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We present some experimental results on tunable sum-frequency generation in a periodically poled lithium-niobate waveguide using a multi-wavelength fiber laser pump stabilized by a nonlinear optical loop mirror. We are able to up-convert to about 629 nm a continuous-wave infrared signal varying from 1497 nm to 1525 nm. Such a wideband conversion efficiency is ensured by the multiple spectral components of the laser pump, which is controlled by an adjustable Fabry–Perot filter. Potential applications, in particular for stellar imaging, are discussed.

We analyze the temporal coherence of an optical infrared radiation in the visible domain by using a Mach–Zehnder interferometer and a wavelength conversion stage in each arm. We exploit a sum frequency generation process in bulk PPLN crystal to convert the infrared radiation at 1.55 μm into 0.63 μm before the interferometric mixing. The applicability of the Wiener–Kintchine theorem through up-conversion processes is here demonstrated by direct comparisons among visible and infrared measurements.

International audience; In the frame of the Optical Hawaiian Array for Nanoradian Astronomy (`OHANA) project, 300-m long silica fibers are necessary to coherently link the Canada France Hawaii and Gemini telescopes. In this paper, we report measurements of the differential chromatic dispersion between two 300-m long silica polarization maintaining fibers for the astronomical J band (1.10 1.40 mum) as a function of the temperature variation on one fiber arm of the interferometer. We demonstrate that the second order coefficient of chromatic dispersion increases linearly with the temperature. Consequently, we propose two methods to compensate this additional and variable differential chromatic dispersion: the first one using a dispersive optical fiber delay line and the second one using a set of CaF2 bulk plates.

In the frame of ’OHANA project (phase II), IRCOM institute characterizes the 300-m long silica fibres which will link the Canada–France–Hawaii-Telescope and the Gemini telescope. In this paper, we report a method to compensate the differential chromatic dispersion between two 300-m long silica polarization-maintaining fibres. We experimentally show that the differential dispersion is not the same on each neutral axis of the fibre. Moreover, thanks to a channeled spectrum analysis, we are able to foresee the evolution of the contrast as a function of the wavelength and the spectral resolution over a given spectral band. Consequently, we are able to adjust the fibre lengths in order to maximize the contrast over J spectral window.

This paper reports on an experimental validation of the photon noise correction applied on interferometric data, in the frame of a laboratory stellar interferometer. The main feature of this study comes from the quantitative comparison between the contrasts and phase closure measurements in photon counting regime and simultaneously, on the same interferometer, in high flux level regime. This experiment uses an end-to-end imaging demonstrator including a three-telescope array linked by optical fiber to the mixing station. Contrasts and phase closure are extracted from a temporal fringe pattern. We show that it is possible to correct properly the interferometric data with light power level reaching 0.7 femto-Watt at a 680 nm mean wavelength. This corresponds to a photon flux close to 2.5 photons/ms and to 25 photons for each snap shot.

Phase closure is a well-known technique able to eliminate phase biases in a three-arm interferometer. This property is very useful to avoid the phase effect of the atmosphere in stellar interferometry. In this paper we theoretically investigate the effect of differential dispersion in a three-arm interferometer. We demonstrate that phase closure can be corrupted by differential dispersion between the interferometric arms. We begin by a general demonstration of such effect and propose a few examples where symmetry properties avoid phase closure errors. An analytical model for gaussian shaped spectrum and second order dispersion development is proposed. This analytical solution is illustrated by experimental results on a fibre version of a stellar interferometer.

Following the first demonstration of an all guided two-beam stellar interferometer designed for space missions, we report an experiment recombining the beams coming from three telescopes using only guided optics components. This additional aperture could give us the possibility to achieve an image reconstruction using the phase-closure technique. We focus this calibration experiment on the interference fringe contrast measurements and the evolution of the phase-closure term versus the differential dispersion effects induced by the stretching of fibre delay lines.

We report laboratory experimental results obtained with end to end image reconstruction breadboard including a 2D object, a highly birefringent fiber linked telescope array, an interferometric mixing assembly and an image restoration algorithm. The full control of birefringent effects allows the acquisition of the object complex Fourier spectrum (phase and modulus). The results consist of an accurate image reconstruction compared with the original source. The image restoration algorithm seeks for the object brightness distribution that satisfies two criteria: goodness of fit with the data and regularization. Future improvements of both the instrumental setup and image restoration algorithm are discussed.