Broadband Ultrafast Nonlinear Optical Limiting at a Porphyrin-Based 2D Polymer

Ultrafast lasers have significantly contributed to the advancement of research and technology; however, high-intensity lasers bring potential risks to precision instruments and the human eye. Developing optical limiting (OL) devices capable of reasonably controlling laser energy to an acceptable energy level is imperative. Nevertheless, achieving both exceptional OL performance and broad-spectrum laser intensity tunability proves highly challenging. In this work, the synthesis of a porphyrin-based 2D polymer (Por-2DP) using a template-assisted self-coupling polymerization, constructing a 2D framework through the carbon-carbon single bond coupling of porphyrin monomer is presented. The resultant Por-2DP demonstrates remarkable broadband nonlinear absorption performance, spanning the visible and near-infrared spectral regions under an ultrafast pulse laser (35 fs) for the first time. OL thresholds at excitation wavelengths of 515, 800, and 1550 nm are determined to be 1.44, 0.48, and 0.54 mJ cm-2, respectively, surpassing reported 2D materials to date. Additionally, the Por-2DP exhibits prominent photostability, enabling sustained operation under intense light conditions for a long time, thereby enhancing OL practical applicability. This study not only introduces a novel OL material and device but also promotes the application of innovative 2D organic polymers in NLO field. Porphyrin-based 2D polymer featuring a highly conjugated system and abundantly pi-delocalized electrons exhibits remarkable ultrafast reverse saturable absorption properties spanning the visible and near-infrared spectral regions, derived from the extended conjugated structure and quantum confinement effects. Additionally, the Por-2DP manifests distinguished optical limiting performance across a broadband spectrum, with the optical limiting threshold exceeding that of reported optical limiting materials. image