Horizontally structured garnet growth via pulsed laser deposition for hybrid crystal thin disc applications

Sloyan, K.A., May-Smith, T.C. and Eason, R.W. (2011) Horizontally structured garnet growth via pulsed laser deposition for hybrid crystal thin disc applications. 11th International Conference on Laser Ablation, , Playa del Carmen, Mexico. 13 - 19 Nov 2011.

Abstract

Thin disc lasers are capable of kilowatt output whilst maintaining high beam quality. A number of recent reports replace the traditional multi-pass quasi-end pumping scheme with the much simpler side pumping. Efficient performance under the latter scheme requires the use of composite crystals or ceramics, including those where dopant is confined to the centre of the disc. Successful growth of appropriate materials (e.g. Yb:YAG) via Pulsed Laser Deposition (PLD) has been demonstrated, and various approaches are being investigated to overcome excessive strain in thick films. With high growth rates and simple setup, PLD would therefore seem an ideal method for growing crystals for thin disc applications, if an appropriate film confinement method can be found. Nanoscale patterning of PLD-grown films using membrane masks has been demonstrated previously by other groups. A different approach is needed, however, to create the much larger structures required for centrally-doped composite thin disc crystals.
We report the growth of ~millimetres diameter, ~microns thickness crystalline garnet circles on 10 mm square Y₃Al₅O₁₂ substrates using two methods of lateral film confinement. The first method consists of growth through a 25 µm thick laser-machined silicon mask applied to the substrate surface. The second uses a metal cone to funnel the ablation plume to an area in the centre of the substrate. The relative merits of each method will be discussed, as well as some of the pitfalls to be wary of, particularly mask/cone-substrate contact and its effect on circle edge slope.
Work is also currently ongoing to combine the cone growth technique with dual beam, dual target deposition. Doped material will be deposited through a cone at the same time as undoped material, to create a single hybrid crystal with a graded interface between the doped and undoped regions. The results of these investigations will also be presented.

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Contributors

Author: R.W. Eason

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