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Volume 25, Issue 1
Displaying 1-19 of 19 articles from this issue
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Norikazu TABATA1997 Volume 25 Issue 1 Pages 1
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (195K) -
Akira FUJISAWA1997 Volume 25 Issue 1 Pages 2
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (133K) -
Hideaki SAITO, Minoru DOSHIDA1997 Volume 25 Issue 1 Pages 3-8
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSAn eyesafe laser is a key component for evolving its application in the field such as a laser range finder and a laser radar. This paper describes the meaning of the eyesafe laser why it should be so important from the view of the eyesafety standard and its atmospheric transmission. This reviews also current interested lasers oscillating at 1.5 and 2 micron regions.View full abstractDownload PDF (1031K) -
Hong K. CHOI1997 Volume 25 Issue 1 Pages 9-14
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSConsiderable progress has been made in mid-IR semiconductor lasers in terms of maximum operating temperature and output power. Antimonide-based type-I quantum-well lasers have exhibited cw operation at 2.0 μm up to 400 K, at 2.7μm to 234 K, at 3.5μm to 175 K, and at 3.9 μm to 128 K. 4-μm lasers pumped by 1-μm diode laser arrays have yielded peak power of 2 W and average power of 240 mW at 92 K. Diode lasers utilizing type-II transitions have exhibited pulsed operation between 2.8 and 4.3 μm, with maximum operating temperature of 255 K at 3.2 μm. Type-II lasers pumped by a high-power Ho:YAG laser have operated pulsed up to 350 K at 3.2 μm and 285 K at 4.1 μm. Quantum cascade lasers emitting at - 5 μm or - 8 μm have operated pulsed up to 320 K and cw to 140 K.View full abstractDownload PDF (1053K) -
Masatoshi SARUWATARI1997 Volume 25 Issue 1 Pages 15-18
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSTechnical Committee No. 76 in the IEC (International Electrotechnical Commission) maintains the international laser safety standard of IEC pub.825, and has amended the standard twice to reflect the recent development in laser related technologies. Main changes include a hazard level increase in the infrared wavelength region, inclusion of LED, and so on. In this review, I will introduce the concept of the laser safety standard including maximum permissible exposure (MPE), laser safety classification, and show the increased classification levels in the infrared region.View full abstractDownload PDF (671K) -
Sammy W. HENDERSON, Kei OTA1997 Volume 25 Issue 1 Pages 19-24
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe current status of coherent laser radar systems in our laboratories, using Thulium and Holmium doped solid-state lasers operating near 2 micron wavelength are reviewed. A 2-gm coherent lidar recently installed at the Japan Defense Agency (JDA) will be described and preliminary results of wind measurement data taken with the system are also presented.View full abstractDownload PDF (1298K) -
Akimasa TANAKA1997 Volume 25 Issue 1 Pages 25-28
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSRecently, the lasers operating at 2-5μm have been expected for applications of science, industry, medical science etc. because of “eyesafe”. This paper reviews the Midium Wavelength InfraRed (MWIR) detectors covering the wavelength range 1.0-6.0μm (λ < 1.4 m: “eyesafe” spectral region). Most recent efforts in the technology of MWIR detectors have been on higher operating temperature making more covenient to use. These detectors are discussed for three wavelength regions: 1.0-2.0, 2.0-3.0, and 3.0-6.0μm.View full abstractDownload PDF (813K) -
Yukio NODA1997 Volume 25 Issue 1 Pages 29-34
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSAs commercially available infrared fibers transmitting light with the wavelength of 1 to 3μm, the three possiblities of silica, fluoride and chalcogenide glass fibers can be selected. In this review, firstly, the features of these fibers are briefly summarized. As an application of the fibers, next, a fiber chemical sensing is described including the various examples and focusing an on-or in-line process monitoring system recently developed in industries.View full abstractDownload PDF (1049K) -
Minoru DOSHIDA1997 Volume 25 Issue 1 Pages 35-40
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSResearch and development on 2μm eyesafe fiber lasers have been reviewed. The excellent laser performance of the high slope efficiency, low launched threshold power, and widely tunable range has been demonstrated in the rare-earth doped 2μm fiber lasers at room temperature.View full abstractDownload PDF (1012K) -
Yoshiaki MIYAJIMA1997 Volume 25 Issue 1 Pages 41-44
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSRare earths doped fiber amplifiers have been investigated actively and are now used in many optical fiber transmission systems. It offers high gain, high efficiency, low noise, low insertion loss and polarization insensitive characteristics. This paper reviews the latest results on fiber amplifiers doped with erbium (Er), neodymium (Nd), praseodymium (Pr) and thurium (Tm) ions from the viewpoint of spectroscopic characteristics. Also reviewed are the improvement in minimum recieved power by using optical fiber amplifier as a pre-amplifier.View full abstractDownload PDF (669K) -
Atsushi SATO, Kan-ichi SOUSUMI, Kazuhiro ASAI, Toshikazu ITABE1997 Volume 25 Issue 1 Pages 45-49
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe have demonstrated normal mode and Q-switched operations of flashlamp pumped Cr, Tm (, Ho):YAG lasers. When operation in the normal mode, output energies of 2.3 J and a slope efficiency of 2 % have been achieved, and the thermal lensing has been observed in the laser rod at the high repetition rate. In addition, the TEM00 mode single Q-switched pulse with a pulse energy of 54 mJ and a pulse width of 206 ns was obtained by using a fused silica AO Q-switch as a mode selector. The comparison of Q-switched operations employing a LiNbO3 Pockels cell and the AO Q-switch is also described.View full abstractDownload PDF (819K) -
Hayato NAKAJIMA, Takanobu YAMAMOTO, Fumio MATSUZAKA, Hiroshi HARA, Mas ...1997 Volume 25 Issue 1 Pages 50-54
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSA compact and removable eye-safe laser radar system for atmospheric environmental monitoring has been developed. The height of the mixed layer equaled to the height where the scattering intensity by the laser radar drastically decreased. The measurement with the radiosonde showed that that mixed layer corresponded to the height where the potential temperature changed. A value of the atmospheric extinction coefficient, α, at 2.1 pm was calculated to be 0.05 km-1 with the humidity of 50 % and depended on the relative humidity. In addition, this paper also reports observation of smoke plume from a smokestack.View full abstractDownload PDF (949K) -
Keiji KOBAYASHI, Yasunori SAITO, Takuya D. KAWAHARA, Akio NOMURA1997 Volume 25 Issue 1 Pages 55-60
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSLidar measurements of stratospheric aerosol layers over Nagano-shi (36.7°N, 138.2°E) have been made for 38 months since the volcanic eruption of Mt. Pinatubo in the Philippines on June 15, 1991. At the initial stage until September, 1991, the non-uniform volcanic aerosol layer above 20 km was observed, which moved slowly toward to high latitudes in the easterly wind region. The integrated backscattering coefficient (IBC) reached the maximum value in December, 1991 and then decreased gradually with the decay time of 7.5 months although the re-increase was observed in November, 1992. The time variation of temperature deviation from the averaged value calculated from rawinsonde data at Wajima shows that stratospheric warming and tropospheric cooling happened in April to May, 1992 and 1993. The comparison of the surface temperature between four cities, Nagano, Matsumoto, Shizuoka and Niigata, during those tropospheric cooling periods demonstrates that inland cities were 0.6-1.0 deg. cooler than coast cities.View full abstractDownload PDF (1182K) -
Jun SAKUMA, Toshie ITOH, Akiko HARASAKI, Toshio SATOH, Masakatsu SUGII1997 Volume 25 Issue 1 Pages 61-66
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe have developed a TEA CO2 laser MOPA system designed to improve beam quality required for high power harmonic generation. The CO2 laser output of the master oscillator optimized to produce a short-spike and suppressed-tail was 4-pass amplified to generate a high peak power of the order of 10 MW under single-transverse-mode oscillation at a repetition rate of 60Hz. By using this laser as a pumping source and by using AgGaSe2 crystals as a frequency converter, the SHG output at 5.3μm with an average power of 3.90 W and the THG output at 3.53μm with that of 2.18 W were demonstrated; these powers are, to our knowledge, the highest ever reported.View full abstractDownload PDF (975K) -
Naoya MATSUOKA, Tomokazu TOKORO, Masayuki YASUDA, Taro UCHIYAMA1997 Volume 25 Issue 1 Pages 67-71
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSRecently a CO2 laser excited by microwave discharge has been studied to achieve higher efficiency and a lower cost laser system. In this study a stripline was used to guide microwave with TEM mode. This mode has almost homogeneous intensity distribution of electric field and almost homogeneous discharge could be obtained. In the experimental set-up, 2.45 GHz microwave power was fed to an antenna mounted in a rectangular waveguide. Microwave with TE10 mode was propagated through space in the waveguide, then transformed into TEM mode with the obliquely connected stripline. A laser tube (25 mm-bore) was inserted perpendicularly to the stripline. The gas mixture used in this work was He:Ne:CO2 = 81:15.6:3.4. The maximum output power of 56 W (9.5 % efficiency) and the maximum efficiency of 12.6 % (34.2 W output power) were obtained at 25 Torr gas pressure.View full abstractDownload PDF (747K) -
Kenichi OHASHI, Kazunari SHINBO, Keizo KATO, Futao KANEKO1997 Volume 25 Issue 1 Pages 72-76
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSTetracyanoquinodimethane (TCNQ) Langmuir-Blodgett (LB) films with and without adsorbed electronic donors of p-phenylenediamine (PD) and N, N, N', N'-tetramethyl-p-phenylenediamine (TMPD) were prepared. The structures of the LB films were investigated by attenuated total reflection (ATR) method using a visible laser. The thickness of the non-adsorbed TCNQ LB film obtained from the ATR results was larger than the molecular length of TCNQ. This is thought to be caused by the formation of the bi-monolayers. In contrast, the adsorbed TCNQ LB films had monolayer structures by adsorbing donors. The atomic force microscope (AFM) images showed that non-adsorbed TCNQ LB film had a rough and terraced surface. This is considered to be due to the formation of microcrystal-like domains which were not observed in the adsorbed TCNQ LB films.View full abstractDownload PDF (865K) -
Lalit B. SHARMA, Tiejun ZHANG, Hiroyuki DAIDO, Guan M. ZENG, Yoshiaki ...1997 Volume 25 Issue 1 Pages 77-81
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe describe a compact Nd:glass chirped pulse amplification laser system capable of producing laser pulses of 150mJ energy and - 1ps duration at 1.053 μm wavelength. This laser system has been used for the generation of subpicosecond pulses at 0.263μm by frequency doubling of the fundamental pulses in a Type-II KDP crystal using a predelay technique. At a laser intensity of approximately 50 GW/cm2, the frequency doubling of a 1.5 ps fundamental pulse with this scheme results in a pulse of 0.63 ps duration with an energy conversion efficiency of 40 %. Also, we have characterized experimentally the intense X-ray line emission, especially for the K-shell emission, produced by this laser system.View full abstractDownload PDF (793K) -
Mitsuo MAEDA, Takayuki TAKAO, Yuji OKI, Kaoru IGARASHI, Hideaki KUSAMA1997 Volume 25 Issue 1 Pages 82-87
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSIn order to develop a high-efficiency pulsed dye laser, laser efficiencies of various dyes were measured at three different pumping wavelengths of the Cu vapor laser (511 nm and 578 nm) and the frequency-doubled Nd:YAG laser (532 nm) in the same condition. A simulation model for Rhodamine 6G (R-6G) dye laser was also developed to analyze the effect of excitation wavelengths. Some Rhodamine dyes show higher efficiency than those of R-6G in simultaneous two-wavelength pumping by a Cu vapor laser. A dye mixture of Cresyl Violet 670 and Rhodamine 640 was as efficient as R-6G in the 653-660nm region.View full abstractDownload PDF (1044K) -
-Relationship between Material Removal Volume and Sound Pressure Level-Tsuneo KURITA, Tomohiko ONO, Noboru MORITA1997 Volume 25 Issue 1 Pages 88-93
Published: January 15, 1997
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSIt is well known that sound is generated when laser processing is carried out and its intensity changes according to the variations of processing conditions. The purpose of this research is to clarify experimentally the relationship between the material removal volume and the pressure level of processing sound. The main findings of this research are as follows. (1) At the case of laser drilling by a low frequency Q-switched YAG laser, the linear relationship can be obtained between the mean removal volume of ceramic material and the maximum sound pressure level around 14 kHz under the constant processing conditions of the laser power and the initial diameter of hole. (2) The relationship between the depth of groove which is processed by a high frequency Q-switched YAG laser and the value of sound pressure level can be represented by a linear equation when the initial width of groove is kept nearly constant.View full abstractDownload PDF (1169K)
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