概要

Magneto-optical (MO) materials based topological photonic crystals (PhCs) can support the backscattering-immune
light propagation, due to their non-trivial topological bandstructures.
Unfortunately, weak MO responses in the optical band restrict obtainable topological bandgap sizes and hinder
the realization of robust chiral edge states in the optical regime.
A way to improve MO responses is the use of epsilon-near-zero (ENZ) materials with
vanishing xx (diagonal permittivity).
However, the potential of such materials has not yet been investigated in the enhancement of a topological bandgap.
Here, we numerically demonstrate the enlargement of topological bandgap by using ENZ-MO materials by calculation results
obtained from COMSOL Multiphysics.
The investigated PhCs with a honeycomb lattice is composed of ENZ-MO materials filled triangular areas in a Si slab.
Without magnetization (off-diagonal permittivity is zero), the ENZ PhC exhibits two bands touching at a Dirac point.
With magnetization (Im(xy)=0.1), the complete topological gap is opened with a 4.5% gap-mid gap
ratio (i.e. a 69-nm gap at 1.55 micron wavelength) at xx=0.01, which is 3 orders of magnitude
larger than the previous report (42 pm).
Our results suggest that introducing ENZ property could boost the performance of topological
MO PhCs in the optical regime.

発表者

刘 天際
東京大学 先端科学技術研究センター　特任助教

共同著者

KOBAYASHI Nobukiyo（Research Institute for Electromagnetic Materials）
IKEDA Kenji（Research Institute for Electromagnetic Materials）
OTA Yasutomo（Keio University）
IWAMOTO Satoshi（The University of Tokyo）

キーワード

Topological photonics, epsilon-near-zero, magneto-optical effect

資料公開

不可