Bound States in the Continuum for 2D Periodic nanostructures analyzed by Finite-difference Time-Domain method with Pade Approximation for high Q factor

Abstract

Photonic bound states in the continuum (BIC) are found in photonic crystal structures with infinite lifetime or infinite cavity quality factor This peculiar property is due to the coupling of certain guided resonant modes that leads the cancellation of radiation channels BIC has great potential in the applications of lasers sensors and filters The purpose of this study is to investigate and characteristics BIC in Plasmonic and dielectric structures by the Finite-difference time-domain (FDTD) method First single layered dielectric periodic structure is analyzed through the transmission spectrum to find the guided resonant mode By shifting double layer dielectric periodic structure a dark guided resonances mode which can be identified as BIC appears Without shifting the double layered structure an oblique angle incident excitation could also observe such BIC states The Photonic Band structure is calculated to further analyze the appearance of the BIC states Due to the infinite life time of BIC it is difficult to analyze the quality factor of BIC A combination of Pad? approximant and Fast Fourier Transform (FFT) is developed to shorten the simulated time and obtain the correct cavity quality factors to help identifying BIC in FDTD calculation Finally a single layered metallic periodic structure is found to exhibit a quasi BIC state with propagating surface plasmon polaritons

Date of Award	2019
Original language	English
Supervisor	Shih-hui Chang (Supervisor)