Macroscopic effects on the Terahertz generation from the two-color filamentation

We recently investigated the influence of laser propagation in gas medium on Terahertz (THz) yield. The dependence of THz yield on the distance between two spatially discrete foci was reproduced when the two collimated driver beams were focused separately. In this study, we further account of the THz field propagation and the interference of local THz sources in the far field; thus, the THz spectra are even reproduced successfully. We provide full explanations for the spectral characteristics of THz radiation generated by using two different driver configurations of overlapping and separating foci. The spectral broadening using the separating foci driver mainly benefits from the improvement of phase matching in the far field due to adjusting the amplitude and phase distribution of the driver beam. Our theoretical modeling effectively validates the availability of the photocurrent model for THz radiation across a wide spectral range.