主講人：Keisuke Takano，Assistant Professor at Shinshu University

時間：2024年11月11日14：00

地點：ZOOM Meeting 958 2694 5490

舉辦單位：數理學院

主講人介紹：Dr. Takano received a Bachelor’s degree in 2005, Master’s degree in 2007 and Ph.D. in Engineering in 2010 from Osaka University, Japan. He began his research career as a postdoctral fellow at Institute of Laser Engineering, Osaka University in 2010, and later became an Assistant Professor there in 2014. In 2017, He joined Center for Energy and Environmental Science, Shinshu University as an Assistant Professor. After working at KIOXIA Corporation (formerly Toshiba Memory Corporation) in 2018, He returned to Faculty of Science at Shinshu University as an Assistant Professor in 2022. His research interests include laser terahertz science, metamaterials, and time-varying media.

內容介紹：Flexible manipulation of terahertz frequency up- and down-conversion expands the bandwidth of terahertz communications. Traditionally, nonlinear optical effects have been employed for frequency conversion, but their efficiency is low in the terahertz range. To address this, frequency conversion in time-varying systems has attracted attention, and up-conversion has been demonstrated at the temporal boundaries induced by optical excitation in a semiconductor waveguide [Miyamaru et al., Phys. Rev. Lett. 127, 053902 (2021)]. In this waveguide, optical pumping narrowed the confinement region, facilitating frequency up-conversion. In contrast, a method for down-conversion in waveguides has been nontrivial. We demonstrated frequency down-conversion of terahertz waves at the temporal boundaries in waveguides, focusing on coupling transverse-magnetic and electromagnetic modes. Experiments showed a power efficiency of frequency down-conversion from 0.42 to 0.36 THz of more than 20%. Combining the proposed down-conversion with up-conversion establishes a basis for arbitrary frequency conversion of terahertz waves in time-varying systems.