title: Minimization of the impact of a broad bandwidth high-gain nonlinear preamplifier to the amplified spontaneous emission pedestal of the Vulcan petawatt laser facility.
abstract: To generate petawatt pulses using the Vulcan Nd:glass laser requires a broad bandwidth high-gain preamplifier. The preamplifier used is an optical parametric amplifier that provides a total gain of 10(8) in three amplification stages. We report on a detailed investigation of the effect of the Vulcan optical parametric chirped pulse amplification (OPCPA) preamplifier on contrast caused by the amplified spontaneous emission (ASE) pedestal that extends up to 2 ns before the arrival of the main pulse. The contrast after compression is improved to 4x10(8) of the intensity of the main pulse using near-field apertures between the stages of the OPCPA preamplifier. Further reduction of the level of the ASE pedestal can be achieved at the cost of a reduction in amplified bandwidth by solely phosphate glass amplification after initial preamplification rather than a mixed glass amplification scheme.
authors: Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, UK. i.o.musgrave@rl.ac.uk
authors: I O
authors: IO
authors: Musgrave
authors: C
authors: C
authors: Hernandez-Gomez
authors: D
authors: D
authors: Canny
authors: J
authors: J
authors: Collier
authors: R
authors: R
authors: Heathcote