Understanding Nonlinear Pulse Propagation in Liquid Strand-Based Photonic Bandgap Fibers

Abstract

Ultrafast supercontinuum generation crucially depends on the dispersive properties of the underlying waveguide. This strong dependency allows for tailoring nonlinear frequency conversion and is particularly relevant in the context of waveguides that include geometry-induced resonances. Here, we experimentally uncovered the impact of the relative spectral distance between the pump and the bandgap edge on the supercontinuum generation and in particular on the dispersive wave formation on the example of a liquid strand-based photonic bandgap fiber. In contrast to its air-hole-based counterpart, a bandgap fiber shows a dispersion landscape that varies greatly with wavelength. Particularly due to the strong dispersion variation close to the bandgap edges, nanometer adjustments of the pump wavelength result in a dramatic change of the dispersive wave generation (wavelength and threshold). Phase-matching considerations confirm these observations, additionally revealing the relevance of third order dispersion for interband energy transfer. The present study provides additional insights into the nonlinear frequency conversion of resonance-enhanced waveguide systems which will be relevant for both understanding nonlinear processes as well as for tailoring the spectral output of nonlinear fiber sources.

Liquid‐Core Optical Fibers—A Dynamic Platform for Nonlinear Photonics

“…In follow-up work, the group also demonstrated the use of tailored fluids to accurately adjust the waveguide dispersion at the edge of a bandgap of microstructured fibers to enhance nonlinear light conversion. [181] Solid substituents, such as molecules with large hyperpolarizability, represent another interesting option for future research. For example, a recent work by Keyser et al [182] reports on functionalizing LCFs on the molecular level by doping the liquid core with hydrogen-free charge-transfer molecules.…”

“…In follow‐up work, the group also demonstrated the use of tailored fluids to accurately adjust the waveguide dispersion at the edge of a bandgap of microstructured fibers to enhance nonlinear light conversion. [ 181 ]…”

Specialty Photonic Crystal Fibers and Their Applications

“…For example, an endlessly single-mode solid-core PCF can then be turned into a photonic bandgap fiber [45]. In their research paper Understanding Nonlinear Pulse Propagation in Liquid Strand-Based Photonic Bandgap Fibers [46], a team from the University of Jena (Germany) explores the effects of injecting liquid carbon disulfide (CS 2 ) in the air channels of a silica-made PCF on the guidance and nonlinear properties of the resulting hybrid fiber, which exhibits distinct transmission bands as previously shown in photonic bandgap fibers [47]. They then generate broad supercontinua in the CS 2 -filled fiber, reporting a strong influence of the location of the pump wavelength with respect to the band edge on the dynamics.…”