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Toralf Scharf

Cette personne a quitté l’EPFL

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Publications associées (106)

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Scaling effect and its impact on wavelength-scale microlenses

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim

We revisit the scaling laws in micro-optical systems to highlight new phenomena arising beyond a conventional optical regime, especially when the size of the system approaches to the operational wavelength. Our goal is to visualize the impact of the scalin ...

Spie-Int Soc Optical Engineering2017

Correction of spherical surface measurements by confocal microscopy

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Refractive microlenses are nowadays widely used in optical systems. Characterizing their surface is essential to ensure their quality and to optimize their fabrication process. This is realized by optical surface profilers thanks to their vertical resoluti ...

IOP Publishing2020

Polarization sensitive diffuser

Hans Peter Herzig, Toralf Scharf

With help of liquid crystal polymers (LCP) a polarization sensitive diffuser has been realized. By using convex microstructures made of LCP and an index matching layer, two distinct functions depending on the orientation of the device and the polarization ...

2008

A metamaterial based on coupled metallic nanoparticles and its band-gap property

Toralf Scharf

2008

Unconventional Optical Responses of Wavelength-scale Microlenses: beyond Refraction Limit

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim

Miniaturized optical systems show often unconventional responses compare to larger systems of the same design. We investigate such new phenomena using microlenses, and demonstrate characteristics beyond the refraction limit of the micro-optical systems. ...

Ieee2016

Fabrication and Characterization of 1-D diffusing elements

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim, Roland Andreas Bitterli

Certain high power laser applications require thin homogeneous laser lines. In this paper we describe the concept, fabrication and characterization of a 1-D diffuser that generates such a line. The device is based on an array of concave cylinder lenses wit ...

2009

Inverse design and demonstration of high-performance wide-angle diffractive optical elements

Toralf Scharf, Dong Cheon Kim

Diffractive optical elements are ultra-thin optical components required for constructing very compact optical 3D sensors. However, the required wide-angle diffractive 2D fan-out gratings have been elusive due to design challenges. Here, we introduce a new ...

2020

Improvements on the uniformity of large-area microlens arrays in Fused Silica

Toralf Scharf, Wilfried Noell, Raoul Kirner, Jeremy Béguelin

The uniformity of large microlens arrays in Fused Silica is governed by the production process. It comprises photolithographic patterning of a spin-coated layer of photoresist on a 200mm wafer with a molten resist reflow process and subsequent dry etching. ...

OPTICAL SOC AMER2019

Gas Detection with a Micro FTIR Spectrometer in the MIR Region

Nico de Rooij, Danick Briand, Hans Peter Herzig, Toralf Scharf

We report on the application of a silicon micromachined lamellar grating interferometer in a Fourier Transform Infrared (FTIR) spectrometer for the detection of gases in the mid-infrared (MIR) region. The FTIR spectrometer was equipped with MIR optical fib ...

Elsevier2009

Optical properties of waveguide-coupled nanowires for sub-wavelength detection in microspectrometer applications

Toralf Scharf, Alessandro Crespi

In this paper we experimentally investigate optical interactions between gold nanowires and fs-laser written waveguides in a view of applications for stationary-wave integrated Fourier-transform spectrometers in a movable mirror configuration. For this pur ...

European Optical Society2015

Dot pattern generation using thick sinusoidal phase grating under Gaussian beam illumination

Toralf Scharf, Maryam Yousefi

Far-field dot pattern generation is analyzed for a Gaussian beam source that illuminates a sinusoidal phase grating which is placed at a certain distance behind the beam waist. We obtain a bigger field of view with more numbers of points using a Gaussian b ...

SPIE-INT SOC OPTICAL ENGINEERING2019

High-power modular LED-based illumination systems for mask-aligner lithography

Hans Peter Herzig, Toralf Scharf, Johana Bernasconi

Mask-aligner lithography is traditionally performed using mercury arc lamps with wavelengths ranging from 250 nm to 600 nm with intensity peaks at the i, g and h lines. Since mercury arc lamps present several disadvantages, it is of interest to replace the ...

2018

Inverse design of diffractive optical elements using step-transition perturbation approach

Toralf Scharf, Dong Cheon Kim

Diffractive optical elements are ultra-thin optical components required for a variety of applications because of their high design flexibility. We introduce a gradient-based optimization method based on a step-transition perturbation approach which is an e ...

WALTER DE GRUYTER GMBH2021

Improved calibration of vertical scanning optical profilometers for spherical profiles measurements

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

A new method for calibrating optical scanning profilometers is presented. Especially adapted to spherical and aspherical profile measurements, it shows an increase of accuracy bigger than one order of magnitude for radius of curvature measurements. Calibra ...

2018

Engineering photonic nanojets

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim

Photonic Nanojets are highly localized wave fields emerging directly behind dielectric microspheres; if suitably illuminated. In this contribution we reveal how different illumination conditions can be used to engineer the photonic Nanojets by measuring th ...

Optical Society of America2011

Experimental demonstration of ray-rotation sheets

Toralf Scharf

We have built microstructured sheets that rotate, on transmission, the direction of light rays by an arbitrary, but fixed, angle around the sheet normal. These ray-rotation sheets comprise two pairs of confocal lenticular arrays. In addition to rotating th ...

2018

Nanostructured surface fabricated by laser interference lithography to attenuate the reflectivity of microlens arrays

Hans Peter Herzig, Toralf Scharf, Pierre-Yves Baroni

A subwavelength-scale square lattice optical nanostructure is fabricated using an interference photolithography process on the surface of a quartz microlens array. This nanostructuring of the quartz surface introduces an antireflective effect, reducing ref ...

2010

Correction of surface error occurring in microlenses characterization performed by optical profilers

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Characterizing the surface of microlenses by optical profilers has the important advantages of measurement speed, flexibility and automation. Nevertheless, the accuracy of such characterization is limited by error occurring in non-flat measurements. Here, ...

SPIE-INT SOC OPTICAL ENGINEERING2019

High-resolution interference microscopy of binary phase diffractive optical elements

Toralf Scharf, Dong Cheon Kim, Michail Symeonidis

In this work, we apply the high-resolution interference microscopy technique to investigate the intensity and phase of light transmitted through a binary phase element. Using a combination of simulation and experimental results, we identify specific featur ...

2019

An RCWA Analysis of Solar Cell Back Reflectors: Comparison between Modelling and Experiment

Christophe Ballif, Hans Peter Herzig, Toralf Scharf, Franz-Josef Haug, Vincent Paeder, Ali Naqavi, Karin Söderström

We present a comparison between spectrally-resolved reflection measurements of gratings and theoretical predictions from RCWA approach. Diffraction intensities vary significantly with polarization, and surface plasmon absorption is observed around the onse ...

2010