J. P. Perez

LEISHMANIA INFECTION OF CANINE SKIN FIBROBLASTS IN VIVO

In this paper we describe two cases of naturally occurring leishmaniasis in dogs in which Leishmania sp. amastigotes are found within the cytoplasm of fibroblasts. The infected cells were identified histologically, immunohistochemically, and ultrastructurally as fibroblasts. This is the first report of leishmaniasis in any species in which amastigotes were identified in vivo within fibroblasts.

Design and properties of high-power highly coherent single-frequency VECSEL emitting in the near- to mid-IR for photonic applications

We demonstrate high power (multiwatt) low noise single frequency operation of tunable compact verical-external- cavity surface-emitting-lasers exhibiting a low divergence high beam quality, of great interest for photonics applications. The quantum-well based lasers are operating in CW at RT at 1μm and 2.3μm exploiting GaAs and Sb technologies. For heat management purpose the VECSEL membranes were bonded on a SiC substrate. Both high power diode pumping (using GaAs commercial diode) at large incidence angle and electrical pumping are developed. The design and physical properties of the coherent wave are presented. We took advantage of thermal lens-based stability to develop a short (0.5 < 5mm) external cavity without any intracavity filter. We measured a low divergence circular TEM00 beam (M2 = 1.2) close to diffraction limit, with a linear light polarization (> 30 dB). The side mode suppression ratio is > 45 dB. The free running laser linewidth is 37 kHz limited by pump induced thermal fluctuations. Thanks to this high-Q external cavity approach, the frequency noise is low and the dynamics is in the relaxation-oscillation-free regime, exhibiting low intensity noise (< 0.1%), with a cutoff frequency > 41MHz above which the shot noise level is reached. The key parameters limiting the laser power and coherence will be discussed. These design/properties can be extended to other wavelengths.

MWIR InSb detector with nBn architecture for high operating temperature

In this communication, we report results obtained on a new InSb/InAlSb/InSb ‘bariode’, grown by MBE on (100)- oriented InSb substrate. Because of a very weak valence band offset with InSb (~ 25meV), InAlSb is a good candidate as a barrier layer for electrons. However, due to lattice mismatch with the InSb substrate, careful growth study of InAlSb was made to insure high crystal quality. As a result, InSb-based nBn detector device exhibits dark current density equals to 1x10-9A.cm-2 at 77K: two decades lower than Insb standard pin photodiode with similar cut-off wavelength. Moreover, compared to standard pn (or pin) InSb-based photodetectors fabricated by implanted planar process or by molecular beam epitaxy (MBE), we demonstrate that the reachable working temperature, around 120 K, of the InSbbased nBn detector is respectively higher than 40 K and 20 K than the previous. Such result demonstrates the potentiality of Insb detectors with nBn architecture to reach the high operating temperature.

InSb photodetectors with PIN and nBn designs

InSb pin photodiodes and nBn photodetectors were fabricated by Molecular Beam epitaxy (MBE) on InSb (100) n-type substrate and characterized. MBE Growth conditions were carefully studied to obtain high quality InSb layers, exhibiting in pin photodiode design dark current density values as low as 13nA.cm-2 at -50mV and R0A product as high as 6x106 WΩcm2 at 77K. Then, a new unipolar nBn InSb/InAlSb/InSb detector structure on InSb substrate were designed in order to suppress generation-recombination dark current. The first InSb nBn devices were fabricated and preliminary electrical characterizations are reported.

Mediastinal plasma cell tumor in a sheep.

An extramedullary plasmacytoma was found in a 10-year-old sheep. The tumor involved the mediastinum, where a 25 × 15 × 10-cm encapsulated mass was found. The lungs had multiple metastases ranging from 0.5 to 2 cm in diameter, and the portal vein contained a 10-cm-long mass. The cytologic and histopathologic analyses were consistent with a moderately differentiated plasmacytoma. The immunophenotype of the tumor cells was lambda light chain IgG+, CD79a-, and CD3-. Occasional granulomas were observed at the periphery of the mediastinal and pulmonary tumors. Microbiologic culture yielded growth of Corynebacterium from these granulomas. This is the first report of plasmacytoma in sheep. The tumor most likely arose from mediastinal lymph nodes and metastatized to the lungs and portal vein.

InAs/InAsSb superlattice structure tailored for detection of the full midwave infrared spectral domain

We studied the Ga-free InAs/InAsSb type-II superlattice (T2SL) period, thickness and antimony composition, in order to define an optimized structure suitable for detection of the full mid-wavelength infrared domain (MWIR). The SL structures were fabricated by MBE on n-type GaSb substrates and exhibited cut-off wavelengths between 5μm and 5.5μm at 150K. The growth procedure used to achieve strain-balanced structures is reported and first structural and optical results, made of high-resolution Xray diffraction pattern, AFM image scan, photoluminescence (PL) and time resolved photoluminescence measurements (TRPL), are presented and analyzed.

Design, fabrication, and characterization of InSb avalanche photodiode

In this communication, the potentiality of InSb material as an avalanche photodiode (APD) device is investigated. Current density-voltage (J-V) characteristics at 77K of InSb pin photodiodes were simulated by using ATLAS software from SILVACO, in dark conditions and under illumination. In order to validate parameter values used for the modeling, theoretical J-V results were compared with experimental measurements performed on InSb diodes fabricated by molecular beam epitaxy. Next, assuming a multiplication process only induced by the electrons (e-APD), different designs of separate absorption and multiplication (SAM) APD structure were theoretically investigated and the first InSb SAM APD structure with 1μm thick multiplication layer was then fabricated and characterized.