0000000000017356
AUTHOR
Daniele Modotto
showing 16 related works from this author
Modal attraction on low order modes by Kerr effect in a graded refractive index multimode fiber
2018
Modal attraction towards low order modes in a GRIN multimode fiber was experimentally observed at high power and characterized, thus enriching the dynamics of the Kerr self-cleaning effect leading to quasi fundamental mode generation.
Multidimensional shaping of spatiotemporal waves in multimode nonlinear fibers
2019
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. The second approach introduces a longitudinal tapering of the core diameter of multimode active and passive fibers, which permits to generate ultra-wideb…
Spatiotemporal light-beam compression from nonlinear mode coupling
2017
We experimentally demonstrate simultaneous spatial and temporal compression in the propagation of light pulses in multimode nonlinear optical fibers. We reveal that the spatial beam self-cleaning recently discovered in graded-index multimode fibers is accompanied by significant temporal reshaping and up to four-fold shortening of the injected sub-nanosecond laser pulses. Since the nonlinear coupling among the modes strongly depends on the instantaneous power, we explore the entire range of the nonlinear dynamics with a single optical pulse, where the optical power is continuously varied across the pulse profile.
Seeded intermodal four-wave mixing in a highly multimode fiber
2018
International audience; 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-mu m 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 sideb…
Dispersion-optimized multicladding silicon nitride waveguides for nonlinear frequency generation from ultraviolet to mid-infrared
2016
Nonlinear frequency conversion spanning from the ultraviolet to the mid-infrared (beyond 2.4 μm) is experimentally demonstrated in multicladding silicon nitride (𝑆𝑖𝑋𝑁𝑌) waveguides. By adjusting the waveguide cross-section the chromatic dispersion is flattened, which enhances both the efficiency and the bandwidth of the nonlinear conversion. How accurately the dispersion is tailored is assessed through chromatic dispersion measurements and an experiment/simulation comparison of the dispersive waves' wavelength locations. Undesirable fluctuations of both the refractive index and the dimensions of the waveguide during the fabrication process result in a dispersion unpredictability of at l…
Spatio-temporal beam dynamics in multimode nonlinear optical fibers
2017
We overview recent advances in the spatio-temporal nonlinear dynamics of optical pulses propagating in multimode optical fibers. The Kerr effect leads to spatial beam self-cleaning in a graded-index multimode optical fiber, followed by sideband series generation spanning multiple octaves. Effectively single mode supercontinuum spanning from the visible to the mid-infrared was also demonstrated. Enhancement of Kerr beam self-cleaning was observed in active fiber with quasi-step index profile. Moreover, mutual self-cleaning was recently reported for both the fundamental and the second harmonic beams in optically poled multimode fibers with cubic and quadratic nonlinearity.
Nonlinear Multimode Fiber Optics
2018
We overview recent advances in the nonlinear optics of multimode optical fibers, including ultrabroadband sideband and supercontinuum generation, Kerr and Raman beam cleanup, modal modulation instabilities, four wave mixing, and second harmonic beam cleaning.
Spatial Beam Evolution in Nonlinear Multimode Fibers
2021
We discuss some recent results illustrating the role of input wave-front shaping, propagation dynamics and output beam diagnostics in order to observe spatial beam cleaning in nonlinear multimode fibers and amplifiers.
Second harmonic generation and beam cleaning in optically poled multimode graded-index fibers
2017
Recent experimental results have confirmed that nonlinear effects in multimode graded-index (MM-GRIN) fibers lead to a wealth of observable spatiotemporal effects. In spite of the large number of modes supported by the fiber, by increasing the input power the transverse profile evolves in a clean bell-shaped beam [1, 2]. Next, the input laser line experiences a strong spectral broadening and Geometric Parametric Instability (GPl) peaks are observed [3].
Spatiotemporal pulse shaping with multimode nonlinear guided waves
2018
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.
Second harmonic generation in multimode graded-index fibers: spatial beam cleaning and multiple harmonic sideband generation
2017
We study experimentally and numerically the spectral and spatial dynamics of second harmonic generation in an all-optically poled multimode graded-index fiber. In contrast with poled single-mode fibers, in a multimode graded-index fiber a pump can generate a series of sharp sidebands around its second harmonic (SH) that originate from the sub-millimetric periodic evolution of the intensity at the fundamental frequency. The mutual interaction between the fundamental and its SH may also strongly affect the spatial distribution of guided light for both colors: when increasing the pump power, both fundamental and SH output beams evolve from disordered multimode speckles into two bell-shaped bea…
Control of signal coherence in parametric frequency mixing with incoherent pumps: Narrowband mid-infrared light generation by downconversion of broad…
2012
International audience; We study, with numerical simulations using the generalized nonlinear envelope equation, the processes of optical parametric and difference- and sum-frequency generation (SFG) with incoherent pumps in optical media with both quadratic and third-order nonlinearity, such as periodically poled lithium niobate. With ultrabroadband amplified spontaneous emission pumps or continua (spectral widths > 10 THz), group-velocity matching of a near-IR pump and a short-wavelength mid-IR (MIR) idler in optical parametric generation may lead to more than 15-fold relative spectral narrowing of the generated MIR signal. Moreover, the SFG process may also lead to 6-fold signal coherence…
Nonlinear dynamics of spatio-temporal waves in multimode fibres
2017
International audience
Kerr Beam Self-Cleaning in Multimode Fibers
2018
We overview recent experimental results of beam self-cleaning observed in various types of multimode fibers. We analyze the output spatial beam shapes and their connection with the refractive index profile of the fibers.
Adaptive Kerr-Assisted Transverse Mode Selection in Multimode Fibers
2019
Multimode optical fibers (MMFs) have recently regained interest because of the degrees of freedom associated with their different eigenmodes. In the nonlinear propagation regime in particular, new phenomena have been unveiled in graded-index (GRIN) MMFs such as geometric parametric instabilities and Kerr beam self-cleaning [1, 2]. The speckled pattern observed at the output of the MMF at low powers, is transformed at high powers into a bell-shaped beam close to the fundamental mode. Recent work has also demonstrated that Kerr beam self-cleaning can lead to a low-order spatial mode, different from a bell-shape, by adjusting the laser beam in-coupling conditions [3]. An attractive way to syst…
Spatiotemporal beam shaping in nonlinear multimode fibers
2018
Kerr beam self-cleaning in graded-index multimode fibers is accompanied by power-dependent temporal pulse reshaping. We explore the complex nonlinear dynamics with a single long pulse, where the optical power is continuously varied across its profile.