Enabling infinite <i>Q</i> factors in absorbing optical systems
Radosław Kołkowski, Andriy Shevchenko
Abstract
Abstract Resonant optical structures have widespread applications in science and technology. However, their quality ( Q ) factors can be significantly deteriorated, if some of their parts exhibit optical absorption. Here, we show that by coupling a lossy mode of such a structure to two independent lossless modes, one can create a nonradiating and absorption‐free bound state in the continuum (BIC). The Q factor of such a BIC is theoretically unlimited despite interaction with an absorbing structure. We use this mechanism to design a plasmonic metasurface with Q factors that are close to 10 7 in the visible spectral range. The proposed mechanism is general and can be used to engineer ultrahigh‐ Q resonances in various systems containing absorbing structures.