3-(Fluoropyrrolidinium)MnCl₃ Perovskite Featuring Strong Third-Order Nonlinear Absorption for Ultralow-Threshold Optical Limiting

The escalating demand for laser protection in military, industrial, and commercial sectors has intensified the pursuit for advanced optical limiting (OL) materials capable of safeguarding against high-intensity laser threats. Despite the progress, current OL materials are beset with challenges such as low linear transmittance, narrow operational bandwidths, and inadequate response speeds, which hinder their effectiveness in practical applications. In this work, an organometallic hybrid perovskite of 3-(fluoropyrrolidinium)MnCl₃ demonstrated significant reverse saturable absorption properties, with an ultralow starting threshold of 9 mJ/cm² and a substantial third-order nonlinear absorption coefficient of 4.1 × 10^-5 m/W at 532 nm. Combined femtosecond transient absorption spectroscopy and density functional theory (DFT) calculations revealed that the strong nonlinear optical response originates from an excited-state absorption-dominated carrier dynamics process. This work establishes a novel material platform for developing high-sensitivity laser protection devices.