Quasibound state in the continuum (quasi‐BIC) is a long‐lived state with a high quality factor (Q factor). Here quasi‐BICs in nematic liquid crystal (LC) layer embedded between a distributed Bragg reflector (DBR) and a metal layer are studied. First, a special class of true BICs between the DBR and the metal film with field localization provided by the Brewster transverse electric (TE) reflection in the DBR is experimentally demonstrated. It is demonstrated that the Q factor of the quasi‐BIC can be tuned by the LC optical axis rotation in a wide range being only restricted by metal losses. The change of coupling with the radiation channel leads to a critical coupling condition, providing a total absorption of incident light. The acquired quasi‐BIC resonance is extremely sensitive to the temperature due to the narrow nematic temperature range of the LC. The quasi‐BIC transforms to BIC at the LC‐isotropic clearing point, due to closing of the radiation channel.

中文翻译：

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具有温度可调Q因子和Brewster角的临界耦合点的连续谱中的拟束缚态

连续体中的准结合状态（准BIC）是具有高品质因数（Q系数）的长寿命状态。这里研究了嵌入在分布式布拉格反射器（DBR）和金属层之间的向列液晶（LC）层中的准BIC。首先，通过实验证明了DBR和金属膜之间的一类真正的BIC，其具有通过DBR中的Brewster横向电（TE）反射提供的场局部化。事实证明，准LC的Q因子可以通过LC光轴在很宽的范围内旋转而仅由金属损耗来调节。与辐射通道耦合的改变导致临界耦合条件，从而提供了入射光的全部吸收。由于LC的向列温度范围狭窄，因此获得的准BIC谐振对温度极为敏感。由于辐射通道的关闭，准BIC在LC各向同性的清除点转换为BIC。