Fabrication of optical structures using SU-8 photoresist and chemically assisted ion beam etching

We develop a method for the fabrication of optical structures in GaAs substrates using UV holographic lithography in SU-8 resist, pro- cessed to fabricate a mask, followed by chemically assisted ion-beam etching (CAIBE). The technique is based on simple processing steps without procedures of mask transfer, enabling easy fabrication of optical structures. A predevelopment relief behavior is investigated to optimize the processing parameter to form an etching mask in SU-8. By adjusting both exposure dose and time in the postexposure bake (PEB), an SU-8 mask with a flexible duty cycle and high profile quality can be easily produced. Furthermore, an optical structure with a rectangular shaped profile and a 1-mm period in a GaAs substrate is produced by optimizing the processing parameters during the CAIBE process.