Study of reactive ion etching process to fabricate the PMMA-based polymer waveguide

To fabricate a PMMA-based polymer waveguide, the reactive ion etching (RIE) process is systematically studied and the fabrication techniques are established. The etch rate and sidewall morphology in oxygen plasma are investigated as a function of the radio frequency power and gas flow rate. The optimum etch parameters are given, taking into account simultaneously minimum sidewall roughness and directional etching. An innovative approach is reported to smooth sidewalls through a treatment process using resolution and recuring. In comparison with the RIE process without treatment, the sidewall roughness is improved by a factor of about 3. The observed near-field pattern illustrates the waveguide, fabricated by using this technique, achieves single-mode transmission at 1550 nm wavelength.