title: Broadband 2 × 2 adiabatic 3  dB coupler using silicon-on-insulator sub-wavelength grating waveguides.
abstract: We report on a compact, broadband, 2×2 adiabatic 3 dB coupler using sub-wavelength gratings (SWGs) for silicon-on-insulator waveguides. In our device, two SWG waveguides that support two transverse electric modes and have tapered waveguide widths were used to achieve an adiabatic mode evolution of the two-waveguide system for broadband 3 dB power splitting. We present results for a SWG adiabatic 3 dB coupler that has an overall coupler length of 50 μm and achieves broadband power splitting over a 130 nm wavelength range with an imbalance of no greater than ±0.3  dB and with low excess losses of less than 0.5 dB.
authors.forename: Han
authors.initials: H
authors.lastname: Yun
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Zeqin
authors.initials: Z
authors.lastname: Lu
authors.forename: Stephen
authors.initials: S
authors.lastname: Lin
authors.forename: Lukas
authors.initials: L
authors.lastname: Chrostowski
authors.forename: Nicolas A F
authors.initials: NA
authors.lastname: Jaeger