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We have used a femtosecond time-resolved core-level surface PES system based on the 92-eV harmonic source to study the surface carrier dynamics that induces the transient SPV on semiconductor surfaces. We clarified the temporal evolution of the transient SPV characterized by the time of the photo-generated carrier separation and recombination. This result demonstrates the potential of this technique for clarifying the initial stage of the surface carrier dynamics after photoexcitation.

The integration of III-V semiconductor materials with Si technology is of great interest for optoelectronic integration circuits. We have studied the growth and structural aspects of GaP nanowires (NWs) grown on Si substrate in a metalorganic vapor phase epitaxy system. Au colloid particles dispersed on Si substrate were used as catalysts to conduct the NW growth. The growth temperature considerably affected the growth rate and shape of GaP NWs. The growth rate showed a maximum value of 14.69 nm/s at 480 °C. When growth temperature increased the radial growth on NW sides was enhanced and the NWs therefore exhibited a tapering shape. GaP NWs with a uniform diameter could be grown at a growth temperature as low as 420 °C using a two-temperature process. The NW diameter could be well controlled by using size-selective Au colloid particles. The growth rate dependence showed that the thin NWs grew more slowly than thick ones and the V/III source ratio had a significant effect on the growth rate dependence. An analysis of the GaP/Si interface by transmission electron microscopy indicated that the NWs were epitaxially grown on the Si(111) substrate. Based on these experimental results, the growth mechanism of the GaP NWs on Si was discussed. [ABSTRACT FROM AUTHOR]

The growth and structural aspects of GaP nanowires (NWs) grown on Si substrate in a metalorganic vapor phase epitaxy system are studied. The analysis of the GaP/Si interface by transmission electron microscopy has shown that the NWs are epitaxially grown on the Si(111) substrate.

The degradation mechanism of a vertical-cavity surface-emitting laser (VCSEL) with an air-post structure is analyzed for stable optical parallel interconnection communication. It is clarified that the degradation is caused by the behavior of latent defects in the GaAs active layer. Decreasing the defects in the active region as well as decreasing the threshold current is important for obtaining a long-lifetime VCSEL [ABSTRACT FROM PUBLISHER]

The paper describes a method for the automatic detection of atrial fibrillation, an abnormal heart rhythm, based on the sequence of intervals between heartbeats. The RR interval is the interbeat interval, and deltaRR is the difference between two successive RR intervals. Standard density histograms of the RR and deltaRR intervals were prepared as templates for atrial fibrillation detection. As the coefficients of variation of the RR and deltaRR intervals were approximately constant during atrial fibrillation, the coefficients of variation in the test data could be compared with the standard coefficients of variation (CV test). Further, the similarities between the density histograms of the test data and the standard density histograms were estimated using the Kolmogorov-Smirnov test. The CV test based on the RR intervals showed a sensitivity of 86.6% and a specificity of 84.3%. The CV test based on the deltaRR intervals showed that the sensitivity and the specificity are both approximately 84%. The Kolmogorov-Smirnov test based on the RR intervals did not improve on the result of the CV test. In contrast, the Kolmogorov-Smirnov test based on the ARR intervals showed a sensitivity of 94.4% and a specificity of 97.2%. [ABSTRACT FROM AUTHOR]

We investigated the waveguide loss and transmission characteristics for optical interconnection using vertical-cavity surface-emitting lasers (VCSELs) and multimode polymeric waveguide circuits with crossings. The excess loss with 100 crossings is 2.2 dB when the image magnification from a VCSEL to a waveguide is 2.3. We obtained error-free (i.e., bit error rate <10-11) optical interconnection at 1.0625 Gbps regardless of the number of crossings or the magnification. These results suggest the practicality of large-scale optical interconnection between VCSEL-based smart-pixel chips using multimode waveguides with more than 100 crossings [ABSTRACT FROM PUBLISHER]

Background: It has been reported that nicorandil restores blood flow to reperfused myocardium in patients with acute myocardial infarction. However, whether nicorandil might decrease infarct size remains unclear. The aim of this study was to assess the effect of nicorandil on infarct size with thallium-201/beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP) dual-isotope single photon emission computed tomography.Methods: A total of 62 patients were randomly assigned to receive intravenous nicorandil (4 mg in 5 minutes at admission, immediately followed by 6 mg/hr over a 24-hour period) or placebo. All patients were divided into 4 groups: Group N-a, 16 patients with preexisting angina treated with nicorandil; N-b, 15 patients without preexisting angina treated with nicorandil; C-a, 14 patients with preexisting angina given placebo; C-b, 17 patients without preexisting angina given placebo. Tl-201/BMIPP imaging was performed in the 62 patients within 7 days after admission. Dual-isotope single photon emission computed tomographic images were quantified by severity index with a polar map.Results: The BMIPP severity index was similar among the 4 groups. Only the thallium severity index in the N-a group was significantly less (P<.05). The ratio of the thallium severity index to that of BMIPP in the N-a group was significantly decreased compared with those of the other groups.Conclusion: Nicorandil has a protective effect in patients with acute myocardial infarction and preexisting angina treated with primary balloon angioplasty. [ABSTRACT FROM AUTHOR]

We demonstrate the polarization stability of 850-nm-wavelength vertical cavity surface-emitting lasers (VCSELs) grown on (311)B substrates under continuous-wave (CW) and dynamic operation. To clearly verify the polarization stability of VCSELs on (311)B substrates due to the anisotropic optical gain, the characteristics of both VCSELs on (311)B and (100) substrates were compared experimentally. Under CW operation, very small difference in both orthogonal polarization suppression ratio and the distribution of polarization direction was observed between VCSELs on (311)B and (100) polyimide-buried structures. On the other hand, significantly larger orthogonal polarization suppression ratio was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the orthogonal polarization suppression ratios of the VCSEL on (311)B substrates were more stable than those on (100) substrates. The data transmission characteristics also indicate large differences in the dependence of the bit error rate on bias current and the power penalty between polarization resolved and unresolved systems between VCSELs on (311)B and (100) substrates. The beneficial effect of the polarization stability of VCSELs on (311)B substrates due to their anisotropic optical gain is clearly demonstrated [ABSTRACT FROM PUBLISHER]

The fabrication procedure of smart pixels based on a hybrid integration of compound semiconductor photonic devices with silicon CMOS circuits is described. According to the 0.8-μm design rule, CMOS receiver/transmitter circuits are designed for use in vertical-cavity surface-emitting laser (VCSEL)-based smart pixels, and 16×16 and 2×2 Banyan-switch smart-pixel chips are also designed. By using our polyimide bonding technique, we integrated GaAs pin-photodiodes hybridly on the CMOS circuits. The photodetector (PD)/CMOS hybrid receiver operated error free at up to 800 Mb/s. Successful optical/optical (O/O) operation (a bit rate up to 311 Mbit/s) of the 2×2 Banyan-switch smart-pixel chip implemented with another VCSEL chip is also demonstrated [ABSTRACT FROM PUBLISHER]

We report vertical GaP nanowires self-arranged in lines formed from Au islands that were initially arranged at single-layer steps on Si(111) substrates. These Au islands are spontaneously arranged by controlling the deposition. There are three aspects to the growth of vertical GaP wires: the cosupply of TMGa and PH3, two growths at different temperatures, and a low PH3 flow rate. The grown wires are quite ordered in lines of several micrometers. Electrical measurement confirmed selective current flow at the wires and we confirmed photoluminescence from the wires. This bottom-up technique is promising for nano-hetero-device integration on Si circuits. [ABSTRACT FROM AUTHOR]

We have investigated GaAs/AlGaAs nanowires capped with AlGaAs layers for optical device applications. GaAs nanowires are not so stable during AlGaAs capping growth at high temperature. However, AlGaAs nanowires retain their shapes, and GaAs nanowires sandwiched between AlGaAs wires were capped at temperatures as high as 700°C. The capped structures showed sharp photoluminescence peaks at around 730 nm at 4 K, which originated from excitons in quantum wires. We confirmed that the AlGaAs capping layers were grown smoothly around nanowires so that surface recombination centers in GaAs nanowires were reduced compared with air-exposed GaAs wires. [ABSTRACT FROM AUTHOR]

We report a record low threshold current of 1.55-μm vertical-cavity surface-emitting laser (VCSEL). Thin-film wafer-fusion technology enables InP-based buried heterostructure VCSELs to be fabricated on GaAs-AlAs distributed Bragg reflectors. Threshold current density is independent of mesa size, and a 5-μm VCSEL exhibits a threshold current as low as 380 μA at 20°C and a single transverse mode up to the maximum optical output power under continuous-wave operation [ABSTRACT FROM PUBLISHER]

The polarization stability of 850-nm InAlGaAs strained quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) grown on GaAs (311)B substrate was investigated by comparing it with that of GaAs unstrained QW VCSEL grown on GaAs (311)B substrate. Photoluminescence measurement showed that strained QWs grown on GaAs (311)B substrate had larger anisotropy in optical gain than unstrained QWs. The VCSEL with strained QWs showed an orthogonal polarization suppression ratio (OPSR) as high as 21 dB under CW operation. Time-dependent OPSR measurement indicated that the strained QW VCSEL had higher polarization stability than the unstrained QW VCSEL under zero-bias modulation [ABSTRACT FROM PUBLISHER]

All metal-organic chemical vapor deposition (MOCVD) grown 850-nm-wavelength refractive-index-guided semiconductor-buried vertical-cavity surface-emitting laser is proposed and their performance is investigated. P/n-InGaP current-blocking region enables both selective regrowth and the formation of refractive-index-guided region which surrounds multiquantum-well active/core regions. We have achieved room temperature CW operation of the new types of vertical-cavity surface-emitting lasers. The minimum threshold current was 9.5 mA with 18 μm square mesa size at 30°C. The device lased at up to 70°C, and the maximum output power exceeds 1 mW at above 30°C. The near field pattern indicates the single-lobed output beam at low bias current [ABSTRACT FROM PUBLISHER]

The polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) under dynamic operation was investigated by comparing the characteristics of VCSELs grown on (311)B and (100) GaAs substrates. Significantly larger suppression ratios of the two orthogonal polarization modes was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the polarization direction was more stable in the VCSEL on (311)B substrates than that on (100) substrates. Error-free transmission was realized from VCSELs on (311)B substrates with and without a polarizer in both back-to-back and 100-m multimode fiber transmission [ABSTRACT FROM PUBLISHER]

Examines the growth of vertical-cavity surface-emitting laser structures grown on gallium arsenide (311)B substrates by metalorganic chemical vapor deposition. Quality of carbon doped gallium arsenide and aluminum arsenide obtained by optimized growth conditions; Threshold current, voltage and maximum power of the substrates at 20 micrometer diameter size.