Publications de Yves Bellouard

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Digital holographic microscopes using two orthogonal polarized reference waves provides real-time polariscopes. Birefringence induced by internal stress is imaged in optical fibers and in fused silica substrates, where lines are written with low-energy femtosecond pulses.

Femtosecond-laser-written patterns at the surface of brittle materials may show at random times spontaneous alternations from regular to disordered structures and vice versa. Here, we show that these random transitions carry relevant statistical informatio ...

Whispering gallery mode resonators can support high-quality resonances, which are commonly accessed through evanescent coupling using a tapered fibre that is aligned using external translation stages. To reduce complexity, we first introduce a compact system that consists of a tapered fibre passively aligned to the resonator. The resonator and the mechanical structure that holds it are both fabricated monolithically in a single substrate using fs-laser induced modifications and chemical etching, while the r

This work presents a compact (31.5×10.7×4mm3) video encoder system with a commercial imager, flash, a custom 2×2 microlens array, and an image signal processing (ISP) chip using novel 2×2 intra-frame compression. Leveraging the subframe redundancies inherent to the microlens array, the system achieves >59× compression with >32dB PSNR. With this, the ISP chip fabricated in 28nm CMOS attains 90.6 pJ/pixel energy efficiency at 1280×800, 65fps video stream.

We present multi-wavelength single-shot ptychography, a technique which is ideally suited for imaging dynamically evolving plasmas. Through improvements to single-shot ptychography and a novel probe constraint, wavelength-multiplexed single-shot ptychograp ...

We present the first experimental demonstration of wavelength-multiplexing in single-shot ptychography. Specifically, we experimentally reconstruct the complex transmission profile of a wavelength-independent and wavelength-dependent object simultaneously ...

Inscribing in the bulk of transparent materials with UV femtosecond lasers has recently shown its advantages compared to standard IR laser machining. Amongst the other things, faster waveguide writing and higher etching rate were achieved. Here, we further explore the potential of UV lasers on modifying fused silica. In particular, we show the capability of inscribing self-organized nanoscale periodic patterns that we characterize and classify. We suggest a link between these features and the etching rate a

Optical components like resonator or waveguides often have stringent requirements in term of positioning accuracy during packaging. While this can be done routinely in a laboratory environment, permanently positioning and aligning optical elements with nan ...

Chalcogenide glass has the broadest reported transparency in the infrared, making them particularly attractive for spectroscopy and infrared imagery. Yet, it remains a difficult material to shape in arbitrary form. In this paper, we explore the combination of femtosecond laser-exposure and subsequent chemical etching steps to produce arbitrary 3D shapes out of a chalcogenide glass substrate coated with a SiO 2 thin film. In this context, we discuss how laser parameters locally influence the etching rate.

Femtosecond laser irradiation applied to Fused Silica (the amorphous form of SiO2) defines a novel technology platform for highly integrated all-optical microsystems and beyond. In contrast with common approaches that rely on combining materials to achieve ...

An optical-delay-line assembly (1) comprises a substrate (2), an optical assembly (3), and a movement device (4). the optical assembly (3) is arranged on the substrate (2) and is configured to guide an optical signal (s1) generated from a source of electromagnetic waves (5), preferably from an optical input (6) of the substrate (2) to an optical output (7) of the substrate (2), along an optical path (p1). the movement device (4), when being exposed to energy, is configured to deform at least in the region o

Laser-inscribing arbitrary patterns with a sub-wavelength resolution in the bulk of transparent materials is of great importance for enabling reliable and versatile nano-manufacturing. Here, we propose a seeding-writing near-field enhancement based method ...

Femtosecond laser exposure of fused silica in the nonablative regime can lead to various localized bulk modifications of the material structure. In this paper, we show that these laser-induced modifications can be used to tune silica thermal expansion prop ...

Spatial frequency modulated imaging (SPIFI) employs a structured line-shaped illumination, able to resolve beyond conventional resolution limits for coherent light with high speed. It produces image harmonics, with each order carrying a higher resolution. To date this method used rotating reticles to produce the necessary structured illumination, limiting image acquisition to about 100 μs. Here, we introduce a single-shot approach. We show that a super-resolved 1D image can be acquired with a single femtose

Efficient and robust free-space light coupling in integrated systems is a challenging task for photonic devices. Here we propose a femtosecond laser process combined with CW laser thermal reflow for manufacturing a fiber-to-fiber free-space light-coupling device in fused silica. The monolithic free-space coupler design consists of two fiber holders and two ball lenses, used to achieve both, fiber-output collimation and fiber-injection. The device proved to efficiently work at 633 nm for single mode fiber co

When exposed to ultrafast lasers, materials can be transformed in their volume, leading to intriguing nano-crystallization and sub-wavelength pattern formations. We will discuss occurrences in various glass substrates and applications in light harvesting and nano-mechanics. Full-text article not available; see video presentation

A tightly focused femtosecond laser-beam in the non-ablative regime can induce a shockwave sufficiently intense to reach local pressures in the giga-Pascal range or more. In a single beam configuration, the location of the highest-pressure zone is nested w ...

The method comprises at least the following steps: - exposing a substrate to focused laser irradiation at a preselected series of locations that trace a subset of the substrate volume that is connected to the surface of the substrate; some subsets of subst ...

The use of femtosecond lasers to introduce controlled stress states has recently been demonstrated in silica glass. We use this technique, in combination with chemical etching, to generate and control stress-induced birefringence over a well-defined region ...

In a substrate (1) for holding a multitude of components (6.1, 6.2, 6.3, 6.4, 6.5, 6.6) of an optical laser cavity, wherein the substrate (1) comprises a multitude of slots (2.1, 2.2, 2.3, 2.4, 2.5, 2.6), wherein each slot (2.1, 2.2, 2.3, 2.4, 2.5, 2.6) is ...

Yves Bellouard

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Real-Time Birefringence Measurement with Digital Holographic Microscopy

Unraveling Brittle-Fracture Statistics from Intermittent Patterns Formed During Femtosecond Laser Exposure

Towards all-glass monolithic realization of arbitrary whispering gallery mode resonators

A 90.6 pJ/pixel 1280×800 65 fps cm-Scale Fully Integrated Video Encoder System Utilizing a 2×2 Microlens Array

Wavelength-Multiplexed Single-Shot Ptychography

Wavelength-multiplexed single-shot ptychography

UV femtosecond laser induced self-organisation of micro-structures in the bulk of fused silica

Non-contact sub-nanometer optical repositioning using femtosecond lasers

Three-dimensional Microstructuring of Chalcogenide Glass by Femtosecond Laser Exposure and Subsequent Chemical Etching

Femtosecond laser-based production of 3D micro- and nano-devices in transparent substrate: a step toward system-materials

Optical-delay-line assembly

Sub-wavelength femtosecond laser based nanostructuring of complex patterns in the bulk of fused silica

Local tuning of fused silica thermal expansion coefficient using femtosecond laser

Spatial frequency modulated imaging with a single femtosecond pulse

Free-space monolithic reflow-based fused silica fiber-to-fiber couplers

Ultrafast Laser Volume Nanostructuring of Transparent Materials: From Nanophotonics to Nanomechanics

Femtosecond laser-shockwave induced densification in fused silica

Small-scale metal castings, small-scale metal/transparent composite structures and process to produce same

Femtosecond laser direct-write waveplates based on stress-induced birefringence

Substrate comprising slots for holding optical components of a laser cavity