Key Takeaways & Executive Findings
- •• • At 163 K, mixed-phase MAPbI3 nanoplatelets achieve zero wavelength shift under pump density variation, eliminating a critical instability that plagues perovskite lasers for interferometric and quantum applications. • • Lasing threshold drops from 18.4 μJ cm⁻² at 293 K to 4.5 μJ cm⁻² at 163 K, a 75.5% reduction, enabling lower-power operation and reduced thermal load in integrated photonic circuits. • • Tetragonal phase exhibits a blueshift of 0.4 nm μJ⁻¹ cm², while orthorhombic phase shows a redshift of 1 nm μJ⁻¹ cm²; the opposing signs allow cancellation in the mixed phase, with a thermo-optic coefficient of 7.5 × 10⁻⁴ K⁻¹. • • Finite element simulations validate experimental shifts: tetragonal resonance moves from 780.86 nm at 296.62 K to 779.66 nm with a 10.70 K rise; orthorhombic shifts from 794.78 nm to 796.50 nm with a 1.69 μJ cm⁻² pump increase, confirming the mechanism for phase-dependent stability.
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Abstract
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.
1. Introduction
Perovskite lasers have attracted intense interest due to their high absorption coefficient, tunable bandgap, and solution processability, with MAPbI3 nanoplatelets offering natural whispering gallery mode cavities and quality factors up to 2180. However, a persistent bottleneck is the pump-density-induced wavelength shift: as pump density increases, sample heating alters the refractive index and optical path length, causing emission shifts. For instance, MAPbI3 nanowires exhibit a 0.2 nm shift from 787.1 to 786.9 nm as pump density rises from 580 to 630 nJ cm⁻², and CsPbBr3 nanocuboids shift from 539.4 to 539.0 nm over 44–60 μJ cm⁻². Such instability disqualifies these lasers from precision applications like interferometry and quantum state preparation, where even sub-nanometer drift displaces interference fringes or corrupts photonic states.
Existing strategies to mitigate wavelength drift have focused on external temperature stabilization or cavity design, but these add complexity and do not address the intrinsic thermo-optic response. This work introduces mixed-phase engineering: by stabilizing MAPbI3 nanoplatelets in a coexisting orthorhombic-tetragonal phase at 163 K, the opposing wavelength shifts of each phase—blueshift in tetragonal, redshift in orthorhombic—cancel completely. The result is a pump-insensitive laser with a threshold of 4.5 μJ cm⁻², compared to 18.4 μJ cm⁻² at 293 K. This approach directly resolves the wavelength stability bottleneck without external feedback, offering a materials-level solution for micro/nano lasers requiring fixed emission wavelengths.
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Guohui Li, Yulong Ji, Ruofan Zhao, Lin Xue, Ye Zhang, Kaibo Zheng, Yanxia Cui (2025). Stable-wavelength perovskite nanoplatelet laser via mixed-phase engineering. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3513-6
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Frequently Asked Questions
What is the failure mechanism that causes wavelength shift in perovskite lasers under varying pump density?
Pump absorption raises the sample temperature via the Beer-Lambert law, altering the refractive index and optical cavity length. In MAPbI3 nanoplatelets, the thermo-optic coefficient is 7.5 × 10⁻⁴ K⁻¹, leading to a 1 nm μJ⁻¹ cm² redshift in the orthorhombic phase and a 0.4 nm μJ⁻¹ cm² blueshift in the tetragonal phase. The mixed phase cancels these opposing shifts at 163 K.
How does the lasing threshold at 163 K compare to room temperature, and what enables the reduction?
The threshold decreases from 18.4 μJ cm⁻² at 293 K to 4.5 μJ cm⁻² at 163 K, a 75.5% reduction. This is attributed to reduced non-radiative recombination and improved gain at lower temperature, as well as the mixed-phase stabilization that suppresses thermal drift.
Can this mixed-phase approach be scaled for commercial production, and what are the cost implications?
The method relies on temperature-controlled synthesis of MAPbI3 nanoplatelets, which is compatible with solution processing. However, maintaining 163 K operation requires cryogenic cooling, adding operational cost. For applications where wavelength stability is paramount, such as quantum photonics, the trade-off may be justified. Further work is needed to achieve similar stability at higher temperatures.
What is the evidence that the wavelength shift cancellation is due to phase coexistence rather than other effects?
Finite element simulations show opposite resonance shifts: tetragonal phase shifts from 780.86 nm to 779.66 nm with a 10.70 K rise, while orthorhombic shifts from 794.78 nm to 796.50 nm with a 1.69 μJ cm⁻² pump increase. Experimental data at 163 K show no shift, confirming that the mixed phase balances these opposing thermo-optic responses.
What are the limitations of this study regarding long-term stability and practical deployment?
The study does not report degradation rates or lifetime under continuous operation. Perovskite materials are known to degrade under moisture, oxygen, and UV exposure. The requirement for 163 K operation limits use to cooled environments. Future research must address encapsulation and higher-temperature phase engineering to enable widespread adoption.
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