Relativistic cross-phase modulation driven compression of Terawatt laser pulses to Sub-7 fs Regime: A scalable approach to petawatt systems

A numerical mechanism for the dramatic temporal compression of ultra-intense laser pulses investigated by solving the coupled nonlinear envelope equations incorporating group velocity dispersion (GVD), relativistic self-phase modulation (SPM), and cross-phase modulation (XPM). We demonstrate the co-propagation dynamics of pump and probe pulses in a under dense plasma, we report a signature of relativistic XPM that induces a symmetric spectral broadening, facilitating the self-compression of a 100 fs sech² probe pulse down to 6.65 fs at Terawatt (TW) power levels. This 15-fold compression is achieved without external dispersion compensation, relying solely on the intrinsic plasma medium. Furthermore, we analyse the scalability of this technique, highlighting how the damage free nature of plasma optics allows this Sub-7 fs compression scheme to be extended to Petawatt (PW) class lasers, providing a robust driver for next-generation high field physics experiments.