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Volume 21, Issue 12
Displaying 1-8 of 8 articles from this issue
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Kazuo HOTATE1993 Volume 21 Issue 12 Pages 1225
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSDownload PDF (147K) -
Yoshiaki AKIMOTO1993 Volume 21 Issue 12 Pages 1226-1233
Published: December 29, 1993
Released on J-STAGE: August 04, 2010
JOURNAL FREE ACCESSFive frequency stabilized laser types were recommended as the optical frequency / wavelength standards for the practical realization of the meter which was redefined in 1983. Since 1983, work in national laboratories, Bureau International des Poids et Mesures and elsewhere has substantially improved the reproducibility of the radiations which are suitable for the practical realization of the meter. In addition, science and technology demand improved accuracy in the realization of the meter. In the present situation, Comite International des Poids et Mesures should be replaced by the new list of recommended radiations in this September. This article has reviewed frequencies and wavelengths of the list for a new recommendation which was discussed in a working group of Comite Consultatif pour la Definition du Metre in 1992. A research trend of frequency stabilization for semiconductor lasers and solid state lasers is also covered. Furthermore frequency stability, accuracy and reproducibility of the stabilized lasers required as the optical frequency / wavelength standards are described. In particular, spectral broadening due to pressure, power and transit time, and residual broadening are discussed in detail, using an example, the saturated absorption spectrum of methane at 3.39 μm.View full abstractDownload PDF (882K) -
B. PENG, Teturo IZUMITANI1993 Volume 21 Issue 12 Pages 1234-1244
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSThe stable borosilico-phosphate new base glass which has good chemical durability, low ex-pansion coefficient, low nonlinear refraction index and can dope high concentration of dopant has been developed. Yb3+-Er3+ codoped borosilico-phosphate glass probably is candidates for economical nuclear fusion system pumping by diode laser because it can satisfy the require-ments of K. Naito (Osaka Univ.) for economical nuclear fusion system which are (a) a thermal shock parameter large than 3 W/cm, (b) saturation parameter of -10 J/cm2, (c) fluorescence lifetime longer than 4 ms, (d) a nonlinear refraction index small than 3 × 10-13 esu. The strong fluorescence intensity in Yb3+-Er3+ codoped borosilico-phosphate glass at 1.54 μm also can be used for eye safe range finder laser. The Yb3+ doped special phosphate glass which has a high concentration of modifier was developed. It also may be used for economical nuclear fu-sion system since it has some advantages below: a) the lifetimes are almost 5 times longer than Nd3+ doped phosphate glass (LHG8) which is using for nuclear fusion system, b) the emission intensities are stronger than LHG8, c) the emission wavelength are close that of LHG8. The energy transfer and energy backtransfer in Yb3+-Er3+ and Yb3+-Nd3+ systems were in-vestigated.View full abstractDownload PDF (1107K) -
Kazuhiro WATANABE1993 Volume 21 Issue 12 Pages 1245-1254
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSThe performance characteristics of a 100MHz-RF-excited slab CO2 laser are shown in terms of resonator setup conditions and discharge gap spacings. On varying the gap spacings from 2.25 down to 1.5mm, the optimum gas pressure shifted in such a way that the product of pressure and gap spacing remains constant in our experimental conditions. The optimum gas pressure for each gap spacing increased with RF input power. A laser output power of 210W was obtained with a corresponding conversion efficiency of 10.5 % and with a near-diffraction limited beam quality showing beam divergence angles of 5.1 and 1.7 mrad for stable and unstable directions, respectively. The experimental results obtained are discussed in details from the viewpoints of the E/P (electric field/pressure) value, sheath width in discharge plasma, and average gas temperature of the RF discharge region.View full abstractDownload PDF (1141K) -
Toshifumi HASAMA1993 Volume 21 Issue 12 Pages 1255-1265
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSA terawatt XeCl laser system, which consists of a subpicosecond dye oscillator-amplifier system, a small-aperture XeCl preamplifier, and a large-aperture final amplifier with a gain cross-section of 10cm×10cm, is described. The characteristics of optical pulses are given at each stage of the XeCl laser system, based on autocorrelation, spectrum, and energy mesurements. An energy output of 340mJ in a beam cross-section of 7cm×10cm is obtained by double-pass amplification of a 310fs pulse in the final amplifier. The system withouta preamplifier leads to a terawatt-class subpicosecond pulse with a high contrast ratio of > 100 : 1 relative to ASE background and an output energy of 195mJ.View full abstractDownload PDF (1318K) -
Masahiro UEDA, Kazuhiko ISHIKAWA, Chen JIE, Sanae MIZUNO, Mitsuru TSUK ...1993 Volume 21 Issue 12 Pages 1266-1272
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSAn optical method for a thickness measurement of a polyethylene foam sheet has been developed based on the light theory. The accuracy of the method depends mainlyon the heterogeneous light transmissivity through the foam sheet due to its internal cell structureand a displacement of the foam sheet along the optical path caused by the movement of the sheet which is common condition in its production in industries. A 40 times averaging smooth out the fluctuation of the transmitted light power within ±4% and then the error rate of the thickness measurement within 2% for the thickness of 2mm. The error rate due to the displace-ment has been found approximately same as the averaging method by means of a proper optical arrangement, and then the total error of this method within 4%.View full abstractDownload PDF (821K) -
Toshiyuki UENO, Nobuo TAKEUCHI, Hisashi YOSHIDA, Hideo YAMADA, Akio TA ...1993 Volume 21 Issue 12 Pages 1273-1278
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSAuthors have already reported on the principle of the random modulation CW (RM-CW) lidar, where a CW laser light is modulated by a pseudo-random M-sequence code and the received light signal from a measuring object is demodulated by the M-sequence. We have also designed and constructed a real time signal processor whose spatial resolution (9m) was limited by the clock period of the M-sequence generator. This paper discusses a method to improve the spatial resolution by introducing a time delay between a light modulating clock and a data sampling clock. The result of an experiment with 1 meter spatial resolution is shown.View full abstractDownload PDF (606K) -
1993 Volume 21 Issue 12 Pages 1282-1283
Published: December 29, 1993
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSDownload PDF (316K)
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