Quasi-2D perovskite photonic crystals for single-mode lasing via synergistic material and structural optimization by nanoimprint lithography

Quasi-2D organic-inorganic hybrid metal halide perovskites are promising gain media for coherent light sources. However, uncontrolled crystallization and low-fidelity pattern transfer make it difficult to ensure the quality of the resulting structures. We combine 3-phosphonopropionic acid (3-PPA), which optimizes phase distribution and passivates defects, with nanoimprint lithography (NIL) that modulates crystallization kinetics to fabricate patterned quasi-2D (PEA) 2 Cs n-1 Pb n Br 3n + 1 perovskite films. As a result, the amplified spontaneous emission (ASE) threshold decreases from 5.52 to 2.11 µJ/cm 2 . Under 400 nm femtosecond-pulse excitation, the photonic crystal cavity exhibits single-mode surface-emitting lasing at 456.65 nm. As the pump fluence progressively increases from 0.23 to 0.59 µJ/cm 2 , the single-mode lasing intensity exhibits a monotonic growth. This work offers a promising route for integrating crystallization control, defect passivation, and photonic engineering.