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 108 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 4×108 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.
© 2007 Optical Society of America
Lasers and Laser Optics
Original Manuscript: April 5, 2007
Revised Manuscript: July 16, 2007
Manuscript Accepted: July 21, 2007
Published: September 26, 2007
I. O. Musgrave, C. Hernandez-Gomez, D. Canny, J. Collier, and R. Heathcote, "Minimization of the impact of a broad bandwidth high-gain nonlinear preamplifier to the amplified spontaneous emission pedestal of the Vulcan petawatt laser facility," Appl. Opt. 46, 6978-6983 (2007)