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Volume 33, Issue 4
Displaying 1-9 of 9 articles from this issue
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Kunihiko WASHIO2005 Volume 33 Issue 4 Pages 218
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSDownload PDF (180K) -
Adolf GIESEN, Friedrich DAUSINGER2005 Volume 33 Issue 4 Pages 219-222
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSThe results for cw- and q-switched operation as well as for amplification of short (ns) and ultra-short (ps, fs) pulses demonstrate the potential of the thin disk laser design. The scaling laws for this laser design show that the power limit for cw-operation is far beyond 10 kW for one single disk and the energy limit is higher than 1 J from one disk in pulsed operation. First results for laser materials processing demonstrate the potential of the thin disk laser design. Finally, a short overview of the industrial realization of the thin disk laser technology will be given.View full abstractDownload PDF (948K) -
Syuhei YAMAMOTO, Takayuki YANAGISAWA, Yoshihito HIRANO2005 Volume 33 Issue 4 Pages 223-227
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSThin disk geometry for laser active medium has advantages for high-average-power operation with good beam quality. However it is difficult to obtain high pumping efficiency due to the small thickness of the crystal. To improve the pumping efficiency, we have developed a side-pumped Yb: YAG/YAG composite disk laser with a stacked-LD tight-focusing technique. The maximum output power was 235-W from one disk with the optical efficiency of 0.38.View full abstractDownload PDF (3711K) -
Takunori TAIRA, Masaki TSUNEKANE, Traian DASCALU2005 Volume 33 Issue 4 Pages 228-235
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSWe present a simple concept for high-power microchip lasers by employing edge-pumped scheme for Yb: YAG core and YAG clad composite structure. Continuous-wave (CW) output power was up to 90 W from a 400-μmthick diffusion bonded Yb: YAG/YAG structure with a 10 at.% Yb: YAG square core of 2×2 mm2; the slope efficiency and optical-to-optical efficiency with respect to the pump power were 40% and 28%, respectively. Measurements of the optical phase distortions induced by pumping gives a focus shift bellow 0.05 m and shows the absence of astigmatic effects, indicating the axial heat flow in this pumping configuration. The newly developed microchip has circular, Yb: YAG single crystal core with 5mm-diameter, surrounded by transparent, undoped YAG ceramic pump wave-guide. Near 900 W pump light from fourfold stack with 6 diodes directly coupled to the edge windows of the ceramic wave-guide with 300μm-thickness. Output powers of 380 W (peak) was reached in quasi-continuous-wave (QCW)(10ms, 10Hz) operation. lmproved slope efficiencies and optical conversion were 50% and 44%, respectively.View full abstractDownload PDF (6992K) -
Sakae KAWATO, Keiichi SUEDA, Takao KOBAYASHI2005 Volume 33 Issue 4 Pages 236-242
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSEnd-pumped micro-thicknness slab laser architectures, named as thin-rod and thin-slab, are proposed for highpower and efficient pulse amplification of quasi-four-level lasers. Advantages of the architectures exist in its high gain and efficient energy storage characteristics. It also exhibits high cooling efficiency by large cooling area with small slab volume. Thin-rod laser architecture has been investigated for average output power of several tens W and thin-slab laser architecture has been investigated for average output power above hundreds W. From free running operation of the thin-rod regenerative amplifier, average output power of 18 W was obtained at pulse repetition rate of 100 kHz. A high-average-power and high-efficiency thin-slab Yb: YAG laser has been developed with cw output power of 257 W, slope effieciency of 59% and optical conversion efficiency of 49%.View full abstractDownload PDF (4284K) -
Junji KAWANAKA2005 Volume 33 Issue 4 Pages 243-248
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSLaser characteristics of diode-pumped Yb-doped materials have been improved at low temperature dramatically for high power operation. A laser system in the materials has been changed from quasi-three-level to four-level at low temperature. An emission cross section is enlarged and the reduced saturation fluence enables efficient energy extraction of the storage energy even by using commercially obtainable optics. In addition, thermal conductivity of laser crystals is considerably improved. In a diode-pumped laser oscillator with a cryogenically cooled Yb: YAG crystal, quantum-defect-limited operation has been demonstrated at 90 % optical slope efficiency. A Yb: YLF chirped-pulse regenerative amplifier has been developed at low temperature and 36-mJ, 800-fs pulses have been obtained at 20 Hz.View full abstractDownload PDF (1102K) -
Isamu MIYAMOTO2005 Volume 33 Issue 4 Pages 249-253
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSSingle-mode fiber lasers have many advantages over conventional solid-state lasers, which include high beam quality, no need for cooling, high conversion efficiency, compactness, long life time and so on, attracting attention as an industrial tool for materials processing due to rapid increase in the output power. Present article overviews recent status of the applications of high-power single-mode fiber laser to laser materials processing including microwelding and micromachining.View full abstractDownload PDF (12716K) -
Akira SHIRAKAWA, Ken-ichi UEDA2005 Volume 33 Issue 4 Pages 254-261
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSThe recent progress of high-power fiber lasers is remarkable. Advantages of a fiber laser in characteristics such as efficient cooling property, high-damage threshold, ultra-low loss, and waveguide structure enable the outstanding high-power operation with excellent beam quality. In this paper, the advances of fiber lasers are reviewed. The power limitation of Yb-doped double-clad fiber laser is discussed, which clarifies the importance of scaling the fiber mode-field diameter and the launching capability of pump power for higher power operation. Key techniques of side-pumping geometry and photonic-crystal fibers are discussed. For further power and brightness scaling, the research on beam combining of many fiber lasers is also getting activated and briefly introduced.View full abstractDownload PDF (7946K) -
Akira SUMITANI, Takanobu ISHIHARA, Kiichiro UCHINO2005 Volume 33 Issue 4 Pages 262-266
Published: April 15, 2005
Released on J-STAGE: March 26, 2014
JOURNAL FREE ACCESSThe effect of small amounts of gaseous additives and impurities on ArF laser performance has been studied. It has been found that the output characteristics of the ArF laser improves significantly at a xenon concentration of 10 ppm but strongly deteriorates at impurity concentrations above 10 ppm of e.g. O2, CF4 and HF, especially, at high laser repetition rates. A new laser discharge chamber has therefore been developed using metal seals and coating the inner chamber walls with thin fluoride layers. The layers prevent impurities that are otherwise generated through chemical reactions between the fluorine of the laser gas and the chamber wall. The output stability of the ArF excimer laser has been very successfully improved by the new chamber design for repetition rates up to 4 kHz.View full abstractDownload PDF (837K)
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