Low Threshold Bound State in the Continuum Lasers in Hybrid Lattice Resonance Metasurfaces

Bound states in the continuum (BICs) have attracted much attention in recent years due to the infinite quality factor (Q-factor) resonance and extremely localized field. In this study, BICs have been demonstrated by dielectric metasurfaces with hybrid surface lattice resonance (SLR) in the experiment. By breaking the symmetry of geometry, SLR can be easily switched between BICs and quasi-BICs. Comparing with literature, switching between BICs and quasi-BICs is usually accompanied by wavelength shift. Here, a design rule is proposed to prevent the wavelength shift when the Q-factor is changing. Also, such a design also makes subsequent identification of the laser threshold more credible. Due to the high Q-factor, low threshold laser is one of the intuitive applications of BICs. Utilize the high localized ability of BICs, low threshold BICs laser can be achieved by the dielectric metasurface immersed with Rhodamine 6G. Interestingly, due to the high Q-factor resonance of BICs, the laser signals and images can be observed in almost transparent samples. Not only the BICs laser is demonstrated in the experiment, but also the mechanism of BICs is deeply analyzed. This study can help readers better understand this novel feature of BICs, and provide the way for engineer BICs metasurfaces. The device can provide various applications, including laser, optical sensing, non-linear optics enhancement, and single-photon source.