Published/Posted: December 20, 2020
Authors: Dacha, S. K.; Murphy, T. E.
arXiv: 2005.00135Abstract: Nonlinear propagation of signals in single-mode fibers is well understood, and is typically observed by measuring the temporal profile or optical spectrum of an emerging signal. In multimode fibers, the nonlinearity has both a spatial and a temporal element, and a complete investigation of the interactions between propagating modes requires resolving the output in both space and time. We report here spatiotemporal measurements of a time-dependent mode interference effect, arising from the Kerr nonlinearity, of two selectively excited LP0m modes of a step-index few-mode fiber. We describe a method to selectively excite two propagating modes through the use of a phase mask directly patterned on the entrance face of the fiber. The output is resolved by raster-scanning a near-field tapered single-mode optical fiber probe that is connected to a high-speed detector. The results show that in the presence of nonlinearity, the output exhibits a spatiotemporal character that cannot be adequately characterized by a camera image or pulse shape alone.
S. K. Dacha and T. E. Murphy, "Spatiotemporal characterization of nonlinear intermodal interference between selectively excited modes of a few-mode fiber", Optica 7(12) 1796-1803 (2020)
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