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Proceedings Paper

Czochralski growth of Ti:sapphire laser crystals
Author(s): Reinhard Uecker; Detlef Klimm; Steffen Ganschow; Peter Reiche; Rainer Bertram; Mathias Roßberg; Roberto Fornari
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Paper Abstract

The laser efficiency of Ti3+:Al2O3 (Ti:Sapphire) is affected by residual absorption in the infrared region (800 nm) of the laser emission caused by Ti3+-Ti4+ pairs. Consequently, the ratio of the absorption coefficients at pump wavelength and at maximum of residual absorption forms the most important figure of merit (FoM) of Ti:Sapphire laser crystals. In general, to achieve sufficient FoM commercial Ti:Sapphire crystals are subject to a post-growth annealing under strongly reducing atmosphere to shift the balance between Ti3+ and Ti4+ ions in favour of the former ion. However, due to the low diffusion velocities under these conditions, this process is very time-consuming, especially for larger crystals. To save this step the crystal growth process of Ti:Sapphire was performed in a special gas mixture to stabilize the Ti3+ ions during the growth. The stability range of Ti3+ at growth temperature was estimated on the basis of thermodynamic equilibrium calculations. Ti3+ ions exist at about 2050°C only in very small "window" regarding the oxygen partial pressure. This "window" remains very small during cooling too. To meet these conditions, i.e. to create the optimum growth atmosphere the oxygen partial pressure of different gas mixtures was calculated. That way a gas mixture was found which allowed the growth of Ti:Sapphire crystals with diameter up to 55 mm and a FoM > 100 without subsequent annealing. Under these conditions the formation of aluminium suboxides and therewith of oxygen which can be trapped in the crystal as gaseous inclusions was suppressed efficiently.

Paper Details

Date Published: 15 October 2005
PDF: 9 pages
Proc. SPIE 5990, Optically Based Materials and Optically Based Biological and Chemical Sensing for Defence II, 599006 (15 October 2005); doi: 10.1117/12.634322
Show Author Affiliations
Reinhard Uecker, Institute for Crystal Growth (Germany)
Detlef Klimm, Institute for Crystal Growth (Germany)
Steffen Ganschow, Institute for Crystal Growth (Germany)
Peter Reiche, Institute for Crystal Growth (Germany)
Rainer Bertram, Institute for Crystal Growth (Germany)
Mathias Roßberg, Institute for Crystal Growth (Germany)
Roberto Fornari, Institute for Crystal Growth (Germany)

Published in SPIE Proceedings Vol. 5990:
Optically Based Materials and Optically Based Biological and Chemical Sensing for Defence II
Anthony W. Vere; James G. Grote; Francois Kajzar; John C. Carrano; Arturas Zukauskas, Editor(s)

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