Generation of ultra-broadband coherent supercontinua in tapered and dispersion-managed silicon nanophotonic waveguides

Abstract

Tapered and dispersion managed (DM) silicon nanophotonic waveguides are investigated for the generation of optimal ultra broadband supercontinuum (SC). DM waveguides are structures showing a longitudinally dependent group velocity dispersion that results from the variation of the waveguide width with the propagation distance. For the generation of optimal SC, a genetic algorithm has been used to find the best dispersion map. This allows for the generation of highly coherent supercontinuums that span over 1.14 octaves from 1300 nm to 2860 nm and 1.25 octaves from 1200 nm to 2870 nm at -20 dB level for the tapered and DM waveguides respectively, for a 2 µm, 200 fs and 6.4 pJ input pulse. The comparison of these two structures with the usually considered optimal fixed width waveguide shows that the SC is broader and flatter in the more elaborated DM waveguide, while the high coherence is ensured by the varying dispersion.

Two-octave spanning supercontinuum generation in stoichiometric silicon nitride waveguides pumped at telecom wavelengths

“…This enables an efficient conversion of ultrashort pulses also with short interaction lengths while preserving coherence. For instance, pulses with up to a few hundred femtoseconds have been used for efficient SCG in short optical waveguides while maintaining a high degree of coherence [12][13][14]. As a second advantage the integrated optical approach offers a route for high-volume and low-cost fabrication, in particular when the waveguide platform is compatible with metal-oxidesemiconductor (CMOS) fabrication facilities.…”

Octave spanning supercontinuum generation in dispersion-managed silicon waveguides

“…(a). The positions where the slope changes as well as the waveguide width at those points are given in the Table in Fig 1. These widths where optimized by numerical simulations following the same methodology as in [3]. The pump source is a mode-locked Cr:ZnSe laser delivering 70 fs and is tunable in the wavelength range [2130-2260] nm, i.e.…”

“…Following works on SC generation in optical fibres, cascaded waveguides, tapers and more complex dispersion managed integrated structures are investigated numerically and experimentally (see e.g. [3][4][5]). The interest of varying the dispersion along the propagation lies in the possibility to locally adapt the phase matching conditions required for the generation of new frequencies through the four-wave mixing process.…”

Low-loss silicon core fibre platform for mid-infrared nonlinear photonics

“…2d, indicating that the waist region is in the anomalous dispersion regime for the 3 μm pump. Interestingly, the varying dispersion profile of the taper provides another benefit in that it allows for multiple phase-matching conditions to be satisfied simultaneously, which can result in a flatter and more coherent SC 38,39 . Although varying dispersion profiles can also be produced by splicing different sections of fibre together, each with a different dispersion parameter 40 , tapering is preferred for our SCFs owing to their short lengths and high core/cladding index contrast, which can result in high losses at the coupling interfaces if the mode properties are not well matched.…”