Nonlinear Refraction and Absorption in Polymers Used for Femtosecond Direct Laser Writing

Direct laser writing (DLW) has been recognized as a unique technique for three-dimensional (3D) prototyping with resolution beyond the diffraction limit. One trend in DLW technologies is the use of polymers, given their favorable mechanical properties and optical quality, rendering them promising for the next generation of nonlinear photonic devices. However, absorptive properties that facilitate DLW processes may also hinder the performance of polymers as all-optical devices. Furthermore, the increasing use of ultrashort pulse lasers makes refractive index dispersion a factor of fundamental importance in studying candidate materials for broadband applications. Here, we study the suitability of resins commonly used in DLW for all-optical broadband applications. We provide linear and nonlinear refractive and absorptive spectra of acrylate-based resins with different compositions, and IP-S and IP-Dip from Nanoscribe. We found nonlinear refractive indices four times higher than reported values for fused silica, one of the most widely used photonic materials, and we evaluate the potential of these materials using group velocity dispersion and figures of merits as comparative metrics.