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<p>Whispering gallery modes (WGMs) have emerged as a unique platform to produce extreme localization and enhancement of light waves due to their high-quality (<i>Q</i>) factors. This study theoretically demonstrates the excitation of dark WGMs in individual elliptical dielectric disks under the normal incidence of a plane wave, where the <i>Q</i> factors can be pushed even higher. This is achieved by turning the dark WGM into a quasi-bound state in the continuum (QBIC) case, where the dark WGM and a bright anapole mode are involved in the interferences. By adjusting the geometric parameters of the elliptical disk, the <i>Q</i> factor of the QBIC-WGM can be further enhanced by more than 40% compared to the intrinsic WGM. In addition, by introducing an additional degree of freedom, namely a gap, stacked elliptical disks can be constructed to achieve QBIC-WGM, and it is found that both the response and <i>Q</i> factor of this QBIC mode are stronger than that of the intrinsic WGM. Our results demonstrate that by establishing a QBIC situation, the WGMs in disks can be excited with normal incidence, which is experimentally more feasible. Furthermore, the <i>Q</i> factors of WGMs can be pushed even higher, which could find applications in enhanced light-matter interactions.</p>

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Enhancing Quality Factors of Dark Whispering Gallery Modes via Quasi-bound States in the Continuum in Subwavelength All-Dielectric Disks

  • 期刊论文

  • 发表日期：

    2025年7月8日

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  • Xiao-Jing Du,
  • Lin Ma,
  • Yue You,
  • Jun He,
  • Zhong-Jian Yang

摘要

Whispering gallery modes (WGMs) have emerged as a unique platform to produce extreme localization and enhancement of light waves due to their high-quality (Q) factors. This study theoretically demonstrates the excitation of dark WGMs in individual elliptical dielectric disks under the normal incidence of a plane wave, where the Q factors can be pushed even higher. This is achieved by turning the dark WGM into a quasi-bound state in the continuum (QBIC) case, where the dark WGM and a bright anapole mode are involved in the interferences. By adjusting the geometric parameters of the elliptical disk, the Q factor of the QBIC-WGM can be further enhanced by more than 40% compared to the intrinsic WGM. In addition, by introducing an additional degree of freedom, namely a gap, stacked elliptical disks can be constructed to achieve QBIC-WGM, and it is found that both the response and Q factor of this QBIC mode are stronger than that of the intrinsic WGM. Our results demonstrate that by establishing a QBIC situation, the WGMs in disks can be excited with normal incidence, which is experimentally more feasible. Furthermore, the Q factors of WGMs can be pushed even higher, which could find applications in enhanced light-matter interactions.