All-Optical Control of Vortex Lasing in Silicon-Organic Lattices.

This paper reports a silicon-organic hybrid lattice that can lase with vortex emission and allow all-optical control. We combine an array of amorphous silicon nanodisks with gain from dye molecules in organic solvents to generate vortex lasing from bound states in the continuum under pulsed optical pumping. Irradiating the device with an additional continuous wave green laser beam can cause optical heating in silicon and lead to negative change in the refractive index of the organic solvents; meanwhile, the green laser beam can provide additional gain. Dynamic tuning of the lasing wavelength is achieved by varying the intensity of the controlling beam. Furthermore, the vortex beam lasing can be switched to single-lobed beam lasing by moving the controlling spot to break the in-plane symmetry within the pumping spot. Our findings could shed new light on active silicon topological devices.

Unidirectional Lasing from Mirror-Coupled Dielectric Lattices.

This paper reports how a hybrid system composed of transparent dielectric lattices over a metal mirror can produce high-quality lattice resonances for unidirectional lasing. The enhanced electromagnetic fields are concentrated in the cladding of the periodic dielectric structures and away from the metal. Based on a mirror-image model, we reveal that such high-quality lattice resonances are governed by bound states in the continuum resulting from destructive interference. Using hexagonal arrays of titanium dioxide nanoparticles on a silica-coated silver mirror, we observed lattice resonances with quality factors of up to 2750 in the visible regime. With the lattice resonances as optical feedback and dye solution as the gain medium, we demonstrated unidirectional lasing under optical pumping, where the array size was down to 100 µm × 100 µm. Our scheme can be extended to other spectral regimes to simultaneously achieve strongly enhanced surface fields and high quality factors.