Optical and structural micro-engineering of planar waveguiding films using multi-beam pulsed laser deposition

May-Smith, T.C., Sloyan, K.A. and Eason, R.W. (2011) Optical and structural micro-engineering of planar waveguiding films using multi-beam pulsed laser deposition. 11th International Conference on Laser Ablation, , Playa del Carmen, Mexico. 13 - 19 Nov 2011.

Abstract

A fundamental limitation of materials science is the availability of different materials with contrasting functional properties, and the compatibility of different combinations due to various mismatches between structural properties. In the field of planar waveguide fabrication, this limitation can be overcome by the growth of hybrid crystals with mixed compositions. Further to this, advanced optical structures may be fabricated by grading the crystal composition with depth. With such an approach, it is possible to produce custom refractive index profiles, variable dopant concentration with depth, and buffer layers for applications such as cladding-pumped structures and gain-selective devices. Also it will be possible to tailor structural properties such as lattice/thermal expansion, while providing further benefits such as particulate burial and stress engineering.
Multi-beam pulsed laser deposition (PLD) is an ideal technique for the fabrication of these advanced materials and structures. Mixing and grading can simply be achieved by varying the relative repetition rates of lasers ablating different targets. Film composition can be varied in-situ by changing the deposition parameters to adjust stoichiometric transfer. Intrinsic stress engineering can be achieved by using laser fluence as an ion energy parameter. The high quality growth of garnet crystal has been well established and several different structure designs have been fabricated while the required experimental techniques and devices to automate the process were developed, including multilayers, mixed layers and superlattices, using the different garnet compositions available. Current work is now focussed on the fabrication of mixed and graded layers in particular for buffer layers and enhanced device functionality.
We will present a review of our results to date with multi-beam PLD, including important new parameters and techniques required. We will also report on the relative merits of different mixed materials and graded layer designs such as stepped, linear, Gaussian and superlattice (fixed, tapered and cross-tapered period).

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Contributors

Author: R.W. Eason

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