Global fitting equation for constant-loss inverted taper.

Building on the Lagrangian approach to inverted taper coupler design, the constant-loss inverted taper geometry is calculated for rectangular waveguide systems with a range of core refractive indices (3.0 - 3.6), cladding refractive indices (1.0 - 1.6), and waveguide thicknesses (200 - 300 nm). A new approach to describing these taper devices is proposed based on the normalized effective index. This results in an empirical equation that accurately describes the geometry of all simulated constant-loss inverted tapers.