Nonlinear two-photon pumped vortex lasing based on quasi-bound states in the continuum from perovskite metasurface.

The experimental observation of nonlinear two-photon pumped vortex lasing from perovskite metasurfaces is demonstrated. The vortex lasing beam is based on symmetry-protected quasi-bound states in the continuum (QBICs). The topological charge is estimated to be +1 according to the simulation result. The quality factor and lasing threshold are around 1100 and 4.28 mJ/cm 2 , respectively. Theoretical analysis reveals that the QBIC mode originates from the magnetic dipole mode. The lasing wavelength can be experimentally designed within a broad spectral range by changing the diameter and periodicity of the metasurface. The finite array size effect of QBIC can affect the quality factor of the lasing and be used to modulate the lasing. Results shown in this study can lead to more complex vortex beam lasing from a single chip and previously unidentified ways to obtain ultrafast modulation of the QBIC lasing via the finite array size effect.