Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization

TL;DR

This paper demonstrates the design, fabrication, and characterization of silicon nitride waveguides with engineered dispersion profiles, achieving ultra-flat dispersion and broad supercontinuum generation through geometrical and refractive index optimization.

Contribution

It introduces a novel approach to dispersion engineering in silicon nitride waveguides by optimizing geometry and refractive indices, enabling ultra-flat dispersion and broad supercontinuum generation.

Findings

Achieved ultra-flat dispersion of -84.0 +/- 0.5 ps/nm/km over 1700-2440 nm.

Successfully tuned zero-dispersion wavelength across a large spectral range.

Generated nearly three-octave supercontinuum in optimized waveguides.

Abstract

Dispersion engineering in silicon nitride (SiX NY ) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multi-cladding arrangement. Ultra-flat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during the fabrication of the SiX NY waveguides are a limitation for obtaining ultra-flat dispersion profiles. Single- and multi-cladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in both single-cladding waveguides and multi-cladding waveguides with small refractive index contrast (3 %). A flat dispersion profile with 3.2 ps/nm/km variation over 500 nm is obtained in a multi-cladding waveguide fabricated with a refractive index contrast of 37 %. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multi-cladding SiX NY waveguide.