Direct measurement of proton-beam-written polymer optical waveguide sidewall morphorlogy using an atomic force microscope

Proton-beam writing (PBW) is a direct-write micromachining technique capable of fabricating low-loss single-mode polymer waveguides with straight and smooth sidewalls. Recently, the sidewall morphologies of such proton beam written polymer waveguide structures were directly measured using an atomic force microscope (AFM). Statistical information such as the rms roughness and the correlation length of the sidewall profile obtained from the AFM scans allows us to quantify the quality of the sidewalls and optimize the fabrication parameters using PBW. For structures fabricated using a stage scanning speed of ∼10μm∕s, a rms roughness of 3.8±0.3nm with a correlation length of 46±6nm was measured.