Spectral-temporal-spatial customization via modulating multimodal nonlinear pulse propagation

Abstract

Multimode fibers (MMFs) are gaining renewed interest for nonlinear effects due to their high-dimensional spatiotemporal nonlinear dynamics and scalability for high power. High-brightness MMF sources with effective control of the nonlinear processes would offer possibilities in many areas from high-power fiber lasers, to bioimaging and chemical sensing, and to intriguing physics phenomena. Here we present a simple yet effective way of controlling nonlinear effects at high peak power levels. This is achieved by leveraging not only the spatial but also the temporal degrees of freedom during multimodal nonlinear pulse propagation in step-index MMFs, using a programmable fiber shaper that introduces time-dependent disorders. We achieve high tunability in MMF output fields, resulting in a broadband high-peak-power source. Its potential as a nonlinear imaging source is further demonstrated through widely tunable two-photon and three-photon microscopy. These demonstrations provide possibilities for technology advances in nonlinear optics, bioimaging, spectroscopy, optical computing, and material processing.

Tutorial: How to build and control an all-fiber wavefront modulator using mechanical perturbations

“…a step-index (SI) or a graded index (GRIN) fiber. The modes of SI fibers have larger modal areas and more closely spaced propagation constants for the same numerical aperture, which leads to increased mode coupling and higher sensitivity to bending [39,59]. Thus, using an SI fiber allows more control per actuator, which may decrease the required amount of actuators.…”

“…Qiu et al have recently shown that one can resolve this challenge using a fiber piano [59,79]. The control of the wavefront was achieved during nonlinear light propagation in multimode fibers using a fiber piano that was built using 3D printing and low-cost stepper motors.…”