We present a novel variation of the pulsed laser deposition (PLD) technique, aimed at reducing the number of particulates produced and consequently the linear propagation loss observed in the resulting crystal waveguides. The approach relies upon configuring the system to effectively provide bi-directional ablation, whereby the incidence angle of the fixed pulsed laser beam with respect to the target surface changes sign, depending upon the rotation angle and position of the target. Such an alternating ablation direction is intended to reduce the buildup of undesirable periodic surface structures, such as directional cones, believed to be a major source of particulates within the growing film while keeping the plume stationary with respect to the substrate. We show that targets ablated using this technique have fewer directional structures and a decreased surface roughness. Furthermore, using PLD-grown Y 3 Ga 5 O 12 as the exemplar crystal film, we compare growths with uni-and bi-directional ablation and demonstrate reduction from ~ 0.9 to ~ 0.23 dB/cm in the average waveguide propagation losses via the latter.

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This paper reports a study of the effect of laser pulse repetition rate and substrate temperature on the properties of crystalline Sc2O3 films grown on <0001>-oriented sapphire via pulsed laser deposition (PLD). For the range of substrate laser-heating powers investigated, optimum <111>-film growth was obtained at the highest available repetition rate of 100 Hz. Scanning electron microscopy and X-ray diffraction measurements revealed that a decrease in the repetition rate favours highly textured/island growth. The repetition rate was also proven to affect the lattice constant of the films, with a difference up to 0.3% between the films grown at high and low repetition rates. The general trend indicates that the out-of-plane lattice constant of the film shifts closer to the bulk value when the pulse repetition rate is increased. However, the lattice constant could also be reduced through in-situ post-growth annealing, which had the additional benefit of reducing the width of the (222) rocking curve peak. This work provides further evidence that energetic-PLD dynamics leads to higher quality PLD-grown crystalline films and for this material undermines the old adage that lower pulse repetition rates lead to higher quality thin-film crystalline growth.

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