Rib waveguides for mid-infrared silicon photonics

TLDR

The paper presents first‑ever design rules for single‑mode, polarization‑independent strained silicon‑on‑insulator rib waveguides at 3.39 µm. The authors varied waveguide geometry parameters and used Chebyshev bivariate interpolation (≤1 % error) to map the zero‑birefringence surface, while experimental stress‑level data informed the effect of top oxide thickness and cladding stress on waveguide performance. The study identifies the polarization‑insensitive, single‑mode operating locus across waveguide heights.

Abstract

Design rules for both single-mode and polarization-independent strained silicon-on-insulator rib waveguides at the wavelength of 3.39 μm are presented for the first time to our knowledge. Waveguide geometries with different parameters, such as waveguide height, rib width, etch depth, top oxide cover thickness and sidewall angle, have been studied in order to investigate and define design rules that will make devices suitable for mid-IR applications. Chebyshev bivariate interpolation with a standard deviation of less than 1% has been used to represent the zero-birefringence surface. Experimental results for the upper cladding stress level have been used to determine the influence of top oxide cover thickness and different levels of upper cladding stress on waveguide characteristics. Finally, the polarization-insensitive and single-mode locus is presented for different waveguide heights.