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

摘要

Dispersion engineering in silicon nitride (SiX NY ) waveguides isinvestigated through the optimization of the waveguide transversal dimensionsand refractive indices in a multi-cladding arrangement. Ultra-flat dispersionof -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/kmbetween 1670 and 2500 nm is numerically demonstrated. It is shown that typicalrefractive index fluctuations as well as dimension fluctuations during thefabrication of the SiX NY waveguides are a limitation for obtaining ultra-flatdispersion profiles. Single- and multi-cladding waveguides are fabricated andtheir dispersion profiles measured (over nearly 1000 nm) using a low-coherencefrequency domain interferometric technique. By appropriate thicknessoptimization, the zero-dispersion wavelength is tuned over a large spectralrange in both single-cladding waveguides and multi-cladding waveguides withsmall refractive index contrast (3 %). A flat dispersion profile with 3.2ps/nm/km variation over 500 nm is obtained in a multi-cladding waveguidefabricated with a refractive index contrast of 37 %. Finally, we generate anearly three-octave supercontinuum in this dispersion flattened multi-claddingSiX NY waveguide.