Search results for "BEAM"
showing 10 items of 2126 documents
Real time measurement of long parabolic optical similaritons
2008
International audience; Long optical similaritons using a Raman fibre amplifier are generated. These pulses, with a highly parabolic profile, are monitored in real time on a high speed oscilloscope. Tunability of both the temporal and spectral widths of the pulses is then investigated.
Self-focusing in Terbium Gallium Garnet using Z-scan
1998
International audience; When illuminated near its resonance with an Ar ion laser beam (lambda=488 nm), laser induced thermal self-focusing is observed in Terbium Gallium Garnet. The crystal exhibits a strong intensity dependent refractive index change Dn. The Z-scan technique is used to study the beam waist change due to Dn. The refractive index is found to be well described by a quadratic spatial distribution model. Both the sign and the distribution coefficient of Dn are determined.
Analysis of the angular acceptance of surface plasmon Bragg mirrors
2007
International audience; We analyze an important aspect of the behavior of surface plasmon polariton (SPP) Bragg mirrors: the dependence of the angular acceptance for reflection on the incidence angle. By means of leakage radiation microscopy, both in direct and Fourier space, we observe that the angular acceptance diminishes for increasing incidence angles. This effect, which can considerably affect the design of devices based on these elements, is shown to be the consequence of the decrease of the bandgap width with increasing incidence angle. (c) 2007 Optical Society of America.
Caustic Interpretation of the Abruptly Autofocusing Vortex beams
2021
We propose an effective scheme to interpret the abruptly autofocusing vortex beam. In our scheme, a set of analytical formulae are deduced to well predict not only the global caustic, before and after the focal plane, but also the focusing properties of the abruptly autofocusing vortex beam, including the axial position as well as the diameter of focal ring. Our analytical results are in excellent agreement with both numerical simulation and experimental results. Besides, we apply our analytical technique to the fine manipulation of the focusing properties with a scaling factor. This set of methods would be beneficial to a broad range of applications such as particle trapping and micromachi…
Nonlinear spatial self-cleaning in multimode amplifying fiber and fiber laser cavity
2017
During the last years, multimode fibers (MMFs) were used as an experimental platform for the observation of complex nonlinear propagation phenomena, thanks to their additional spatiotemporal degrees of freedom with respect to single mode fibers. Multimode solitons [1], geometric parametric instability [2], self-induced beam cleaning (SBC) [3] and supercontinuum generation have been reported [4]. In all of these situations considered so far the MMFs were standard graded-index fibers: the intermodal interactions took place in a conservative system (propagation losses were negligible). In this work we have experimentally investigated the Kerr SBC in three dissipative systems: a MMF with signif…
Polarization control in spun and telecommunication optical fibers
2011
International audience; We consider the counterpropagating interaction of a signal and a pump beam in a spun fiber and in a randomly birefringent fiber, the latter being relevant to optical telecommunication systems. On the basis of a geometrical analysis of the Hamiltonian singularities of the system, we provide a complete understanding of the phenomenon of polarization attraction in these two systems, which allows to achieve a control of the polarization state of the signal beam by adjusting the polarization of the pump. In spun fibers, all polarization states of the signal beam are attracted toward a specific line of polarization states on the Poincaré sphere, whose characteristics are d…
Supercontinuum spectral-domain ghost imaging
2018
International audience; Ghost imaging is a technique that generates high-resolution images by correlating the intensity of two light beams, neither of which independently contains useful information about the shape of the object. Ghost imaging has been demonstrated in both the spatial and temporal domains, using incoherent classical light sources or entangled photon pairs. Here we exploit the recent progress in ultrafast real-time measurement techniques to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations. We demonstrate the application of this technique to broa…
Mitigation of self-phase modulation by sinusoidally time varying phase
2018
The propagation of intense ultra-short optical pulses in a Kerr medium such as an optical fibre remains a critical issue for many optical systems. This is because the self-phase modulation (SPM) of the propagating pulse usually causes a severe broadening of the pulse spectrum that is typically accompanied by an oscillatory structure. Several strategies have been proposed and successfully deployed to counteract the deleterious effects of SPM in fiber-optic systems, including spatial or temporal scaling to reduce the impact of nonlinearity. Other approaches rely on the exploitation of the peculiar properties of parabolic shaped pulses and self-similar evolution. However, none of these last te…
Comparison between 2 Different Composite Nd3+:YVO4 Crystals in a Fibre Coupled Diode Pumped Laser
2008
International audience; We detail the performances of two composite Nd3+YVO4crystals, realised with two different sticking techniques. We tested them inside a fibre coupled diode end pumped laser.
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…