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Volume 25, Issue 7
Displaying 1-11 of 11 articles from this issue
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Mitsuo MAEDA1997 Volume 25 Issue 7 Pages 491
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
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Tsunemasa AGUCHI1997 Volume 25 Issue 7 Pages 492
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
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Yoichi YAMADA1997 Volume 25 Issue 7 Pages 493-497
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSExciton-related mechanisms of optical gain formation in wide-band-gap semiconductors are reviewed. In particular, typical two models are focused. One is based on the concept of exciton localization, and the other is based on the radiative decay process of biexcitons. In addition, biexciton formation and its contribution to the formation of optical gain in ZnS-based quantum-well structures are discussed on the basis of our recent experimental results.View full abstractDownload PDF (996K) -
Shuji NAKAMURA1997 Volume 25 Issue 7 Pages 498-503
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSHigh-power InGaN single-quantum-well (SQW) structure blue/green light-emitting diodes (LEDs) with an output power of 3-5mW were fabricated. The continuous-wave operation of bluish-purple InGaN multi-quantum-well (MQW) -structure laser diodes (LDs) was achieved at room temperature with a lifetime of 35 hours. The threshold current and the voltage of the LD were 80mA and 5V, respectively. Photocurrent spectra of the InGaN SQW LEDs and MQW LDs were measured at room temperature. The energy difference between the absorption due to the excitons at n = 1 quantized energy levels and the emission energy of the blue/ green InGaN SQW LEDs and MQW LDs were 290, 570 and 190meV. Both spontaneous and stimulated emission of the LDs originated from this deep localized energy state which is equivalent to a quantum dot-like state. When the temperature or the operating current of the LDs was varied, large mode hopping of the emission wavelength was observed.View full abstractDownload PDF (904K) -
Norikazu NAKAYAMA, Akira ISHIBASHI, Naoya EGUCHI1997 Volume 25 Issue 7 Pages 504-509
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSRecent progress and future prospects of ZnSe-based II-VI laser diodes are described. Continuous wave (CW) operation at room temperature has been reported in the emission wavelength of 485-540nm. Lasers operating in the 500-530nm range have exhibited good performance, such as a 6.9mA threshold current, a 3.3V threshold voltage, a 87mW light output power in CW operation. Moreover, the highest CW operating temperature of 80°C at 10mW, and 60°C at 30mW has been reported. A device lifetime exceeding 100h was achieved under a lmW constant output condition at room temperature. Recently, we have demonstrated the readout of high-density optical disks with a 7.7GB capacity using a 515-nm ZnSe-based laser.View full abstractDownload PDF (1260K) -
Hiromitsu SAKAI, Tetsuya TAKEUCHI, Hiroshi AMANO, Isamu AKASAKI1997 Volume 25 Issue 7 Pages 510-513
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSMechanism of stimulated emission from binary GaN films have been elucidated. Structural properties of ternary GaInN single layer and GaInN/GaN multiple quantum well have been characterized using high-resolution x-ray diffraction in detail. It was found that the intrinsic piezoelectric field affects seriously on the stimulated emission properties of GaInN-based MQWs.View full abstractDownload PDF (652K) -
Toshiya YOKOGAWA1997 Volume 25 Issue 7 Pages 514-519
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSBlue vertical-cavity surface-emitting lasers (VCSELs) have experienced much progress recently. An electrically pumped ZnSe-based blue VCSEL with a SiO2/TiO2 dielectric multilayer mirror has been demonstrated. Electrically pumped lasing was achieved at 77K with a threshold current of 3mA. A low far-field radiation angle of 7°was observed above the threshold in a 10μm-diameter device, which indicates the spatial coherence expected for lasing.View full abstractDownload PDF (1030K) -
Yoshinobu MAEDA, Takao SAKAKIBARA, Masatoshi MIGITAKA1997 Volume 25 Issue 7 Pages 520-524
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe dependence of the negative nonlinear absorption effect on modulation degree of an incident laser was investigated in an erbium doped yttrium aluminum garnet crystal which has a five-level system: absorption can occur between a ground level and an excited level (4I15/2-4I9/2) and between two other excited levels (4I13/2-2H11/2) in Er3+. According as modulation degrees of the incident laser decreased, the transmitted laser waveform was inverted against the incident one for incident modulation degree under 90% and sample lengths greater than 2mm. By calculating rate equations based on an analytical model for the five-level system, it was confirmed that the enhanced absorption was caused by stimulated emission from 4S3/2 level to 4I13/2 level and close agreement between observed and calculated values was obtained in the relation between transmitted modulation degree and incident one.View full abstractDownload PDF (918K) -
Tomoyuki UCHIMURA, Tsunehisa SATAKE, Mitsuo NAKAJIMA, Kazuhiko HORIOKA1997 Volume 25 Issue 7 Pages 525-528
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSOptical quality of a free-vortex type aerodynamic laser window was directly measured with a Michelson Interferometer. Although it was spatially and/or temporally degraded by the fluid-dynamical effects, the temporal fluctuation level was 4kHz at worst. The transversely averaged density and the turbulence of the jet were gradually increased along the flow direction. By heating the working gas up to 450K, the density gradient was moderated down to 2/3.View full abstractDownload PDF (1029K) -
Jing CHEN, Masahiro UEDA, Keiji TANIGUCHI, Katsuhiko ASADA1997 Volume 25 Issue 7 Pages 529-530
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSAn optical sensor system has been proposed for measuring the degree of parched coffee berry. The principle of the method is based on a scattering intensity of the light on parched coffee berry. The system consists of a sensor head including light source and light receiver, an amplifier, an A/D converter, a computer and a display. The results show that the optimum degree of coffee berry can be obtained when the scattering intensity is about 83% of the maximum intensity and that the scattering intensity depends only on the degree of parched coffee berry and does not depend on the wavelength of the light source.View full abstractDownload PDF (262K) -
Koichi SHIMODA1997 Volume 25 Issue 7 Pages 531-535
Published: July 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (812K)
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