Mid-Infrared, Ultra-Broadband, Low-Loss, Compact Arbitrary Power Splitter Based on Adiabatic Mode Evolution

We designed and demonstrated TE-mode arbitrary power splitters based on adiabatic mode evolution. The power splitters are designed with a footprint of smaller than 12 x 2.9 mu m(2), fabricated on a 400-nm silicon-on-insulator platform, requiring only a single etch step. The optimization process and the conditions for arbitrary-power splitting are performed using three-dimensional-FDTD simulations. We prove this concept through the fabrication of asymmetrical adiabatic evolution-based power splitters with splitting ratios of 50:50, 60:40, and 70:30. The fabricated devices are shown to agree closely with simulation results. Broadband operation with low insertion loss of 0.11-0.6 dB is demonstrated across the 3.66-3.89 mu m wavelength range (230 nm). This component has applications in a multitude of areas such as spectroscopic optical sensing and optical phased arrays photonic integrated circuits etc.