An ultrawide-band semiconductor optical amplifier having an extremely high penalty-free output power of 23 dBm achieved with quantum dots

A semiconductor optical amplifier (SOA) having a gain of >25 dB, noise figure of <5 dB, and 3-dB saturation output power of >19 dBm, over the record widest bandwidth of 90 nm among all kinds of optical amplifiers, and also having a penalty-free output power of 23 dBm, the record highest among all the SOAs, was realized by using quantum dots.     

A method for calibrating the line-focus-beam acoustic microscopy system

Absolute accuracy of the line-focus-beam (LFB) acoustic microscopy system is investigated for measurements of the leaky surface acoustic wave (LSAW) velocity and attenuation, and a method of system calibration is proposed. In order to discuss the accuracy, it is necessary to introduce a standard specimen whose bulk acoustic properties, (e.g., the independent elastic constants and density) are measured with high accuracy. Single crystal substrates of gadolinium gallium garnet (GGG) are taken as standard specimens. The LSAW propagation characteristics are measured and compared with the calculated results using the measured bulk acoustic properties. Calibration is demonstrated for the system using two LFB acoustic lens devices with a cylindrical concave surface of 1-mm radius in the frequency range 100 to 300 MHz.     

Quantification of the number of EP3 receptors on a living CHO cell surface by the AFM

The distribution of EP3 receptors on a living cell surface was quantitatively studied by atomic force microscopy (AFM). Green fluorescent protein (GFP) was introduced to the extracellular region of the EP3 receptor on a CHO cell. A microbead was used as a probe to ensure certain contact area, whose surface was coated with anti-GFP antibody. The interactions between the antibodies and GFP molecules on the cell surface were recorded to observe the distribution of the receptors. The result indicated that EP3 receptors were distributed on the CHO cell surface not uniformly but in small patches coincident with immunohistochemical observation. Repeated measurements on the same area of cell surface gave confirmation that it was unlikely that the receptors were extracted from the cell membrane during the experiments. The measurement of single molecular interaction between GFP and the anti-GFP antibody was succeeded on the cell surface using compression-free force spectroscopy. The value of separation work required to break a single molecular pair was estimated to be about 1.5 x 10(-18)J. The number of EP3 receptor on the CHO cell surface was estimated using this value to be about 1 x 10(4) under the assumption that the area of the cell surface was about 5,000 microm(2). These results indicated that the number of receptors on a living cell surface could be quantified through the force measurement by the AFM.     

Motion and shape recovery based on iterative stabilization for modest deviation from planar motion

We describe an iterative stabilization method that can simultaneously recover camera motion and 3D shape from an image sequence captured under modest deviation from planar motion. This technique iteratively applies a factorization method based on planar motion and can approximate the observed image points to the 2D points projected under planar motion by stabilizing the camera motion. We apply the proposed method to aerial images acquired by a helicopter-borne camera and show better reconstruction of both motion and shape than Christy-Horaud's perspective factorization. Moreover, we confirm that the reprojection errors calculated from the recovered camera motion and 3D shape are very similar to the optimum results yielded by bundle adjustment.     

The solution structure and conformational dynamics of tumor necrosis factor-{alpha} and a (Cys69 - Asp; Cys101 - Arg) analog as examined by IR spectroscopy and hydrogen exchange

An analog of human tumor necrosis factor- (TNF-) was createdwith Cys69 and CyslOl replaced with Asp and Arg respectively.We have undertaken a comparative study of the solution conformationand dynamics of the native and analog molecules using a combinationof Fourier transform IR spectroscopy and hydrogen-deuterium(H-D) exchange kinetics. IR spectroscopic results indicate thatthe analog molecule adopts a gross structure similar to thatof the native molecule but significant differences in the conformationof the ß-sheets are observed. Increased bandwidthsobserved for several of the amide I components also suggesta less rigid structure for the analog molecule. Further, bymonitoring the frequency shifts of the individual amide I componentbands as a function of hydrogen exchange, we have enhanced ourability to assign these components to individual protein secondarystructures, particularly the high frequency ß-strandmode. Hydrogen exchange kinetic studies indicate that the Asp–Arganalog adopts a looser, more flexible solution structure relativeto the natural sequence molecule.     

Quantum-Dot Semiconductor Optical Amplifiers

This paper reviews the recent progress of quantum-dot semiconductor optical amplifiers developed as ultrawideband polarization-insensitive high-power amplifiers, high-speed signal regenerators, and wideband wavelength converters. A semiconductor optical amplifier having a gain of > 25 dB, noise figure of < 5 dB, and 3-dB saturation output power of > 20 dBm, over the record widest bandwidth of 90 nm among all kinds of optical amplifiers, and also having a penalty-free output power of 23 dBm, the record highest among all the semiconductor optical amplifiers, was realized by using quantum dots. By utilizing isotropically shaped quantum dots, the TM gain, which is absent in the standard Stranski-Krastanow QDs, has been drastically enhanced, and nearly polarization-insensitive SOAs have been realized for the first time. With an ultrafast gain response unique to quantum dots, an optical regenerator having receiver-sensitivity improving capability of 4 dB at a BER of 10^-9 and operating speed of > 40 Gb/s has been successfully realized with an SOA chip. This performance achieved together with simplicity of structure suggests a potential for low-cost realization of regenerative transmission systems.     

High-Sensitivity Measurement of Thermal Deformation in a Stacked Multichip Package

The thermal deformation of a stacked multichip package, which is a newly developed electronic package, was measured by phase-shifting moireacute interferometry. We developed this method using a wedged glass plate as a phase shifter to obtain displacement fields having a sensitivity of 30nm/line. This method also enabled the quantitative determination of the strain distributions in all observation areas. Thermal loading was applied from room temperature (25degC) to elevated temperatures of 75degC and 100degC where the thermal strains were examined and compared. The results showed that the longitudinal strain epsiv_xx was concentrated at the ends of two silicon chips, and the longitudinal strain epsiv_yy increased between the two silicon chips. The shear strain gamma_xy increased at the end of the lower silicon chip from 0.17% to 0.30% when the temperature increased by 25degC     

Progress in GaN-based quantum dots for optoelectronics applications

Our recent progress in GaN-based quantum dots (QDs) for optoelectronics application is discussed. First, we discussed an impact of the use of GaN-based QDs on semiconductor lasers, showing theoretically that reduction of threshold current by using the QDs in GaN-based lasers is much more effective compared to those in GaAs-based or InP-based lasers. Then discussed are our growth technology including self-assembling growth of InGaN QDs on sapphire substrates by atmospheric-pressure metalorganic chemical vapor deposition. Using the self-assembling growth technique, we have succeeded in obtaining lasing action in an edge-emitting laser structure with the InGaN QDs embedded in the active layer under optical excitation with the emission wavelength of 410 nm. Toward UV light wavelength emission, we have recently established self-assembled GaN QDs of high quality and high density under very low V-III ratio. We clearly observed two photoluminescence peaks from both the QDs and the wetting layer at room temperature, which clearly shows the nanostructures are formed with the Stranski-Krastanow growth mode.     

Dispersion of Poly(phenylene ether) in a Poly(phenylene sulfide)/Poly(phenylene ether) Alloy

We have devised and developed a new method for the preparation of a poly(phenylene sulfide)/poly(phenylene ether) (PPS/PPE) alloy, which has micro‐dispersed PPE in the PPS matrix. PPS was chemically treated to activate the reactivity of the PPS end‐group by extrusion in the presence of diphenylmethane diisocyanate (MDI) in its molten state at 300°C. The reactive processing of the MDI‐treated PPS with maleic anhydride‐modified PPE gave a PPS/PPE alloy with micro‐dispersed PPE in the PPS matrix. The PPS/PPE alloy showed mechanical properties superior to those of PPS at elevated temperature (150°C) and also showed precision‐molding ability superior to that of PPS.