Photon-photon scattering in collisions of intense laser pulses

A scenario for measuring the predicted processes of vacuum elastic photon-photon scattering and four-wave mixing with intense modern lasers is investigated. The numbers of measurable scattered photons are calculated for the collision of two, Gaussian-focused, pulsed lasers. It is shown that a single intense 10 PW optical laser beam split into two counter-propagating pulses is sufficient for measuring the elastic process. Moreover, when these pulses are sub-cycle, by also considering the collision of two sech pulses, the results suggest that the frequency-shifting, four-wave mixing process should be measurable too.