High- Q perfect light absorption enabled by degenerate merging BICs

作者：Kai Nan Qi, Junyang Ge, Xiang Shen, Yixiao Gao · 发表于：Optics Express · 年份：2025 · DOI：10.1364/oe.567508 · 被引用次数：6 · 研究领域：Optical Coatings and Gratings、Photonic and Optical Devices、Near-Field Optical Microscopy

Achieving high- Q light absorption within a thin dielectric film is highly desired for optoelectronic applications. However, controlling the absorption linewidth remains challenging, as it requires simultaneous control over both radiative and non-radiative loss to satisfy the critical coupling condition. In this paper, we report the design of a metasurface-based, polarization-independent perfect light absorber with a tunable absorption Q factor. The radiative decay rate can be tuned by adjusting the lattice constant of the metasurface, leveraging the mechanism of degenerate merging bound states in the continuum (BICs). Meanwhile, the non-radiative loss rate is controlled by introducing a waveguiding layer that modulates the overlap between the resonant field and the absorbing medium. This dual-control mechanism enables the metasurface absorber to achieve arbitrarily high absorption Q factors at a desired wavelength under critical coupling. Our approach offers a versatile platform for narrowband light absorption with tunable spectral linewidths, opening new opportunities for photodetection and spectral sensing applications.