Stationary Wave Integrated Fourier Transform Spectrometers (SWIFTS) are based on the sampling of a stationary wave using nano-sampling centres on the surface of a channel waveguide. Single nanogroove sampling centres above the waveguide surface will radiate the sampled signal with wide angular distribution, which is not compatible with the buried detection area of infrared detectors, resulting in crosstalk between pixels. An implementation of multiple diffraction nano-grooves (antenna) for each sampling position is proposed as an alternative solution to improve directivity towards the detector pixel by narrowing the scattering angle of the extracted light. Its efficiency is demonstrated from both simulated and measured far field radiative patterns exhibiting a promising method to be used for future integrated IR-SWIFTS. The implementation of the antennas will allow for a high resolution spectrometer in Infra-Red (here 1550nm) with no crosstalk problem (ref. [1]). These antennas, combined with the technology used (direct laser writing) will provide a robust, low-cost efficient tool that can be implemented as a 3D-3T spectro-interferometer (multi telescope beam-combiner), useful for astrophysics applications, such as phase closure studies.
Direct laser writing is a powerful technique for the development of astrophotonic devices, namely by allowing 3D structuring of waveguides and avoiding in-plane crossings that can induce losses and crosstalk in multi-telescope beam combiners. In this work, a multiplexed device is proposed in order to increase the spectral bandwidth to hundreds of nm, for a central wavelength of 1580nm. Our device is fabricated by ultrafast laser inscription of type I waveguides in bulk IR-grade fused silica glass. A first part of the study was devoted to finding the optical fabrication parameters in terms of depth, speed and number of tracks needed to achieve an optimal waveguide, single mode in the near IR. A second part was focused to the fabrication of different optical lanterns, from one multimode input to several (4 or 16) single mode outputs. The optical chip consists of a multimode input slit-waveguide, that adiabatically converts into an aligned matrix of 4 or 16 single-mode channel waveguides, with a pitch corresponding to the detector pixel size. Two separations (20 μm and 64 μm) were studied, in order to avoid crosstalk between parallel waveguides (directional coupling) and from extracted flux into the detector (pixel crosstalk). A final part is dedicated to the spectrometer realization, based on the sampling of a stationary wave inside the waveguide.
The astronomical L band is particularly well suited for the hunt of low mass companions and the study of planet forming discs. In this paper, we present the concept of a spectro-interferometer with application to high precision interferometry, in projects such as Hi-5: a high-contrast thermal near-infrared imager for the VLTI. The interest of our system is that it allows, for the first time, spectro-interferometry in the mid-infrared (L-Band), in an integrated optic device, with a resolution of R=2000 in a 500μm long sampling zone. Fringe scan and photometry balancing are achieved on-chip, using an external applied voltage. This kind of devices has already been used for high contrast interferometry (36dB rejection ratio) and spectrometry, and first developments have been achieved in passive spectro-interferometers. This first demonstrator is a key milestone towards an interferometric nulling combiner dedicated to high contrast observations
The design of an efficient and stable solar selective coating for Concentrating Solar Power central receivers requires a
complex study of the materials candidates that compose the coating. Carbon-transition metal nanocomposites were
studied in this work as absorber materials because they show appropriate optical properties with high absorption in the
solar region and low thermal emittance in the infrared. Furthermore metal carbides are thermal and mechanical stable in
air at high temperatures.
In this work a solar selective coating was grown by a dual source filtered cathodic vacuum arc. The complete stack
consists on an infrared reflection layer, an absorber layer of carbon-zirconium carbide nanocomposites and an
antireflection layer. The aim of this research is optimize the absorber layer and for that, the metal content was controlled
by adjusting the pulse ratio between the two arc sources. The elemental composition was determined by Ion Beam
Analysis, X-Ray diffraction measurements show the crystal structure and the optical properties were characterized by
spectroscopic ellipsometry measurements. The reflectance spectra of the complete selective coating were simulated with
the optical software CODE. Bruggeman effective medium approximation was employed to average the dielectric
functions of the two components which constitute the nanocomposite in the absorber layer. The optimized coating
exhibited a solar absorptance of 95.41% and thermal emittance of 3.5% for 400°C. The simulated results were validated
with a deposited multilayer selective coating.
A systematic study of TiO2 films deposited by dc filtered cathodic vacuum arc (FCVA) was carried out by varying the deposition parameters in a reactive oxygen atmosphere. The influence of the oxygen partial pressure on film properties is analyzed. Composition was obtained by Rutherford backscattering spectroscopy (RBS) measurements, which also allow us to obtain the density of the films. Morphology of the samples was studied by scanning electron microscopy (SEM) and their optical properties by ellipsometry. Transparent, very dense and stoichiometric TiO2 films were obtained by FCVA at room temperature.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.