Optical surfaces delivers parabolic mirrors for petawatt laser

Jon Lawson

Optical Surfaces Ltd has delivered three off-axis parabola of 175mm diameter to the UK's prestigious Rutherford Appleton Laboratory.

Using a new technique – Optical Surfaces highly experienced and skilled production team manufactured a very fast parent F 0.6 parabola from which three fast focusing off-axis parabolic mirrors with surface accuracy of better than lambda/8 P-V, surface quality of 20/10 scratch/dig and surface slope error of lambda/10/cm P-V were produced.

The world class Gemini laser based at the Rutherford Appleton Laboratory, delivers Petawatt power laser pulses to targets only a few microns in size. The temperatures, pressures and magnetic fields at the laser focus reach levels that otherwise exist only inside stars, making Gemini a unique facility for scientists to conduct experiments that cannot be attempted anywhere else. Laser-plasma interactions under these conditions can produce energetic beams of electrons and protons as well as bright, coherent sources of X-rays and can also address fundamental questions in astrophysics and plasma physics. The laser focus is routinely generated with the use of precise parabolic focusing optics, which can only be made by a few companies in the world.

The order for the most recent focusing optic was tendered and awarded to Optical Surfaces Ltd. The key focusing mirror was particularly challenging as it was required to have a hole through the optic, on the focusing axis. This hole facilitates the co-propagation of a much longer focal length beam enabling a whole range of additional science to be explored.

Dr Aris Kouris, of Optical Surfaces Ltd, commented: “To enable a range of new experiments on their Gemini laser, Rutherford ordered three off-axis paraboloids - one with a slanted conical hole in the centre and two without a hole. Due to tight operational constraints the delivery of the OAP with the hole had to be within a specific timeframe. For this reason, and due to the very demanding specification for this optic, we developed a new manufacturing technique that enabled us to speed up the manufacturing time of the parent parabola significantly. The method has successful and we managed to deliver it within the requested timeframe.”


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