Sadayuki Uchiyama

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We introduced ion-beam assisted deposition in order to improve the quality of Al/sub 2/O/sub 3/ and SiO/sub 2/, which were used as part of the mirrors of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers (VCSELs). The refractive index of Al/sub 2/O/sub 3/ was improved to 1.63 from 1.56 and the one of SiO/sub 2/ increased to 1.47 from 1.45.(More)
The nonlinear gain factor of 1.26 /spl mu/m GaInNAs-based SQW lasers, that includes a small amount of Sb to improve the crystalline-quality, was investigated for the first time. GaInNAs-based lasers have an extremely large differential gain of 1.06 /spl times/ 10/sup -15/ cm/sup 2/ in spite of the single-QW; however, at the same time, the lasers have an(More)
The magnetic anisotropy sensor (MAS) is a stress sensor that detects internal stresses induced by the inverse magnetostrictive effect. In this study, the sample is a cold rolled steel plate used in a car body. For flux penetration depths greater than the sample thickness (0.75 mm), the MAS detects the average of the internal stress distribution, producing(More)
Nondestructive methods for measurement of mechanical stress are important to studies of magnetic materials. Magnetic anisotropy sensors (MAS), which have been employed in stress and torque sensors, can also be utilized in the noncontact detection of magnetic anisotropy in materials to estimate stress or defects in them. However, because MAS is a probe type(More)
A novel method is proposed for transverse mode control of an oxide confined vertical cavity surface emitting laser (VCSEL) by a dielectric aperture (DA) formed on the top surface. From I-L characteristics and far field patterns (FFP), the diameter of the DA is optimized to be 10 /spl mu/m. Suppression of higher order transverse modes is confirmed by(More)
We have developed a single-shot intensity-measurement system using a silicon positive-intrinsic-negative (PIN) photodiode for x-ray pulses from an x-ray free electron laser. A wide dynamic range (10(3)-10(11) photons/pulse) and long distance signal transmission (>100 m) were required for this measurement system. For this purpose, we developed(More)
The magnetic anisotropy sensor (MAS) enables the noncontact measurement of mechanical stresses in ferromagnetic materials. The output voltage from the MAS is due to the inverse magnetostriction effect. To measure a tensile or bending stress, a MAS output voltage vs. stress characteristic is needed for each type of stress. This paper deals with the(More)
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