54 research outputs found
ΠΠ»ΠΈΡΠ½ΠΈΠ΅ ΠΎΡΠ½ΠΎΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΈΡΠΈΠ½Ρ Π·ΡΠ±ΡΠ°ΡΡΡ ΠΊΠΎΠ»Π΅Ρ Π½Π° ΠΎΠ±ΡΠ΅ΠΌ Π·ΡΠ±ΠΎΡΠ΅Π·Π½ΡΡ ΡΠ°Π±ΠΎΡ
In order to optimize the soldering process of laserbars onto heatsinks with Indium solder, several investigations have been made. First the growth of the Indium oxide film is examined. With this knowledge four different reduction methods are selected. Formic acid as a wet chemical reduction, a plasma activated Hydrogen/Argon gas, a gas enriched with formic acid, and a protective layer of Gold were investigated and compared for an optimized reduction of the oxide film of the Indium solder. A cross section of the solder interface after the soldering process is made in order to see the distribution of the metals. High diffusion of the solder with its contact partners is a sign of a good connection. Enough pure Indium has to be available after the soldering process in order to use its creek properties to reduce the mechanical stress in the laserbar
ΠΠ± ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠΈ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΡ ΡΠ°ΡΡΡΠΎΡΠ½ΠΈΠΉ ΠΌΠ΅ΠΆΠ΄Ρ ΡΠ°Π·Π²Π΅Π΄ΠΎΡΠ½ΡΠΌΠΈ Π²ΡΡΠ°Π±ΠΎΡΠΊΠ°ΠΌΠΈ Π² ΡΠ²ΡΠ·ΠΈ Ρ ΡΠ°Π·Π»ΠΈΡΠ½ΡΠΌΠΈ ΡΠ°Π·ΠΌΠ΅ΡΠ°ΠΌΠΈ ΡΡΠ°ΡΡΠΊΠΎΠ² ΠΈ Π°Π½ΠΈΠ·ΠΎΡΡΠΎΠΏΠ½ΠΎΡΡΡΡ ΡΠ΅Π» ΠΏΠΎΠ»Π΅Π·Π½ΡΡ ΠΈΡΠΊΠΎΠΏΠ°Π΅ΠΌΡΡ
The main challenge to address single emitters in a high-power diode-laser-bar is the thermal and electrical management to avoid crosstalking. Especially p-side up assembly leads to increasing thermal influence of neighboring emitters due to the low thermal conductivity of GaAs. Electro-magnetic fields inside and outside the laser-bar, for example caused by high frequency modulation (10 MHz) at a high current (up to 1 A), induce voltages into neighboring electrical circuits, hence the output power of neighboring emitters can be affected
ΠΠ΅ΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΡΠΉ ΡΠ΅ΠΆΠΈΠΌ Π±Π°ΠΆΠ΅Π½ΠΎΠ²ΡΠΊΠΎΠΉ ΡΠ²ΠΈΡΡ ΠΈ Π½Π΅ΡΡΠ΅ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΡΠ΅ Π·ΠΎΠ½Ρ ΠΌΠ΅Π»ΠΎΠ²ΡΡ ΠΎΡΠ»ΠΎΠΆΠ΅Π½ΠΈΠΉ (ΠΡΡΠΎΠ»ΡΡΠΊΠ°Ρ ΠΌΠ΅Π³Π°Π²ΠΏΠ°Π΄ΠΈΠ½Π°)
ΠΠΎ Π·Π°ΠΌΠ΅ΡΠ°ΠΌ ΠΏΠ»Π°ΡΡΠΎΠ²ΡΡ
ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡ Π²Π΅ΡΡ
Π½Π΅ΡΡΡΠΊΠΈΡ
ΠΎΡΠ»ΠΎΠΆΠ΅Π½ΠΈΠΉ ΠΏΠΎΡΡΡΠΎΠ΅Π½Π° ΠΊΠ°ΡΡΠ° ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ Π³Π΅ΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡ Π±Π°ΠΆΠ΅Π½ΠΎΠ²ΡΠΊΠΎΠΉ ΡΠ²ΠΈΡΡ ΠΡΡΠΎΠ»ΡΡΠΊΠΎΠΉ ΠΌΠ΅Π³Π°Π²ΠΏΠ°Π΄ΠΈΠ½Ρ ΠΈ ΡΡΡΡΠΊΡΡΡ Π΅Π΅ ΠΎΠ±ΡΠ°ΠΌΠ»Π΅Π½ΠΈΡ. ΠΠΎ Π³Π΅ΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠΌΡ ΠΊΡΠΈΡΠ΅ΡΠΈΡ Π²ΡΠ΄Π΅Π»Π΅Π½Ρ ΠΎΡΠ°Π³ΠΈ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΠΉ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ Π±Π°ΠΆΠ΅Π½ΠΎΠ²ΡΠΊΠΈΡ
Π½Π΅ΡΡΠ΅ΠΉ. ΠΠ΅ΡΡΠΎΠΏΠΎΠ»ΠΎΠΆΠ΅Π½ΠΈΡ ΡΠΏΠΈΡΠ΅Π½ΡΡΠΎΠ² ΠΎΡΠ°Π³ΠΎΠ² ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄ΠΎΠ²Π°Π½Ρ Π² ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΠΏΠ΅ΡΠ²ΠΎΠΎΡΠ΅ΡΠ΅Π΄Π½ΡΡ
Π·ΠΎΠ½ Π΄Π»Ρ Π²ΡΡΠ²Π»Π΅Π½ΠΈΡ ΠΎΠ±ΡΠ΅ΠΊΡΠΎΠ² Π² ΠΌΠ΅Π»ΠΎΠ²ΠΎΠΌ Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ½ΠΎΡΠ½ΠΎΠΌ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ΅
ΠΠ²ΡΠΎΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π·Π°ΠΊΠΎΡΠ°ΡΠΈΠ²Π°Π½ΠΈΠ΅ ΠΎΡΠ΄Π΅Π»ΡΠ½ΡΡ ΡΠ°Π· Π»ΠΈΠ½ΠΈΠΉ Π΄Π»Ρ Π»ΠΈΠΊΠ²ΠΈΠ΄Π°ΡΠΈΠΈ Π΄ΡΠ³ΠΎΠ²ΡΡ ΠΊΠΎΡΠΎΡΠΊΠΈΡ Π·Π°ΠΌΡΠΊΠ°Π½ΠΈΠΉ
During the last few years high power diode laser arrays have become well established for direct material processing due to their high efficiency of more than 50%. But standard broad-area waveguide designs are susceptible to modal instabilities and filamentations resulting in low beam qualities. The beam quality increases by more than a factor of four by using tapered laser arrays, but so far they suffer from lower efficiencies. Therefore tapered lasers are mainly used today as single emitters in external resonator configurations. With increased output power and lifetime, they will be much more attractive for material processing and for pumping of fiber amplifiers. High efficiency tapered mini bars emitting at a wavelength of 980 nm are developed, and in order to qualify the bars, the characteristics of single emitters and mini bars from the same wafer have been compared. The mini bars have a width of 6 mm with 12 emitters. The ridge waveguide tapered lasers consist of a 500 Β΅m long ridge and a 2000 Β΅m long tapered section. The results show very similar behavior of the electro-optical characteristics and the beam quality for single emitters and bars. Due to different junction temperatures, different slope efficiencies were measured: 0.8 W/A for passively cooled mini bars and 1.0 W/A for actively cooled mini-bars and single emitters. The threshold current of 0.7 A per emitter is the same for single emitters and emitter arrays. Output powers of more than 50 W in continuous wave mode for a mini bar with standard packaging demonstrates the increased power of tapered laser bars
ΠΠΎΠ²ΡΡΠ΅Π½ΠΈΠ΅ Π½Π°ΡΡΠΏΠ½ΠΎΠΉ ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ Π·Π°ΠΊΠΈΡΠΈ-ΠΎΠΊΠΈΡΠΈ ΡΡΠ°Π½Π°, ΠΏΠΎΠ»ΡΡΠ°Π΅ΠΌΠΎΠΉ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ ΠΏΠ΅ΡΠΎΠΊΡΠΈΠ΄Π½ΠΎΠ³ΠΎ ΠΎΡΠ°ΠΆΠ΄Π΅Π½ΠΈΡ ΠΈΠ· ΡΠ°ΡΡΠ²ΠΎΡΠΎΠ² ΡΠΎΠ²Π°ΡΠ½ΠΎΠ³ΠΎ Π΄Π΅ΡΠΎΡΠ±Π°ΡΠ°
High beam quality can be achieved by accurate adjustment of the mechanical and microoptical components in the manufacturing process of high power diode laser stacks. A characterization device which can determine these parameters by automatically measuring the radiation properties of high-power diode-laser stacks has been developed. The result is a mechanically robust, easy to use characterization device of high reliability suited for applications in quality control and product optimization
Π‘Π²Π΅Π΄Π΅Π½ΠΈΡ ΠΎΠ± Π°Π²ΡΠΎΡΠ°Ρ
ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ Π² Π°Π»ΡΠ°Π²ΠΈΡΠ½ΠΎΠΌ ΠΏΠΎΡΡΠ΄ΠΊΠ΅ Π°Π²ΡΠΎΡΡ ΠΈ ΠΎΠ±Π»Π°ΡΡΠΈ ΠΈΡ
Π½Π°ΡΡΠ½ΡΡ
ΠΈΠ½ΡΠ΅ΡΠ΅ΡΠΎΠ², ΠΊΠΎΠ½ΡΠ°ΠΊΡΠ½Π°Ρ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΡ
Macropinocytotic uptake and infection of human epithelial cells with species B2 adenovirus type 35
The human adenovirus serotype 35 (HAdV-35, short Ad35) causes kidney and urinary tract infections, and infects respiratory organs of immunocompromised individuals. Unlike other adenoviruses, Ad35 has a low seroprevalence which makes Ad35-based vectors promising candidates for gene therapy. Ad35 utilizes CD46 and integrins as receptors for infection of epithelial and hematopoietic cells. Here, we show that infectious entry of Ad35 into HeLa, human kidney HK-2 cells and normal human lung fibroblasts strongly depended on CD46 and integrins but not heparan sulfate, and variably required the large GTPase dynamin. Ad35 infections were independent of expression of the carboxy-terminal domain of AP180 which effectively blocks clathrin-mediated uptake. Ad35 infections were inhibited by small chemicals against the serine/threonine kinase Pak1 (p21-activated kinase), protein kinase C (PKC), sodium-proton exchangers, actin and acidic organelles. Remarkably, the F-actin inhibitor jasplakinolide, the Pak1 inhibitor IPA-3 or the sodium-proton exchange inhibitor EIPA blocked the endocytic uptake of Ad35. Dominant-negative proteins or small interfering RNAs against factors driving macropinocytosis, including the small GTPase Rac1, Pak1 or the Pak1 effector C-terminal binding protein 1 (CtBP1) potently inhibited Ad35 infection. Confocal laser scanning microscopy, electron microscopy and live cell imaging showed that Ad35 colocalized with fluid phase markers in large endocytic structures that were positive for CD46, alpha v integrins and also CtBP1. Our results extend earlier observations with HAdV-3 (Ad3), and establish macropinocytosis as an infectious pathway for species B human adenoviruses in epithelial and hematopoietic cells
Exact field ionization rates in the barrier suppression-regime from numerical TDSE calculations
Numerically determined ionization rates for the field ionization of atomic
hydrogen in strong and short laser pulses are presented. The laser pulse
intensity reaches the so-called "barrier suppression ionization" regime where
field ionization occurs within a few half laser cycles. Comparison of our
numerical results with analytical theories frequently used shows poor
agreement. An empirical formula for the "barrier suppression ionization"-rate
is presented. This rate reproduces very well the course of the numerically
determined ground state populations for laser pulses with different length,
shape, amplitude, and frequency.
Number(s): 32.80.RmComment: Enlarged and newly revised version, 22 pages (REVTeX) + 8 figures in
ps-format, submitted for publication to Physical Review A, WWW:
http://www.physik.tu-darmstadt.de/tqe
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