Publications associées à Mechanical Slit Mask Mechanism for the James Webb Space Telescope Spectrometer

Narrowband Optical Coupler Using Fano Interference in First Order Diffraction

Olivier Martin, Benjamin Gallinet, Fabian Michael Lütolf, Giorgio Quaranta

Light coupling in waveguides has been extensively investigated in a variety of contexts, from photonic integrated circuits to biosensing and near-eye displays for augmented reality. Here, narrowband diffraction is reported using a Fano interference effect ...

AMER CHEMICAL SOC2021

Diffraction artefacts from twins and stacking faults, and the mirage of hexagonal, polytypes or other superstructures

Cyril Cayron

Recently, a hexagonal phase has been reported in high carbon steels in several studies. Here, we show that the electron microscopy results used in these studies were erroneously interpreted. The extra-spots in the diffraction patterns and the odd contrasts ...

2020

Imaging plasma formation in isolated nanoparticles with ultrafast resonant scattering

Daniela Rupp, Christoph Bostedt, Alessandro Colombo

We have recorded the diffraction patterns from individual xenon clusters irradiated with intense extreme ultraviolet pulses to investigate the influence of light-induced electronic changes on the scattering response. The clusters were irradiated with short ...

2020

Light pattern generation with hybrid refractive microoptics under Gaussian beam illumination

Toralf Scharf, Maryam Yousefi

The generation of wide-angle diffraction patterns can be done in different ways using either thin diffractive optical elements with small features sizes or arrays of microoptics with large optical paths that are thick diffractive optical elements. Our aim ...

2020

Dynamic behaviour of a Francis turbine during voltage regulation in the electrical power system

François Avellan, Elena Vagnoni

Hydroelectric units can be operated in synchronous condenser mode to provide reactive power to the electrical power system (EPS) for voltage regulation. In this operating mode, the hydraulic turbine consumes active power and in case of hydroelectric units ...

2020

Resonant Waveguide Gratings for Color-Selective Diffraction

Giorgio Quaranta

Resonant waveguide gratings (RWGs), also known as guided mode resonant (GMR) gratings or waveguide-mode resonant gratings, are dielectric structures where these resonant diffractive elements benefit from lateral leaky guided modes and can operate from UV t ...

EPFL2019

Spatial coherence properties of an LED-based illumination system for mask-aligner lithography

Hans Peter Herzig, Wilfried Noell, Toralf Scharf, Johana Bernasconi, Raoul Kirner

A high-power LED-based illumination system has been developed as a replacement for the mercury arc lamps used in mask-aligner lithography. LEDs are arranged in a grid array and placed in the entrance aperture of individual reflectors. Those reflectors decr ...

SPIE2019

Prediction of hydro-acoustic resonances in hydropower plants by a new approach based on the concept of swirl number

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior, Arthur Tristan Favrel, Loïc Andolfatto

Hydropower plant units operating in off-design conditions are subject to cavitation flow instabilities, potentially inducing hydro-acoustic resonances under certain conditions. They can be predicted by using one-dimensional numerical models of hydropower p ...

Taylor & Francis Ltd2019

Mask-aligner Talbot lithography using a 193 nm CW light source

Wilfried Noell, Toralf Scharf, Raoul Kirner, Andreas Vetter

We present and discuss Talbot mask-aligner lithography, relying on a continuous wave laser emitting at 193nm for the illumination. In this source, a diode laser at 772nm is amplified by a tapered amplifier in master-oscillator power-amplifier configuration ...

2018

Use of compact Laser Doppler Velocimetry in reduced scale model testing of hydraulic machines

François Avellan, Andres Müller, Vincent Berruex, Loïc Andolfatto, Masashi Sakamoto

Laser based flow survey methods such as Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV) have long been used for studying the flow in hydraulic machines. Even if the results have crucially improved our understanding of potentially destab ...

2018

New insight in Francis turbine cavitation vortex rope: role of the runner outlet flow swirl number

François Avellan, Christophe Nicolet, Andres Müller, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

At part load operation, Francis turbines experience the development of a cavitation vortex rope in the draft tube, whose precession acts as a pressure excitation source. In case of resonance, the resulting pressure pulsations lead to unacceptable torque an ...

Taylor & Francis Ltd2018

High power ultraviolet LED illumination systems: coherence properties and applications in photolithography

Johana Bernasconi

Mask-aligner photolithography is a technology used to replicate patterns from a mask to a photosensitive substrate. It is widely used in the fabrication of MEMS and micro-optical components, and for other applications with dimensions in the micrometer rang ...

EPFL2018

Measurements of Cavitation Compliance in the Draft Tube Cone of a Reduced Scale Francis Turbine Operating at Part Load

François Avellan, Christophe Nicolet, Christian Landry, Joao Gomes Pereira Junior, Arthur Tristan Favrel

Francis turbines operating at part load conditions typically experience a cavitation vortex rope immediately at the runner outlet. As the compliance of this cavitation flow is much higher than the one in cavitation-free conditions, a decrease in the value ...

2018

Limitations of Proximity Lithography Printing : Simulations, Experiments, and Applications

Krishnaparvathy Puthankovilakam

Photolithography is one of the earliest technologies used to transfer patterns to a substrate. It is also known as optical lithography since it uses light to transfer the pattern. The main exposure techniques exist in the industry are projection printing, ...

EPFL2017

Absorption Enhancement in Solar Cells With Periodic Interface Textures of Asymmetric Shape

Christophe Ballif, Karin Söderström, Franz-Josef Haug

We investigate light scattering interface textures for solar cells with the intention to obtain a more fundamental understanding of the absorption enhancement. Therefore, we study simplified structures with the periodic interface texture of sinusoidal and ...

Ieee-Inst Electrical Electronics Engineers Inc2015

Energy-selective neutron imaging for materials science

Steven Luc X Peetermans

Common neutron imaging techniques study the attenuation of a neutron beam penetrating a sample of interest. The recorded radiograph shows a contrast depending on traversed material and its thickness. Tomography allows separating both and obtaining 3D spati ...

EPFL2015

Scaling unreinforced masonry for reduced-scale seismic testing

Katrin Beyer, Sarah Petry

When testing multi-storey structures, most testing facilities require the testing of a reduced-scale model. A literature review on tests of scaled masonry structural components revealed that scaling of masonry was rather challenging and often significant d ...

Springer Verlag2014

Large-scale sub-100 nm compound plasmonic grating arrays to control the interaction between localized and propagating plasmons

Olivier Martin, Arash Farhang, Thomas Gerd Siegfried

Compound plasmonic resonances arise due to the interaction between discrete and continuous metallic nanostructures. Such combined nanostructures provide a versatility and tunability beyond that of most other metallic nanostructures. In order to observe suc ...

Spie-Soc Photo-Optical Instrumentation Engineers2014

Portable advanced off-axis camera for quantitative phase microscopy

Christian Depeursinge

We propose and experimentally demonstrate a device in which common-path interferometry combined with off-axis holographic geometry is used to realize a digital holographic camera which can be attached to the camera port of a conventional transmission micro ...

Spie-Int Soc Optical Engineering2014

Designing Augmented Reality for the Classroom

Sébastien Cuendet, Pierre Dillenbourg, Quentin Bonnard

Augmented reality (AR) has recently received a lot of attention in education. Multiple AR systems for learning have been developed and tested through empirical studies often conducted in lab settings. While lab studies can be insightful, they leave out the ...

Elsevier2013