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Float zone growth and spectral properties of Cr,Nd:YVO4 single crystals for potential use in solar-pumped solid state lasers

Mikio Higuchi 1Kazuki Kiyohara 1Sho Namiki 2Takayo Ogawa 2Satoshi Wada 2

1. Hokkaido University, Sapporo 060-8628, Japan
2. RIKEN, Wako 351-0198, Japan


Solar-pumped solid state lasers are one of the promising systems to utilize the solar energy. In previous studies, Cr,Nd:YAG has been used as a gain medium; however, its spectral properties are not sufficient for efficient energy conversion. Nd:YVO4 is known as an excellent gain medium for Nd-lasers because of excellent optical properties. In this study, we grew Cr,Nd:YVO4 single crystals by the floating zone method and investigated their spectral properties.

A ceramic feed rod was prepared with a composition of Y1-x-yCrxNdyVO4 where x=0.005-0.02 and Y=0.25-2. Single crystals were grown under conditions of growth rate: 10-20 mm/h, seed orientation: [110], atmosphere: air or O2/N2 mixed gas.

When the growth rate was 20 mm/h, the grown crystals showed green gradation parallel to the growth direction. Little gradation was observed for the crystal grown at 10 mm/h, but the green color was not so deep. These results imply that segregation and evaporation of Cr-component simultaneously occur during crystal growth. The most effective way to obtain a crystal with homogeneous Cr-concentration was to prolong the growth length more than 40 mm.

Cr,Nd:YVO4 showed strong absorption in the wavelength region of 350-500 nm. Although the peak wavelength of 400 nm does not correspond to the solar radiation peak, the absorption coefficient of Cr,Nd:YVO4 is significantly large in despite of relatively low Cr-concentration of less than 1 at%. The absorption cross section of Cr,Nd:YVO4 at 430 nm, where Cr,Nd:YAG has the maximum absorption is about 33ยด10-20 cm2, which is 4.7 times as large as that of Cr,Nd:YAG. By pumping at 400 nm, Cr,Nd:YVO4 showed strong fluorescence band around 900 nm and 1060 nm by Nd3+. No fluorescence band of Cr3+ was observed in the visible region, which implies that most of the energy absorbed by Cr3+ is effectively transferred to Nd3+. These results demonstrate that Cr,Nd:YVO4 single crystals are one of the promising materials for solar-pumped solid state laser systems.


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Related papers

Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Mikio Higuchi
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-29 04:09
Revised:   2013-05-14 04:34