Efficient fiber-optical interface for nanophotonic devices

We demonstrate a method for efficient coupling of guided light from a single-mode optical fiber to nanophotonic devices. Our approach makes use of single-sided conical tapered optical fibers that are evanescently coupled over the last ~10 μm to a nanophotonic waveguide. By means of adiabatic mode transfer using a properly chosen taper, single-mode fiber-waveguide coupling efficiencies as high as 97(1)% are achieved. Efficient coupling is obtained for a wide range of device geometries, which are either singly clamped on a chip or attached to the fiber, demonstrating a promising approach for integrated nanophotonic circuits, and quantum optical and nanoscale sensing applications.