Ultrafast `pulsetrain-burst' machining has proven to deliver qualitative advantages for the processing of hard materials. This approach to tailoring the delivery of radiant exposure uses microsecond bursts of picosecond or femtosecond pulses. The mixed-timescale mode reaps the rewards of providing laser-material interactions at ultrashort timescales, while allowing for some control of heat and stress dissipation over longer timescales. As a result, our group has been able to ablate hard materials such as aluminum , as well as optically transparent materials like fused silica [2,3] beyond the capabilities of more conventional methods that employ slower repetition rates. It is well known that gross differences in the end results of materials-processing are the result of the manner in which the laser fluence is delivered - wavelength, continuous-wave vs. pulsed, pulse shape, and the pulse duration itself all have significant impact, and each parameter-value has significant advantages. For brittle materials, where limited tolerance to heat and tensile stress sets limits on the etch-depth possible for multi-kHz repetition rates, 'pulsetrain-burst' machining has enabled us to drill deeper and more cleanly, while eliminating damage due to thermal cycling and over-pressure shocks.
Two high speed systems for spectrometer based frequency domain optical
coherence tomography are presented. A device operating at 800 nm, based on the Basler Sprint CMOS camera with linerates of up to 312,000 lps and a device based on the Goodrich SUI LHD 1024 px camera at 1060 nm with 47,000 lps are applied in a clinical environment to normal subjects. The feasibility of clinical high and ultra high-resolution optical coherence tomography (OCT) devices for retinal imaging at different wavelengths, capable of isotropic sampling with 70 to 600 frames per second at 512 depth scans/frame for widefield imaging and high density sampling at 1 Gvoxel are demostrated.
Ultra-high speed optical coherence tomography employing an ultra-broadband light source has been combined with adaptive optics utilizing a single high stroke deformable mirror
and chromatic aberration compensation. The reduction of motion artefacts, geometric and chromatic aberrations (<i>pancorrection</i>) permits to achieve an isotropic resolution of 2-3 μm in the
human eye. The performance of this non-invasive imaging modality enables to resolve cellular structures including cone photoreceptors, nerve fibre bundles and collagenous plates of the lamina
cribrosa, and retinal pigment epithelial (RPE) cells in the human retina <i>in vivo</i> with superior detail. Alterations of cellular morphology due to cone degeneration in a colour-blind subject
are investigated in ultra-high resolution with selective depth sectioning for the first time.