Broadband, Polarization-Insensitive Lensed Edge Couplers for Silicon Photonics

We have designed, fabricated and tested edge couplers for silicon photonics with etched lenses targeting industry-standard SMF-28 fibers as well as future alignment and dust-tolerant expanded-beam connectors. These edge couplers are based on a Si inverse taper combined with a SiON ridge waveguide and etched lens fabricated on a silicon-on-insulator (SOI) platform. The lens structures were designed for coupling to SMF-28 fibers with a 1/e mode field diameter (MFD) of 10.4 micrometers in the telecommunications C-band. Alternate lens designs targeted expanded beams with 30 micrometer horizontal MFD. The measured SMF-28 lensed couplers exhibited a 1 dB bandwidth exceeding 150 nanometers, polarization dependent loss (PDL) of less than 1 dB and coupling efficiency better than -4.8 dB across the S-, C- and L-bands with only horizontal beam expansion.