Active metaphotonics based on two dimensional materials
일 시 : 2022년 05월 18일 수요일 16:30
연 사 : 장 민 석 교수 (KAIST 전기및전자공학부)
장 소 : 온라인 (https://us02web.zoom.us/j/87510545422, 회의 ID: 875 1054 5422)
HOST : 윤 재 웅 교수님
초 록
Active metasurfaces have been proposed as one attractive means of achieving high- resolution spatiotemporal control of optical wavefronts, having applications such as LIDAR and dynamic holography. Currently, dynamic metasurfaces are faced with two central problems. First, tuning the resonances of meta-atoms does not only affect the phase of optical wavefront, it also leads to sharp changes in the magnitude of the reflected/transmitted light. Second, most tunable materials exhibit only a modest change in optical index, and they cannot sufficiently tune the resonances of the meta-atoms over the full, desired 2π range. Consequently, complete tunable coverage of the full 0-2π phase range while maintaining a constant and significant light amplitude has so far remained elusive.
In this presentation, we unveil a novel electrically -tunable metasurface design strategy that operates near the avoided crossing of two resonances, one a spectrally narrow, over-coupled resonance and the other with a high resonance frequency tunability. This strategy displays an unprecedented upper limit of 4π range of dynamic phase modulation with no significant variations in optical amplitude, by enhancing the phase tunability through utilizing two coupled resonances. A proof-of-concept metasurface is illustrated using quasi-bound states in the continuum (qBICs) and graphene plasmon resonances, with results showing a 3π phase modulation capacity with a uniform reflection amplitude of ~0.65.