报告题目：Real-space observations of polaritons in layered 2D materials exposed by s-SNOM
报告人：Dr.Zhigao Dai (戴志高 博士) Department of Materials Science and Engineering, Monash University, Australia
主 持 人：崔小强 教授
Phonon polaritons arise from the resonant excitation of lattice vibrations in polar crystals during the light illumination. Recently, hyperbolic phonon polaritons originated from opposite signs of dielectric tensor were rediscovered in natural hexagonal boron nitride which show potential application in near-field optical guiding, imaging, and focusing. The emerging demands in nano-optics inspired us to search for new layered materials that can out-perform existing natural and artificial hyperbolic materials or exhibit unique properties. Herein, we report real-space mapping of highly confined phonon-polaritons in a natural layered oxide, α-phase molybdenum trioxide (α-MoO3), via scattering-type scanning near-field optical microscopy (s-SNOM). Our results reveal sub-diffractional focusing and directional guiding characteristics of phonon polaritons in α-MoO3. The observed phonon polaritons show a small wavelength and a large confinement factor with confined volumes as small as 10−7 λ03. By tailoring the layered oxide into resonators with different geometries, we observed directional guiding in triangle and rectangle resonators with sub-diffractional size. Owning to the realisation of strongly confined phonon-polaritons with directional guiding layered oxides α-MoO3 and beyond, might be new terraces for exploring light–matter interactions and engineering nanophotonic devices.
Zhigao Dai received his Ph.D. degree in Condensed Matter Physics from Wuhan University in 2015. Then, he worked as a postdoctoral fellow at the Department of Materials Science and Engineering, Monash University, Australia. He has published 45+ SCI papers, including 15+ first author or corresponding author published in top journals including Light: Sci. Appl., Small, and Appl. Phys. Lett . Times of citations is over 650, with h-index 16. His current research interest focuses on plasmon, phonon, exciton polaritons in the low-dimension materials and their applications.