Mutual modulation between terahertz electrical signals and lightwaves in solidstate devices

在这个项目中，我们已经进行了调查，旨在功能设备，使太赫兹电信号的光波控制，反之亦然。(1)系统阐明了半导体量子威尔斯中太赫兹介电响应以及电子和空穴的载流子动力学：（1）阐明了聚合物微带线中太赫兹脉冲的特性。(2)提出了在微带线中嵌入量子阱薄膜的技术。(3)量子威尔斯阱中载流子的光激发引起的THz波传播的变化被清晰地探测到。(4)证明了量子限制载流子的太赫兹介电响应是一种极化，并表明弛豫时间可以被认为是能量弛豫的时间。（5）在THz脉冲传输的变化过程中发现了光生载流子弛豫现象。(2)太赫兹脉冲对光波的强度调制和相干非线性响应：没有得到足够的结果。(3)量子级联激光器（QCL）产生的连续太赫兹波对量子威尔斯阱光学响应的调制：我们成功地研制了基于双金属波导的太赫兹QCL和GaSb/AlSb系统的QCL，这是获得低阈值和高强度输出所必需的。(4)利用量子威尔斯的线性响应观测空间坐标系中的太赫兹脉冲。通过对实际器件结构的电磁波模拟，我们证明了观测是可以实现的。(5)太赫兹脉冲在单根导线上的传播特性：阐明了电导率虚部在单根导线波导中的作用。研究还表明，这种作用出现在太赫兹区域，这是无线电波和光波之间的交叉。

In this project, we have performed an investigation aiming at the functional devices enabling a control of lightwaves by THz electrical signals and vise versa.(1) Systematic elucidation of the THz dielectric response and the carrier dynamics of the electrons and holes in semiconductor quantum wells: (1) The characteristics of THz pulses in polymer microstrip lines were clarified. (2) Technology of embedding quantum well thin films in the microstrip lines was developed. (3) The changes of the THz wave propagation by the carriers photo-excited in the quantum wells were clearly detected. (4) It was proven that the THz dielectric response of the quantum confined carriers is a type of polarization, and shown that the relaxation time can be considered to be that of the energy relaxation. (5)The photo-carrier relaxation was detected in the change of the THz pulse propagation.(2) Modulation of the intensity and the coherent nonlinear response of lightwaves by THz pulses: sufficient results were not obtained.(3) Modulation of optical response of quantum wells by the CW-THz waves from Quantum cascade lasers (QCLs): We have successfully developed the THz-QCLs based on double-metal waveguide and QCLs of GaSb/AISb systems, which were necessary to obtain low threshold and high intensity output.(4) Observation of THz pulses in spatial coordinate using a linear response of quantum wells:. With electromagnetic wave simulations on a realistic device structure, we have shown that the observation can be realized.(5) Elucidation of the propagation characteristics of THz pulses on single conductor wires: The role of the imaginary part of the conductivity in the waveguiding by single wires was clarified. It was also shown that the role shows up in THz regime, which is a crossover between radio- and light-waves.