Multiphotonic Tuning of Nonlinearities Exhibited by Plasma Polypyrrole

Polypyrrole (PPy) synthesized via plasma polymerization (PPPy) offers a unique combination of electrical conductivity, biocompatibility and stability. This advanced material has emerged as a promising platform for next-generation optoelectronics and multiphotonic biosensors. However, fully unlocking its potential has been hindered by processing challenges that restrict the fabrication of tailored specimens for precise optical and mechanical characterization. This work overcomes these limitations by isolating and analyzing the nonlinear optical (NLO) response of PPPy across three distinct architectural paradigms: Electrospinning, Coating on SiO₂ Slides, and Dust of Polymer. Using open- and closed-aperture Z-scan techniques, we demonstrate that PPPy exhibits highly pronounced, architecture-dependent NLO behaviors. Notably, the Electrospinning PPPy morphology triggered a full order-of-magnitude enhancement in the nonlinear refractive index (n₂) alongside low-threshold nonlinear absorption (β × 10^-8 cm/W). Irradiance-dependent properties further revealed an optical anisotropy, directly governed by the structural and morphological orientation inherent to each processing method. Since optical nonlinearities are closely related to mechanical and electronic properties, these findings provide a critical blueprint for developing macromolecular architectures, opening new pathways for biocompatible cutting-edge multiphotonic platforms, innovative coatings and surface modifications for tailored implants.