Pulsed laser deposition of thin film magneto-optic materials and lasing waveguides

Abstract

The aim of this thesis was to study and improve the properties of optical materials deposited by the film growth technique called Pulsed Laser Deposition (PLD), a relatively fast, inexpensive and versatile deposition method using a laser to ablate a target and transfer material on top of a substrate. The materials of interest were titanium-doped sapphire (Ti:sapphire or Ti:Al2O3) for fabrication of compact, low-loss, high-efficiency and high-power waveguide lasers, which could be also operated in ultra-fast highrepetition-rate pulsed mode, and magneto-optic garnets, e.g. yttrium iron garnet (YIG, Y3Fe5O12), for fabrication of low-loss magneto-optic and microwave devices with high performance.

Deposition conditions were optimised for Ti:sapphire and YIG film growth and a multilaser multi-target PLD system (multi-PLD) was used to tune the composition of YIG film by co-ablation of two different targets (e.g. YIG and Y2O3 or Fe2O3 or Bi2O3 or CeO2). Ti:sapphire waveguides were fabricated and their optical performances (e.g. transmission losses and lasing characteristics) measured. A study of the effect of compositional variation on structural, optical and magnetic properties of magneto optic garnet films was carried out and it demonstrated the feasibility of the multi-PLD approach, which was shown to be capable to grow complex crystalline oxide materials, such as YIG and yttrium ferrite (YFeO3), from ablation of their precursor targets (Y2O3 or Fe2O3) with different ablation rates and deposition of material on different substrates and, in particular, yttrium aluminium garnet (YAG or Y3Al5O12) and sapphire (Al2O3). Some YIG films were also used to demonstrate Laser-Induced Forward Transfer (LIFT) of crystalline materials and the applicability of PLD-grown YIG films in novel meta-material microwave devices.

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ORCID for R.W. Eason: orcid.org/0000-0001-9704-2204

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