Synergistic strain and defect engineering for bandgap-tailored GaAs microwires: Enabling mid-infrared pulsed laser generation

III–V semiconductor wires (SWs) are key components in photodetectors, solar cells, and lasers. Gallium arsenide (GaAs) SWs stand out due to their high thermal conductivity, mature fabrication, and silicon compatibility. However, their intrinsic bandgap limits mid-infrared (MIR) applications. Bandgap engineering is critical for addressing this limitation. In this work, first-principles calculations are employed to analyze the synergistic modulation characteristics of strain and point defects on the bandgap of GaAs microwires (MWs). Results reveal that combining As_Ga antisite defects (Ga sites replaced by As atoms) with uniaxial tensile strain drastically reduces the bandgap of large-diameter GaAs MWs by up to ∼80 %, outperforming V_Ga (Ga atom vacancy) or Ga_As antisite defects (As sites replaced by Ga atoms). Experimentally, a synergistic strain·and·defect·engineered GaAs MW-based optical switch was integrated into a bulk laser system, achieving passively Q-switched dual-wavelength lasing at 1.97 μm and 2.72 μm, which was the first demonstration of GaAs MWs enabling MIR pulsed lasers. The results presented here indicate that the synergistic band structure regulation by antisite defects and uniaxial tensile strain effectively expands the response wavelength range of GaAs SW-based optical devices and provides a reference for bandgap regulation in a III–V SW system.