电光聚合物在全光技术实现THz波产生与检测中的研究进展

Progress of Electro-Optic Polymer in the Field of Generation and Detection of Terahertz Waves by All-Optical Technique

摘要：
研究和开发基于超短波和低能量激光系统的高振幅、宽频带的太赫兹系统一直是太赫兹应用领域的一个热点。与传统电光晶体材料相比，以电光聚合物薄膜作为太赫兹波产生和检测的最大的优势在于：一方面电光聚合物不具有晶格结构相应的不存在声子的吸收和太赫兹折射率的散射问题，避免光谱间隙的产生；另一方面电光聚合物薄膜与已用于宽频太赫兹系统中的超薄电光晶体材料相比，更易于加工和处理。另外，可以自行设计得到低相位失配和高电光系数的电光聚合物材料，得到高效率和宽频带的太赫兹辐射源。可以预见，电光聚合物在这一领域的应用必将有宽阔的发展空间和学术研究意义。介绍电光聚合物的电光效应及二阶非线性生色团合成等相关理论问题基础上，综述了近二十多年来，电光聚合物在基于全光技术实现太赫兹波产生与检测系统中的研究进展，主要包括：掺钛蓝宝石飞秒激光激发下，共聚型和主客体型电光聚合物实现太赫兹波产生与检测；光纤飞秒激光激发下，主客体型电光聚合物实现太赫兹波的产生与检测。
Abstract：
Research on and development of the high amplitude,broadband terahertz system based on ultra-short pulse,low-pow-er laser system is a hot spot in the field of terahertz.So far,for all the reported THz bandwidths broader than 10 THz,there al-ways exist strong dispersion and absorption gaps associated with the lattice resonance in either the photoconductive materials or crystalline EO materials.If such THz sources and detectors are employed in spectroscopic studies,spectral information in these gaps cannot be extracted.One of the advantages of using amorphous electro-optic polymer films as THz emitters and sensors is that there is no dispersion or absorption resulting from the lattice resonance effect,making a gap-free THz spectrum possible. Another advantage of electro-optic polymer films is the ease of fabrication and handling,in contrast to the extremely thin crystal-line electro-optic materials used for existing broadband THz system.In addition,we can engineer the electro-optic polymeric ma-terials to achieve small phase mismatch and high electro-optic coefficients such that brightness and broad bandwidth of THz radi-ation can be obtained.In this thesis a theoretical description of electro-optic effect based on electro-optic polymer and the second-order nonlinear chromophores synthesis is reviewed.In the past 20 years,progress in electro-optic polymer in the field of genera-ting and detecting terahertz radiation by all-optical techniques is summarized,including the terahertz systems based on copolymer and the guest-host polymer induced by Titanium doped sapphire femtosecond laser and based on the guest-host polymer at com-munication wavelengths

国家青年自然科学基金项目，中国博士后基金项目

低温铝诱导晶化制备纳米晶硅薄膜的物相和光学性能研究

Research on the Phase and Optical Properties of nc-Si Films Prepared by Low Temperature Aluminum Induced Crystallization

摘要：
采用射频磁控溅射镀膜系统，在玻璃衬底上制备了非晶硅（α-Si）/铝（Al）复合薄膜，结合氮气（N2）气氛中低温快速光热退火制备了纳米晶硅（nc-Si ）薄膜；利用光学显微镜、共焦光学显微仪、X 射线衍射（XRD）仪、拉曼散射光谱（Raman）仪和紫外-可见光-近红外分光光度计（UV-VIS-NIR）对纳米晶硅薄膜的表面形貌、物相及光学性能进行了表征，研究了退火工艺对薄膜性能的影响。结果表明：300℃，25 min光热退火可使α-Si/Al膜晶化为纳米晶硅薄膜，晶化率为15．56％，晶粒尺寸为1．75 nm；退火温度从300℃逐渐升高到400℃，纳米晶硅薄膜晶粒尺寸、晶化率、带隙逐渐增加，表面均匀性、晶格畸变量逐渐减小；退火温度从400℃逐渐升高到500℃，纳米晶硅薄膜的晶粒尺寸、晶化率继续增加，带隙则逐渐降低；采用纳米晶硅薄膜的吸光模型验证了所制备的纳米晶硅薄膜的光学特性，其光学带隙的变化趋势与吸光模型得出的结果一致。
Abstract：
In the present paper,nanocrystalline silicon thin films on glass substrates were prepared by rapid thermal annealing (RTA)of RF magnetron sputtered system andα-Si/Al films at a low temperature in N2 atmosphere.Optical metallographic mi-croscope,confocal optical microscopy,X-ray diffractometer,Raman scattering and UV-Vis-NIR spectrometers were used to characterize the surface morphology and the phase and optical properties of nc-Si films.The influence of annealing process on the nc-Si films properties was studied.The results showed that nc-Si films were obtained after aluminum induced crystallization of theα-Si/Al films at 300 ℃,withthe crystallization rate 15. 56% and the grain size 1. 75 nm.The surface uniformity and lattice distortion of nc-Si films reduced,while grain size,degree of crystallization and the optical band gap of the films increased with increasing annealing temperature from 300 to 400 ℃.As the annealing temperature increased from 400 to 500 ℃,although the degree of crystallization and grain size increased,the tendencies of all other characteristics were opposite.On the contrary,the surface uniformity and the lattice distortion increased,but the optical band gap of nc-Si films reduced.The optical properties of the resulting films were confirmed by the absorption model of nc-Si thin films,where the tendency of band gap changes is in con-sistent with the optical modeling.

国家自然科学基金联合基金项目

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