Publications de Yves Bellouard

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This paper describes a microgripper used for the micro-assembly of an artificial scaffold for tissue engineering. The porous sponge-like scaffold is a three dimensional construct built by tiny unit parts of biodegradable polymer. This application requires the assembly of several parts by applying a suitable level of force. In this framework, a monolithicshape memory alloy (SMA) microgripper was developed. It consists of two small fingers for grasping, an active part that changes its shape when heated and a

The question of whether static stress in fused silica relaxes at room temperature is still under debate. Here, we report experimental data investigating the behavior of fused silica at room temperature when subjected to static tensile stress up to 2 GPa st ...

The progress made in ultrafast laser technology towards high repetition rate systems have opened new opportunities in micromanufacturing. Non-linear absorption phenomena triggered by femtosecond pulses interacting with transparent materials allow material ...

Over the past several years, non-ablative femtosecond laser exposure with spatially overlapping (i.e., spatially cumulative) pulses has emerged as a key process in three-dimensional writing of patterns in bulk of dielectric substrates. When temporally non- ...

In the non-ablative regime, femtosecond laser pulse duration is known to affect the nature of the modification induced in the microstructure of fused silica. It has been demonstrated than below 200 fs, two different regimes are found, one at low energy, le ...

Non-ablative femtosecond laser processing of transparent substrates involves cumulative, multi-timescale dynamics that hinder precise control of induced structural modifications. Here, we demonstrate a feedback-compatible diagnostic based on mid-infrared transmission monitoring using a continuous-wave QCL emitting at 4.46 µm. This approach enables in situ observation of structural dynamics induced by femtosecond laser irradiation at repetition rates up to 250 kHz. The technique shows sensitivity to key tran

The structuring of mid-IR materials, such as chalcogenide glass (ChG), at the micro and nano scales, is of high interest for the fabrication of photonic devices in general, and for spectroscopy applications in particular. One efficient method for producing ...

Free-space optics allows for design freedom and control, but miniaturization and manufacturability are limited. Here, we present a method for manufacturing complex miniaturized free-space optical systems that combines contactless femtosecond laser-activate ...

Retinal vein occlusion (RVO) is a major cause of vision loss in patients over 50 years old. RVO can be treated by cannulation of the retinal vein to remove clots. However, cannulation of small retinal veins is challenging as the required puncture force (~10 mN) is well below human sensing capability [1]. In this paper, we introduce a passive compliant tool for retinal vein cannulation having predetermined stroke and threshold force which allows safe and precise puncturing independent of actuation input. Our

Since the first demonstration of the process in 1995, fused silica is a widely used material for direct femtosecond waveguide writing. However, the high exposure dose requirement requires a low writing speed, which limits potential applications. By using ultraviolet light at 343 nm with yet, comparably longer pulses (450 fs) than normally used, we demonstrate high-speed low-loss waveguide writing, at a rate, approximately 1,000 times faster than typically used writing parameters. The fabricated waveguides a

Among recent advanced manufacturing techniques introduced over the last decades, non-ablative femtosecond laser processing has gained a lot of attention thanks to its applicability to a variety of substrates and its unique ability to locally process transparent materials in their volumes. The laser-induced taxonomy of structural modifications is rich and, despite the extreme brevity of the laser-matter interaction, includes nano-crystallization events as recently reported in various amorphous substrates. Ye

To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irra ...

From a shape change point of view, the shape memory effect is not intrinsically reversible. Therefore developing Shape Memory Alloys (SMA) actuators, i.e. devices producing a motion, requires a suitable method to bypass this intrinsic property. Since the shape memory effect discovery, different methods, either intrinsic like the «Two-Way Shape Memory Effect » or extrinsic like the use of a biasing element have been investigated. In this paper, a new method based on a local annealing of the material is prese

We investigate the use of ultrafast lasers exposure to induce localized crystallization and elemental redistribution in amorphous dielectric multi-layers, composed of alternating Si3N4 and SiO2 layers of sub-micrometer thickness. Specifically, we report on ...

We demonstrate a three-dimensional (3D) monolithic micro-actuator fabricated by non-ablative femtosecond laser micromachining and subsequent chemical etching. The actuating principle is based on dielectrophoresis. An analytical modeling of this actuation s ...

We investigate both theoretically and experimentally a laser-based controlled tuning of the nonlinear behaviors of a single mechanical resonator. Thanks to localized three-dimensional modifications induced by femtosecond-laser irradiation, a Duffing-like o ...

Single-shot spatial frequency-resolved imaging (SPIFI) is demonstrated for the first time, to our knowledge, using only a single 30 fs pulse. Earlier single-shot SPIFI configurations integrated a train of laser pulses, operated in an image plane conjugate to the object plane, and required a 2D detector. Here, a single pulse is selected, the data are collected in the Fourier plane, and the signal can be captured with 1D detection. The resultant improvement in spatial frequency support, characteristic of sing

Sub-100 fs pulses are desirable for various applications in glass micromachining and there exist several devices for retrospective pulse compression. The physical process behind the compression mechanism influences the pulse characteristics, in particular its temporal shape and the broadened spectrum. We investigate the impact of two compression methods on fused silica micromachining: Optical parametric amplification generates a tuneable almost Gaussian-shaped spectrum with low conversion efficiency. Self-p

Lately, the use of ultrafast in-volume laser-based processing of transparent materials has gained ground as a 3D-printing method of functional materials, photonics devices and high-density storage media. In this talk, we discuss the use of wide-field third-harmonic imaging that offers a non-destructive means for investigating and characterizing laser-written in-volume complex structures. Specifically, the method is used for identifying laser-induced modifications and establishing their taxonomy over a large

Using micro-cantilever deflection, we study laser-induced densification in bulk fused silica in the sub-50 fs, non-ablative regime. We estimate induced densification from deflection measurements, with a maximum value of 0.014%. ...

Yves Bellouard

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A Monolithic Shape Memory Alloy Microgripper for 3-D Assembly of Tissue Engineering Scaffolds

On the behavior of uniaxial static stress loaded micro-scale fused silica beams at room temperature

Ultrafast Laser to Tailor Material Properties: An Enabling Tool in Advanced Three-dimensional Micromanufacturing

Laser-induced densification of fused silica using spatially overlapping sub-30fs pulses

Non-ablative femtosecond laser exposure of fused silica in the sub-50 fs regime (Conference Presentation)

Laser-based in situ monitoring of femtosecond-laser in-bulk processing of glass

Ultrafast Laser Direct-Writing of Self-Organized Microstructures in Ge-Sb-S Chalcogenide Glass

All-glass miniature GHz repetition rate femtosecond laser cavity

Safe Puncture Tool for Retinal Vein Cannulation

High-speed low-loss waveguide writing in fused silica using UV femtosecond laser pulses

Femtosecond laser-induced crystallization processes in amorphous Al2O3/Nb2O5 multilayers studied with operando X-ray micro-diffraction

Ablation in Externally Applied Electric and Magnetic Fields

Laser annealing of shape memory alloys : A versatile tool for developing smart micro-devices

Ultrafast laser interaction with transparent multi-layer SiO2/Si3N4 films

Monolithic transparent 3D dielectrophoretic micro-actuator fabricated by femtosecond laser

Laser-Induced Transition between Nonlinear and Linear Resonant Behaviors of a Micromechanical Oscillator

Fourier-plane spatial frequency modulation imaging: enhanced resolution imaging with a single, ultrashort pulse

Tailoring glass properties and microstructure with sub-100 femtosecond pulses

Wide-field third-harmonic imaging of femtosecond laser-induced in-volume modifications

Quantification of Bulk Densification in Fused Silica Induced by Femtosecond Laser Exposure in the Sub-50 fs Regime