Resonance-enhanced multi-octave supercontinuum generation in antiresonant hollow-core fibers

Abstract

Ultrafast supercontinuum generation in gas-filled waveguides is an enabling technology for many intriguing applications ranging from attosecond metrology towards biophotonics, with the amount of spectral broadening crucially depending on the pulse dispersion of the propagating mode. In this study, we show that structural resonances in a gas-filled antiresonant hollow core optical fiber provide an additional degree of freedom in dispersion engineering, which enables the generation of more than three octaves of broadband light that ranges from deep UV wavelengths to near infrared. Our observation relies on the introduction of a geometric-induced resonance in the spectral vicinity of the ultrafast pump laser, outperforming gas dispersion and yielding a unique dispersion profile independent of core size, which is highly relevant for scaling input powers. Using a krypton-filled fiber, we observe spectral broadening from 200 nm to 1.7 μm at an output energy of ∼ 23 μJ within a single optical mode across the entire spectral bandwidth. Simulations show that the frequency generation results from an accelerated fission process of soliton-like waveforms in a non-adiabatic dispersion regime associated with the emission of multiple phase-matched Cherenkov radiations on both sides of the resonance. This effect, along with the dispersion tuning and scaling capabilities of the fiber geometry, enables coherent ultra-broadband and high-energy sources, which range from the UV to the mid‐infrared spectral range.

Poor-man’s model of hollow-core anti-resonant fibers

“…We will only use the real part n eff,L for the model, while the imaginary part will be used to extract information about the resonances as we will now see, using that 2k 0ñeff,L is equivalent to the loss parameter α. We note that this approach is not the same as used in [9,10], where similar Lorentzian shapes were added to n instead of n 2 . This gives subtle but noticeable differences in the linewidth shape, and we argue that the shape we use from a physical standpoint is sounder.…”

“…Currently the accepted approach to model these fibers is to use this so-called Marcatili-Schmeltzer (MS) capillary model in nonlinear Schrödinger-like equations (NLSEs) and neglect the resonances and how they affect the dispersion and loss. Only recently did some of us include data from a full finite-element model (FEM) simulation of the dispersion and loss into the NLSE [7,8] and this was followed up recently by others where a Lorentzian extension of the MS model was implemented [9,10].…”

Resonance‐Induced Dispersion Tuning for Tailoring Nonsolitonic Radiation via Nanofilms in Exposed Core Fibers

“…Spectral broadening using supercontinuum generation (SCG) relies on nonlinear material responses at high light intensities. Such intensities are realized in fiber optics via ultrashort optical pulses and strongly confining geometries, having led to applications such as nonlinear light generation, [ 1,2 ] spectroscopy, [ 3 ] nonlinear pulse compression, [ 4 ] and optical switching. [ 5 ] The key to efficient SCG is precise management of modal dispersion.…”

Multi-stage generation of extreme ultraviolet dispersive waves by tapering gas-filled hollow-core anti-resonant fibers

“…An additional challenge in our case is that in the tapering section the fiber is scaled down in critical parameters (core size, thickness of cladding AR elements). Currently the accepted approach to model these fibers is to use the the so-called Marcatili-Schmeltzer (MS) , while other approaches employed a Lorentzian extension of the MS model [45,46]. It is clear that accurate modeling of the resonances and the losses of these fibers is crucial, especially for predicting the UV behavior where the glass in the cladding becomes very lossy.…”