Compact edge coupler with <1dB/facet insertion loss in the C-band

This work presents a compact trident edge coupler fabricated on silicon nitride platform. We report an insertion loss as low as 0.7 dB/facet, with a polarization dependent loss of 0.2-0.3 dB over C-band, when coupled with a taper lensed fiber. The trident edge couplers are fabricated in a single etch step, without the need for substrate removal, and with a device footprint of less than 100 μm. The combination of high efficiency, compact footprint, and non-stringent critical dimensions makes the trident coupler an excellent candidate for applications requiring extremely low fiber-to-chip coupling loss.