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Low-loss, high-bandwidth fiber-to-chip coupling using capped adiabatic tapered fibers



Saeed Khan, Jeff Shainline, Richard Mirin, Sae Woo Nam, Sonia Buckley, Jeff Chiles


We demonstrate adiabatically tapered fibers terminating in sub-micron tips that are clad with a higher-index material for coupling to an on-chip waveguide. This cladding enables coupling to a high-index waveguide without losing light to the buried oxide. A technique to clad the tip of the tapered fiber with a higher-index polymer is introduced. Conventional tapered waveguides and forked tapered waveguide structures are investigated for coupling from the clad fiber to the on-chip waveguide. We find the forked waveguide facilitates alignment and packaging, while the conventional taper leads to higher bandwidth. The insertion loss from a fiber through a forked coupler to a sub-micron silicon nitride waveguide is 1.1 dB and the 3 dB bandwidth is 90 nm. The coupling loss in the packaged device is 1.3 dB. With a fiber coupled to a conventional tapered waveguide, the loss is 1.4 dB with a 3 dB bandwidth extending beyond the range of the measurement apparatus, estimated to exceed 250 nm.
APL Photonics


Khan, S. , Shainline, J. , Mirin, R. , Nam, S. , Buckley, S. and Chiles, J. (2020), Low-loss, high-bandwidth fiber-to-chip coupling using capped adiabatic tapered fibers, APL Photonics, [online], (Accessed February 27, 2024)
Created May 1, 2020, Updated October 5, 2022