SUPERCARRIER MODULATION WITH A FEMTOSECOND LASER AND ITS APLLICATIONS FOR NEW FUNCTIONAL PHOTONIC DEVICES

本项目主要研究高温超导体的太赫兹辐射、高温超导体中的超快载流子动力学、超快光超电流调制引起的光涡旋的产生、新型光子器件和系统的提出和发展。我们成功地观测到了YBCO、TBCCO、BSCCO和Pr掺杂的YBCO的太兹辐射，并发现了TBCCO在弱磁飞行下的光激发约瑟夫森等离子体发射。利用泵浦和探针太赫兹发射光谱在时间分辨率为100fs的时域内观察了载流子动力学。研究发现，掺入YBCO后，太赫兹发射强度明显增强，这是由于超导体与衬底界面处的太赫兹反射减弱所致。我们发现了光学涡旋产生的新效应，可以用传统的超导规律来解释。用超快光超电流调制解释了其机理。我们提出了将这种新效应应用于检测和处理飞秒光信号，并演示了利用光涡流产生技术检测单次飞秒光信号。作为一项应用研究，我们开发了激光太赫兹发射显微镜（LTEM），观察了高温超导体的超电流分布。结果表明，作为一种非接触、无损、自由空间的评价系统，LTEM是一种很有潜力的观测高温超导系统中超流和涡旋的工具。我们还通过制作光电混合器和高温超导约瑟夫森结混合器件，研制了光子微波转换器。我们提出这种光子微波转换器作为一种潜在的检测精确波长的系统。我们提出了光控太赫兹磁通晶体管作为光通信信号与单磁通量子逻辑电路之间的光直接接口。制作了初步装置，并在光激发下进行了测试。这一成果开辟了“超导体光子学”的新研究领域，将为太赫兹技术提供关键突破。少

This project investigates terahertz radiation from high-Tc superconductors (HTSs), ultrafast carrier dynamics in HSTs, optical vortex generation due to ultrafast optical supercurrent modulation, proposal and developments of new photonic devices and systems.We successfully observed THz radiation from YBCO, TBCCO, BSCCO, and Pr doped YBCO, and discovered optically-excited Josephson plasma emission from TBCCO under weak magnetic flied. The carrier dynamics was observed in time domain with a time resolution of 100 fs using pump and probe THz emission spectroscopy. It was found that Pr-doping into YBCO strongly enhances THz emission intensity, which is attributable to the decrease in THz reflection at the interface between superconductors and substrate. We discovered new effect in optical vortex generation, can to be explained by the conventional rule of superconductivity. The mechanism was explained by ultrafast optical supercurrent modulation. We proposed to apply this new effect to detec … More t and process femtosecond optical signals, and demonstrated to detect a single shot femtosecond optical signal via otpcal vortec generation.As an application research we developed Laser-Terahertz Emission Microscope (LTEM) and observed supercurrent distribution ih high-Tc superconductors. It proven that the LTEM is a potential tool to observe supercurrent and vortices in HTSs as the noncontact, nondestructively and free-space evaluation system.We also developed photon microwave converter by fabricating photomixer and HTS Josephson junction hybrid device. We proposed this photon microwave converter as a potential system to detect accurate optical wavelength.We propose optically-controlled-terahertz flux-flow transistor as an optical direct interface between optical communication signals and single flux quantum logic circuits. The preliminary device was fabricated and tested under optical excitation.The results obtained here has opened new research field "Superconductor Photonics", which will provide a key breakthrough for terahertz technology. Less