Nonlinear Polarization Rotation and Amplification at Extreme Intensities

We extend four-wave parametric amplification at extreme intensities to include cross-polarized wave generation, and control the resulting state of polarization. Using a femtosecond pump beam at extreme intensities greater than 10 TW/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to amplify a weak seed, we find that the induced birefringence can lead to near orthogonal pulse generation. We discuss methods to control the degree of polarization rotation, and routes to exploiting the improved pulse contrast for high power laser systems.