28 research outputs found

    On-chip parametric amplification with 26.5~dB gain at telecommunication wavelengths using CMOS-compatible hydrogenated amorphous silicon waveguides

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    We present the first study of parametric amplification in hydrogenated amorphous silicon waveguides. Broadband on/off amplification up to 26.5~dB at telecom wavelength is reported. Measured nonlinear parameter is 770~W−1m−1\textrm{W}^{-1} \textrm{m}^{-1}, nonlinear absorption 28~W−1m−1\textrm{W}^{-1} \textrm{m}^{-1}, bandgap 1.611.61~eV.Comment: 3 pages, 2 figures, accepted to Optics Letter

    Low power inelastic light scattering at small detunings in silicon wire waveguides at telecom wavelengths

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    When a pump beam is propagating through a silicon nanophotonic waveguide, a very small fraction of the light is scattered to other frequencies. At very low intensity, the amount of scattered light is proportional to the power of the pump beam. We show that the scattering intensity increases linearly within the temperature range 300-575 K and that the photon flux decreases as the inverse of the frequency detuning {\nu} over the investigated bandwidth 0.4 THz < |{\nu}| < 2.5 THz. The simplest interpretation of these observations is that the pump beam is scattered on a 1 dimensional thermal bath of excitations. Finally, the implications of this scattering process for quantum optics applications of silicon nanophotonic structures are discussed.Comment: 11 pages, 5 figures, to submit to Journal of the Optical Society

    Distribution, ecology and conservation of Ommatotriton vittatus and Salamandra infraimmaculata in Syria

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    The distribution, ecology and conservation status of the Syrian urodeles Salamandra infraimmaculata and Ommatotriton vittatus are poorly known. We present the results of a field study, conducted in February 2009. Salamandra infraimmaculata was found at six localities, ranging from 228 to 960 m a.s.l., and co-occurred with O. vittatus at three localities. All localities were near small, clear streams or springs. Temperatures ranged from 9.4 to 16.4 degrees C, pH 7.5-8.5, GH 3-18 and KH 3-18. The distribution model of S. infraimmaculata reveals that the distribution of this species is nearly entirely shaped by precipitation in the coldest quarter "92.9% contribution to the model". The rarity of suitable surface waters is probably the main reason for the supposed scarcity of this species in northwestern Syria. Tapping a water source for drinking water resulted in one case in extensive mortality of larvae. Ommatotriton vittatus was found at nine different localities, ranging from 172 to 960 m a.s.l. Habitat characteristics, water quality and morphological data were recorded. The average total length of adult O. vittatus was 116 mm (range 93-138 mm, n = 22) for males and 93 mm (range 86-108 mm, n = 34) for females. Mean weight was 6.7 g for males and 3.9 for females. The mean body condition index of females was comparable to that of males. Water temperatures ranged from 8.7 to 14.6 degrees C, pH 7.5-8.5, GH 3-18 and KH 3-18. The distribution model of O. vittatus reveals that the distribution of this species is mainly shaped by precipitation, both during the winter and summer periods. The collection of large numbers of adult O. vittatus for fish bait was observed
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