Comparison of Scalar and Vector WFM Method Through the Design of High-Δ Waveguide Lenses

Abstract

We demonstrate that the high refractive index difference (<inline-formula> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula>) waveguide design using a wavefront matching (WFM) method requires a full-vector propagation analysis. The investigation was implemented through the comparison of some pairs of high-<inline-formula> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> waveguide lenses designed by a scalar or full-vector WFM method. The results show that a full-vector WFM method is superior to a scalar WFM method for the design of waveguide lenses with the <inline-formula> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> of 20&#x0025; or higher. Finally, we experimentally demonstrate that the necessity of a full-vector propagation analysis for the design of Si waveguide lenses using a WFM method. Calculation and measurement results agree well and the insertion loss of a pair of Si waveguide lenses designed by a full-vector WFM method is 0.78 dB lower than that designed by a scalar WFM method at the wavelength of 1550 nm.