Lenses for low-loss chip-to-fiber and fiber-to-fiber coupling fabricated by 3D direct-write lithography

We demonstrate low-loss coupling to single-mode fibers and photonic integrated circuits (PIC) using in-situ fabrication of free-form microlenses on device facets. Measured coupling losses down to 0.8 dB (0.5 dB) are achieved for chip-fiber (fiber-fiber) interfaces.