Experimental Emulator of Pulse Dynamics in Fractional Nonlinear Schrödinger Equation

A nonlinear optical platform is presented to emulate a nonlinear Lévy waveguide that supports the pulse propagation governed by a generalized fractional nonlinear Schrödinger equation (FNLSE). This approach distinguishes between intra-cavity and extra-cavity regimes, exploring the interplay between the effective fractional group-velocity dispersion (FGVD) and Kerr nonlinearity. In the intra-cavity configuration, stable fractional solitons enabled by an engineered combination of the fractional and regular dispersions in the fiber cavity are observed. The soliton pulses exhibit their specific characteristics, viz., “heavy tails” and a “spectral valley” in the temporal and frequency domain, respectively, highlighting the effective nonlocality introduced by FGVD. Further investigation in the extra-cavity regime reveals the generation of spectral valleys with multiple lobes, offering potential applications to the design of high-dimensional data encoding. To elucidate the spectral valleys arising from the interplay of FGVD and nonlinearity, an innovative “force” model supported by comprehensive numerical analysis is developed. These findings open new avenues for experimental studies of spectral-temporal dynamics in fractional nonlinear systems.