Understanding noise and coherence properties of supercontinuum generation in non-instantaneous liquid core fibers

• Applicant: Professor Dr. Markus A. Schmidt
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264438699

Supercontinuum generation (SCG) allows distributing electromagnetic energy via nonlinear optical effects across defined spectral domains. One particular effective scheme relies on the fission of higher-order solitons into their fundamental counterparts within optical fibers being associated with the emission of dispersive waves. Since SCG originates from nonlinear material responses, it reveals a comparably high susceptibility to phase and amplitude noise. This susceptibility imposes variations within the ensemble of generated spectra, which can be detrimental for applications requiring using individual spectra. This forms a demand for studying the correlation between generated spectra, i.e., the coherence of the SCG process. Within solid glass fibers SCG evolves from a highly coherent into an incoherent state for higher peak powers or longer pulses, having led to the definition of the coherence limit via the soliton number. This limit is fundamentally associated with the instantaneous temporal response of solid glass materials. Within the preceding project first evidence that fibers with liquid cores allow for highly coherent SCG at soliton numbers solely solid glass systems deliver incoherent spectra was found in simulations. This improvement is associated with the non-instantaneous contribution to the nonlinear response of the liquid core, resulting from molecular processes that are solely due to the liquid environment and do not exist in solid materials.The main objective of the proposed project is to understand the impact of a non-instantaneous contribution to the nonlinear temporal response on the coherence properties of supercontinua generated in liquid core fibers. The project targets investigating noise and first-order degree of correlation within the ensemble of generated spectra both from the theoretical as well as in particular from the experimental perspective. Specific scientific questions are for instance the impact of a hybrid temporal response on soliton fission and dispersive wave formation and if these are valid descriptions of the corresponding physics. Another issue is the currently used coherence limit, with first indications suggesting that the liquid core fiber concept allows breaking through that limit, providing coherent SCG at higher input power levels. Overall, the project aims to demonstrate new nonlinear physics with respect to the coherence of soliton-based SCG based on a waveguide platform incorporating a hybrid temporal response function, which is highly relevant for applications that demand individual spectra.

• DFG Programme: Research Grants