A robust strategy for realizing highly-efficient passive alignment of fiber ribbons to integrated polymer waveguides

The connection between ribbon fibers and optical waveguides is an ideal method for achieving precise coupling with other standard devices and is a key technology for the practical application of various integrated optical devices. However, traditional methods are time-consuming, labor intensive, and prone to misalignment between the ribbon fibers and the optical waveguides. How to accurately and reliably aligning optical waveguides with ribbon fibers remains an urgent technical challenge in the field of optical transmission systems. Herein, this work presented here introduced a new cost-effective method for self-aligning optical fibers on substrate and achieving high-precision passive coupling between waveguides and fibers using layered structure design and selective exposure techniques. This method utilized a single selective photolithography step for structuring both the polymer waveguide and the U-grooves and thus minimizing the horizontal and vertical displacement of optical fibers and polymer waveguides. The related test results showed that the optical fibers and polymer waveguides were mechanically self-aligned within 4-μm accuracy in both the horizontal and vertical directions. The characterization of the fiber-to-waveguide link revealed total exceed losses of 0.13 dB per coupling interface. And the coupling loss ascribed to the misalignment between the optical fiber and the polymer waveguide was about 0.1 dB. The device performance remained stable after the thermal shock cycling and high-humidity/temperature tests, demonstrating excellent environmental reliability of the waveguide device. This work provided a fruitful attempt for realizing high-efficient passive alignment of array fibers to integrated polymer waveguides through robust stack design combined with selective exposure techniques.