Lasing characteristics and stress-tuning effects in GaN beam microcavities

A novel microcavity based on gallium nitride (GaN) beams is demonstrated, and its lasing characteristics and stress-bandgap coupling mechanisms are systematically investigated. GaN beams with varying lengths (50-150 μm) are fabricated via micro-nanofabrication, and their optomechanical responses under gravity -induced bending are analyzed through COMSOL simulations and confocal micro-photoluminescence (μ-PL) spectroscopy. Results reveal a linear correlation between beam length and internal stress distribution, with the maximum stress reaching 1.0736 × 10^-4 MPa and a vertical displacement of 0.5268 pm. Stress-induced bandgap narrowing triggers a redshift in Fabry-Perot (FP) lasing, quantified by Q factors of up to 1486. A theoretical model elucidates the synergistic modulation of spectral properties via piezoelectric polarization and deformation potential effects, establishing a quantitative linear stress-bandgap relationship. Experimental validation confirms that bending strain in GaN beams reduces the bandgap through lattice deformation potentials and piezoelectric internal fields, resulting in a linear redshift in emission wavelength with stress. This work provides a pathway towards high-resolution, high-sensitivity and low-mode-volume optomechanical sensors with dual functionality in light emission and sensing.