  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.
