Gil Fanjoux

Black-light continuum generation in a silica-core photonic crystal fiber

We report the observation of a broadband continuum spanning from 350 to 470 nm in the black-light region of the electromagnetic spectrum as a result of picosecond pumping a solid-core silica photonic crystal fiber at 355 nm. This was achieved despite strong absorption and a large normal dispersion of silica glass in the UV. Further investigations reveal that the continuum generation results from the interplay of intermodally phase-matched four-wave mixing and cascaded Raman scattering. We also discuss the main limitations in terms of bandwidth and power due to temporal walk-off, fiber absorption, and the photo darkening effect, and we suggest simple solutions.

Generation of multicolor vector Kerr solitons by cross-phase modulation, four-wave mixing, and stimulated Raman scattering

We numerically and experimentally show the existence of multicolor vector spatial solitons in a Kerr planar waveguide through the combined effects of cross-phase modulation, four-wave mixing, and stimulated Raman scattering. Mutual spatial guiding of the Raman-Stokes, anti-Stokes, and pump waves is achieved in the high-conversion regime mainly by cross-phase modulation and phase-matched four-wave mixing induced by a power imbalance between Stokes and anti-Stokes components, leading to the generation of a clear-cut sech-shape three-frequency spatial soliton.

Dynamics of second-harmonic generation in a photovoltaic photorefractive quadratic medium

We investigate second-harmonic generation (SHG) in a photorefractive photovoltaic medium such as lithium niobate. Our numerical model reveals the complex dynamics of the parametric process during the buildup of the index modification due to the photorefractive (PR) nonlinearity. We investigate a condition in which no external field is applied to the crystal, resulting in a defocusing nonlinearity, as well as the case in which an external bias is applied, producing a self-focusing effect that can enhance the conversion efficiency of the parametric process. We also find the conditions for the initial phase matching and for the background illumination leading to a stable self-confined propagation of the second-harmonic generated light. The developed numerical model shows that as a general case SHG in a self-focusing PR medium results in mode beating inside the generated waveguide, as experimentally observed.

All-optical tunable pulse frequency chirp via slow light

We theoretically investigate slow light via stimulated Raman scattering, paying special attention to the picosecond regime where chromatic dispersion and cross-phase modulation must be considered. In addition to the control of the Raman pulse walk-off, we demonstrate that the cross-phase-modulation-induced frequency chirp can also be all-optically tuned via Raman slow light. We further demonstrate that this new implication is a consequence of the fact that the group velocity is significantly more affected than the phase velocity in slow-light media.

Cancellation of Raman pulse walk-off by slow light

We theoretically demonstrate in a nonlinear optical fiber system with a narrowband Raman gain that pulse walk-off between the pump and the Raman Stokes waves can be fully compensated for by Raman slow light, leading to group-velocity matching between the interacting waves, greater useful interaction length, and thereby enhanced Raman amplification efficiency. Limitations due to Kerr effect are further discussed.

Stimulated Raman–Kerr scattering in an integrated nonlinear optofluidic fiber arrangement

We describe a novel optofluidic fiber arrangement that allows for nonlinear effects enhancement between fluids and laser light while suppressing the generation of cavitation bubbles. By filling this optofluidic system with toluene and pumping it with a nanosecond microchip laser, we demonstrate the efficient generation of a broadband Raman frequency comb spanning from 532 to more than 1000 nm. It is further shown that the Raman frequency comb dramatically broadens toward broadband continuum light due to the stimulated Raman-Kerr scattering.

Beam steering using optical parametric amplification in Kerr medium: a space-time analogy of parametric slow-light

In a way analogous to a light pulse that can be optically delayed via slow light propagation in Kerr-type nonlinear media, we theoretically demonstrate that beam steering and spatial walk-off compensation can be achieved in noncollinear optical parametric amplification. We identify this effect as a result of the quadratic phase shift induced by parametric amplification that leads to the cancellation of the spatial walk-off and collinear propagation of all beams though they have different wavevectors. Experimental evidence is reported of a soliton array steering in a Kerr slab waveguide.

The generation of spatial soliton arrays in a planar Kerr waveguide from seeded spontaneous parametric down conversion

The possibility of generating spatial soliton arrays in a nonlinear Kerr waveguide by the spontaneous modulation instability (MI) process strongly depends on the relaxation time of the nonlinear material response and on the characteristics of the spatio-temporal noise added on the injected beam. We address this issue in this paper by considering parametric down conversion generated in a quadratic crystal as a noise source before the Kerr waveguide. By a full spatio-temporal numerical simulation, we show first that the spontaneous MI process occurs if the spatially noisy beam launched into the waveguide presents a minimal spatial coherence. Second, soliton arrays are formed in an instantaneous Kerr medium only for a temporally quasi-coherent input beam. If the Kerr effect is non-instantaneous, soliton arrays can be formed for temporally noisy beams until a threshold level of temporal coherence is reached.

Raman-Induced Slow Light on Spatial Soliton in Kerr Media

We report the experimental observation of the slow light phenomenon induced on spatial solitons in a Kerr CS2planar waveguide through Stimulated Raman scattering. Optical delay of 120-ps on 3-cm soliton propagation was achieved.

Tunable Optical Delay Using Parametric Amplification in Highly-Birefringent Optical Fibers

We theoretically study parametric amplification or cross-phase modulation instability in highly-birefringent optical fibers and demonstrate tunable picosecond pulse optical delay or advancement via slow and fast light propagation.