Low-loss flexible Parylene photonic waveguides for optical implants

Abstract

We demonstrate compact, low-loss (<5 dB/cm) Parylene C photonic waveguides in a flexible, biocompatible, all-polymer platform suitable for implantable applications. The scattering loss due to the sidewall roughness resulting from the reactive ion etching of Parylene C was identified as the primary source of propagation loss. A fabrication process utilizing the conformal coating of Parylene C was developed to significantly reduce waveguide propagation loss (by more than 30 dB/cm). We also performed thermal annealing at 300°C to smoothen the sidewalls; however, it was found to adversely affect the waveguide performance.