a Parametric Process in Lithium Niobate

【作者】 蒋呈阅

【导师】 刘劲松;

【作者基本信息】 华中科技大学 , 光学工程, 2013, 博士

【摘要】 太赫兹波的众多独特性质使得它在成像、无损检测、环境监测、通信、安全等领域均有重大的科学研究价值和广阔的应用前景。基于铌酸锂晶体参量过程的太赫兹波产生与探测技术具有窄线宽、连续可调谐、室温运转、结构紧凑等优点,近年来受到越来越多的关注。本论文围绕基于铌酸锂晶体中电磁耦子的受激拉曼散射开展了太赫兹波辐射源、窄带太赫兹波长计、辐射源的泵浦阈值和太赫兹波探测的理论和实验研究。主要研究内容有以下几个方面:(1)推导出了一般情况下晶体中电磁耦子受激拉曼散射的耦合波方程组。(2)实验研究了两种不同耦合输出方式的太赫兹波辐射源:即硅棱镜耦合式太赫兹波参量振荡器(TPO)和浅表面垂直出射式TPO。分析了限制频率调谐范围的主要因素。定量考察了晶体光折变效应对太赫兹波输出效果的影响。测量了三种不同配置的浅表面垂直出射式TPO的太赫兹波输出效率、频率调谐范围。(3)设计开发了一款适用于2THz以下频率的新型太赫兹波长计用于直接测量窄带太赫兹波长。(4)建立了TPO的阈值理论模型,以典型硅棱镜耦合式TPO为对象实验研究了其泵浦阈值。分析了TPO的损耗来源,并讨论了降低泵浦阈值的有效方法。(5)建立了描述铌酸锂晶体参量过程探测太赫兹波的稳态理论模型,推导出其解析表达式并利用数值计算方法考察了模型的合理性。应用稳态模型分析了探测器对不同频率太赫兹波的响应情况,并研究了各物理量的温度特性对探测效果的影响,分析了影响其探测效果的主要因素。考虑到实际泵浦脉冲的准单色性,建立了准单色理论模型,并研究了各种因素对探测效果的影响。(6)设计并搭建了铌酸锂晶体参量过程产生、探测太赫兹系统。分析了系统的噪声来源并确定了系统的主要噪声源。定量比较了参量过程有、无谐振腔晶体探测太赫兹波、高莱盒及热释电探测器的探测性能。

【Abstract】 Terahertz wave with many unique properties has significant scientific research valuesand wide applications in the field of imaging, non-destructive testing, environmentalmonitoring, communication, security and so on. Recently, Generation and detectionterahertz wave using a parametric process in lithium niobate has attracted more and moreattention due to its advantages such as narrow linewidth, continously tunable, roomtemperature operation, compact structure, etc. Based on the stimulated Raman scattering ofpolariton in lithium niobate, in this thesis, we focus on terahertz wave radiation source,narrow linewidth terahertz wavelength meter, threshold pump of terahertz wave radiationsource, and the theories and experiments of terahertz wave detection. The detailed researchcontents can be found as follows.(1) We derive the coupled-wave equations that describing the stimulated polaritonscattering in a crystal.(2) We experimentally investigate two different coupling methods, which are siliconprisms coupler TPO and surface emitted TPO. The main factors which limit the frequencytuning range are discussed. Moreover, the impacts of the photorefractive effect in lithiumniobate on the terahertz wave output are quantitatively studied. For surface emitted TPO,terahertz wave output efficiencies and frequency tuning ranges of three differentconfigurations are measured.(3) A terahertz wavelength meter for direct wavelength measurements of narrowlinewidth terahertz wave is designed and fabricated.(3) We theoretically and experimentally study the threshold pump of a typical TPO.The losses of the TPO are discussed. Moreover, we also provide some effective methods tolower the pump threshold.(4) We have established the steady-state theoretical model for detection of terahertzwave using a parametric process in lithium niobate, and obtained its analytical expression.To test the established model, numerical calculation method is employed. The frequencyresponse characteristics and temperature effects of the detector are analyzed by using thesteady-state theoretical model. We also establish the time-dependent theoretical model to explain the practical situation. The effects of various factors on the detection sensitivitiesare discussed.(5) We construct the system consisted of both terahertz wave generation and detectionusing a parametric process. The main system noise sources are analyzed and discussed. Wehave measured the signal-to-noise of terahertz wave detection with the parametric processmethod with and without a resonator, Golay cell and pyroelectric detector.

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