Control of surface structures for PVA/AA photopolymer functionalization by ultrafast laser processing

Ultrafast laser processing provides a powerful approach for tailoring the surface morphology of photosensitive materials with high spatial precision. In this work, we investigate the formation of surface relief structures in poly(vinyl alcohol)/acrylamide (PVA/AA) photopolymers under femtosecond laser irradiation, focusing on the role of the repetition rate in the photopolymerization process.

Experiments were performed at 1030 nm using 220 fs pulses, analyzing single-pulse irradiation and multipulse regimes, where repetition rates of 1 kHz and 60 kHz were explored. The resulting structures exhibit a Gaussian-like morphology associated with the diffusion-driven monomer redistribution. A systematic study of the structure height as a function of the fluence reveals a clear dependence on both the number of pulses and the repetition rate.

In particular, lower repetition rates lead to larger structure heights under identical irradiation conditions, indicating that the temporal spacing between pulses enhances monomer diffusion towards the irradiated region. These results highlight the role of repetition rate as a key parameter governing the balance between photopolymerization and mass transport, enabling controlled surface structuring in photopolymer materials