Bound states in the continuum (BICs) have attracted considerable research attention due to their infinite quality factor (Q-factor) and extremely localized fields, which drastically enhances light–matter interactions and yields high potential in topological photonics and quantum optics. In this study, the room temperature directional lasing normal to a BIC metasurface is demonstrated with hybrid surface lattice resonances. Compared to the plasmonic nanolasers, the BIC metasurface lasers possess directional radiation and a larger emission volume. The high Q-factor resonance of BIC metasurface overcomes the limitation of a large mode volume in achieving low-threshold lasing. In addition, a design rule is proposed to prevent the occurrence of wavelength shift when the Q-factor changes; thus, the lasing thresholds for different BIC metasurfaces can be compared. In this work, the high localization ability of BICs is used to achieve the low lasing threshold (1.25 nJ) at the room temperature. The “light in–light out” diagram of the aforementioned laser based on simulations and experiments exhibits a large spontaneous emission coupling factor (β = 0.9) and the S-curve. The device developed in this study can be used in various applications, such as quantum emitters, optical sensing, nonlinear optics, and topological states engineering.

中文翻译：

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混合晶格共振超表面中连续谱激光器的低阈值束缚态

连续介质中的束缚态 (BIC) 因其无限的品质因数 ( Q- factor ) 和极其局域化的场而引起了相当多的研究关注，这极大地增强了光与物质的相互作用并在拓扑光子学和量子光学中产生了巨大的潜力。在这项研究中，通过混合表面晶格共振证明了垂直于 BIC 超表面的室温定向激光。与等离子体纳米激光器相比，BIC 超表面激光器具有定向辐射和更大的发射体积。BIC 超表面的高Q因子共振克服了大模式体积在实现低阈值激光方面的限制。此外，提出了一个设计规则，以防止当Q-因素变化；因此，可以比较不同 BIC 超表面的激光阈值。在这项工作中，BIC 的高定位能力用于在室温下实现低激光阈值 (1.25 nJ)。基于模拟和实验的上述激光器的“光输入-光输出”图表现出很大的自发发射耦合因子（β = 0.9）和 S 曲线。本研究中开发的器件可用于各种应用，例如量子发射器、光学传感、非线性光学和拓扑状态工程。