Fraunhofer Institute For Angewandte Optik Und Feinmechanik

Jena, Germany

Fraunhofer Institute For Angewandte Optik Und Feinmechanik

Jena, Germany

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Heusinger M.,Friedrich - Schiller University of Jena | Banasch M.,Vistec Electronic Beam GmbH | Zeitner U.D.,Friedrich - Schiller University of Jena | Zeitner U.D.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik
Optics Express | Year: 2017

In this paper we report different methods to improve the stray light performance of binary spectrometer gratings fabricated by electron beam lithography. In particular, we report the optimization concerns about spurious stray light peaks, also known as "Rowland ghosts". As already known these Rowland ghosts arise from a non-optimized stitching process of special subareas needed in order to fabricate large area gratings. One approach to reduce the impact of the stitching errors is the technique of "multi-pass-exposure" (MPE). Furthermore, the potential of a direct improvement of the stitching accuracy via special calibration parameters is examined. In both cases the effects on the stray light performance were determined by angle resolved scattering measurements. The achieved results show that specific calibration parameters of an e-beam writer have a strong influence on the strength of the Rowland ghosts and that their recalibration combined with an adapted writing regime reduces the peaks significantly. © 2017 Optical Society of America.


Paetzold U.W.,Jülich Research Center | Smeets M.,Jülich Research Center | Meier M.,Jülich Research Center | Bittkau K.,Jülich Research Center | And 6 more authors.
Applied Physics Letters | Year: 2014

We present a systematic experimental study on the impact of disorder in advanced nanophotonic light-trapping concepts of thin-film solar cells. Thin-film solar cells made of hydrogenated amorphous silicon were prepared on imprint-textured glass superstrates. For periodically textured superstrates of periods below 500nm, the nanophotonic light-trapping effect is already superior to state-of-the-art randomly textured front contacts. The nanophotonic light-trapping effect can be associated to light coupling to leaky waveguide modes causing resonances in the external quantum efficiency of only a few nanometer widths for wavelengths longer than 500nm. With increasing disorder of the nanotextured front contact, these resonances broaden and their relative altitude decreases. Moreover, overall the external quantum efficiency, i.e., the light-trapping effect, increases incrementally with increasing disorder. Thereby, our study is a systematic experimental proof that disorder is conceptually an advantage for nanophotonic light-trapping concepts employing grating couplers in thin-film solar cells. The result is relevant for the large field of research on nanophotonic light trapping in thin-film solar cells which currently investigates and prototypes a number of new concepts including disordered periodic and quasi periodic textures. © 2014 AIP Publishing LLC.


Paetzold U.W.,Forschungszentrum Juelich GmbH | Moulin E.,Forschungszentrum Juelich GmbH | Michaelis D.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | Bottler W.,Forschungszentrum Juelich GmbH | And 5 more authors.
Applied Physics Letters | Year: 2011

We report on the fabrication and optical simulation of a plasmonic light-trapping concept for microcrystalline silicon solar cells, consisting of silver nanostructures arranged in square lattice at the ZnO:Al/Ag back contact of the solar cell. Those solar cells deposited on this plasmonic reflection grating back contact showed an enhanced spectral response in the wavelengths range from 500 nm to 1000 nm, when comparing to flat solar cells. For a particular period, even an enhancement of the short circuit current density in comparison to the conventional random texture light-trapping concept is obtained. Full three-dimensional electromagnetic simulations are used to explain the working principle of the plasmonic light-trapping concept. © 2011 American Institute of Physics.


Kohler S.,University of Leipzig | Benz C.,University of Leipzig | Becker H.,Microfluidic ChipShop GmbH | Beckert E.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | And 2 more authors.
RSC Advances | Year: 2012

In this work we present an approach towards economic free-flow electrophoresis chips fabricated by injection molding as mass replication process. This is achieved by the development of a free-flow electrophoresis chip design suitable for one step molding fabrication. Integrated partitioning bars are incorporated as key elements for bubble segregation. A defined open gap of 20 μm in height and 500 μm in width was integrated between the separation chamber and the electrode channels, acting as a barrier for gas bubbles while maintaining electrical contact by the fluidic junction. Additionally, we present an approach to avoid internal electrodes in FFE microchips for a facile mass production process. The injection molded thermoplastic μFFE chips are ready to use without subsequent labor-intensive implementation of membranes or comparable structures serving as salt bridges. © 2012 The Royal Society of Chemistry.


Weber T.,Friedrich - Schiller University of Jena | Kasebier T.,Friedrich - Schiller University of Jena | Kley E.-B.,Friedrich - Schiller University of Jena | Tunnermann A.,Friedrich - Schiller University of Jena | Tunnermann A.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik
Optics Letters | Year: 2011

In this Letter, we present an iridium wire grid polarizer with a large spectral working range from IR down to the UV spectral region. The required grating period of 100 nm for an application below a wavelength of 300 nm was realized using a spatial frequency doubling technique based on ultrafast electron beam writing. The optical performance of the polarizer at a wavelength of 300 nm is a transmittance of almost 60% and an extinction ratio of about 30 (15 dB). Furthermore, the oxidation resistance is discussed. © 2011 Optical Society of America.


Schroder S.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | Herffurth T.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | Trost M.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | Duparre A.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik
Applied Optics | Year: 2010

Roughness-induced light scattering critically affects the performance of optical components, in particular at short wavelengths.We present a stand-alone instrument for angle-resolved scattering and reflectance measurements at 13:5nm in the extreme-ultraviolet (EUV) spectral range. The achieved dynamic range allows even the scattering of high-quality EUV mirrors on extremely smooth substrates to be investigated. For Mo/Si multilayers, total scatter losses of several percent have been observed, depending on the substrate qualities as well as on roughening and smoothing effects during coating. Different approximate models for estimating the impact of roughness on scatter losses are discussed and compared with experimental results. © 2010 Optical Society of America.


Kroker S.,Friedrich - Schiller University of Jena | Kasebier T.,Friedrich - Schiller University of Jena | Bruckner F.,Friedrich - Schiller University of Jena | Bruckner F.,University of Birmingham | And 4 more authors.
Optics Express | Year: 2011

We report on a novel concept for reflective diffractive cavity couplers based on resonant waveguide gratings instead of multilayer coatings. The diffracting or rather beam splitting properties are induced to the subwavelength structures by a periodic parameter modulation of the ridges. Since such a perturbation of the highly reflective system also enhances transmission stacks of two and three reflectors are considered to retrieve transmittivities as low as possible. Our calculations show that transmissions of less than 10 -4 are possible for different configurations based on silicon and silica. The results of first technological tests for the realization of stacked T-shape structures are presented. With a total effective layer thickness not exceeding 1.1 μm the discussed approaches are expected to remarkably reduce the urgent problem of coating thermal noise of conventional components for high-precision metrology. © 2011 Optical Society of America.


Hellwig T.,University of Munster | Schnack M.,University of Munster | Walbaum T.,University of Munster | Walbaum T.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | And 2 more authors.
Optics Express | Year: 2014

We present the experimental realization of transverse mode conversion in an optical fiber via an optically induced long-period grating. The transient gratings are generated by femtosecond laser pulses, exploiting the Kerr effect to translate intensity patterns emerging from multimode interference into a spatial refractive index modulation. Since these modulations exist only while the pump beam is present, they can be used for optical switching of transverse modes. As only a localized part of the grating was written at a time and the probe beam was co-propagating with the pump beam the required pulse energies could be reduced to 120 nJ which is about a factor of 600 lower than in previous quasi-continuous-wave experiments. Accompanying numerical simulations allow a better understanding of the involved effects and show excellent agreement to the experimental results. © 2014 Optical Society of America.


Ratzsch S.,Friedrich - Schiller University of Jena | Kley E.-B.,Friedrich - Schiller University of Jena | Tunnermann A.,Friedrich - Schiller University of Jena | Tunnermann A.,Fraunhofer Institute For Angewandte Optik Und Feinmechanik | Szeghalmi A.,Friedrich - Schiller University of Jena
Optics Express | Year: 2015

Encapsulation of grating structures facilitates an improvement of the optical functionality and/or adds mechanical stability to the fragile structure. Here, we introduce novel encapsulation process of nanoscale patterns based on atomic layer deposition and micro structuring. The overall size of the encapsulated structured surface area is only restricted by the size of the available microstructuring and coating devices; thus, overcoming inherent limitations of existing bonding processes concerning cleanliness, roughness, and curvature of the components. Finally, the process is demonstrated for a transmission grating. The encapsulated grating has 97.5% transmission efficiency in the -1st diffraction order for TM-polarized light, and is being limited by the experimental grating parameters as confirmed by rigorous coupled wave analysis. ©2015 Optical Society of America.


Steiner S.,Friedrich - Schiller University of Jena | Kroker S.,Friedrich - Schiller University of Jena | Kasebier T.,Friedrich - Schiller University of Jena | Kley E.-B.,Friedrich - Schiller University of Jena | And 2 more authors.
Optics Express | Year: 2012

We report on a novel concept for transmissive optical elements based on resonant waveguide gratings (RWGs), which enables the realization of direction selective filters. Hereby, the broadband reflectivity of an RWG for nearly normal incidence angles is combined with high diffractive efficiency in transmission for a specific angle of incidence. Silicon is used as material with high refractive index and good compatibility with semiconductor fabrication. By adjusting the grating parameters different transmission angles and angular widths of the transmission range are feasible. First experimental results of the introduced filters provide a high transmission up to 63% at an incidence angle of 45° with a full width at half maximum of 20°. © 2012 Optical Society of America.

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