References of "Habraken, Serge"
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See detailDESIGN AND MODELIZATION OF ACONVEX GRATING FOR AN HYPERSPECTRAL IMAGER OF THE CHANDRAYAAN 2 INSTRUMENT FOR THE MOON PROBE IN THE INFRARED
Sabushimike, Bernard ULg; Horugavye, Georges ULg; Piron, Pierre ULg et al

in International Journal of Latest Research in Science and Technology (2016), 5(2), 69-74

For hyperspectral imaging, diffraction gratings based spectrometers exhibit high spectral resolution and optical performance. Among those spectrometers, the Offner type (which consists of an entrance slit ... [more ▼]

For hyperspectral imaging, diffraction gratings based spectrometers exhibit high spectral resolution and optical performance. Among those spectrometers, the Offner type (which consists of an entrance slit, two concave mirrors and convex grating) offers a lot of advantages. In this paper, we propose the design and modelization of a convex grating which covers a spectral band ranging from 0.7 μm to 5 μm with a minimum diffraction efficiency of 20% at 800 nm, 50% at 3000 nm and 25% at 5000 nm. For a so wide band, a grating with a single blaze cannot satisfy these requirements. We will therefore propose an approach of multi-blaze grating which is subdivided into different sections each with its own blaze angle. Meanwhile, we perform the diffraction efficiency prediction using the scalar and rigorous theories to prove the compliance of this design with the technical specifications. The rigorous theory will also allow us to study the polarization sensitivity of this grating and the calculation of the diffraction efficiency of a grating with a profile degraded by manufacturing errors to assess the impact on the diffraction efficiency and the sensitivity to polarization [less ▲]

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See detailPerformance evaluation of mid-IR vortex coronagraphs with centrally obscured segmented pupils
Carlomagno, Brunella ULg; Absil, Olivier ULg; Ruane, Garreth J. et al

Poster (2015, October)

In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L ... [more ▼]

In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L band). The AGPM (Annular Groove Phase Mask) is a vortex phase mask with impressive characteristics: small inner working angle, high throughput, achromaticity. A non-perfectly circular pupil and non-flat input wavefront result in a starlight leakage, degrading the performance of the vortex coronagraph. In this work, we present end-to-end performance simulations using Fourier optical propagation to determine the quality of the starlight rejection obtained with an infrared vortex coronagraph. We first analyse the performance facing E-ELT pupil variations (segmentations, central obscuration, spiders, missing segments), then pointing jitter and random adaptive optics residual phase screens are introduced to derive more realistic performance. Finally, more advanced concepts of the infrared vortex coronagraph are presented, in order to compensate for performance degradation. [less ▲]

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See detailA Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency
Piron, Pierre ULg; Delacroix, Christian; Huby, Elsa ULg et al

in Shaklan, Stuart (Ed.) Techniques and Instrumentation for Detection of Exoplanets VII (2015, September 11)

The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a ... [more ▼]

The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a telescope element provides a continuous helical phase ramp for an on axis sources, which creates the orbital angular momentum. Thanks to that phase, the intensity of the central source is canceled by a down-stream pupil stop, while the off axis sources are not affected. However due to experimental conditions the nulling is hardly perfect. To improve the null, a Mach-Zehnder interferometer containing Dove prisms differently oriented can be proposed to sort out light based on its orbital angular momentum (OAM). Thanks to the differential rotation of the beam, a π phase shift is achieved for the on axis light affected by a non zero OAM. Therefore the contrast between the star and its faint companion is enhanced. Nevertheless, due the Dove prisms birefringence, the performance of the interferometer is relatively poor. To solve this problem, we propose to add a birefringent wave-plate in each arm to compensate this birefringence. In this paper, we will develop the mathematical model of the wave front using the Jones formalism. The performance of the interferometer is at first computed for the simple version without the birefringent plate. Then the effect of the birefringent plate is be mathematically described and the performance is re-computed. [less ▲]

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See detailOptical study of diffraction grating/Fresnel lens combinations applied to a spectral-splitting solar concentrator for space applications
Michel, Céline ULg; Loicq, Jerôme ULg; Thibert, Tanguy ULg et al

in Applied Optics (2015), 54(22), 6666-6673

This paper presents a new design of a planar solar concentrator with spectral splitting of light for space applications. This concentrator spectrally splits the incident light into mainly two parts. Each ... [more ▼]

This paper presents a new design of a planar solar concentrator with spectral splitting of light for space applications. This concentrator spectrally splits the incident light into mainly two parts. Each part is then focused onto specific spatially separated photovoltaic cells, allowing for independent control of respective cells output power. These advantages of both spectral splitting and light focusing are here combined thanks to a specific diffraction grating superimposed on a Fresnel lens. The theoretical principle of the optical design is presented, with optimization of each element and improvement steps, including optimization of grating period evolution along the lens, and testing of two kinds of gratings (a blazed and a lamellar one). First numerical results are presented, highlighting the possibility to design a concentrator at about 10× or more for each cell, with an output power larger than that of a classical concentrator focusing on a GaAs SJ cell, and less than 10% of losses for tracking errors up to ±0.8°. Some experimental results are also presented. [less ▲]

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See detailPolarization holography for vortex retarders recording: laboratory demonstration
Piron, Pierre ULg; Blain, Pascal ULg; Décultot, Marc ULg et al

in Applied Optics (2015), 54(15), 4765--4770

This paper will present a prototype of the first set of vortex retarders made of liquid crystal polymers recorded by polarization holography. Vortex retarders are birefringent plates characterized by a ... [more ▼]

This paper will present a prototype of the first set of vortex retarders made of liquid crystal polymers recorded by polarization holography. Vortex retarders are birefringent plates characterized by a rotation of their fast axis. Liquid crystals possess birefringent properties and they are locally orientable. Their orientation is defined by the perpendicular to the local orientation of the recording field. Polarization holography is a purely optical recording method. It is based on the superimposition of coherent and differently polarized beams. It is used to shape the electric field pattern to enable the recording of vortex retarders. The paper details the mathematical model of the superimposition process. The recording setup is exposed; it is characterized by a nearly common path interferometer. Two sets of measurements allowing the prediction of the retarder’s features are presented and compared. Finally, the experimentally recorded retarder is shown, its characteristics are investigated and compared to the predicted ones. [less ▲]

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See detailOptical Study of a Spectrum Splitting Solar Concentrator based on a Combination of a Diffraction Grating and a Fresnel Lens
Michel, Céline ULg; Loicq, Jerôme ULg; Thibert, Tanguy ULg et al

Poster (2015, April 14)

This poster presents recent improvements of our new solar concentrator design for space application. The concentrator is based on a combination of a diffraction grating (blazed or lamellar) coupled with a ... [more ▼]

This poster presents recent improvements of our new solar concentrator design for space application. The concentrator is based on a combination of a diffraction grating (blazed or lamellar) coupled with a Fresnel lens. Thanks to this diffractive/refractive combination, this optical element splits spatially and spectrally the light and focus approximately respectively visible light and IR light onto electrically independent specific cells. It avoid the use of MJs cells and then also their limitations like current matching and lattice matching conditions, leading theoretically to a more tolerant system. The concept is reminded, with recent optimizations, ideal and more realistic results, and the description of an experimental realization highlighting the feasibility of the concept, and the closeness of theoretical and experimental results. [less ▲]

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See detailCalibration and testing of wide-field UV instruments
Frey, Harald; Mende, Stephen; Loicq, Jerôme ULg et al

Conference (2015, April)

As with all optical systems the calibration of wide-field ultraviolet systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes these calibrations ... [more ▼]

As with all optical systems the calibration of wide-field ultraviolet systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes these calibrations difficult is the need for working in vacuum substantially extending the required time and effort compared to visible systems. In theory a ray tracing and characterization of each individual component of the optical system (mirrors, windows, grating) should provide the transmission efficiency of the combined system but potential unknown effects (contamination, misalignment, measurement errors) will make the final error too large for most applications. Therefore it is desirable to test and measure the optical properties of the whole system in vacuum and compare the overall response to the response of a calibrated photon detector. Based on the experience with the IMAGE Spectrographic Imager (SI) and Wide-band Imaging Camera (WIC), and the ICON-FUV instrument we will discuss the steps and procedures for the proper radiometric sensitivity and pass-band calibration, spot size, imaging distortions, flat field and field of view determination. [less ▲]

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See detailExperimental astrochemistry: from ground-based to space-borne laboratories (Foreword)
De Becker, Michaël ULg; Cottin, Hervé; Fleury-Frenette, Karl ULg et al

in Bulletin de la Société Royale des Sciences de Liège (2015, January), 84(4-6),

The investigation of the origin and evolution of molecules in space environments, either in interstellar or interplanetary conditions, constitutes a topic of high importance in modern space sciences. The ... [more ▼]

The investigation of the origin and evolution of molecules in space environments, either in interstellar or interplanetary conditions, constitutes a topic of high importance in modern space sciences. The presence of diversified and complex molecules motivates astrochemists to explore their formation mechanisms along with the physical conditions ruling these physico-chemical processes. Beside theoretical approaches aiming at simulating these processes, experimental techniques are nowadays frequently applied. Both laboratory and space experiment projects allow to reproduce to some extent the adequate conditions to understand some of these processes. The most recent results based on these techniques, and the prospects for future investigations, including the use of space platforms, were the scientific motivation of this workshop. These proceedings summarize a part of the content of this workshop, including abundant references to the relevant bibliography. [less ▲]

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See detailElucidating the opto-electrical properties of solid and hollow titania scattering layers for improvement of dye-sensitized solar cells
Thalluri, Venkata Visveswara Gopala Kris; Henrist, Catherine ULg; Spronck, Gilles ULg et al

in Thin Solid Films (2015)

The light scattering method has been adapted in dye-sensitized solar cells (DSCs) for optical absorption enhancement. In DSC's, particle-size of TiO2 should be inline with the scattering wavelength range ... [more ▼]

The light scattering method has been adapted in dye-sensitized solar cells (DSCs) for optical absorption enhancement. In DSC's, particle-size of TiO2 should be inline with the scattering wavelength range. Scattering particles can be used either by forming a bilayer structure with TiO2 nanocrystalline film or into the bulk of TiO2 nanocrystalline film. For improving the DSCs performances these scattering layers aim to refract/reflect the incident light by extending the traveling distance of UV-Visible/near-IR light within the dye-sensitized TiO2 nanocrystalline film. In this work, the scattering layers with two different particle-sizes (~200 nm-solid and ~400 nm-hollow) were deposited as an additional layer on the top of dye-sensitized TiO2 nanocrystalline film and the morphological properties were studied. By using various opto-electrical characterization techniques, the influence of these scattering layers for two different classes of DSCs prepared from N3 (UV-Vis) and SQ2 (near-IR) dyes were investigated. [less ▲]

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See detailOptical Study of a Spectrum Splitting Solar Concentrator based on a Combination of a Diffraction Grating and a Fresnel Lens
Michel, Céline ULg; Loicq, Jerôme ULg; Thibert, Tanguy ULg et al

in AIP Conference Proceedings (2015), 1679

This paper presents recent improvements of our new solar concentrator design for space application. The concentrator is based on a combination of a diffraction grating (blazed or lamellar) coupled with a ... [more ▼]

This paper presents recent improvements of our new solar concentrator design for space application. The concentrator is based on a combination of a diffraction grating (blazed or lamellar) coupled with a Fresnel lens. Thanks to this diffractive/refractive combination, this optical element splits spatially and spectrally the light and focus approximately respectively visible light and IR light onto electrically independent specific cells. It avoid the use of MJs cells and then also their limitations like current matching and lattice matching conditions, leading theoretically to a more tolerant system. The concept is reminded, with recent optimizations, ideal and more realistic results, and the description of an experimental realization highlighting the feasibility of the concept and the closeness of theoretical and experimental results. [less ▲]

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See detailRealizing the diamond annular groove phase masks for the mid infrared region: five years of successful process development of diamond plasma etching
Forsberg, Pontus; Vargas Catalan, Ernesto; Delacroix, Christian ULg et al

in Navarro, Ramon; Cunningham, Colin; Barto, Allison (Eds.) Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation (2014, August 07)

The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in ... [more ▼]

The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in diamond. To improve the AGPM performance, antireflective sub-wavelength gratings are etched on the backside of the components, and such gratings are also discussed. Components for the N-band (around 10 μm) and the L-band (around 3.8 μm) have been successfully fabricated. We are currently developing the process further to improve the precision of the gratings and produce an AGPM for the K-band (around 2.2 μm). © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. [less ▲]

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See detailL'-band AGPM vector vortex coronagraph's first light on LBTI/LMIRCam
Defrère, D.; Absil, Olivier ULg; Hinz, P. et al

in Proceedings of SPIE - The International Society for Optical Engineering (2014, July 21)

We present the first observations obtained with the L'-band AGPM vortex coronagraph recently installed on LBTI/LMIRCam. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from ... [more ▼]

We present the first observations obtained with the L'-band AGPM vortex coronagraph recently installed on LBTI/LMIRCam. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from diamond subwavelength gratings. It is designed to improve the sensitivity and dynamic range of high-resolution imaging at very small inner working angles, down to 0.09 arcseconds in the case of LBTI/LMIRCam in the L' band. During the first hours on sky, we observed the young A5V star HR8799 with the goal to demonstrate the AGPM performance and assess its relevance for the ongoing LBTI planet survey (LEECH). Preliminary analyses of the data reveal the four known planets clearly at high SNR and provide unprecedented sensitivity limits in the inner planetary system (down to the diffraction limit of 0.09 arcseconds). © 2014 SPIE. [less ▲]

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See detailThe VORTEX project: first results and perspectives
Absil, Olivier ULg; Mawet, Dimitri; Delacroix, Christian ULg et al

in Marchetti, Enrico; Close, Laird; Véran, Jean-Pierre (Eds.) Adaptive Optics Systems IV (2014, July 21)

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the ... [more ▼]

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the diffraction limit of the telescope), a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric sub-wavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about 6e-5 at 2λ/D. Three of them have now been installed on world-leading diffraction-limited infrared cameras, namely VLT/NACO, VLT/VISIR and LBT/LMIRCam. During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit (0.1"). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imager and on future extremely large telescopes (ELTs). In particular, we will briefly describe our current efforts to improve the manufacturing of mid-infrared AGPMs, to push their operation to shorter wavelengths, and to provide deeper starlight extinction by creating new designs for higher topological charge vortices. Within the VORTEX project, we also plan to develop new image processing techniques tailored to coronagraphic images, and to study some pre- and post-coronagraphic concepts adapted to the vortex coronagraph in order to reduce scattered starlight in the final images. [less ▲]

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See detailThe VORTEX coronagraphic test bench
Jolivet, Aïssa ULg; Piron, Pierre ULg; Huby, Elsa ULg et al

in Navarro, Ramon; Cunningham, Colin; Barto, Allison (Eds.) Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation (2014, July 18)

In this paper, we present the infrared coronagraphic test bench of the University of Liège named VODCA (Vortex Optical Demonstrator for Coronagraphic Applications). The goal of the bench is to assess the ... [more ▼]

In this paper, we present the infrared coronagraphic test bench of the University of Liège named VODCA (Vortex Optical Demonstrator for Coronagraphic Applications). The goal of the bench is to assess the performances of the Annular Groove Phase Masks (AGPMs) at near- to mid-infrared wavelengths. The AGPM is a subwavelength grating vortex coronagraph of charge two (SGVC2) made out of diamond. The bench is designed to be completely achromatic and will be composed of a super continuum laser source emitting in the near to mid-infrared, several parabolas, diaphragms and an infrared camera. This way, we will be able to test the different AGPMs in the M, L, K and H bands. Eventually, the bench will also allow the computation of the incident wavefront aberrations on the coronagraph. A reflective Lyot stop will send most of the stellar light to a second camera to perform low-order wavefront sensing. This second system coupled with a deformable mirror will allow the correction of the wavefront aberrations. We also aim to test other pre- and/or post-coronagraphic concepts such as optimal apodization. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. [less ▲]

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See detailDevelopment of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)
Delacroix, Christian ULg; Absil, Olivier ULg; Carlomagno, Brunella ULg et al

in Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)

One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal ... [more ▼]

One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2pi radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation. [less ▲]

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See detailMid-IR AGPMs for ELT applications
Carlomagno, Brunella ULg; Delacroix, Christian ULg; Absil, Olivier ULg et al

in Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)

The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This ... [more ▼]

The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument. [less ▲]

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See detailInvestigation of spectral impacts on the performance of a concentration device using a Fresnel lens combined with a double junction cell
Loicq, Jerôme ULg; Galante, Nicolas ULg; Thibert, Tanguy ULg et al

in Proceedings of SPIE (2014, May 15)

This experimental study was carried out within the context of high concentration photovoltaics. The paper presents the results of an experimental investigation relating to the quantification of the ... [more ▼]

This experimental study was carried out within the context of high concentration photovoltaics. The paper presents the results of an experimental investigation relating to the quantification of the impacts of the chromatic effect on the performance of a double junction GaInP/GaAs solar cell. Chromatic effects are the result of material dispersion caused by the refractive optics component. This study aims to evaluate the effect of the spectral modification of the incident beam on the whole solar concentrator system performance. Such considerations are fundamental in producing a highly accurate design, with which to achieve the best possible system performance. Efficiency is evaluated within the vicinity of the focus of a Fresnel lens designed for concentration. On the optical axis, rays with different wavelengths are not focalized at the same points. The spectral content of the beam depends, therefore, upon the position of the cell along the optical axis. It is assumed that spectral content modification may have an impact on cell performance and, as a consequence, on system efficiency as a whole. Efficiency of the optical Fresnel lens and of the cell were evaluated in relation to spectral content modification. [less ▲]

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See detailSpectral splitting planar solar concentrator : Design and Experimental testing Preliminary results
Blain, Pascal ULg; Michel, Céline ULg; Clermont, Lionel ULg et al

in Proceedings of SPIE (2014, May 15), 9140

We present a new concept in solar concentrator: spectral splitting. It implies reflective, refractive and diffractive elements that allow two spectrally differentiated beams to reach different and/or ... [more ▼]

We present a new concept in solar concentrator: spectral splitting. It implies reflective, refractive and diffractive elements that allow two spectrally differentiated beams to reach different and/or unmatched lattice solar cells. Those cells efficiencies are then enhanced. The aimed geometrical concentration factor is 5× and the theoretical optical efficiency of that concentrator concept reaches 82%. [less ▲]

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See detailFirst prototypes of vortex retarders obtained by polarization holography
Piron, Pierre ULg; Blain, Pascal ULg; Décultot, Marc ULg et al

in Proceedings of SPIE (2014, May), 9099

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders ... [more ▼]

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders are birefringent plates characterized by a uniform phase retard and a rotation of their fast axis along their center. Liquid crystals are anisotropic molecules possessing birefringent properties. They are locally orientable and their orientation defines the fast axis orientation of the retarder. Their alignment depends on the local orientation of the recording electric field. The superimposition of several polarized beams will be used to shape the electric field to achieve the recording of vortex retarders. The mathematical aspects of the superimposition process, as well as several numerical simulations are exposed. Finally, the first prototypes are presented, characterized and compared to the numerical simulations. [less ▲]

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See detailStudy of a solar concentrator for space based on a diffractive/refractive optical combination
Michel, Céline ULg; Loicq, Jerôme ULg; Thibert, Tanguy ULg et al

Conference (2014, April 16)

The present work proposes a theoretical optical study of a new planar solar concentrator for space applications. The concentrator focuses light onto three spatially separated photovoltaic cells (three ... [more ▼]

The present work proposes a theoretical optical study of a new planar solar concentrator for space applications. The concentrator focuses light onto three spatially separated photovoltaic cells (three single-junctions, dedicated to two different light spectra), allowing for independent control of the output power of each cell. The design, based on a blazed diffraction grating superimposed on a Fresnel lens, combines advantages of both spectral splitting and light focusing. Theoretical model and optimization of the optical design are presented, including the variation of the grating period along the lens. Numerical results are detailed, highlighting the possibility to design a concentrator at more than 10× for each cell, with an optical efficiency of ~71% and less than 10% of losses for tracking errors < ±0.85°. A thermal study completes the work, as well as a first theoretical comparison with a planar Fresnel based solar concentrator focusing on a GaAs cell. [less ▲]

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