Optical properties of photoresists for femtosecond 3D printing: refractive index, extinction, luminescence-dose dependence, aging, heat treatment and comparison between 1-photon and 2-photon exposure

TLDR

Femtosecond 3D printing is a key technology for producing nano‑ and micro‑scale optical devices, and precise knowledge of visible and near‑infrared dispersion is essential for designing such elements. This study measures the refractive index of several commercial photoresists (IP‑S, IP‑Dip, IP‑L, OrmoComp, IP‑Visio, PO4) under varying UV doses, aging, heat treatment, and two‑photon exposure. Refractive indices were obtained with a modified, automated Pulfrich refractometer using total internal reflection, and dispersion curves were fitted with both Cauchy and Sellmeier models. The work reports Abbe and Schott catalog numbers for nearly fully polymerized resists, along with quantitative extinction and luminescence data for all tested photoresists.

Abstract

Femtosecond 3D printing has emerged as an important technology for manufacturing nano- and microscopic optical devices and elements. Detailed knowledge of the dispersion in the visible and near-infrared spectral range is crucial for the design of these optical elements. Here we provide refractive index measurements for different UV-doses, aging times, heat treatment and 2-photon exposed structures for the photoresists IP-S, IP-Dip, IP-L, OrmoComp, IP-Visio, and PO4. We use a modified and automized Pulfrich refractometer setup, utilizing critical angles of total internal reflection with an accuracy of 5·10−4 in the visible and near-infrared spectral range. We compare Cauchy and Sellmeier fits to the dispersion curves. We also give Abbe numbers and Schott Catalog numbers of the almost entirely polymerized resists. Additionally, we provide quantitative extinction and luminescence measurements for all photoresists.