Infrared light induced degradation of polymeric materials used in optical devices

This paper summarizes the current understanding of laser-induced damage in polymeric material systems. A detailed literature review including macroscopic and microscopic models for high optical intensity induced degradation and damage of polymeric systems is given. This is followed with experimental results and discussion on degradation of two different commonly used polymeric systems (acrylic and epoxy) due to exposure to medium optical intensity infrared light. We show that in acrylic systems, degradation occurs slowly over time at infrared wavelengths as high as 1480 nm and optical power densities as low as 5×10⁴ W/cm² via a multi-photon absorption process. We show that in bisphenol based epoxy systems (bisphenol based epoxies are widely used as structural adhesives in many optical devices), degradation also occurs via a multi-photon absorption process. The degradation process in both cases is very sensitive to both wavelength and optical power density. Finally, we give preliminary design guidelines for the use of bisphenol-based epoxies in high optical power density applications.