Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Demanding Large Aspheric Optics Delivered to UK Laser Lab


Optical Surfaces Ltd. (Kenley, UK) has delivered a pair of ground-breaking target chamber focusing mirrors for the Astra Gemini dual-beam petawatt laser facility at the Rutherford Appleton Laboratory (RAL) in the United Kingdom.

The highly aspheric, f1.6, 175mm diameter off-axis parabolic mirrors have a focal length of 285mm coupled with an off-axis angle of 27 degrees. To achieve the demanding specification and close matching, the pair was cut from an f0.6, 450mm diameter Zerodur parent. Despite the extreme aspheric correction of 1.8mm, a form accuracy of lambda/13 and slope errors of less than lambda/10 per centimeter were achieved.

The off-axis parabolic mirrors will operate as critical beam focusing components that will help increase the intensity of the existing Astra laser by three orders of magnitude from 1019 Wcm-2 in a single beam to 1022 Wcm-2 on target in each of two beams. To make best use of this enhanced power the Rutherford Laboratory stipulated state-of-the-art tolerances for the off-axis parabolic focusing mirrors to maximize beam intensity while keeping the target outside the beam aperture.

The Astra Gemini project will create the most intense laser in the world. The new development will provide the UK with a unique dual-beam facility, delivering a total power of 1 petawatt (1,000 million million watts). The development will, when completed in June, enable scientists to create and investigate extreme conditions in a controlled way in the laboratory. These conditions include temperatures as high as those found on the surface of the sun and colossal magnetic fields that are found in the polar fields of neutron stars.

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