Single-shot two-photon exposure of commercial photoresist for the production of three-dimensional structures

We report the use of an amplified femtosecond laser for single-shot two-photon exposure of the commercial photoresist SU-8. By scanning of the focal volume through the interior of the resist, three-dimensional (3-D) structures are fabricated on a shot-by-shot basis. The 800-nm two-photon exposure and damage thresholds are 3.2 and $8.1 \mathrm{TW}/{\mathrm{cm}}^2$, respectively. The nonlinear nature of the two-photon process allows the production of features that are smaller than the diffraction limit. Preliminary results suggest that Ti:sapphire oscillators can achieve single-shot two-photon exposure with thresholds as low as $1.6 \mathrm{TW}/{\mathrm{cm}}^2$ at 700 nm, allowing 3-D structures to be constructed at megahertz repetition rates.