Mr. Luke McKinney Profile

Luke McKinney

at Univ of Toronto

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Author

Publications (3)

Proceedings Article | 8 September 2006 Paper

Optical coherence and beamspread in ultrafast-laser pulsetrain-burst hole drilling

Jesse Dean, Paul Forrester, Martin Bercx, David Graper, Luke McKinney, Felix Frank, Marc Nantel, Robin Marjoribanks

Proceedings Volume 6343, 63432A (2006) https://doi.org/10.1117/12.707967

KEYWORDS: Coherence (optics), Aluminum, Interferometers, Visibility, CCD cameras, Charge-coupled devices, Near field, Laser drilling, Laser beam propagation, Gaussian beams

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Pulsetrain-burst machining has been shown to have advantages over single-pulse laser processing of materials and biological tissues. Ultrafast lasers are often able to drill holes in brittle and other difficult materials without cracking or swelling the target material, as is sometimes the case for nanosecond-pulse ablation; further, pulsetrain-bursts of ultrafast pulses are able to recondition the material during processing for instance, making brittle materials more ductile and striking advantages can result. In the work we report, we have investigated hole-drilling characteristics in metal and glass, using a Nd:glass pulsetrain-burst laser (1054 nm) delivering 1-10 ps pulses at 133 MHz, with trains 3-15 μs long. We show that as the beam propagates down the channel being drilled, the beam loses transverse coherence, and that this affects the etch-rate and characteristics of channel shape: as the original Gaussian beam travels into the channel, new boundary conditions are imposed on the propagating beam principally the boundary conditions of a cylindrical channel, and also the effects of plasma generated at the walls as the aluminum is ablated. As a result, the beam will decompose over the dispersive waveguide modes, and this will affect the transverse coherence of the beam as it propagates, ultimately limiting the maximum depth that laser-etching can reach. To measure transverse beam coherence, we use a Youngs two-slit interference setup. By measuring the fringe visibility for various slit separations, we can extract the transverse coherence as a function of displacement across the beam. However, this requires many data runs for different slit separations. Our solution to this problem is a novel approach to transverse coherence measurements: a modified Michelson interferometer. Flipping the beam left-right on one arm, we can interfere the beam with its own mirror-image and characterise the transverse coherence across the beam in a single shot.

Proceedings Article | 13 October 2005 Paper

Mitigating intrinsic defects and laser damage using pulsetrain-burst (>100 MHz) ultrafast laser processing

Luke McKinney, Felix Frank, David Graper, Jesse Dean, Paul Forrester, Maxence Rioblanc, Marc Nantel, Robin Marjoribanks

Proceedings Volume 5970, 59701L (2005) https://doi.org/10.1117/12.629985

KEYWORDS: Silica, Plasma, Laser damage threshold, Etching, Micromachining, Dielectrics, Laser optics, Picosecond phenomena, Laser processing, Multilayers

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Proceedings Article | 7 January 2004 Paper

Optimizing an EUV source for 13.5 nm

Gerry O'Sullivan, Anthony Cummings, Grainne Duffy, Padraig Dunne, Andrew Fitzpatrick, Paddy Hayden, Luke McKinney, Nicola Murphy, Dave O'Reilly, Emma Sokell, John White

Proceedings Volume 5196, (2004) https://doi.org/10.1117/12.504715

KEYWORDS: Plasmas, Tin, Ions, Extreme ultraviolet, Xenon, Pulsed laser operation, Picosecond phenomena, Absorption, Ionization, Chromium

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