Holographic photopolymer with high sulfur content for high refractive index modulation

Paola Galli; Richard A. Evans; Chiara Bertarelli; Andrea Bianco

doi:10.1117/12.2589160

26 April 2021 Holographic photopolymer with high sulfur content for high refractive index modulation

Paola Galli, Richard A. Evans, Chiara Bertarelli, Andrea Bianco

Proceedings Volume 11774, Holography: Advances and Modern Trends VII; 1177404 (2021) https://doi.org/10.1117/12.2589160
Event: SPIE Optics + Optoelectronics, 2021, Online Only

Abstract

The thiol-ene polymerization between a tetrafunctional thiol and a cyclic allylic sulfide (CAS) monomer is used to generate a crosslinked structure with high concentration of sulfur atoms, which allows for the manufacturing of volume phase holographic gratings with high refractive index modulation (▵n). The writing chemistry is dispersed in a cellulose acetate butyrate (CAB) matrix together with Irgacure^® 784 as free radical photoinitiator, making the system sensible to blue light. After the writing step, the performances of the grating can be further improved by means of a thermal treatment, which induces a strong enhancement of the refractive index modulation. This effect could be explained as a reorganization of the polymeric chains that leads to a marked separation between the writing chemistry and the polymeric binder and to local variations of the material density. This hypothesis is supported by different experimental evidences. Values of ▵n up to 0.0346 are reached, which are among the largest reported in the literature.

Conference Presentation

Citation Download Citation

Paola Galli, Richard A. Evans, Chiara Bertarelli, and Andrea Bianco "Holographic photopolymer with high sulfur content for high refractive index modulation", Proc. SPIE 11774, Holography: Advances and Modern Trends VII, 1177404 (26 April 2021); https://doi.org/10.1117/12.2589160

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