【作者】 徐新龙；

【导师】 李福利； 汪力；

【作者基本信息】 首都师范大学 ， 物理， 2003， 硕士

【摘要】 THz(10¹²Hz)时域光谱技术是20世纪90年代发展起来的一种新型的光谱测量技术，它使用频率介于远红外和微波之间的相干电磁辐射脉冲作为探测源，利用电光取样或光电导取样的方法直接记录THz辐射电场的振幅时间波形，通过傅立叶变换得到测量信号振幅和相位的光谱分布，进而获得材料在THz波段的复介电常数，即色散及吸收等信息。与通常利用Kramers-Kronig关系来提取材料光学常数的方法相比，这一技术更为简单、可靠，并且具有测量精度高的优点。THz时域光谱技术的研究虽然已经走过了十几年的路程，但是商业化的光谱仪只能在光谱表征方面做一些有限的工作，而不能进行定量测定工作。 本论文在T．D．Dorney和L．D．Duvillaret等人提出的模型的基础上研究了从THz时间波形中提取材料的光学常数（实折射率和消光系数）的原理、方法，并对于如何得到材料的其他物理参数进行了探讨。利用模拟的方法进行了误差分析。这些分析结果，可以用于指导物理参数测量实验和分析实验数据。实验方面，利用物理所搭建的透射型THz时域光谱系统研究了一些红外材料在THz波段的特性，分析了它们的介电性质。实验结果有助于这些材料作为红外透镜、激光窗口、集成光学器件，蓝光半导体激光器件、光探测器件、非线性光学器件、波导调制器件、THz发射器件等的研究。主要有以下方面： 一、总结分析了透射型、反射型、差分型、椭偏型THz时域光谱系统提取材料光学常数的原理、方法，利用Newton迭代的方法编程解决了实验数据处理方面的一些问题。同时对其他物理参数的提取进行了比较详尽的探讨。 二、首次利用模拟THz辐射脉冲入射到共振吸收的样品上的方法分析了厚度、角度、平移台错位、背景噪声及激光器噪声等对于光学常数测量产生的影响。具体估算出我们所用的透射型THz时域光谱系统的测量精度范围：折射率可以精确到1％而消光系数κ可以精确到5％。模拟发现，相位测量的量级基本上决定了光谱系统的抗噪声能力，因此在实验设计和样 中 文 摘 要品制备的过程中应该充分考虑这个问题。同时发现相位测量除了在低频区会发生2。跳变外，在共振区也可能发生2。跳变，因此在实验数据处理时应该特别加以注意。 三、利用透射型 THz时域光谱技术，对 Znse（110）单晶在 THz波段的色散和吸收性质进行了测量和分析。根据Drude理论获得了Znse的静电介电常数及高频介电常数，并观察到Znse体单晶在THz波段的多声子吸收效应。 四、利用THZ波段时域光谱测量和分析方法，第一次得到了混晶HgCdTe、ZnCdTe在0．5习．OTHz范围内的折射率和吸收系数曲线，分析了它们在THz波段范围内的介电性质。观察到HgCdTe在ZTA（）的双声子共振吸收，以及 ZnCdTe在 1．6THz～2．ZTHz附近由 LO（X）－LA（X）等多声子差频效应导致的较宽的吸收带。更多还原

【Abstract】 THz(1012 Hz) time-domain spectroscopy(TTDS) developed in 1990s is a new technique for spectroscopy measurement. A coherent electromagnetic pulse in the range between the far-infrared and microwave region is used as a detection source. The amplitude of the wave is recorded by electro-optical or photoconductive sampling. After fast Fourier transform, the amplitude and phase of the wave is given, then the complex refractive index standing for the absorption and dispersion of the material in THz region is extracted. Compared with the treatment using Kramers-Kronig relation, TTDS is simpler, more reliable, and more precise. Although TTDS has been developed for more than ten years, commercially available THz spectrometer can only make some qualitatively rather than quantitatively analysis.In this paper, a model developed by T.D.Dorney and D.Duvillaret et al is used to discuss the principle and method for optical constants extracting. The real refractive index and extinction coefficient of materials and the extraction of other material parameters are also discussed. The deviation of the optical constants obtained experimentally from their true values is analyzed using a stimulation method. These stimulation results can be used to direct the experiment and to analyze the experiment data. In experimental study, the dielectric characteristic of some infrared materials is analyzed by the transmission TTDS. The experiment results are valuable to the research of infrared lens, laser window, integrated optical device, the device for blue semiconductor laser, optical detector, nonlinear device, optical waveguide, THz emitter and other devicesThe following is a brief summary of the works conducted in this thesis and the results achieved.1.The principle and method of extracting the optical constants from transmission, reflection, differential, and ellipsometry TTDS are reviewed andanalyzed systematically. The programs using Newton algorithm are developed to solve the equations. The extraction of other material parameters is also discussed in detail.2.Using the simulation method and a lorentzian oscillator model, the influence of the deviation in experimental parameters, including the thickness of samples, the incident angle, the misalignment of the time delay line, the background noise and the laser noise is analyzed. The precision of the optical constants measured by transmission TTDS is evaluated. The stimulation shows that the phase measurement dominates the anti-noise ability of TTDS. On the other hand, the phase will show a 2 n jumping not only in low frequency region but also in resonant,region.3. Using the transmission TTDS, we measured and analyzed the absorption and dispersion of bulk ZnSe(l 10). According to the Drude theory, we obtain the low-frequency and high-frequency dielectric constant of ZnSe. We also observed the absorption caused by multi-phonon processes in ZnSe.4. Using TTDS measurement and analysis, the characteristic of mixed crystal HgCdTe and ZnCdTe in THz region is analyzed. We also observed the absorption by 2TA(X) in HgCdTe and multi-phonon processes by LO(X)-LA(X) in ZnCdTe.更多还原