Femtosecond laser fabrication of micro and nano-disks in single layer graphene using vortex Bessel beams

International audienceWe report the fabrication of micro and nano-disks in single layer chemical vapor deposition graphene on glass substrate using femtosecond laser ablation with vortex Bessel beams. The fabricated graphene disks with diameters ranging from 650 nm to 4 μm were characterized by spatially resolved micro-Raman spectroscopy. The variation of ablation threshold was investigated as a function of the number of pulses showing an incubation effect. A very high degree of size control of the fabricated graphene disks is enabled using a sequence of femtosecond pulses with different vortex orders

Micromachining along a curve: Femtosecond laser micromachining of curved profiles in diamond and silicon using accelerating beams

International audienceWe report femtosecond laser micromachining of micron-size curved structures using tailored accelerating beams. We report surface curvatures as small as 70 μm in both diamond and silicon, which demonstrates the wide applicability of the technique to materials that are optically transparent or opaque at the pump laser wavelength. We also report the machining of curved trenches in silicon. Our results are consistent with an ablation-threshold model based on calculated local beam intensity, and we also observe asymmetric debris deposition which is interpreted in terms of the optical properties of the incident accelerating beam

Filamentation of high-angle nondiffracting beams and applications to ultrafast laser processing

International audienceWe report on filamentation of nondiffracting beams and show that the intense light-matter interaction regime achieved on long distances allows for an enhanced control on ultrashort laser deep ablation

Femtosecond laser material processing with nondiffracting light

International audienceAlthough versatile and widely used, femtosecond laser micro-nanomachining faces a challenge for the fabrication of high aspect ratio or deep structures. The control of the profile along the longitudinal dimension is extremely difficult. In this context, our approach is based on controlling the direction of light rather than shaping the intensity pattern in one plane. Here we review our recent work in this field using Bessel beams and accelerating beams. In Bessel beams, light propagates along the generatrix of a cone, with a fixed radial wavevector. Contrary to Gaussian beams, the femtosecond filamentation regime of Bessel beams can be stationary, and can generate extended plasma tracks in dielectrics. This allowed us to generate nanochannels in glass with aspect ratio up to 100:1 [1]. Numerical simulations of the nonlinear propagation in this regime show the importance of the conical structure in generating extremely dense plasmas [2]. Airy beams and more generally accelerating beams constitute another family of beams that possess quasi-nondiffracting behaviour and their nonlinear propagation can also be stationary. Their primary intensity lobe propagates along a curved trajectory that can be arbitrarily shaped even in the nonparaxial regime. Since this lobe is adjacent to a region where no light propagates, accelerating beams can be used for direct curved edge profiling and trench processing in transparent and opaque materials [3,4]. Our results show that controlling the linear and nonlinear propagation of ultrashort femtosecond laser pulses by nondiffracting beams is a key new technological approach for laser processing

Faisceaux non-diffractants et accélérants. Applications à la micro et nanostructuration par laser femtoseconde

National audienceLors des processus d'ablation par laser, le contrôle des profils des flancs d'ablation est un aspect important. Nous avons récemment développé une approche permettant de répondre à ce problème, à partir du contrôle de la direction de la lumière dans des faisceaux femtoseconde. Nous adressons des modes particuliers (stationnaires) de la filamentation dans les diélectriques afin de contrôler la répartition spatiale du dépôt d'énergie dans la matière. Des structures à haut rapport de forme et l'usinage direct de profils courbes seront présentés

Progress in Preforming Whispering Gallery Mode Resonant Disks via Femtosecond Laser Machining

International audienceWhispering gallery mode resonators (WGMR) have received extensive interest recently, as they provide a promising range of compact and versatile components [1]. Among the available substrates, fluoride crystals have attracted particular attention as they combine good optical and mechanical properties together with excellent linear and non-linear behavior [2]. However, crystalline disks with diameters in the millimeter range have so far been realized through mechanical grinding and polishing, which presents strong drawbacks. In this submission we report on the femtosecond laser cutting and shaping of 12 mm-diameter CaF2 resonant disks. The finalized components featured an intrinsic Q-factor of 9.1 10<sup&gt8</sup&gt with significantly reduced processing times as compared to prior methods

Spatio-temporal structure of femtosecond Bessel beams from spatial light modulators

International audienceWe numerically investigate the spatio-temporal structure of Bessel beams generated with Spatial Light Modulators (SLMs). Grating-like phase masks enable the spatial filtering of undesired diffraction orders produced by SLMs. Pulse front tilt and temporal broadening effects are investigated. In addition, we explore the influence of phase wrapping and show the spatio-temporal structure of SLM-generated femtosecond Bessel beams is similar to Bessel X-pulses at short propagation distance, and to subluminal Pulsed Bessel Beams at long propagation distance

Experimental chaotic map generated by picosecond laser pulse-seeded electro-optic nonlinear delay dynamics

International audienceWe describe experimental studies of the dynamical behavior of a recently proposed electro-optic discrete time nonlinear delay oscillator. With appropriate choice of the oscillator loop parameters and external forcing of the dynamics using a pulsed laser source, the system allows for the physical realization of a high dimensional mathematical nonlinear mapping. The dynamical features observed with this new class of discrete time delay oscillator differ significantly from those observed with similar continuous time nonlinear delay feedback oscillators and reveal the intrinsic discrete time nature of the dynamics. We also discuss specific applications to chaos communications using regularly clocked binary data

Nano-ablation à haut rapport de forme

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