Dual frequency laser with two continuously and widely tunable frequencies for optical referencing of GHz to THz beatnotes

International audienceA dual-frequency 1.55 μm laser for CW low noise microwave, millimeter and sub millimeter wave synthesis is demonstrated, where frequency stabilization is possible on each wavelength independently. The solid state Er:Yb laser output power is 7 mW. The amplitude noise is −150 dBc/Hz at 1 MHz offset frequency. In free running regime, the frequency noise is 3.10^5/f Hz/sqrt(Hz) (800 Hz on a 1μs timescale), better than commercial fibered or semi-conductor sources at this wavelength

AP4 deficiency: A novel form of neurodegeneration with brain iron accumulation?

OBJECTIVE: To describe the clinico-radiological phenotype of 3 patients harboring a homozygous novel AP4M1 pathogenic mutation. METHODS: The 3 patients from an inbred family who exhibited early-onset developmental delay, tetraparesis, juvenile motor function deterioration, and intellectual deficiency were investigated by magnetic brain imaging using T1-weighted, T2-weighted, T2*-weighted, fluid-attenuated inversion recovery, susceptibility weighted imaging (SWI) sequences. Whole-exome sequencing was performed on the 3 patients. RESULTS: In the 3 patients, brain imaging identified the same pattern of bilateral SWI hyposignal of the globus pallidus, concordant with iron accumulation. A novel homozygous nonsense mutation was identified in AP4M1, segregating with the disease and leading to truncation of half of the adap domain of the protein. CONCLUSIONS: Our results suggest that AP4M1 represents a new candidate gene that should be considered in the neurodegeneration with brain iron accumulation (NBIA) spectrum of disorders and highlight the intersections between hereditary spastic paraplegia and NBIA clinical presentations

Polarimetric imaging beyond the speckle grain scale

International audienceWe address an experimental Stokes imaging setup allowing one to explore the polarimetric properties of a speckle light field with spatial resolution well beyond the speckle grain scale. We detail how the various experimental difficulties inherent to such measurements can be overcome with a dedicated measurement protocol involving a careful \emph{speckle registration} step. The setup and protocol are then validated on a metallic reference sample, and used to measure the state of polarization of light in each pixel of highly resolved speckle patterns ($>$2000 pixels per speckle grain) resulting from the scattering of an incident coherent beam on samples exhibiting different polarimetric properties. Evolution of the state of polarization with spatial averaging and across adjacent speckle grains is eventually addressed

Imagerie de Stokes à l'échelle du grain de speckle

National audienc

Polarimetric contrast microscopy by orthogonality breaking

International audienc

Laser déclenché à rétro-injection non résonante : application à la vélocimétrie Lidar-Radar

National audienc

Quantum Dash-based Vertical-External-Cavity Surface-Emitting Laser on InP

International audienceAn Optically-Pumped InAs Quantum Dash-based Vertical-External-Cavity Surface-Emitting Laser (OP-QDH-VECSEL) on InP is demonstrated. In multi-mode operation, the device emits up to 163 mW at T=20°C (pump limited) in the 1615-1628 nm wavelength range. When forced to oscillate in the single-frequency regime, it shows a maximum output power of 7.9 mW at 1610 nm, for a T=19.5°C. The emitted light is linearly polarized along the QDH growth direction ([1-10] crystallographic axis). The single-frequency linewidth of the OP-QDH-VECSEL has been estimated to 22 kHz, for a cavity length of 49 mm

Shot-Noise-Limited Operation of Electrically-Pumped Quantum Wells-Based VECSEL Emitting at Telecom Wavelength

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Fonctionnement Classe A faible bruit d'un laser VECSEL injecté électriquement et émettant à 1,5 µm

International audienceL'oscillation d'un laser VECSEL classe A faible bruit est obtenue pour la première fois à 1,5 µm en pompage électrique. La zone active à base de puits quantiques sur substrat InP est insérée dans une cavité externe de grande finesse afin d'obtenir le régime classe A. Le bruit d'intensité relatif de ce laser (RIN ~-160 dB/Hz) est limité par le bruit de grenaille sur une large bande passante allant de 2 MHz à 20 GHz

Electrically pumped shot-noise limited class A VECSEL at telecom wavelength

International audienceClass A shot-noise limited operation is achieved in an electrically pumped vertical external cavity surface emitting laser (VECSEL), opening the way for integration of such peculiar noiseless laser oscillation in applications where low power consumption and footprint are mandatory. The quantum well active medium is grown on an InP substrate to enable laser oscillation at telecom wavelengths. Single frequency class A operation is obtained by proper optimization of the cavity dimensions, ensuring at the same time a sufficiently long and high-finesse cavity without any intracavity filtering components. The laser design constraints due to electrical pumping are discussed as compared to optical pumping. The intensity noise spectrum of this laser is shown to be shot-noise limited, leading to a relative intensity noise of −160dB/Hz for 3.1 mA detected photocurrent