Seeded intermodal four-wave mixing in a highly multimode fiber

TL;DR

This paper explores seeded intermodal four-wave mixing in a large-core multimode fiber, demonstrating controlled spectral sideband generation and the importance of higher-order dispersion in phase matching, with experimental and theoretical insights.

Contribution

It presents a combined experimental and theoretical study of seeded intermodal four-wave mixing in a graded index multimode fiber, emphasizing the role of higher-order dispersion in phase matching.

Findings

Generation of spectral sidebands in the C band.

Good agreement between experimental results and phase-matching theory.

Observation of multiple pulse structures in temporal measurements.

Abstract

We experimentally and theoretically investigate the process of seeded intermodal four-wave mixing in a graded index multimode fiber, pumped in the normal dispersion regime. By using a fiber with a 100 micron core diameter, we generate a parametric sideband in the C band (1530-1565 nm), hence allowing the use of an Erbium-based laser to seed the mixing process. To limit nonlinear coupling between the pump and the seed to low-order fiber modes, the waist diameter of the pump beam is properly adjusted. We observe that the superimposed seed stimulates the generation of new spectral sidebands. A detailed characterization of the spectral and spatial properties of these sidebands shows good agreement with theoretical predictions from the phase-matching conditions. Interestingly, we demonstrate that both the second and the fourth-order dispersions must be included in the phase matching conditions to get better agreement with experimental measurements. Furthermore, temporal measurements performed with a fast photodiode reveal the generation of multiple pulse structures.