High Coherence at f and 2f of Mid-Infrared Supercontinuum Generation in Silicon Germanium Waveguides

Abstract

Absorption spectroscopy based on supercontinuum generation in the mid-infrared is a powerful technique to analyze the chemical composition of samples. Furthermore, phase-coherent supercontinuum sources can enable fast data acquisition with coherent, stable pulses that allow single-shot measurements. We report here a numerical study of the coherence of an octavespanning mid-infrared supercontinuum source that was experimentally obtained in an air-clad SiGe/Si waveguide. We show that engineering two closely spaced zero-dispersion wavelengths that enclose an anomalous dispersion band centered around a fixed pump wavelength can produce supercontinuum pulses with high spectral density and full coherence at the extreme ends of the spectrum. This work is important for absorption spectroscopy, on-chip optical frequency metrology, and f-to-2f interferometry applications.

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

“…Dual-comb spectroscopy requires high mutual coherence between two interfering combs as well as a high power spectral density. Furthermore, high phase coherence of spectral components separated by an octave is needed to stabilize the SC using an f -to-2 f self-referencing technique [4].…”

Photonic RF and microwave temporal signal processing based on optical Kerr micro-combs

“…Finally, soliton crystals have recently [202][203][204][205] been shown to be able to achieve a range of RF functions without the need for any spectral shapingonly by triggering the different soliton states through different pumping conditions which yields different spectra. This could potentially extend to the mid IR region as well [206][207][208][209][210] since these systems are not fundamentally restricted to operating in the telecom band. This adds an entirely new dimension to microcombs beyond what is possible with DKS states.…”

Ultrahigh bandwidth applications of microcombs: Neural networks and optical data transmission

“…The trade-off is that a reduction of line spacing results in a lower power per-line, impacting the individual comb line OSNR (for the same bandwidth), which may ultimately pose a limit to the spectral efficiency [120]. Finally, soliton crystals should be achievable in mid-IR frequencies for a very wide range of applications [131][132][133][134][135][136]. 'Back to back' is the transmitter directly connected to the receiver, '75 km in-lab fibre' indicates transmission over 75 km of fibre in the lab,'76.6 km field fibre' is after transmission in field-trial link.…”