TY - JOUR

T1 - Pushing the limit of high-Q mode of a single dielectric nanocavity

AU - Huang, Lujun

AU - Xu, Lei

AU - Rahmani, Mohsen

AU - Neshev, Dragomir

AU - Miroshnichenko, Andrey E

PY - 2021

Y1 - 2021

N2 - High-index dielectric resonators support different types of resonant modes. However, it is challenging to achieve a high-Q factor in a single dielectric nanocavity due to the non-Hermitian property of the open system. We present a universal approach of finding out a series of high-Q resonant modes in a single nonspherical dielectric cavity with a rectangular cross section by exploring the quasi bound-state-in-thecontinuum (QBIC). Unlike conventional methods relying on heavy brutal force computations (i.e., frequency scanning by the finite difference time domain method), our approach is built upon Mie mode engineering, through which many high-Q modes can be easily achieved by constructing avoid-crossing (or crossing) of the eigenvalue for pair-leaky modes. The calculated Q-factor of mode TE(5,7) can be up to Q(theory) = 2.3 x 10(4) for a freestanding square nanowire (NW) (n = 4), which is 64 times larger than the highest Q-factor (Q(theory) approximate to 360) reported so far in a single Si disk. Such high-Q modes can be attributed to suppressed radiation in the corresponding eigenchannels and simultaneously quenched electric (magnetic) field at momentum space. As a proof of concept, we experimentally demonstrate the emergence of the high-Q resonant modes [Q approximate to 211 for mode TE(3,4), Q approximate to 380 for mode TE(3,5), and Q approximate to 294 for mode TM(3,5)] in the scattering spectrum of a single silicon NW.

AB - High-index dielectric resonators support different types of resonant modes. However, it is challenging to achieve a high-Q factor in a single dielectric nanocavity due to the non-Hermitian property of the open system. We present a universal approach of finding out a series of high-Q resonant modes in a single nonspherical dielectric cavity with a rectangular cross section by exploring the quasi bound-state-in-thecontinuum (QBIC). Unlike conventional methods relying on heavy brutal force computations (i.e., frequency scanning by the finite difference time domain method), our approach is built upon Mie mode engineering, through which many high-Q modes can be easily achieved by constructing avoid-crossing (or crossing) of the eigenvalue for pair-leaky modes. The calculated Q-factor of mode TE(5,7) can be up to Q(theory) = 2.3 x 10(4) for a freestanding square nanowire (NW) (n = 4), which is 64 times larger than the highest Q-factor (Q(theory) approximate to 360) reported so far in a single Si disk. Such high-Q modes can be attributed to suppressed radiation in the corresponding eigenchannels and simultaneously quenched electric (magnetic) field at momentum space. As a proof of concept, we experimentally demonstrate the emergence of the high-Q resonant modes [Q approximate to 211 for mode TE(3,4), Q approximate to 380 for mode TE(3,5), and Q approximate to 294 for mode TM(3,5)] in the scattering spectrum of a single silicon NW.

U2 - 10.1117/1.AP.3.1.016004

DO - 10.1117/1.AP.3.1.016004

M3 - Article

VL - 3

JO - Advanced Photonics

JF - Advanced Photonics

IS - 1

ER -