Adaptive optics for microscopy, optical data storage and micromachining

Department of Engineering Science, University of Oxford, UK.

Thursday 6^th April 2006, 11.00AM, Seminar Room AR103, Graduate Research Centre.

Many optical techniques that require operational precision on the sub-micrometre scale are adversely affected by the presence of aberrations. We demonstrate the use of adaptive optical methods to overcome these limitations. Optical microscopy is a widely used technique, particularly in the biological sciences. The variations in refractive index that exist within a specimen induce aberrations that vary across the field of view. These aberrations are particularly problematic when high numerical aperture objectives are employed, as is often necessary to achieve the highest resolution. The aberrations lead to reduced image resolution and contrast, especially when imaging deep in biological specimens. Using an adaptive microscope incorporating a deformable membrane mirror, we have demonstrated the correction of specimen-induced aberrations. This has permitted the extension of the range of depths over which high resolution imaging can be performed.

Three-dimensional optical memories are potential successors to CD and DVD technologies. Rather than writing data in a single plane the data are written in a number of layers in a suitable recording substrate. Focussing through the substrate introduces significant amounts of spherical aberration. These aberrations conspire to blur the focal spot, increasing the volume of the written bit, decreasing the resolution of the read-out system and effectively limit the number of usable layers of data. Using a deformable mirror, we have compensated aberrations for recording of data, using multiphoton processes, and read-out of data, using a confocal microscope. Aberration correction for optical micromachining deep inside a substrate is also demonstrated.

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