Low-threshold surface-emitting nanolasers based on guided-mode resonance gratings with deep grooves

Abstract

Periodic dielectric structures, such as guided-mode resonance (GMR) gratings, typically serve as optical cavities. However, due to inherent losses, the quality (Q) factor for GMR cavities tends to be low. Here, we numerically report lasing action from a high-Q cavity in one-dimensional (1D) and two-dimensional (2D) GMR gratings featuring deep grooves. We achieve a high-Q state by adjusting the groove depth to slightly shift the resonance away from the bound states in the continuum, which possess an infinite Q factor. By further aligning the resonance wavelength with the emission band of the gain medium, a nanolaser with a low threshold is achieved. Using a four-level gain system and a finite-difference time-domain approach to simulate the active optical responses, we show that optically pumped lasing with directional beam emission is achieved in a GMR grating coated with an organic gain medium. Additionally, we present groove depth-regulated 2D GMR gratings with high Q factors that are notably polarization-independent. We find that the lasing action is slightly influenced by the polarization angle due to distinct electric field distributions, even though the Q factor remains constant. Our design for low-threshold nanolasers shows promise for various photonic applications, including sensing, optical communications, and bio-imaging.