Generalized retarded response of nonlinear media and its influence on soliton dynamics

Incoherent Shock and Collapse Singularities in Non-Instantaneous Nonlinear Media

We study the dynamics of a partially incoherent optical pulse that propagates in a slowly responding nonlinear Kerr medium. We show that irrespective of the sign of the dispersion (either normal or anomalous), the incoherent pulse as a whole exhibits a global collective behavior characterized by a dramatic narrowing and amplification in the strongly non-linear regime. The theoretical analysis based on the Vlasov formalism and the method of the characteristics applied to a reduced hydrodynamic model reveal that such a strong amplitude-incoherent pulse originates in the existence of a concurrent shock-collapse singularity (CSCS): The envelope of the intensity of the random wave exhibits a collapse singularity, while the momentum exhibits a shock singularity. The dynamic behavior of the system after the shock-collapse singularity is characterized through the analysis of the phase-space dynamics.

Soliton-like pulse propagation in a normal dispersive liquid-core optical fiber

Soliton-like pulse propagation, where the pulse intensity profile is conserved, except for its trailing edge, is found in a normal dispersive CS₂-core optical fiber by a computer simulation. During propagation, it is found that the chirp of a pulse arising from the delayed nonlinear response compensates for the chirp arising from the second-order dispersion near the pulse peak position and the pulse experiences a negative frequency shift and a negative temporal shift. The effects of the instantaneous nonlinear response on the soliton-like pulse propagation are also evaluated, and the calculated spectrum agreed well with the experimental spectrum.

Hybrid soliton dynamics in liquid-core fibres

The discovery of optical solitons being understood as temporally and spectrally stationary optical states has enabled numerous innovations among which, most notably, supercontinuum light sources have become widely used in both fundamental and applied sciences. Here, we report on experimental evidence for dynamics of hybrid solitons-a new type of solitary wave, which emerges as a result of a strong non-instantaneous nonlinear response in CS2-filled liquid-core optical fibres. Octave-spanning supercontinua in the mid-infrared region are observed when pumping the hybrid waveguide with a 460 fs laser (1.95 μm) in the anomalous dispersion regime at nanojoule-level pulse energies. A detailed numerical analysis well correlated with the experiment uncovers clear indicators of emerging hybrid solitons, revealing their impact on the bandwidth, onset energy and noise characteristics of the supercontinua. Our study highlights liquid-core fibres as a promising platform for fundamental optics and applications towards novel coherent and reconfigurable light sources.Here, Chemnitz et al. report experimental evidence for hybrid solitons - a type of solitary wave, which emerges as a result of a strong non-instantaneous nonlinear response in CS2-filled liquid-core optical fibres, demonstrating efficient soliton-driven supercontinuum generation.

Towards integration of a liquid-filled fiber capillary for supercontinuum generation in the 1.2-2.4 μm range

We demonstrate supercontinuum generation in unspliced as well as in integrated CS(2)-filled capillary fibers at different pump wavelengths of 1030 nm, 1510 nm, and 1685 nm. A novel method for splicing a liquid-filled capillary fiber to a standard single-mode optical fiber is presented. This method is based on mechanical splicing using a direct-laser written polymer ferrule using a femtosecond two-photon polymerization process. We maintain mostly single-mode operation despite the multi-mode capability of the liquid-filled capillaries. The generated supercontinua exhibit a spectral width of over 1200 nm and 1000 nm for core diameters of 5 μm and 10 μm, respectively. This is an increase of more than 50 percent compared to previously reported values in the literature due to improved dispersion properties of the capillaries.

Dispersion properties of liquid-core photonic crystal fibers

Dispersion properties of liquid-core photonic crystal fibers (PCFs) with large air fraction in clads between 300 to 2000 nm have been calculated by a multipole method for various liquids including CS(2), toluene, chloroform, and water for different core diameters. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica, and a central hole is filled with liquid to create a core. The results are compared with those obtained by a fully vectorial effective index method, and fitting parameters for core sizes are found for each liquid except for water, where the latter method does not give correct dispersions at short wavelengths. Also, the power ratios inside liquid cores and effective core areas were calculated at different wavelengths.

Influence of the retarded response on an ultrafast nonlinear optofluidic fiber coupler

We demonstrate by numerical simulations of coupled generalized nonlinear Schrödinger equations that the input pulse duration as well as the retarded material response have a crucial impact on the properties of an ultrafast nonlinear optofluidic fiber coupler. This device is composed of two waveguides in close vicinity embedded in a photonic crystal fiber which are filled with a highly nonlinear liquid. We show that in particular the critical peak power above which the coupling between the waveguides is suppressed increases dramatically for short input pulses and long characteristic response times of the liquid. We establish a simple model which describes these effects with high accuracy.