【English title】

Enlargement of topological bandgaps in magneto-optical epsilon-near-zero photonic crystals
 

【Abstract】

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 εxx (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(εxy)=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 εxx=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.
 

【Keywords】　

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

【使用製品】　

COMSOL Multiphysics, 波動光学モジュール, 複合材料モジュール
 

【Co-author】

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

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【講師紹介】　

東京大学 先端科学技術研究センター 特任助教 刘 天際 先生