A possible route to minimisation of strain in thick garnet films grown by pulsed laser deposition for optical waveguide applications

May-Smith, T.C., Sloyan, K.A., Gazia, R. and Eason, R.W. (2009) A possible route to minimisation of strain in thick garnet films grown by pulsed laser deposition for optical waveguide applications. E-MRS 2009 Spring Meeting, , Strasbourg, France. 08 - 12 Jun 2009.

Abstract

Pulsed laser deposition (PLD) of Gd₃Ga₅O₁₂ (GGG) with high crystalline and optical quality has recently been achieved by several research groups. However, the potential of such films (when doped with a laser ion) for device applications such as high-power planar waveguide lasers is still to be realised. Deposition parameters have been optimised in terms of crystalline and optical quality, but, in our experience, the large amount of residual strain in GGG films grown on Y₃Al₅O₁₂ (YAG) substrates can lead to problems (delamination, cracking etc) during edge-polishing for film thicknesses >40 µm.
Films deposited during optimisation runs have been analysed and the effects of deposition parameters on composition and lattice size have been determined. In particular, the results showed that growth at different substrate temperatures can lead to films with the same nominal composition but varying lattice size. Differential thermal expansion between the film and substrate is expected to produce this effect with a trend of increased change in lattice for higher temperatures due to increased residual strain. Lattice values, however, were not found to increase continuously with increasing substrate temperature. This suggests that temperature optimisation may result in reduced thermal expansion mismatch and hence less residual strain. We will discuss optimised deposition parameters for three different PLD systems and report on efforts to obtain strain-free thick films of GGG on YAG.

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Contributors

Author: R.W. Eason

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