Fabrication of a polymeric optical waveguide-on-flex using electrostatic-induced lithography

A method has been developed for the manufacture of polymeric multimode waveguides using an electrostatic field-induced self assembly and pattern formation process. A spin-coated liquid optical polymer placed between two conductive plates experiences an electrostatic force from an applied electric field gradient across the plates. Surface electrohydrodynamics instability patterning is employed to fabricate optical core microstructures using a patterned master plate. The result shows a good replication of the pattern from the master plate to the optical polymer. The process protocols were defined to achieve waveguides with low sidewall roughness together with an optical coupling interface. We have demonstrated multimode waveguide arrays with a 50 μm × 50 μm cross section and 250-μm pitch on a 10 mm × 10 mm flexible substrate. The refractive index and absorption measurement of the electrostatic-induced optical film show insignificant changes when compared with the unexposed film. Using the cutback approach, the propagation loss of the waveguide is measured at -1.97 dB/cm. The whole fabrication process is found to be fast, cost-effective, and no photosensitive material is needed as in the conventional photolithography approach.