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Volume 15, Issue 12
Displaying 1-7 of 7 articles from this issue
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Kunio TADA1987 Volume 15 Issue 12 Pages 1032-1033
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (164K) -
Atsushi KUROBE, Yutaka UEMATSU1987 Volume 15 Issue 12 Pages 1034-1042
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe reduction of the threshold current using quantum well (QW) structures is reviewed both theoretically and experimentally. A theory which takes into account gain flattening due to the two-dimensionality of quantum well is used to analyze experimental results of QW laser structures with various number of quantum wells. The lowesthreshold current density is realized by using single and multi quantum wells at long and short cavity lengths. An optimum cavity length, which minimizes the threshold current, is inversely proportional to thenumber of quantum wells. Close comparison between theory and experiment are made and the theory is found to be useful in optimizing quantum well structures.View full abstractDownload PDF (949K) -
Naohiro TANNO, Hidetoshi FUKUDA1987 Volume 15 Issue 12 Pages 1043-1051
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSA new interferometer by dual-wave-front generation in degenerate four-wave mixing is described with measurements of flame-temperature. The dual wave front created in a nonlinear medium automatically yields a self-referencing operation for a given phase of an incident probe beam. A phase-mismatching problem for nonconjugate wave generation is also considered. The experimental observations are shown using a dye-laser and Na-vapor system.View full abstractDownload PDF (1466K) -
Dependence on the spatial frequency of the written gratingTakeshi YAMAGUCHI, Kihuo UJIHARA1987 Volume 15 Issue 12 Pages 1052-1058
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSGeneration of phase conjugate waves in a photorefractive Bi12SiO20 (BSO) crystal is studied with particular attention to the dependence of the efficiency on the spatial frequency of the written grating. The influence of mis-alignment between input beams is also investigated in detail. Since the diffracted output energy is particularly sensitive to the incident angle of the readout beam, alignning of the readout beam to meet Bragg conditionis of critical importance. It is found that diffraction efficiency is proportional to the square of the fringe spacing, ∧2, under the condition of relatively small spacing ∧while it is proportional to ∧-2 when the spacingexceeds a certain value. The result is consistent with “two-level charge transfer model ”proposed by Peltier etal. From the fringe spacing giving a maximum diffraction efficiency, the density of acceptor traps is determined to be 1.3 ×1015cm-3 in the BSO crystal used.View full abstractDownload PDF (743K) -
Yozo NISHIURA, Mitsuru NISHIKAWA, Akihiro OOKA, Yuji KOHSAKA1987 Volume 15 Issue 12 Pages 1059-1066
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe have studied the way to miniaturerize optics, fiber-coil and electronics for a compact fiber-optic-gyroscope (FOG). The optics were miniaturerized by using small bulk optic parts, and hybrid integrated circuits were developed for the electronics of the FOG. To compensate for the reduction of the Sagnac phase shift due to the small diameter of the fiber coil, a small diametered polarization maintaining single-mode fiber (PMSF) was developed. Long lengths of the fiber could be wound around a small sized coiling space. By using these components, a compact FOG with outer diameter of 60 mm and height of 50 mm was developed. Sensitivity of 0.8 deg/hr and drift of 3.6 deg/hr/hr were observed.View full abstractDownload PDF (853K) -
Sunao YAMADA, Sadanori YOSHIDA, Nariaki SATO, Hirofumi KAWAZUMI, Toshi ...1987 Volume 15 Issue 12 Pages 1067-1072
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe slow conductivity signal is induced by pulsed laser irradiation of pyrene in nonpotar hydrocarbon solvents. Its characteristics under the influence of the space charge effect have been measured in the ms-s region. The time profile of the slow conductivity signal varied dramatically with irradiation position of the laser beam between electrodes; there is a pronounced peak when irradiated at the middle of the two electrodes and there are two peaks (or one peak and one shoulder) when irradiated between the two electrodes. These peaks were assigned to drift of cations and anions, and their mobilities were almost identical.View full abstractDownload PDF (471K) -
Machinability of Metals with Pulsed YAG LaserTakehiro WATANABE, Yoshitaro YOSHIDA, Chikara SHIMO1987 Volume 15 Issue 12 Pages 1073-1084
Published: December 28, 1987
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSIn order to establish the mechanism of laser machining, machinability of various metals with different thermal properties was investigated. Metal plates were irradiated with one shot of the YAG laser pulses, and melting and removing processes were examined by observing machined shapes. The obtained results are as follows. (1) There exist four regions of the irradiation power density, where (a) only the melt zone is formed, (b) both the melt zone and removed zone are formed, (c) only the removed zone is formed, and (d) a laser plume is generated. (2) At a fixed power density the machined depth increases with increasing irradiation time, but is saturated at the depth that depends on the power density. (3) The machining processes in various metals, in spite of the wide variation of thermal properties, can be analyzed with the same machining mechanism. (4) Machinability indexes which give the easiness of machining with the pulsed YAG laser were determined for several materials. (5) Movement of the heat source point in the metal plate was estimated from the relation between the power density and the melt diameter.View full abstractDownload PDF (1162K)
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