Electron-beam lithography for thick refractive optical elements in SU-8

Abstract

We have fabricated refractive optical elements in SU-8 resist using electron-beam lithography. Exposing an 8-μm-thick layer of SU-8 resist with a 30 kV electron beam, we demonstrate fabrication of an f/9 spherical lens, an f/2 spherical lens, and a prism with a 3° tilt. The elements all perform near the diffraction limit, with rms surface variations between 1/10 wave and 1/7 wave. The electron scattering from the thick resist is measured and shown to limit the technique to optical elements with relatively smooth surface figures.