DEVELOPMENT OF TUNABLE LOCAL OSCILLATOER OF THZWAVE BY PHOTOMIXING EXCITATION

本项目研究了光子-微波转换材料中的超快载流子动力学，基于新的思想开发了一种高度可控、稳定的可调谐振荡器和光子微波转换器，并成功地观察到了几种高温超导材料和锰氧化物的太赫兹辐射。研究发现，在弱磁场作用下，TBCCO的约瑟夫森等离子体发射可以被光激发。用时间域法观察了载流子的动力学。太赫兹光谱学。结果表明，氧还原高温超导由于降低了超导体与衬底界面的THz反射，大大增强了THz辐射强度。我们还观察到a-Ge的THz辐射和超快光响应。通过制作光混合器和高温超导约瑟夫森结的混合器件，研制了一种光子-微波转换器，成功地产生和探测了高达2 0 0μ的微波。我们证明了利用所制作的器件产生的微波具有高度的可控性和稳定性。我们提出了这种光子-微波转换器作为检测精确光学波长的潜在系统，并提出了光控太赫兹流量晶体管作为光通信信号与单通量量子逻辑电路之间的光直接接口。初步制作的器件在光激励下进行了测试，结果开辟了超导光子学的新研究领域，将为太赫兹技术提供关键突破。

This project investigates ultrafast carrier dynamics in photon-microwave conversion materials, and develops a highly controllable and stable tunable oscillator and photon microwave converter based on new idea.We successfully observed THz radiation from several kinds of HTSs and Mn oxides. It was discovered that Josephson plasma emission can be optically-excited for TBCCO under weak magnetic field. The carrier dynamics was observed by time domain. THz spectroscopy. It was found that oxygen reduced HTS strongly enhances the THz emission intensity due to the decrease in THz reflection at the interface between superconductors and substrate.We also observed THz radiation and ultrafast photo-response of a-Ge. It was found that a-Ge has potential as a photomixing excitation material for the use of light source with 1.55μm wavelength.We developed a photon-microwave converter by fabricating the hybrid device of photo-mixer and HTS Josephson junction, and succeeded in the generation and detection of the microwaves extending up to 200 GHz. We demonstrated the high controllability and stability of the microwaves generated by using the fabricated devices. We proposed this photon-microwave converter as a potential system to detect accurate optical wavelength.We also proposed an 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.