Fabrication method for passive alignment in polymer PLCs with U-grooves

A method is developed to enhance fabrication tolerance for the passive alignment of polymer waveguides to optical fibers in polymer-based planar lightwave circuit (PLC) devices. For the passive alignment, the waveguides and U-grooves, into which the optical fibers are set, are fabricated on a substrate. In order to eliminate lateral misalignment between the centers of the waveguides and U-grooves due to the steps of photolithography, an optical axis alignment is achieved in one photomask. Reduced-cladding single-mode fibers with an 80-μm diameter are used to reduce vertical misalignment. PLCs based on polymers were implemented on a 4-in Si wafer using the method, and excessive losses of less than 0.4 dB were obtained.