◇ 연사 : 울산대학교 반도체물리학과 김튼튼 교수

◇ 일시 : 2023년 5월 4일 목요일 16시 30분

◇ 장소 : 자연과학대학 4호관 215호 

◇ 주제 : Graphene metasurfaces & THz near-field spectroscopy

◇ 초록 : Metasurfaces have been extensively studied to explore novel and highly efficient optical functionalities. In this talk, we will introduce recent research findings on metasurface designs that exhibit exceptional optical properties beyond those found in natural materials. Specifically, we will show that gate-induced switching and linear modulation of terahertz waves can be achieved in a hybrid material system comprising artificially constructed meta-atoms and an atomically thin graphene layer [1-5]. Unlike intrinsic properties of composite materials, the carefully designed metasurfaces offer abundant capabilities for developing high-performance and integrated optical devices that surpass traditional bulk optical elements. Our research is mainly conducted in the Terahertz (THz) frequency range because THztime-domain spectroscopy because THz time-domain spectroscopy allows for the measurement of both the spectral amplitude and phase of the THz signal through pulsed illumination in the time domain. However, the diffraction limits of THz long-wavelength, which are about a few hundred microns, have previously hindered the observation of physical phenomena occurring within small areas where many physical properties have been discovered. Recently developed THz near-field spectroscopy with a tip-probe antenna can overcome these limitations and measure small samples that were previously challenging to analyze [6]. Additionally, in this presentation, we will highlight our recent research findings on THz near-field spectroscopy in various research fields [7,8]. This outcome holds potential for the basis of studying charge distribution in space over a picosecond time scale, which has been challenging to observe in the past.