Broadband 2 x 2 adiabatic 3 dB coupler using silicon on insulator sub wavelength grating waveguides.
We report on a compact, broadband, 2x2 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 mm 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.
Optics letters