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Here, we are presenting building blocks such as Y-splitters, directional couplers, unbalanced beam splitters... that have been optimised for the L-band in Lithium Niobate. Although such blocks have already been developed in the mid-IR in this material, we are here using a different crystal orientation and newer design that are producing lower losses and birefringence. In particular, a 4-telescope mid-infrared combiner (linked to the NOTT project) was made in order to achieve nulling interferometry in the L-band. We show that we have relatively low loss waveguides, controlled photometric splitters (20/80 flux ratio), as well as functional couplers and beam splitting techniques. Furthermore, we will implement the electro-optic effect in this chip, in order to have internal modulation, and to be able to finely tune the fringes and improve the contrast, allowing for a step further into compact nulling interferometry.
After a brief introduction on the SWIFTS principle, we will focus on the electro-optic modulation of the fringes, and show preliminary results that validate the temporal multiplexing approach and discuss further improvements and the range of application of this active phase spectrometer.
In previous work, we identified the optimal 5T 3D device, as being single-mode between 550-800 nm and showing good internal transmission in all input channels, above 45% at 635nm. The internal transmission (sum of the output values obtained for the four waveguides of the 1x4 splitter as normalized to the output signal obtained from the straight waveguide used as a reference) was measured. Two inputs achieved 80% transmission. The PIC was installed in the FIRST/SUBARU optical bench simulator at LESIA, to inject light into five inputs simultaneously and scan the fringes using independent MEMS segments, inducing a relative OPD modulation. The results of this study, comparing the signature obtained for a single source (star) as compared to a binary, will be presented in this work. We will show that both polarizations are guided, with no crosstalk, and analyze the interferometric performances as a function of the source type, showing that the binary companion can be detected.
Asgard/NOTT: L-band nulling interferometry at the VLTI. II. Warm optical design and injection system
Laser written 3D 3T spectro-interferometer: study and optimisation of the laser-written nano-antenna
NEAT is an astrometric mission proposed to ESA with the objectives of detecting Earth-like exoplanets in the habitable zone of nearby solar-type stars. In NEAT, one fundamental aspect is the capability to measure stellar centroids at the precision of 5 × 10-6 pixel.
Current state-of-the-art methods for centroid estimation have reached a precision of about 2 × 10-5 pixel at two times Nyquist sampling, this was shown at the JPL by the VESTA experiment.1 A metrology system was used to calibrate intra and inter pixel quantum efficiency variations in order to correct pixelation errors.
The European part of the NEAT consortium is building a testbed in vacuum in order to achieve 5 × 10-6 pixel precision for the centroid estimation. The goal is to provide a proof of concept for the precision requirement of the NEAT spacecraft. In this paper we present the metrology and the pseudo stellar sources sub-systems, we present a performance model and an error budget of the experiment and finally we describe the present status of the demonstration.
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