2025/08/04 by Michalis Stavrou, Dimitra Ladika, Edvinas Skliutas +5 · 1 voice
Engineering · Materials Science · #Nonlinear Optical Materials Studies #Nanofabrication and Lithography Techniques #Phase-change materials and chalcogenides
paper · pdf · doi:10.1515/nanoph-2025-0066
openalex publication_date 2025/08/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract Accurate knowledge of nonlinear optical parameters is essential for optimizing energy deposition in ultrafast laser 3D printing, yet these values remain undetermined for many commonly used materials. In this study, we address this gap by experimentally determining the two‐photon absorption (TPA) and non‐linear refraction coefficients ( β and n 2 ) of the widely used SZ2080 TM resist with the photo‐initiators (PI) IRG369 and BIS (Irgacure 369 and 4,4′ bis(diethylamino)‐benzophenone or Michler’s ketone). Using the Z‐scan method at 515 nm with a low repetition rate (1 kHz) to avoid thermal accumulation, we found that the nonlinear response of the host polymer has a considerable contribution to energy deposition despite the addition of the PI, as the host polymer makes up the majority of 99 % in the solution. The TPA cross section σ were 5.7 ± 0.4 GM (1 GM = 10 −50 cm 4 s photon −1 ) for pure SZ2080 TM , GM for IRG and GM for BIS at 515 nm. The nonlinear refractive index n 2 for pure polymer was (85.3 ± 6) × 10 −5 cm 2 /TW, favoring a self‐focusing, and was larger than that for PIs: cm 2 /TW (IRG369) and cm 2 /TW (BIS). Hence, the properties of the host material govern non‐linear light propagation, although, in high numerical aperture focusing, self‐focusing has a minor contribution to the variation of refractive index. Crucially, the determined TPA coefficients for pure SZ2080 TM provide experimental evidence that it can initiate polymerization without PIs, enabling a more sustainable and environmentally friendly fabrication route by avoiding the use of toxic additive compounds. These findings will allow for the estimation of exact energy deposition in 3D laser printing using ultrashort laser pulses and support the development of an initiator‐free additive manufacturing approach.