Most polymeric optical devices are mainly fabricated by photolithography and reactive ion etching (RIE). This paper describes the fabrication of fluorinated polyether (FPE) waveguides by using a metallic hard mask and proximity exposure followed by RIE. In particular, we focused on the effects of various fabrication parameters on the sidewall roughness. According to our study, a high-power, low-pressure oxygen RF plasma environment will provide vertical and smooth sidewalls desired in a cladded waveguide. The sidewall roughness increases with pressure in pure oxygen plasma, while adding nitrogen gas to oxygen during RIE creates a more vertical profile and smoother sidewalls along with low vertical and lateral etch rates. A simple technique is presented to quantify sidewall roughness using an atomic force microscope (AFM). (C) 2004 Elsevier B.V. All rights reserved.