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Plasma mirrors focus laser research

Spontaneous emission of optically amplified light hinders laser performance. Laser beam reflection on plasma mirrors however greatly suppresses the amount of this incoherent light.

Industrial Technologies

Light Amplification by Stimulated Emission of Radiation, simply LASERs, have found a multitude of applications since their discovery back in the 1960's. From cutting metals and identifying enemy targets to internal and cosmetic surgery, lasers are indispensable. These optical devices do nothing more than simply emit light - only this light is a narrow coherent beam. Coherence in simple words describes a laser beam composed of light waves of the same wavelength, phase and polarisation. From this fundamental laser property result many, if not all, of its important applications. To trace elementary particles moving with speeds close to that of light and colliding with each other producing other exotic elementary particles requires laser beams of ultra high intensity and pulses of femtosecond (10[-15]s) duration. Production of short pulses of high intensity is unfortunately accompanied by incoherent spontaneously emitted light. The phenomenon known as amplified spontaneous emission (ASE) is dynamically manifested especially at the rising edge of these ultra-intense femtosecond pulses. To reduce the ASE effect and sharpen the laser beam has been the objective of the SHARP project. The goal has been successfully achieved with the aid of plasma mirrors. After a single reflection on a plasma mirror coated with anti-reflection material the beams' contrast increased by more than 102, with efficiency higher than 60% while retaining its good quality. But, for the relativistic regime when the beam's intensity must exceed 1018 watts per square centimetre two plasma mirrors are required. With this configuration the beam's contrast was greatly increased and a sharp focal spot was achieved. A user friendly hydrodynamic code has been developed to describe the plasma mirror dynamics and is available upon request. Also, detailed descriptions of the project experiments and results have been published in highly accredited scientific journals.

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