Compact Nanolaser Relying on Bound States in the Continuum with Simultaneous Pump and Emission Enhancement

Bound states in the continuum (BICs), characterized by high-Q modes, have demonstrated exceptional capabilities for enhancing light-matter interactions and, when combined with gain media, can enable compact lasers with low threshold power. However, conventional BIC lasers typically rely on the emitting light forming a BIC mode, leading to vertical emission, and often lack mechanisms to enhance pump efficiency. In this work, we propose a photonic crystal laser design that incorporates high-Q modes at both pump and emitting wavelengths. The pump light at 980 nm is designed to form a BIC state near the Gamma-point, while the emitting light at 1550 nm is confined within a bandgap-defined cavity mode at the M-point, allowing efficient in-plane emission. This design leads to a compact footprint of 19.7 x 17.1 mu m2 and predicts a significant reduction in threshold power compared with a laser with a single resonance at the emission wavelength, providing a promising approach for developing compact on-chip lasers with significantly improved efficiency.