[18a-A33-1~10] 3.11 Nanoscale optical science and near-field optics

9:30 AM - 9:45 AM JST(12:30 AM - 12:45 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation Award

[18a-A33-3] Investigation of controllable quasi-BIC modes in magneto-photonic crystals under external magnetic field

〇Siyuan Gao¹, Satoshi Iwamoto², Yasutomo Ota¹ (1.Keio University, 2.RCAST, UTokyo)

Keywords:

Magneto-photonic crystal,quasi-BIC,controllable Q factor

Bound states in the continuum (BIC) are highly valued in photonics for their ability to confine light without radiative losses. Symmetry-protected BIC modes in photonic crystals (PhCs) can transition to quasi-BIC states when symmetries are broken, typically induced by perturbations like phase changes, electric currents, and heat, though these methods often cause large resonance frequency shifts, additional losses, and slow responses. An external stimulus that induces quasi-BIC modes with fewer side effects and faster response is desirable. This study explores the effect of an external magnetic field on a 2D photonic crystal with C4V symmetry composed of MO material, using numerical simulation methods, we identified BIC modes under zero magnetic field and observed that applying a magnetic field introduces non-zero off-diagonal components in the permittivity tensor. With vertically induced magnetic field, BIC modes remain unchanged. When applying in-plane magnetic field, the Q factor of the modes with C4v symmetry was significantly decreased due to the broken symmetry in the field distribution. However, Modes fulfills C2V symmetry remains unaffected. The ability to dynamically control the Q factor opens up new possibilities for designing reconfigurable photonic devices, such as optical sensor and optical switch.