Design and Demonstration of Micro-Mirrors and Lenses for Low Loss and Low Cost Single-Mode Fiber Coupling in 3D Glass Photonic Interposers

This paper presents the first demonstration of a novel fiber coupling structure that enables low-loss and low-cost fiber coupling in an ultra-miniaturized 3D glass photonic interposer. The novel 3D coupling structure consists of a tapered optical waveguide with an integrated lensed turning mirror on one end and a cylindrical lens on the other end, in a 150 μm glass substrate. The lens waveguide and turning mirror provide coupling loss of <;0.5 dB and 90% tolerance of 2 μm for out-of-plane coupling between a Photonic Integrated Circuit and a single-mode fiber. The lens waveguide is fabricated using planar lithography to reduce overall cost. In addition, precision U-grooves in glass are employed to allow for a coefficient of thermal expansion matched interface between the fiber and the substrate, thus enabling low-cost passive alignment.