基于非对称量子阱非线性光学差频产生THz波的研究

As developments move forward, terahertz (THz) technologies not only have an important impact on material characterization and identification but also have potential applications in the fields of communications, imaging technology, medical diagnosis, health monitoring, environmental control, chemical and biological sensing, as well as security and quality-control applications. However, the lack of excellent terahertz source is primary question to limit the development of terahertz technologies. The photonics THz sources possess the superiority of wide scope of spectrum, miniaturization, tunability, operation at room temperature. The technology of difference frequency generation (DFG) with the second order nonlinear optical susceptibility has attracted a great deal of attention in acquiring the tunable, coherent, monochromatic THz radiation source. This project puts forward the method of THz wave based on DFG process to optimize the conversion efficiency and improve output power. In order to achieve high conversion efficiency, high power DFG THz source, we research the structural design and representation of GaAs/AlxGa1-xAs asymmetric quantum well(AQW) because of its high nonlinear coefficient. The linear and nonlinear optical properties of AQW, such as nonlinear coefficient, light absorption, conversion efficiency and design of waveguide, will be researched. This project will also contain the research of the phase matching condition, the way of pump and the mechanism of dual difference frequency resonance. After the experimental verifications have been accomplished, the new concept of THz source will be achieved.

太赫兹技术在通信、成像、探测、光谱分析等领域中具有重要的应用前景，但目前缺乏性能优良的THz辐射源是制约THz波技术快速发展的瓶颈之一。相比电子学方法，利用光子学方法产生THz波具有波谱范围宽、小型化、可调谐、室温运转等特殊的优势。本项目针对目前光子学方法产生THz波相对效率较低、输出功率较小的缺点，从提高THz波转换效率、室温运转和与成熟的半导体工艺相结合的需求出发，提出基于非对称量子阱结构的非线性光学差频方法，重点研究GaAs/AlxGa1-xAs非对称量子阱的结构设计、材料的表征；研究非对称量子阱的线性和非线性光学性质（如非线性系数、光吸收，转换效率、波导层设计等）；研究非线性光学差频的相位匹配条件、激光泵浦方式和双共振差频产生THz波机理等，并进行实验研究和验证，从而实现新型高转换效率、室温运转THz源的新构想。

太赫兹（THz）技术在通信、成像、探测、光谱分析等领域中具有重要的应用前景，但缺乏性能优良的THz辐射源是制约THz波技术快速发展的瓶颈之一。相比电子学方法，利用光子学方法产生THz波具有波谱范围宽、小型化、可调谐、室温运转等特殊的优势。本项目提出基于非对称量子阱结构的非线性光学差频方法产生THz波，通过精确设计GaAs/AlxGa1-xAs非对称量子阱的结构，计算其结构参数，其二阶非线性差频系数达到1.539×10-4m/V ，对泵浦光折射率变化量达0.5，吸收系数达到107m-1量级；精确计算出相位匹配条件与泵浦光波长和强度的关系，其理论THz波峰值功率达到10-2MW/cm2量级；研究了适于非对称量子阱的超材料结构，实现了对输出THz波的直接调制。本项目设计的量子阱结构对泵浦光波长敏感，对泵浦光强具有敏感饱和吸收，除作为THz辐射源外，对THz波光控、传感及光开关等应用器件具有重要参考作用。