Efficient taper optical hydrogel fiber coupler drawn from suspended photocuring 3D printing.

Integrating bio-friendly optical hydrogel fibers (HFs) with solid-state fibers (SFs) could expand the horizons of fiber-optic technology for bio-photonics. However, methods for coupling HF and SF-based systems are inefficient due to the mode field mismatch. Here, a hydrogel fiber coupler with a taper core-cladding structure is demonstrated for efficiently coupling HF to SF and fabricated through suspended photocuring 3D printing. Coupling efficiencies of 8.3 and 9.4 dB are obtained at 632 and 473 nm, respectively, which are 22% better than those of conventional couplers. The working bandwidth covers visible wavelengths, satisfying bioengineering requirements. This research removes obstacles to optical fiber applications in bioscience.