Proton beam writing of low-loss polymer optical waveguides

Proton beam writing is a direct-write micromachining technique capable of producing three-dimensional microstructures with straight and smooth sidewalls. Low-loss channel waveguides in SU-8, a chemically amplified negative tone resist, were fabricated using a focused submicron beam of 2.0 MeV protons with a dose of 30 nC/mm2 and a beam current of approximately 2 pA. Propagation losses of approximately (0.19±0.03) dB/cm were measured at 632.8 nm wavelength. Waveguides of arbitrary design can be easily fabricated using proton beam writing, making the technique ideal for the rapid prototyping of optical circuits.