Fig. 1: Scanning electron microscope (SEM) image and band diagram of a topological polarization singular laser.
From: Topological polarization singular lasing with highly efficient radiation channel
a SEM image of a topological polarization singular laser, where a semiconductor membrane serves as photonic crystal and gain material simultaneously. The lattice constant (\(a\)) is ~1240 nm, and the operation wavelength (\(\lambda\)) is ~1567 nm in free space. The length of the reciprocal lattice vector (\({G}_{0}=\frac{2\pi }{a}\)) is smaller than the diameter of light cone (\(\frac{4\pi }{\lambda }\)), which allows radiation to free space from the second Brillouin zone. b Three-dimensional full wave simulated band diagram of the device. Along \({k}_{x}\) direction, the radiation field from the second Brillouin zone supports a pair of polarization singularities with topological charge of −1. c Schematic of a topological polarization singular laser with paired singular (left emission beam) and radiation (right emission beam) channels. For clarity, only one pair of emission channels is shown.
