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Toralf Scharf

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Publications associées (106)

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Design and Analysis of Binary Fan-out Gratings based on Step-Transition Perturbation Approach

Toralf Scharf, Dong Cheon Kim

Nowadays, diffractive optical elements are used for a variety of applications because of their high design flexibility, compact size, and mass productivity. At the same time, they require having high and complex optical functionalities such as a large numb ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Phase Anomalies in Micro-Optics

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim

We present a comprehensive review on the latest research activities that explore the Gouy phase and indicate the recent experimental progresses for its observations in studies that rely on a longitudinal-differential interferometer. The latter is a far-fie ...

Elsevier, Amsterdam2013

High-resolution interference microscopy with spectral resolution for the characterization of individual particles and self-assembled meta-atoms

Toralf Scharf, Michail Symeonidis

We apply a high-resolution interference microscope with spectral resolution to investigate the scattering response of isolated meta-atoms in real space. The final meta-atoms consist of core-shell clusters that are fabricated using a bottom-up approach. The ...

2019

Near-field phase profile and far-field contrast modulation for micro-lens arrays at the refraction limit

Toralf Scharf, Maryam Yousefi

We investigate the far-field pattern generation for a micro-lens array (MLA) illuminated under different conditions. Plane wave and Gaussian beam illumination are considered for an MLA with a small diameter of 27 microns and 30 microns period. At these dim ...

2020

Multilevel Micro-Structuring of Glassy Carbon Molds for Precision Glass Molding

Hans Peter Herzig, Toralf Scharf, Karin Prater

Replication techniques for diffractive optical elements (DOEs) in soft materials such as plastic injection molding are state of the art. For precision glass molding in glasses with high transition temperatures, molds with extreme thermal resistivity, low c ...

Spie-Int Soc Optical Engineering2015

Adjoint method and inverse design for diffractive beam splitters

Toralf Scharf, Dong Cheon Kim

Diffractive optical elements with a large diffraction angle require feature sizes down to sub-wavelength dimensions, which require a rigorous electromagnetic computational model for calculation. However, the computational optimization of these diffractive ...

SPIE-INT SOC OPTICAL ENGINEERING2020

On-chip near-infrared optical spectrometer based on single-mode Epo waveguide and gold nanoantennas

Toralf Scharf, Irène Antoinette Philipoussis, Joab Di Francesco

We report about optical spectrometry using gold nanostructures printed on top of an integrated optical waveguide. The optical waveguide is a single-mode buried waveguide made from a combination of photo-polymerizable materials and is fabricated by photolit ...

Spie-Soc Photo-Optical Instrumentation Engineers2014

Refraction limit of miniaturized optical systems: a ball-lens example

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

We study experimentally and theoretically the electromagnetic field in amplitude and phase behind ball-lenses across a wide range of diameters, ranging from a millimeter scale down to a micrometer. Based on the observation, we study the transition between ...

Optical Society of America2016

Microlenses on Bragg Reflectors to Create Iridescent Colors

Hans Peter Herzig, Toralf Scharf

In nature strong colors play an important role in scaring away predators or finding a mate. Often, the strongest and brightest colors arise from coherent scattering and reflection on periodic structures on a length scale of several micro- or nanometers. Un ...

2008

Design rules for customizable optical materials based on nanocomposites

Toralf Scharf

Nanocomposites with tailored optical properties can provide a new degree of freedom for optical design. However, despite their potential these materials remain unused in bulk optical applications. Here we investigate the conditions under which they can be ...

OPTICAL SOC AMER2018

Structured amplitude and phase fields behind microstructures: The quest for high contrast modulation at proximity

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim, Johana Bernasconi, Krishnaparvathy Puthankovilakam

Microstructures can be used to realize repetitive and singular high contrast features at different distances behind a structure. For practical applications, the amplitude field needs to be considered. To realize defined amplitude features at long distances ...

Spie-Int Soc Optical Engineering2016

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

Multilevel Micro-Structuring of Glassy Carbon for Precision Glass Molding of Diffractive Optical Elements

Hans Peter Herzig, Toralf Scharf, Karin Prater

A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the ...

Spie-Int Soc Optical Engineering2015

Unified rule based correction for corners in proximity lithography mask using high resolution features

Hans Peter Herzig, Toralf Scharf, Krishnaparvathy Puthankovilakam

Printing industry and printing techniques are increasing its market value by new methodologies. The resolution and accuracy of the pattern transfer is always a challenge for the industry, especially for the proximity printing industries which use mask alig ...

Elsevier2017

Understanding of photocurrent enhancement in real thin film solar cells: towards optimal onedimensional gratings

Christophe Ballif, Hans Peter Herzig, Toralf Scharf, Vincent Paeder, Ali Naqavi, Karin Söderström

Despite the progress in the engineering of structures to enhance photocurrent in thin film solar cells, there are few comprehensive studies which provide general and intuitive insight into the problem of light trapping. Also, lack of theoretical propositio ...

Optical Society of America2011

Structured light engineering using a photonic nanojet

Toralf Scharf, Maryam Yousefi

In this Letter, we present the photonic nanojet as a phenomenon in a structured light generator system that is implemented to modify the source focal spot size and emission angle. The optical system comprises a microlens array that is illuminated by a focu ...

OPTICAL SOC AMER2021

Printing sub-micron structures using Talbot mask-aligner lithography with a 193 nm CW laser light source

Toralf Scharf, Wilfried Noell, Raoul Kirner

A continuous improvement of resolution in mask-aligner lithography is sought after to meet the requirements of an ever decreasing minimum feature size in back-end processes. For periodic structures, utilizing the Talbot effect for lithography has emerged a ...

2018

Are Photonic Nanojets Achromatic?

Toralf Scharf, Myun Sik Kim, Michail Symeonidis

In this work we study the evolution of the photonic nanojet (PNJ) phenomenon as the ratio of the sphere's diameter over the illumination wavelength changes, for microspheres with diameters from 2 mu m to 100 mu m. We measure the focal point position by usi ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Light fields behind microstructures: study of the Babinet-principle in the Fresnel regime

Hans Peter Herzig, Toralf Scharf, Myun Sik Kim, Krishnaparvathy Puthankovilakam

The Babinet’s principle is a general theorem that holds for electromagnetic waves and is often applied to diffraction of light. Diffraction pattern of a body and that of the complement body are compared and the sum of both radiation patterns must be the sa ...

Spie-Int Soc Optical Engineering2017

Polymer based single mode optical waveguide for spectroscopy applications

Hans Peter Herzig, Irène Antoinette Philipoussis, Toralf Scharf

In this work, we present for the first time, two dimensional low loss single mode optical waveguides fabricated with EPO materials. The waveguide geometry has a rectangular shape and it is buried between two EPOCLAD layers. Its refractive index distributio ...

Spie-Int Soc Optical Engineering2013