Dispersion trimming for mid-infrared supercontinuum generation in a hybrid chalcogenide/silicon-germanium waveguide

Abstract

We report a simple post-process technique that harnesses a hybrid chalcogenide/silicon-germanium system for the control of waveguide dispersion. By adding a chalcogenide top cladding to a SiGe/Si waveguide, we can substantially change the dispersive properties, which underpin the generation of a supercontinuum. In our particular example, we experimentally show that a shift from anomalous to normal dispersion takes place. We numerically study the dispersion dependence on the chalcogenide thickness and show how to use this additional degree of freedom to control the position of the zero dispersion wavelengths and hence the spectral span of the supercontinuum. Finally, we compare our approach with more traditional techniques that use geometry for dispersion tailoring.

Mid-infrared supercontinuum generation in silicon-germanium all-normal dispersion waveguides

“…Ge-based, group IV, on-chip platforms have attracted significant attention for nonlinear applications in the mid-IR thanks to the strong nonlinearity and the transparency of Ge across the entire mid-IR band (2-15 µm) [18]. These platforms include Ge-on-SOI [19], Ge-on-Si [18,20], low (<40%) [21,22], and high (>40%) [23] Ge content SiGe-on-Si. Our SiGe-on-Si platform, with around 40% of Ge in the SiGe alloy, offers a good trade-off between nonlinear performances and low propagation loss for the associated waveguides in the mid-IR band [24].…”

Bright octave-span mid-IR supercontinuum generation in silicon germanium waveguide

“…However, the restricted number of design parameters makes post-process dispersion control of waveguides trickier. In this context, we reported a proof of concept demonstration in which the deposition of a chalcogenide top-cladding on nonlinear SiGe/Si waveguides enabled us to tune the group velocity dispersion of the fundamental mode [25]. This demonstrates that the heterogeneous integration of materials can be used as a post-processing technique to tune the waveguide dispersive properties and therefore control SC generation.…”

“…Calculated group velocity dispersion (GVD) for different thicknesses of the chalcogenide layer. The inset shows a schematic of the waveguide (adapted from [25]).…”

“…SEM (b) and AFM (c) images of the waveguide after the deposition of chalcogenide. (adapted from[25]).…”

Coherent Mid-Infrared Supercontinuum Sources in SiliconGermanium Waveguides

“…The same waveguide was then covered with a 1.26 µm thick cladding layer of Ge11.5As24Se64.5 chalcogenide glass, shifting the dispersion curve to all-normal ( fig. 1(b), left) [9]. This allowed to generate a slightly narrower SC (spanning from 3.1 to 5.5 µm), but fully coherent across the entire spectrum ( fig.…”