• L. Corner, L.J. Nevay
  OXFORDphysics, Oxford, Oxon
• L. Corner, R. Walczak
  JAI, Oxford

We present the results of the development of a high power fibre laser system for the laserwire project to measure very low emittance electron beams. We use the output of a commercial 1uJ, 6.49MHz laser system and amplify it in rod type photonic crystal fibre. This is a novel form of optical fibre which has a large core diameter (70um) but still supports only a single Gaussian spatial mode, essential for focusing the beam to the smallest spot size and achieving the highest resolution. We amplify the seed pulses in a burst mode suitable for use in a linear accelerator, which has the advantage of decreasing the pump power required and thus reducing the running cost and heat loading of the laser system. The amplified pulses have energies of ~ 100uJ in the near infrared and excellent beam quality, as specified in the original design, and are frequency converted to the green to give sub-micron spatial resolution.