Fig. 7: Lasing from BICs.
From: Nanophotonic nonlinear and laser devices exploiting bound states in the continuum
a Directional lasing in nanoantenna arrays. Schematic of a GaAs nanopillar array on a fused silica substrate embedded in hydrogen silsesquioxane (HSQ) resist (a1). Measured back-focal plane image (a2) and directivity (a3) of the emission above the lasing threshold. Reprinted by permission from ref. 19, copyright 2018. b Ultrafast control of vortex beam. Schematic of a two-beam pumping experiment and the measured far-field emission patterns under both symmetric and asymmetric excitations (b1). Transition from a BIC microlaser to a linearly polarized laser (b2) and the reverse process (b3). Reprinted by permission from ref. 23, copyright 2020. c Ultralow-threshold super-BIC laser. Scanning electron microscope (SEM) images of a fabricated laser structure consisting of 40 × 40 unit cells (c1). Measured lasing wavelengths and far-field images of symmetry-protected BIC lasers (black dots; right inset) and accidental BIC lasers (red dots; left inset) as a function of the lattice constant (c2). The bottom inset shows the above-threshold spectrum of a super-BIC laser. Measured threshold values divided by the pump area (c3) and Q factors estimated by the peak wavelength and the linewidth at the transparent pumping condition (c4), as a function of the lattice constant. The orange line indicates the Q factor obtained using the resolution-limited linewidth of the spectrometer. Reprinted by permission from ref. 25, copyright 2021. d Lasing from single nanoparticles. SEM image (d1) and simulated near field of a quasi-BIC (d2) in a single GaAs nanocylinder. Evolution of the emission spectrum of the resonator at different pumping fluence values (d3). Reprinted by permission from ref. 24, copyright 2020.
