Refocusing plays a key role in the dynamic X-wave formation during femtoseconds.

简介：
With the development of a laser pulse in water, an investigation into the generation of a nonlinear X wave during femtosecond filamentation has been carried out based on numerical simulations. Specifically, we examine the far-field angularly resolved spectra obtained for various temporal segments of the ultrashort pulse as it propagates through the medium. Our findings reveal that the refocusing characteristic of an ultrashort pulse leads to a dynamic X wave formation, which essentially manifests itself as conical emission.