Stable-wavelength perovskite nanoplatelet laser via mixed-phase engineering
Perovskite lasers suffer from pump-density-induced wavelength shifts, limiting their use in interferometry and quantum information systems. This study demonstrates a wavelength-stable laser using mixed-phase MAPbI3 nanoplatelets. At 293 K, the tetragonal phase exhibits a blueshift of ~0.4 nm μJ⁻¹ cm² with increasing pump density, while at 80 K, the orthorhombic phase shows a redshift of ~1 nm μJ⁻¹ cm². By stabilizing the nanoplatelets in a mixed orthorhombic-tetragonal phase at 163 K, the pump-induced wavelength shifts are completely suppressed. The lasing threshold decreases from 18.4 μJ cm⁻² at room temperature to 4.5 μJ cm⁻² at 163 K. Finite element simulations confirm the opposite shift directions: tetragonal phase resonance shifts from 780.86 nm at 296.62 K to 779.66 nm with a 10.70 K temperature rise, while orthorhombic phase shifts from 794.78 nm to 796.50 nm with a 1.69 μJ cm⁻² pump increase. The thermo-optic coefficient is estimated at 7.5 × 10⁻⁴ K⁻¹. This mixed-phase engineering strategy offers a viable route to pump-insensitive wavelength stability in micro/nano lasers.