We present an overview of the fabrication process and characterization of germanate, germanate-tellurite and tellurite microstructured fibers or step-index fibers with different index contrasts. For microstructured fibers, we exploit the generated SC for methane spectroscopy measurements in the mid-infrared by means of the supercontinuum absorption spectroscopy technique. We demonstrate also an ageing process of microstructured fibers in ambient atmosphere. For stepindex fibers, several compatible core/cladding glasses were explored for fiber manufacturing with a dehydration process, allowing the drawing of low-OH tellurite fibers. We report both numerical and experimental demonstrations supercontinuum (SC) generation in these fibers. Finally we report our latest results in the generation of SC until 5.3 μm in a step-index tellurite fiber.
We report the manufacturing and characterization of Tellurite micro structured fibres (MOFs) with low OH content. The different purification processes used during the fabrication of the TeO2 - ZnO - Na2O glass allowed us to reduce the hydroxyl compounds concentration down to 1ppm mass. A suspended core MOF was drawn from this material and then pumped by nanojoule-level femtosecond pulses at 1.7μm, its zero dispersion wavelength (ZDW), and well above it at 2.5μm. We show the related supercontinuum (SC) generated in the two distinct dispersion regimes of the waveguide. Moreover, the SC spanning was extended in both visible and mid-IR regions (between 600nm up to 3300nm) by the taperisation of the previously tested MOFs.
The remarkable properties (internal gain larger than 100 and close to unity excess noise factor) of Short Wave Infrared
(SWIR) HgCdTe electron-initiated Avalanche Photodiodes (e-APDs) are put to good use to demanding applications, i.e.
spectroscopy and LIDAR. Knowing the requirements of both situations, we have designed specific models based on
highly sensitive single elements APDs and adapted proximity electronics.
On one hand, we use the e-APDs low noise equivalent power (NEP) at 180K (few fW/Hz1/2). We simultaneously
designed a specific Transimpedance Amplifier (TIA) which allows us to take advantage of the low APD NEP. The
combination of both elements along with a dedicated cryostat enables direct LIDAR detection at moderate bandwidth
(BW = 20 MHz) without the need for long time averaging, which is crucial in far field (≥ 5 km) analysis. One the other
hand, we have optimized a low-noise and low-frequency LN2 cooled prototype operating with an external commercial amplifier. It allows us to observe the photoluminescence of Ge nanostructures in the range 1.5-2.5 μm with a
significantly increased SNR along with a reduce pump laser power. The possibility to use these detectors in the photon
counting limit will be discussed in light of our recent results. In parallel, we present preliminary time response
measurements performed on SWIR APD suggesting that a higher GHz BW could be reached with this type of detector.
This is however subjected to optical optimization at the moment.
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