Yb-doped laser ceramics and the laser oscillations

Kazunori Takaichi 2Hideki Yagi 1,2Masaki Tokurakawa 2Akira Shirakawa 2Ken-ichi Ueda 2Shunsuke Hosokawa 1Takagimi Yanagitani 1Alexander A. Kaminskii 3

1. Takuma works Konoshima Chemical co. Ltd., 80 koda takuma-cho mitoyo-gun, Kagawa 769-1103, Japan
2. Institute for Laser Science, University of Electro-Communications, 1-5-1 chofugaoka Chofu, Tokyo 182-8585, Japan
3. Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federation

Abstract

Ytterbium-doped materials are very attractive for laser-diode- (LD-) pumped solid-state lasers. The Yb-doped materials have high quantum efficiency, no concentration quenching, and long lifetime. The broad absorption band in the near-IR region is suitable for pumping with a LD, and the broad emission band is able to generate tunable laser oscillations and ultrashort pulses. So far, many Yb-doped laser materials have been researched and are used for high power lasers and ultrafarst lasers.

Since 1998, it has been possible to fabricate highly transparent ceramics for solid-state lasers by a vacuum sintering technique and nanocrystalline technology. Our fabrication method is fundamentally different from any press methods, for example the cold isotropic press method and hot isotropic press methods, because no pressure is applied through the whole fabrication process. As a result, our ceramics have good homogeneity in terms of grain size and less internal strain. Additionally, this method is suitable for the fabrication of large sized products and production in large numbers.

We have been developing highly transparent Yb-doped Y3Al5O12 and RE2O3 (RE = Y, Sc, and Lu) ceramics for solid-state lasers. From spectroscopic point of view, there is no difference between an Yb:Y3Al5O12 single crystal and the ceramics. For a RE2O3, the ceramics also has same spectroscopic properties as the single crystals.

The LD-pumped Yb:Y3Al5O12 and Yb:RE2O3 ceramic lasers have been demonstrated. For an Yb:Y3Al5O12, a 940-nm LD was used for the excitation. In the cw Yb:RE2O3 lasers, they were pumped at the zero-phonon line (ZPL) of around 976-nm wavelength. ZPL pumping has a few advantages: larger absorption cross section, lower quantum defect. In a ZPL-pumped cw Yb:Y2O3 laser, the extraction efficiency of 72 % was obtained at 1078 nm. An LD-pumped cw mode-locked ceramic laser oscillation was carried out. The pulse duration of 430 fs was obtained.

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Presentation: invited oral at E-MRS Fall Meeting 2005, Laser Ceramic Symposium, by Kazunori Takaichi
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-20 09:37
Revised:   2009-06-07 00:44
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