Ricerc@Sapienza

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.

In order to fully exploit laser beam dynamics in multimode fibers for applications to spatiotemporal laser beam mode-locking, it is necessary to accurately determine the conditions for the occurrence of the effect, by optimizing the spatial and temporal properties of the input laser pulses. We will describe a series of recent experiments that permit to unveil the physical mechanism of Kerr-beam self-cleaning, based on a complex cascade of parametric wave mixing processes.

We experimentally and theoretically investigate complex temporal pulse reshaping that accompanies Kerr beam self-cleaning in multimode optical fibers. We also study the output beam shape dependence on initial conditions.

Nonlinear propagation of optical pulses in multimode fibers is subject to complex spatio-temporal phenomena. We outline different strategies for the control and optimization of nonlinear mode coupling. The first approach involves transverse wavefront shaping of the input beams, which permits to launch an optimized mode combination, that results in the generation of a stable nonlinear mode alphabet at the fiber output.

Spatiotemporal light beam dynamics in multimode optical fibers (MMFs) has emerged in recent years as fertile research domain in nonlinear optics. Intriguing spatiotemporal wave propagation phenomena such as multimode optical solitons and parametric instabilities leading to ultra-wideband sideband series, although predicted quite a long time ago, have only been experimentally observed in MMFs in the last few years.

Spatiotemporal light beam dynamics in multimode opti- cal fibers (MMFs) has emerged as a fertile domain of scientific research in nonlinear optics and physics]. Intriguing spatiotemporal wave propagation phenomena such as multimode optical solitons, and parametric instabilities leading to ultra-wideband sideband series [3] have only been experimentally observed in MMFs over the last few years. Among these, we are interested to study here the phenomenon of spatial self-condensation or self-cleaning of multimode light beams in MMFs.

We overview experiments associated with nonlinear beam propagation in multimode optical fibers. We show that complex spatio-temporal phenomena permit to control the nonlinear beam reshaping across its spatial, temporal and spectral dimensions.

Recent experiments have shown that nonlinear wave propagation in multimode optical fibers leads to complex spatio-temporal phenomena. In this talk, we introduce new approaches for the control and optimization of nonlinear beam reshaping in the spatial, temporal and spectral dimensions. The first approach applies to spatial beam self-cleaning the technique of transverse wavefront shaping, which permits to launch an optimized input mode combination, that results in the stable generation of a whole nonlinear mode alphabet at the fiber output.

We provide a perspective overview of the emerging field of nonlinear optics in multimode optical fibers. These fibers enable new methods for the ultrafast light-activated control of temporal, spatial, and spectral degrees of freedom of intense, pulsed beams of light, for a range of different technological applications.

Optical rogue waves emerge in nonlinear optical systems with extremely large amplitudes, and leave without a trace. In this work, we reveal the emergence of optical polarization rogue waves in supercontinuum generation from a zero-dispersion fiber, pumped by a dissipative soliton laser. Flat spectral broadening is achieved by modulation instability, followed by cascaded four-wave-mixing. In this process, we identify the emergence of optical polarization rogue waves, based on the probability density function of the relative distance among polarization states.