Electron Beam Lithography Produces Microlenses in Hybrid Sol-Gel

In the April 21 issue of Optics Express, scientists at Singapore's Nanyang Technological University discuss the use of a hybrid sol-gel glass to fabricate refractive microlenses with electron beam lithography. According to the researchers, this reduced profile-control problems related to the use of traditional sol-gel, which is extremely sensitive to electron beam exposure.

The hybrid SiO₂/TiO₂ sol-gel glass has transmittance greater than 95 percent for wavelengths from 362 to 2000 nm. Besides extending optics development across the visible to the near-IR range, it gives scientists the flexibility to tailor polymerized film thickness after development by exposing the hybrid sol-gel film to varying electron dosages. One part fabricated with the material is a 250-µm-diameter microlens with a 2.05-µm sag height. Maximum film thickness produced was 4 µm.