We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped fiber gainswitched laser seeding an InF<sub>3</sub> fiber. This innovative fiber presents a specific design that increases non-linear effects and shows very weak background losses. Thanks to the versatility of our gain-switched laser, all the pulse parameters have been widely optimized to generate a supercontinuum emission with the highest average power and the largest spectrum.
This paper introduces a supercontinuum (SC) laser source emitting from 400 nm to beyond 1750 nm, with
adjustable pulse repetition rate (from 250 kHz to 1 MHz) and duration (from ~200 ps to ~2 ns). This device
makes use of an internally-modulated 1.06 μm semiconductor laser diode as pump source. The output radiation
is then amplified through a preamplifier (based on single-mode
Yb-doped fibres) followed by a booster (based
on a double-clad Yb-doped fibre). The double-clad fibre output is then spliced to an air-silica microstructured
optical fibre (MOF). The small core diameter of the double-clad fibre allows reducing the splice loss. The strongly
nonlinear propagation regime in the MOF leads to the generation of a SC extending from the violet to the nearinfrared
wavelengths. On the Stokes side of the 1.06 μm pump line, i.e., in the anomalous dispersion regime, the
spectrum is composed of an incoherent distribution of quasi-solitonic components. Therefore, the SC source is
characterised by a low coherence length, which can be tuned by simply modifying pulse duration, that is closely
related to the number of quasi-solitonic components brought into play. Finally, the internal modulation of the
laser diode permits to achieve excellent temporal stability, both in terms of average power and pulse-to-pulse
Optical Coherence Tomography is an emerging technique for biomedical diagnostic help. This is a non-invasive, high resolution, non-destructive mean for some optical biopsy. Since a few years new developments have been undergone in the field of OCT trying to functionalize OCT measurements. One of them is Spectroscopic OCT where simultaneous access to depth resolution as well as spectral features depth resolved in the media are obtained. These spectroscopic OCT system are mainly based on post processing of classical OCT signals what is time consuming and which add numerical noise. We propose an 'all optical' system for real-time direct display of depth-frequency analysis of media.
We describe a preliminary experimental study of an interferometer built with two 500-meters-long arms made of polarization maintaining optical fibers. The control of the field polarization state along the single-mode fiber arms enables to measure fringe contrast up to 93% with a laser source emitting a 1290nm carrier wavelength. Preliminary contrast measurements achieved with broadband spectrum sources exhibit differential dispersion effect resulting from fiber inhomogeneities. Partial compensation of this effect is achieved by introducing additional fiber pieces on one arm. Moreover, we experimentally characterize the differential chromatic dispersion evolution as a function of the various additional fiber sections. Using the channeled spectrum method, a spectral analysis of the interferometric mixing allows to accurately measure the differential effect of chromatic dispersion i.e. second and third order term of the spectral phase shift.
The phase closure is well known to remove the 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 is corrupted by this spectral behavior. This theoretical analysis is illustrated by experimental results on a fiber version of a stellar interferometer. The good accordance between the numerical simulations and the experimental results valid this model.
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 or integrated optics components. This additional aperture could give us the possibility to achieve an image reconstruction using the phase-closure technique. We focus these calibration experiments on the interference fringe contrast measurements and the evolution of the phase-closure term versus the differential dispersion effects induced by the stretching of fiber delay lines.
We report an experiment demonstrating the potential of optical fibers in the design of stellar interferometers for space missions. For the first time to our knowledge, only guided optics components are used to achieve the different basic functions of a stellar interferometer: optical field propagation from the telescope to the mixing station; delay line to synchronize the field to be mixed; and optical fiber couplers to split and recombine the beams.
We report the first technical results of the Integrated Optics Near-infrared Interferometric Camera developed and characterized at the Observatoire de Grenoble as well as the first tests carried out on the GI2T Interferometer (Observatoire de la Cote d'Azur, France). This near-infrared interferometric camera dedicated to astronomical observations is implemented in a single dewar, which hosts the planar integrated optics beam combiner and a cooled HgCdTe infrared detector, with optical interfaces reduced to optical fibers for signal injection in the component. Thanks to its versatility, this concept allows to combine any number of telescopes in the near infrared range (J, H and K bands). The compactness of the integrated optics components allows various combining schemes (co- and multi-axial ones) and observations in different spectral bands simultaneously. Finally, a camera upgrade with a PICNIC chip is also described. This new set-up under integration at the Observatoire de Grenoble would allow to reach limiting magnitudes of H equals 4 - 6 with the GI2T.