Revealing low-loss dielectric near-field modes of hexagonal boron nitride by photoemission electron microscopy

Author:

Li Yaolong,Jiang Pengzuo,Lyu Xiaying,Li Xiaofang,Qi Huixin,Tang Jinglin,Xue Zhaohang,Yang Hong,Lu Guowei,Sun QuanORCID,Hu XiaoyongORCID,Gao YunanORCID,Gong QihuangORCID

Abstract

AbstractLow-loss dielectric modes are important features and functional bases of fundamental optical components in on-chip optical devices. However, dielectric near-field modes are challenging to reveal with high spatiotemporal resolution and fast direct imaging. Herein, we present a method to address this issue by applying time-resolved photoemission electron microscopy to a low-dimensional wide-bandgap semiconductor, hexagonal boron nitride (hBN). Taking a low-loss dielectric planar waveguide as a fundamental structure, static vector near-field vortices with different topological charges and the spatiotemporal evolution of waveguide modes are directly revealed. With the lowest-order vortex structure, strong nanofocusing in real space is realized, while near-vertical photoemission in momentum space and narrow spread in energy space are simultaneously observed due to the atomically flat surface of hBN and the small photoemission horizon set by the limited photon energies. Our approach provides a strategy for the realization of flat photoemission emitters.

Funder

National Natural Science Foundation of China

Publisher

Springer Science and Business Media LLC

Subject

General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry,Multidisciplinary

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