Room temperature operation of GaInAs-GaInAsP-InP SCH multiquantum-film laser with narrow wire-like active region

GaInAs-GaInAsP-InP SCH (separate-confinement heterostructure) multiquantum-film lasers with approximately 100-nm-wide wirelike active regions were fabricated by two-step low-pressure organometallic vapor-phase epitaxy (LP-OMVPE) growth and wet chemical etching and operated at room temperature. An increase in the threshold current density in such lasers was drastically reduced by using a preheating process in hydrogen atmosphere and a thin InP cover layer growth prior to the regrowth of a GaInAsP optical confinement layer. The fabrication processes presented can be very effective for realization of room-temperature operation of long-wavelength quantum-wire and quantum-box lasers based on GaInAs-InP materials.<>     

Advanced semiconductor lasers

Recent research activities in the field of advanced semiconductor lasers are reviewed with emphasis on highly stable single-wavelength lasers and surface-emitting (SE) lasers for wideband lightwave communication systems and optical parallel information processing. The operational characteristics of DSM (dynamic single-mode) lasers are summarized and requirements for high-performance operation as light sources for high-speed transmission or coherent communications are described. A type of DSM laser called the distributed-reflector (DR) laser is described as an advanced DSM laser which enables high efficiency, high power, and narrow linewidth operations. Specific features and the potential of SE lasers are summarized. Research activities and remaining problems to be solved for a breakthrough in optical parallel information processing are presented. The potential of multidimensional quantum-well structures, such as QW lasers and quantum-box lasers, is discussed in terms of superior characteristics in both stationary and dynamic operations. The present fabrication technologies for realizing high-performance lasers based on multidimensional QW structures are also presented     

跳跃式移动机构的移动机理及实验研究

介绍了一种新型跳跃式移动机构,阐述了该机构的移动机理及其控制方法.跳跃式移动机构采用小型振动电机作为驱动,利用电机内偏心轮的旋转所产生的周期性的向心力及与工作表面的间歇性摩擦力的共同作用,实现机构的跳跃移动,两个不同放置位置的电机的组合运用,可实现机构可调速的直线运动和回转运动,通过一系列实验.验证了跳跃式移动机构可实现二维平面内的自由移动.     

Low-threshold-current CW operation of 1.5 ?m GaInAsP/InP bundle-integrated-guide distributed-Bragg-reflector (BIG-DBR) lasers

Low-threshold-current and high-power operation of 1.5 ?m GaInAsP/InP bundle-integrated-guide (BIG) DBR lasers were obtained. A single-mode operation temperature range of more than 70 deg was demonstrated around room temperature by shortening the active region to 100 ?m. The modulation characteristic was measured up to 2 GHz with a modulation depth of 100%. A maximum value of dynamic wavelength shift was 2 ? at 1.2 times threshold current.     

Gain and the threshold of three-dimensional quantum-box lasers

Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The electronic dipole moment and its polarization dependence are first analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box. Calculated gain is about 10 times that of bulk crystal for 100 Å × 100 Å × 100 Å GaAs/Ga0.8Al0.2As quantum box, and 15 times for Ga0.47In0.53As/InP quantum box with the same size, respectively. The threshold current density are 45 A/cm²and 62 A/cm²for GRINSCH GaAs/(Ga0.8Al0.2As-Ga0.4Al0.6As) and Ga0.47In0.53As/(Ga0.28In0.72As0.6P0.4-InP), respectively, where for the GaInAs/ GaInAsP/InP system the intervalence band absorption and nonradiative recombinations have been assumed to be the same as those obtained for bulk crystals experimentally. These results show the possibility of remarkable reduction in the laser threshold by the quantum-box structures.     

Preparation of Cr(N,O) thin films by RF reactive unbalanced magnetron sputtering

Chromium oxynitride thin films were deposited by radio-frequency (RF) reactive unbalanced magnetron sputtering at various O₂ flow rates onto Si(100) and glassy carbon substrates. The compositions of the thin films were analyzed by Rutherford backscattering spectroscopy. The thin films were found to contain up to 44 at.% oxygen. In Fourier-transform infrared spectra, a peak attributed to the Cr-N bond of CrN was observed, but no peak attributable to the Cr-O bond of Cr₂O₃ was found. The textures of the thin films were observed by transmission electron microscopy, which revealed that samples had a columnar structure. The hardness of the thin films was measured by nanoindentation. The hardness increased from 20 GPa to a maximum value of 31 GPa with increasing oxygen content.     

One-pot synthesis of hierarchically macro/mesoporous Al2O3 monoliths from a facile sol–gel process

Based on the preparation of ordered mesoporous Al₂O₃ powder using P123/isopropoxide aluminum/HNO₃ reaction system, hierarchically macro/mesoporous alumina monoliths were successfully fabricated by introducing PEG8000 as the phase-segregation initiator to generate macropores. The effects of PEG8000 and P123 contents on the monolithic and hierarchical morphology were investigated systematically. With appropriate selection of the starting composition, monolithic skeletons with bimodal macropores interconnected by mesostructured walls can be synthesized in both the dried gels and calcined samples. The well-defined macropores are in close-celled structure dispersed in large-sized mesoporous matrix. The mesopore size can be regulated by adjusting the PEG8000 content while its shape is governed by P123 content. The well-developed alumina monolith, MMA-P20, exhibits high surface area of 287 m²/g and narrowly distributed mesopores with median size of 13 nm after calcinaton.     

Butyrylcholinesterase K variant and cerebral amyloid angiopathy

BACKGROUND and PURPOSE: Cholinesterases are found histochemically in the vessels affected with cerebral amyloid angiopathy (CAA). A gene for the K variant of butyrylcholinesterase (BCHE-K) may be associated with late-onset Alzheimer's disease (AD). In search of genetic risk factors for CAA, we investigated the association of BCHE-K with CAA. METHODS: The association between the severity of CAA and BCHE-K was investigated in 155 autopsy cases of the elderly, including 48 patients with AD. RESULTS: There was no significant association of BCHE-K with the severity of CAA in the total, AD, or non-AD cases. Status of the epsilon4 allele of apolipoprotein E gene did not influence the results. CONCLUSIONS: Our results may suggest that BCHE-K is not a definitive risk factor for CAA in the elderly, although further study with larger samples is necessary to confirm this.     

Production of prostaglandins E1 and E2 by adult human red blood cells

We showed that human adult red blood cells (RBCs) produce prostaglandin E1 (PGE1) and E2 (PGE2). RBCs that were mechanically stressed in the presence of extracellular Ca2+ by being injected rapidly through a fine needle produced PGE1 and PGE2 within 30 min after this mechanical stress. The amounts of PGE1 and PGE2 produced by 1 x 10(9) mechanically stressed RBCs were approximately 50 pg and 100 pg, respectively, which were determined in the cytosolic fraction from sonicated RBCs using a competitive enzyme immunoassay method. A Western blot analysis using anti-cyclooxygenase-2 antibody revealed a band at the 70-kDa position in the samples from RBCs producing PGE1 and PGE2. Treatment with 10 micrograms/mL indomethacin completely inhibited the productions of PGE1 and PGE2. The present results may indicate a new role of RBCs in microcirculation.     

A 0.8-dB insertion-loss, 17.4-dBm power-handling, 5-GHz transmit/receive switch with DETs in a 0.18-/spl mu/m CMOS process

An optimized single-pole double-throw (SPDT) transmit/receive (T/R) switch has been fabricated using depletion-layer-extended transistors (DETs) in a 0.18 /spl mu/m CMOS process. The switch features the highest performance to date of any switch using a CMOS process, of a 0.8 dB insertion-loss, 23 dB isolation and 17.4 dBm power-handling capability at 5 GHz. The low insertion-loss has been achieved with the effects of junction capacitance decrease and substrate resistance increase in the DET, the adoption of low-loss shielded-pads, and several layout optimizations. The high power-handling capability is owing to the combined effect of the adoption of the source/drain dc biasing scheme and the high substrate resistance in the DET.