Topological polarization singular lasing with highly efficient radiation channel

Abstract

Bound states in the continuum (BICs) in photonic crystals describe the originally leaky Bloch modes that can become bounded when their radiation fields carry topological polarization singularities. However, topological polarization singularities do not carry energy to far field, which limits radiation efficiencies of BICs for light emitting applications. Here, we demonstrate a topological polarization singular laser which has a topological polarization singular channel in the second Brillouin zone and a paired linearly polarized radiation channel in the first Brillouin zone. The presence of the singular channel enables the lasing mode with a higher quality factor than other modes for single mode lasing. In the meanwhile, the presence of the radiation channel secures the lasing mode with high radiation efficiency. The demonstrated topological polarization singular laser operates at room temperature with an external quantum efficiency exceeding 24%. Our work presents a new paradigm in eigenmode engineering for mode selection, exotic field manipulation and lasing.

Taming Friedrich–Wintgen Interference in a Resonant Metasurface: Vortex Laser Emitting at an On-Demand Tilted Angle

“…Therefore, our device exhibits two oblique vector vortex lasing emissions as illustrated in Figure 5d. We note that while a high-angle emitting microlaser using BIC concepts has been recently demonstrated 31,43 the reported lasing actions do not take place at a singularity point and exhibit only a Gaussian beam. Our observation is then the first demonstration of oblique vector vortex lasing action.…”

“…As a consequence, the radiation pattern of isolated BICs exhibits a polarization vortex in momentum space , with the vorticity dictated by the topological nature of the resonances. − When combined with high gain materials, one may obtain lasing action of which the emission is a vector vortex beam pinned at the BIC location in momentum space. Up to now, vector vortex lasers based on BICs have been reported for different lattice geometries and gain materials. − Remarkably, the polarization pattern or the lasing wavelength of BIC vector beams could be dynamically tuned by harnessing nonlinearity originated from free-carrier injections, phase change materials, or an exciton–polariton strong coupling regime . However, to our knowledge, all of the vector vortex microlasers in the literature are pinned at the Γ point of the momentum space.…”

Evolution and Combination of Light Line Singularities in Planar Multilayers

“…In general, BICs can be classified into two categories: symmetry-protected BICs (Γ-BICs), deriving from the inherent symmetry of the system, and accidental BICs, deriving from that two or more radiation channels cancel one another in the far field . They can exist in several systems including photonic crystal slabs ,, Fabry–Perot cavity, and metasurfaces, − with various potential applications including biosensors, detectors, , and lasing. − …”