Air-clad broadband waveguide using micromolded polyimide combined with a robust, silica-based inverted opal substrate

A polymer waveguide is fabricated on top of an inverted opal photonic crystal structure to demonstrate an air clad functioning waveguide for the first time to the best of our knowledge. An optically thick layer with a refractive index (n = 1.01) close to air was realized on a silicon wafer by first co-forming a self-assembled 3-D photonic crystal structure with PMMA spheres and a silica backbone. Following the fabrication of polyimide waveguides on this surface by micro-molding, the PMMA spheres were removed to leave behind an inverted opal structure underneath the waveguides with refractive index close to air. Broadband, polarization independent fundamental mode optical waveguiding from 1300 nm to 1600 nm wavelengths was obtained. This original approach overcomes some of the drawbacks associated with conventional polymer waveguides and can be the basis for a range of optical interconnection and sensing applications.