Dodd Walls Center for Quantum and Photonic Technologies

Dodd, New Zealand

Dodd Walls Center for Quantum and Photonic Technologies

Dodd, New Zealand

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Oosterbeek R.N.,University of Auckland | Oosterbeek R.N.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Oosterbeek R.N.,Dodd Walls Center for Quantum and Photonic Technologies | Ward T.,University of Auckland | And 13 more authors.
Optics and Lasers in Engineering | Year: 2016

Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users. © 2016, Elsevier Ltd. All rights reserved.


Hughes-Currie R.B.,University of Canterbury | Ivanovskikh K.V.,ANK Service Ltd. | Ivanovskikh K.V.,Ural Federal University | Reid M.F.,University of Canterbury | And 6 more authors.
Journal of Luminescence | Year: 2015

Results of a vacuum ultraviolet spectroscopic characterization of NaMgF3:Yb2+ are presented. The material demonstrates emission features associated with self-trapped excitons and impurity-trapped excitons. The emission features noticeably overlap giving rise to a broad emission band from 17000 to 35000cm-1 at a sample temperature of 8K. To identify the true profiles of the emission features we have used a deconvolution procedure. The deconvolution was possible due to the thermal quenching of self-trapped excitons at room temperature that allowed for direct observations of the impurity trapped exciton emission band. Energy transfer between host electronic excitations (excitons and e-h pairs) and Yb2+ ions leading to the formation of impurity-trapped excitons is evident from excitation spectra. © 2015 Elsevier B.V.


Horvath S.P.,University of Canterbury | Reid M.F.,University of Canterbury | Reid M.F.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Reid M.F.,Dodd Walls Center for Quantum and Photonic Technologies | And 2 more authors.
Journal of Luminescence | Year: 2016

We report on a method of employing spin Hamiltonian data to enhance the accuracy of crystal-field fits for rare-earth impurity sites of low symmetry in crystalline hosts. As an initial test of this method, we apply it to orthorhombic sites in Li+ and Na+ ion charge compensated Sm3+ centers in codoped CaF2 and SrF2 crystals. This yields a good agreement between theory and experiment, in addition to accurately modelling crystal strains due to the differing ionic radii of Li+ and Na+. © 2015 Elsevier B.V.


Hughes-Currie R.B.,University of Canterbury | Ivanovskikh K.V.,Ural Federal University | Reid M.F.,University of Canterbury | Reid M.F.,MacDiarmid Institute for Advanced Materials and Nanotechnology | And 5 more authors.
Journal of Luminescence | Year: 2016

Results of a vacuum ultraviolet spectroscopic characterization of NaMgF3:Yb2+ are presented. The material demonstrates emission features associated with self-trapped excitons and impurity-trapped excitons. The emission features noticeably overlap giving rise to a broad emission band from 17 000 to 35 000 cm-1 at a sample temperature of 8 K. To identify the true profiles of the emission features we have used a deconvolution procedure. The deconvolution was possible due to the thermal quenching of self-trapped excitons at room temperature that allowed for direct observations of the impurity trapped exciton emission band. Energy transfer between host electronic excitations (excitons and e-h pairs) and Yb2+ ions leading to the formation of impurity-trapped excitons is evident from excitation spectra. © 2015 Elsevier B.V.

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