16 research outputs found
Edge Couplers with relaxed Alignment Tolerance for Pick-and-Place Hybrid Integration of III-V Lasers with SOI Waveguides
We report on two edge-coupling and power splitting devices for hybrid
integration of III-V lasers with sub-micrometric silicon-on-insulator (SOI)
waveguides. The proposed devices relax the horizontal alignment tolerances
required to achieve high coupling efficiencies and are suitable for passively
aligned assembly with pick-and-place tools. Light is coupled to two on-chip
single mode SOI waveguides with almost identical power coupling efficiency, but
with a varying relative phase accommodating the lateral misalignment between
the laser diode and the coupling devices, and is suitable for the
implementation of parallel optics transmitters. Experimental characterization
with both a lensed fiber and a Fabry-P\'erot semiconductor laser diode has been
performed. Excess insertion losses (in addition to the 3 dB splitting) taken as
the worst case over both waveguides of respectively 2 dB and 3.1 dB, as well as
excellent 1 dB horizontal loss misalignment ranges of respectively 2.8 um and
3.8 um (worst case over both in-plane axes) have been measured for the two
devices. Back-reflections to the laser are below -20 dB for both devices within
the 1 dB misalignment range. Devices were fabricated with 193 nm DUV optical
lithography and are compatible with mass-manufacturing with mainstream CMOS
technology
Design of a waveguide-coupled GeSn disk laser
We report on the design of a waveguide coupled GeSn microdisk-laser cavity in
which the germanium virtual substrate serving as a template for GeSn growth is
repurposed for the definition of passive on-chip interconnection waveguides. A
main challenge resides in transferring the optical power from the upper
(Si)GeSn gain stack to the underlying virtual substrate layer and is solved
with laser mode engineering. Designs are based on experimentally realized layer
stacks and waveguide outcoupling efficiencies as high as 27% are shown in
compact resonator geometries with a small, 7 m radius, with 42% of the
power being recycled in the laser cavity
Characterization of CD4+and CD8+T Cell Subsets and Interferon Regulatory Factor 4 (IRF4) in MS Patients Treated with Fingolimod (FTY-720): A Follow-up Study
Fingolimod is a novel immunomodulatory drug used in patients with relapsing multiple sclerosis (MS) which reversibly inhibits egress of lymphocytes from lymph nodes.
In this longitudinal study, the frequency of Interferon- gamma (IFN-gamma)+, IL4+, IL17+ and IL10+ CD4+ and CD8+ T cell subsets were measured in Fingolimod treated patients before and after 12 months'(12M) therapy using flow cytometry and compared to those of naive, Betaferon treated MS patients and healthy individuals. Additionally, the level of transcription factor IRF4 and IL-6, IL-23, TGF-beta 1 cytokines, required for differentiation of IL-17+ T cells, were assessed by RT-PCR and ELISA, respectively.
In Fingolimod treated MS patients, we observed a significant decrease in the percentage of IFN-gamma+/IL17+ CD4+ and CD8+ T cell subsets. In contrast, Fingolimod increased IL10+ CD4+ T cells. We also showed that IFN-gamma+IL17+ co-producing CD8+ T cells were reduced in patients under fingolimod therapy. furthermore, Fingolimod could reduce the expression level of IRF4 in patients while IL6 was increased in the supernatant of cultured peripheral blood mononuclear cells.
Our data showed that Fingolimod treatment alters CD4+ and CD8+ T cell subsets and reduces expression of IRF-4, which affects the proportion of pathogenic memory T cells in peripheral blood
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Strain Engineered Electrically Pumped SiGeSn Microring Lasers on Si
SiGeSn holds great promise for enabling fully group-IV integrated photonics operating at wavelengths extending in the mid-infrared range. Here, we demonstrate an electrically pumped GeSn microring laser based on SiGeSn/GeSn heterostructures. The ring shape allows for enhanced strain relaxation, leading to enhanced optical properties, and better guiding of the carriers into the optically active region. We have engineered a partial undercut of the ring to further promote strain relaxation while maintaining adequate heat sinking. Lasing is measured up to 90 K, with a 75 K T0. Scaling of the threshold current density as the inverse of the outer circumference is linked to optical losses at the etched surface, limiting device performance. Modeling is consistent with experiments across the range of explored inner and outer radii. These results will guide additional device optimization, aiming at improving electrical injection and using stressors to increase the bandgap directness of the active material
Modulation by insulin-like growth factor I of the phosphatase PTEN in astrocytes
Characterization of intracellular pathways underlying the pleiotropic actions of insulin-like growth factor-I (IGF-I) on brain cells is incomplete. We analyzed IGF-I signalling on astrocytes through the canonical phosphatidylinositol 3-kinase (PI3K)/Akt pathway and focused on possible changes in PTEN, a phosphatase that modulates IGF-I signalling by inhibiting Akt activation and, in turn is positively regulated by PI3K. After exposure of astrocytes to IGF-I, PTEN mRNA and protein levels were reduced and its phosphatase activity diminished. Inhibition of PTEN involved activation of a PI3K/protein kinase C (PKC) pathway that decreased in a proteasome-dependent step the levels of the transcription factor Egr-1, a key regulator of PTEN levels in astrocytes, causing decreased binding of Egr-1 to the PTEN promoter. Enhanced mitogenesis in PTEN siRNA-transduced astrocytes after IGF-I suggested that reduced PTEN may be a permissive factor for the mitogenic activity of IGF-I. Subsequent recovery of reduced PTEN required also activation by IGF-I of PI3K to recruit in this case protein kinase A (PKA) which stimulated Egr-1 levels and, consequently PTEN synthesis. Because basal levels of PTEN in astrocytes are also governed by PI3K, IGF-I appears to modulate PTEN in astrocytes by redirecting its homeostasic control through PI3K in a timed fashion. © 2007 Elsevier B.V. All rights reserved.Peer Reviewe