VHE gamma-ray spectral properties of the blazars Mrk 501 and Mrk 421 from CAT observations in 1997 and 1998

The Very High Energy (VHE) gamma-ray emission of the BL Lacertae objects Markarian 501 and Markarian 421 has been observed by the CAT Imaging Atmospheric Cherenkov Telescope in 1997 and 1998. The spectrum extraction method is presented, and the spectral properties of both sources are compared in different activity states. Theoretical implications for jet astrophysics are discussed.Comment: 4 figures, 6 pages. To appear in the proceedings of the GeV-TeV Gamma Ray Astrophysics Workshop "Towards a Major Atmospheric Cherenkov Detector VI", Snowbird, Utah, August 13-16, 199

Calibration of the CAT Telescope

Due to the lack of test-beams in ground-based gamma-ray astronomy, detector calibration has been a major challenge in this field. However, with the use of Cherenkov ring-images due to cosmic-ray muons and of strong gamma-ray signals, the CAT telescope could be rather well monitored and understood. Here we present a few oustanding aspects of this work.Comment: 5 pages, 5 figures. To appear in the proceedings of the GeV-TeV Gamma Ray Astrophysics Workshop "Towards a Major Atmospheric Cherenkov Detector VI", Snowbird, Utah, August 13-16, 199

InAs/InP quantum dot laser grown on (113)B InP substrate

International audienc

Lasers à boites quantiques sur InP, de très faibles courants de seuil et émettant à 1.55 µm

National audienc

Recombination processes in 1.55µm InAs/InP quantum dot lasers

International audienc

Thermal properties of 1.5µm InAs/InP quantum dot lasers

International audienc

First demonstration of a 1.52 µm RT InAs/InP(3 1 1)B laser with an active zone based on a single QD layer

International audienceThis paper presents experimental results obtained on a laser structure containing a single QD layer, epitaxially grown on InP(3 1 1)B substrate. The sample shows laser emission on the ground state in the 1.55 µm telecommunication window at room temperature. Its threshold current density is 320 A cm−2, which is relatively low for an InP-based QD laser. Its modal gain, attributed to a high QD density and low QD size dispersion, explains this first achievement of lasing with a single QD layer on an InP substrate