Near-octave intense mid-infrared by adiabatic down-conversion in hollow anti-resonant fiber

Analytical Lah-Laguerre optical formalism for perturbative chromatic dispersion

We present a generalized perturbative analytical formalism for evaluation and optimization of the chromatic dispersion of complex ultrafast optical systems. Notably, we identify polynomial and recursive relations associated with the chromatic dispersion orders that are identical to the Lah and Laguerre transforms. We explicitly outline the first ten dispersion terms and dispersion slope parameters and visualize the significance of the chromatic dispersion orders for several advanced ultrafast optical and photonic systems consisting of various optical materials and nanostructures, grating and prism-pair compressors, and hollow-core photonic anti-resonant fibers. The derived simple hypergeometric transforms are applicable for evaluation of infinitely high orders for any type of frequency-dependent phase and can facilitate the optimization of complex optical systems with controlled dispersion balance at the single-cycle waveform extreme.

Mid-Infrared Ultra-Short Pulse Generation in a Gas-Filled Hollow-Core Photonic Crystal Fiber Pumped by Two-Color Pulses

We show numerically that ultra-short pulses can be generated in the mid-infrared when a gas filled hollow-core fiber is pumped by a fundamental pulse and its second harmonic. The generation process originates from a cascaded nonlinear phenomenon starting from a spectral broadening of the two pulses followed by an induced phase-matched four wave-mixing lying in the mid-infrared combined with a dispersive wave. By selecting this mid-infrared band with a spectral filter, we demonstrate the generation of ultra-short 60 fs pulses at a 3–4 µm band and a pulse duration of 20 fs can be reached with an additional phase compensator.

Multioctave supercontinuum generation and frequency conversion based on rotational nonlinearity

The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit "instantaneous" optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion. Here, we show that nonlinear compression can be much more efficient when driven in molecular gases by pulses substantially longer than a few cycles because of enhanced optical nonlinearity associated with rotational alignment. We use 80-cycle pulses from an industrial-grade laser amplifier to simultaneously drive molecular alignment and supercontinuum generation in a gas-filled capillary, producing more than two octaves of coherent bandwidth and achieving >45-fold compression to a duration of 1.6 cycles. As the enhanced nonlinearity is linked to rotational motion, the dynamics can be exploited for long-wavelength frequency conversion and compressing picosecond lasers.

Observation of Rapid Adiabatic Passage in Optical Four-Wave Mixing

We observe clear evidence of adiabatic passage between photon populations via a four-wave mixing process, implemented through a dispersion sweep arranged by a core diameter taper of an optical fiber. Photonic rapid adiabatic passage through the cubic electric susceptibility thus opens precise control of frequency translation between broadband light fields to all common optical media. Areas of potential impact include optical fiber and on-chip waveguide platforms for quantum information, ultrafast spectroscopy and metrology, and extreme light-matter interaction science.

Highly-tunable, visible ultrashort pulses generation by soliton-plasma interactions in gas-filled single-ring photonic crystal fibers

Ultrashort laser pulses, featuring remarkable spectral tunability, are highly demanded for nonlinear light-matter interactions in a variety of molecules. Here, we report on the generation of soliton-plasma-driven ultrashort pulses with both bandwidth- and wavelength-tunability in the visible spectral region. Using He-filled single-ring photonic crystal fiber (SR-PCF), we demonstrate in the experiments that the spectral bandwidths of blueshifting solitons can be manipulated by adjusting the input pulse energy, gas pressure and core diameter of the SR-PCF, while the central wavelengths of these solitons can be continuously tuned over 200 nm. We found that in a large-core SR-PCF (24.6-µm core diameter), the bandwidths of blueshifting solitons can be effectively broaden to near 100 nm, pointing out the possibility of generating few-cycle, wavelength-tunable visible pulses using this set-up. In addition, we observed in the experiments that in a small-core SR-PCF (with a core diameter of 17 µm), the blueshifting solitons show little residual light near the pump wavelength, resulting in a high-efficiency frequency up-conversion process. These experimental results, confirmed by numerical simulations, pave the way to a new generation of compact, ultrashort light sources with excellent tunability at visible wavelengths, which may have many applications in the fields of time-resolved spectroscopy and ultrafast nonlinear optics.