High contrast 150-terawatt laser for high field laser-plasma interaction studies

Summary form only given. High power chirped pulse amplification (CPA) lasers are capable of providing enough power to study relativistic regime-of laser-plasma interaction, including effects such as high-energy particle acceleration, relativistic self-focusing and nonlinear Thomson scattering. To achieve this regime focused laser intensity must be over 10/sup 18/ W/cm/sup 2/ (typically-10/sup 19/-10/sup 20/ W/cm/sup 2/). If solid metal target is irradiated the laser intensity contrast on the nanosecond timescale must be better than 12 orders of magnitude to ensure that the target does not disintegrate before the pulse arrives. To improve the pulse contrast in the 25 fs CPA laser system, we are currently building for high field laser-plasma studies at CUOS, we pursue an approach, originally developed at CUOS for longer pulses (/spl sim/100 fs). We pre-amplify the oscillator output pulse to submicrojoule energy level without stretching the pulse, improve the pulse contrast by using a saturable absorber and stretch the pulse thereafter for further amplification.