The effects of ultrafast laser pulse duration on the optical properties of polymers

Ultrafast laser micro-processing of polymers continues to grow in scientific and industrial applications. However, because of interactions between the ultrashort laser pulses and the polymeric material, effectively and efficiently combining these two technologies has proven complicated. Rahaman et al investigated the effect of laser pulse duration and propagation on the optical properties of transparent polypropylene.

“The goal of this research is to understand how different temporal pulse shapes interact with polymeric materials and develop a method that is efficient for ultrafast laser processing of these materials,” said Arifur Rahaman, one of the authors.

An ellipsoidal reflector-based experimental setup was used to generate in situ data. Both specular and diffusive reflection results were collected to measure optical properties during the laser processing. The researchers found polypropylene subjected to single-pulse configurations underwent dramatic morphological changes, which correlated to optical properties.

Specifically, shorter pulse durations, around 167 femtoseconds, are preferred for surface processing of the transparent polymer since strong nonlinear absorption occurs at the surface. Longer pulses, at approximately 1 picosecond, result in sub-surface and back-surface damages and are more efficient for bulk processing of the polymer.

Rahaman notes results from this work can be extended to correlate changes in optical properties with the morphological changes of polymers. In addition, laser parameters can be optimized for other important industrial materials, such as semiconductors, glass, and polymer composites.

Source: “Experimental observation of the effect of pulse duration on optical properties in ultrafast laser micro-processing of polymers,” by Arifur Rahaman, Xinpeng Du, Aravinda Kar, and Xiaoming Yu, Journal of Laser Applications (2021). The article can be accessed at https://doi.org/10.2351/7.0000462 .

This paper is part of a Journal of Laser Applications special collection called Proceedings of the International Congress of Applications of Lasers & Electro-Optics (ICALEO 2020). More papers can be found at https://lia.scitation.org/toc/jla/collection/10.2351/jla.2021.ICALEO2020.issue-1 .