We present a new solar concentrator concept. This concept is based on spectral splitting. It implies reflective, refractive and diffractive elements that allow two spectrally differentiated beams to reach different and/or unmatched lattice solar cells. The aimed geometrical concentration factor is 5× and the theoretical optical efficiency of that concentrator concept reaches theoretically 82%. The following study will discuss the concept of such a solar concentrator. A practical application to dye sensitized solar cells is given. The manufacturing and design of the element is then exposed. Those elements have been tested in the laboratory. Good agreements with theoretical simulations are demonstrated.
The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation
for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several
possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales
Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA,
Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial
de Liege develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current
work aiming at evaluating these prototypes on the Synapse test bench at the Institut d'Astrophysique Spatiale
in Orsay, France.
The Annular Groove Phase Mask coronagraph (AGPM) is an intrinsically achromatic vectorial vortex. It consists
of integrated subwavelength optical elements whose space-variant polarization properties can be engineered and
optimized to synthesize one of the theoretically most efficient coronagraphs. This paper briefly recalls the
principles of the AGPM, presents the benefit of its implementation inside a polarimetric differential imager,
realistic numerical simulations assessing its performances, as well as the current status of the near-infrared and
visible prototype manufacturing operations.
One of the most critical units of nulling interferometers is the Achromatic Phase Shifter. The concept we propose
here is based on optimized Fresnel rhombs, using the total internal reflection phenomenon, modulated or not.
The total internal reflection induces a phase shift between the polarization components of the incident light.
We present the principles, the current status of the prototype manufacturing and testing operations, as well as
preliminary experiments on a ZnSe Fresnel rhomb in the visible that have led to a first error source assessment
study. Thanks to these first experimental results using a simple polarimeter arrangement, we have identified the
bulk scattering as being the main error source. Fortunately, we have experimentally verified that the scattering
can be mitigated using spatial filters and does not decrease the phase shifting capabilities of the ZnSe Fresnel
Thermal infrared (IR) lenses require efficient anti-reflection coating. Moth-eye (or egg-box) 2D subwavelength gratings
have demonstrated their ability to reach a very high transmission for a wide wavelength and angular range. The use in
thermal IR is simplified by the lower resolution for lithographic technology, compared to visible waveband. However,
deeper structures must be engraved and lithography must be adapted to IR materials. In order to be cost-effective, the
patterning must be produced by replication techniques, such as embossing. Our laboratory is now experimenting hot
embossing of moth-eye patterns in chalcogenide substrates.
In this paper, theoretical analysis, micro-lithographic technology and manufacturing processes are detailed.
We propose a new family of achromatic phase shifters that uses the modulated total internal reflection (TIR) phenomenon. These components can be seen as enhanced Fresnel rhombs for infrared applications like nulling interferometry and polarimetry. The TIR phenomenon comes with a differential phase shift between the polarization components of the incident light. Modulating the index transition at the TIR interface allows compensating for the intrinsic material dispersion in order to make the subsequent phase shift achromatic over broad bands. The modulation can be induced by a thin film of a well-chosen medium or a subwavelength grating whose parameters are specially optimized. We present results from theoretical simulations together with preliminary fabrication outcomes.
This paper presents an innovative architecture where a micro-prism structure performs an in-line and wavelength-dependent extraction of the light injected at the edge of the device. This partial extraction of light is carried out by holographic mirrors coated onto each micro-prism oblique side. Thanks to the fabrication process, customization is possible and the number and the performances of each extractive faces can easily be tailored at will. These devices can be advantageous for any kind of applications where a high spectral selectivity is required or when a discrete extraction of spectral components has to be performed.
This paper presents the concept and study of an innovative device dedicated to compact illumination devices. Partially reflecting micro-prisms are sealed inside a plastic plate. Light injected by an edge of the panel is propagating under total internal reflection condition. Partial light extraction is performed by the micro-prism surfaces. Fan-out application is also described in the field of optical network.
This paper presents the concept and feasibility demonstration of an improvement of the LCD projector optics. An innovative concept of integration of an holographic filter in the optical head allows for laser pointer tracking. The filter retrieves the positioning information of the pointer on a PSD (Position Sensitive Device). The detector is interfaced with the LCD matrix in order to project a pattern on the screen. Several software options can be implemented for remote control of the slide show. We present the holographic geometry optimization, the experimental recording, and results.