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  1. Article ; Online: Orbital angular momentum in the near-field of a fork grating.

    Dettlaff, Krispin M / Mavrona, Elena / Zolliker, Peter / Hack, Erwin

    Optics express

    2023  Volume 31, Issue 10, Page(s) 15757–15771

    Abstract: Light beams with Orbital Angular Momentum (OAM) are explored in applications from microscopy to quantum communication, while the Talbot effect revives in applications from atomic systems to x-ray phase contrast interferometry. We evidence the topological ...

    Abstract Light beams with Orbital Angular Momentum (OAM) are explored in applications from microscopy to quantum communication, while the Talbot effect revives in applications from atomic systems to x-ray phase contrast interferometry. We evidence the topological charge of an OAM carrying THz beam in the near-field of a binary amplitude fork-grating by means of the Talbot effect, which we show to persist over several fundamental Talbot lengths. We measure and analyze the evolution of the diffracted beam behind the fork grating in Fourier domain to recover the typical donut-shaped power distribution, and we compare experimental data to simulations. We isolate the inherent phase vortex using the Fourier phase retrieval method. To complement the analysis, we assess the OAM diffraction orders of a fork grating in the far-field using a cylindrical lens.
    Language English
    Publishing date 2023-05-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.486143
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Fabrication of freestanding photonic devices combining polymer films with microfabrication techniques and 3D printing.

    Hack, Erwin / Shorubalko, Ivan / Graf, Jil / Zolliker, Peter / Mavrona, Elena

    Optics express

    2023  Volume 31, Issue 18, Page(s) 29968–29974

    Abstract: We report a technological concept for freestanding photonic elements based on metamaterials fabricated on polymer films by clean-room processes and framed using 3D printing. A spin-coated cyclic olefin copolymer (TOPAS) of variable thickness down to one ... ...

    Abstract We report a technological concept for freestanding photonic elements based on metamaterials fabricated on polymer films by clean-room processes and framed using 3D printing. A spin-coated cyclic olefin copolymer (TOPAS) of variable thickness down to one micrometer was used as the substrate onto which metamaterials were fabricated using optical lithography. We demonstrate the possibility of applying a second TOPAS layer to protect the device or to allow for stacking another metamaterial layer. To obtain freestanding elements, frames were 3D printed directly on top of the metamaterial before lift-off from the carrier wafer. This ensured maintaining the flatness of the elements. Both the cleanroom process and the 3D printing enabled the design and manufacturing of elements in different sizes and shapes, e.g., to adapt to specific experimental set-ups and holder geometries or to be compatible with standard optical mounts. While TOPAS is transparent for wavelengths from UV to the far infrared, except for a few infrared absorption lines, we illustrate the concept with the simulation and manufacturing of THz band-pass filters. The performance of the fabricated filters was assessed using THz time-domain spectroscopy. The process is scalable to other wavelength ranges and has the potential for upscaling in manufacturing.
    Language English
    Publishing date 2023-09-14
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.497433
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Retrieving the Talbot length of arbitrary 2D gratings.

    Dettlaff, Krispin M / Mavrona, Elena / Zolliker, Peter / Hack, Erwin

    Optics letters

    2022  Volume 47, Issue 7, Page(s) 1814–1817

    Abstract: The Talbot effect has been revived in many fields of modern optics. As a key number of self-imaging, the fundamental Talbot length plays a crucial role in many applications. However, the inspection of the Talbot carpet for determining the Talbot length ... ...

    Abstract The Talbot effect has been revived in many fields of modern optics. As a key number of self-imaging, the fundamental Talbot length plays a crucial role in many applications. However, the inspection of the Talbot carpet for determining the Talbot length is applicable only if the 2D field distribution behind the grating is represented by a 1D cross section. In this Letter, we show an effective way to overcome this limitation to explore the self-imaging of gratings with complex 2D periodicities. For that purpose, the near-field diffraction is analyzed using the Pearson correlation coefficient of the intensity distribution in Fourier space. We report results on linear, ring, and spiral gratings.
    Language English
    Publishing date 2022-04-01
    Publishing country United States
    Document type Journal Article
    ISSN 1539-4794
    ISSN (online) 1539-4794
    DOI 10.1364/OL.455448
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Real-Time High Resolution THz Imaging with a Fiber-Coupled Photo Conductive Antenna and an Uncooled Microbolometer Camera.

    Zolliker, Peter / Shalaby, Mostafa / Söllinger, Elisa / Mavrona, Elena / Hack, Erwin

    Sensors (Basel, Switzerland)

    2021  Volume 21, Issue 11

    Abstract: We present a real-time THz imaging method using a commercial fiber-coupled photo conductive antenna as the THz source and an uncooled microbolometer camera for detection. This new combination of state-of-the-art components is very adaptable due to its ... ...

    Abstract We present a real-time THz imaging method using a commercial fiber-coupled photo conductive antenna as the THz source and an uncooled microbolometer camera for detection. This new combination of state-of-the-art components is very adaptable due to its compact and uncooled radiation source, whose fiber coupling allows for a flexible placement. Using a camera with high sensitivity renders real-time imaging possible. As a proof-of-concept, the beam shape of a THz Time Domain Spectrometer was measured. We demonstrate real time imaging at nine frames per second and show its potential for practical applications in transmission geometry covering both material science and security tasks. The results suggest that hidden items, complex structures and the moisture content of (biological) materials can be resolved. We discuss the limits of the current setup, possible improvements and potential (industrial) applications, and we outline the feasibility of imaging in reflection geometry or extending it to multi-spectral imaging using band pass filters.
    Language English
    Publishing date 2021-05-28
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s21113757
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Terahertz Birefringent Biomimetic Aerogels Based on Cellulose Nanofibers and Conductive Nanomaterials.

    Zeng, Zhihui / Mavrona, Elena / Sacré, Daniel / Kummer, Nico / Cao, Jingming / Müller, Luca A E / Hack, Erwin / Zolliker, Peter / Nyström, Gustav

    ACS nano

    2021  Volume 15, Issue 4, Page(s) 7451–7462

    Abstract: Biomimetic, lamellar, and highly porous transition-metal carbide (MXene) embedded cellulose nanofiber (CNF) aerogels are assembled by a facile bidirectional freeze-drying approach. The biopolymer aerogels have large-scale, parallel-oriented micrometer- ... ...

    Abstract Biomimetic, lamellar, and highly porous transition-metal carbide (MXene) embedded cellulose nanofiber (CNF) aerogels are assembled by a facile bidirectional freeze-drying approach. The biopolymer aerogels have large-scale, parallel-oriented micrometer-sized pores and show excellent mechanical strength and flexibility, tunable electrical properties, and low densities (2.7-20 mg/cm
    Language English
    Publishing date 2021-04-19
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1936-086X
    ISSN (online) 1936-086X
    DOI 10.1021/acsnano.1c00856
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Terahertz refractive index matching solution.

    Mavrona, Elena / Appugliese, Felice / Andberger, Johan / Keller, Janine / Franckié, Martin / Scalari, Giacomo / Faist, Jèrôme

    Optics express

    2019  Volume 27, Issue 10, Page(s) 14536–14544

    Abstract: We report on the fabrication and characterisation of a terahertz (THz) refractive index matching solution (TeraSol) based on barium titanate ( ... ...

    Abstract We report on the fabrication and characterisation of a terahertz (THz) refractive index matching solution (TeraSol) based on barium titanate (BaTiO
    Language English
    Publishing date 2019-06-03
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.27.014536
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Elastic constants, viscosity and response time in nematic liquid crystals doped with ferroelectric nanoparticles

    Podoliak, Nina / Blach, Jean-François / Buchnev, Oleksandr / Henninot, Jean-François / Herrington, Mark / Kaczmarek, Malgosia / Kanaras, Antonios G / Mavrona, Elena / Stratakis, Emmanuel / Warenghem, Marc

    RSC advances. 2014 Sept. 24, v. 4, no. 86

    2014  

    Abstract: We report on the role of ferroelectricity on the physical and electro-optic parameters in suspensions of nanoparticles in cyclohexane based, fluorinated nematic liquid crystals. The dielectric and elastic constants, response time, and viscosity of the ... ...

    Abstract We report on the role of ferroelectricity on the physical and electro-optic parameters in suspensions of nanoparticles in cyclohexane based, fluorinated nematic liquid crystals. The dielectric and elastic constants, response time, and viscosity of the suspensions were analyzed experimentally and compared with the undoped samples. Our study shows a decrease in the splay elastic constant and an increase in the dielectric constants, together with an increase in the average rotational viscosity.
    Keywords cyclohexanes ; liquid crystals ; nanoparticles ; viscosity
    Language English
    Dates of publication 2014-0924
    Size p. 46068-46074.
    Publishing place The Royal Society of Chemistry
    Document type Article
    ISSN 2046-2069
    DOI 10.1039/c4ra06248e
    Database NAL-Catalogue (AGRICOLA)

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