Thermoset polymers as host for optical limiting

The human eye, sensors, and photoreceptors can be damaged if they are submitted to laser beams with high intensities and low divergence. In the military field, an optical sensor can be damaged by pulsed laser radiations when exposed beyond its capacities. In order to have a protection against such threats, passive optical limiting is used. A mix between a reactive oligomer and a monomer, with methacrylate functions, is studied in the present work giving a thermoset matrix. To prevent the monomer evaporation, which results in the formation of bubbles in the final material, related to the reaction exotherm, an oligomer and a monomer with a high boiling temperature are used as precursors, giving a good alternative to a thermoplastic matrix like polymethyl methacrylate (PMMA). We report the experimental results of transient thermally induced optical nonlinearities (i.e., nonlinear refraction) in methacrylate-based polymer filters at a nanosecond timescale, focus will be made to compare third order nonlinear refractive index from thermally induced refractive index. Optical filters are obtained by chemical bulk processes. In the present work, both thermoplastics and thermosets matrices were synthesized in order to characterize their optical limiting properties by mean of an appropriate custom-made optical setup as well as their nonlinear refractive indices measured by the z-scan technique. Optical measurements in the nonlinear regime are achieved at the wavelength of 1064 nm. To the best of the authors' knowledge, such a work dealing on 3D-network methacrylate-based host has never been published.