Quasi-monoenergetic electron beams produced by colliding cross-polarized laser pulses in underdense plasmas

The interaction of two laser pulses in an underdense plasma has been proven to be able to inject electrons into plasma waves, thus providing a stable and tunable source of electrons. Whereas previous works focused on the 'beatwave' injection scheme in which two lasers with the same polarization collide in a plasma, this present paper studies the effect of polarization and more specifically the interaction of two colliding cross-polarized laser pulses. It is shown both theoretically and experimentally that electrons can also be preaccelerated and injected by the stochastic heating occurring at the collision of two cross-polarized lasers and thus, a new regime of optical injection is demonstrated. It is found that injection with cross-polarized lasers occurs at higher laser intensities.