Spatial variations of the intensity of THz radiation emitted by extended media in two-color laser fields

Abstract

The specific features of the terahertz (THz) emission from the extended media illuminated by the two-color laser fields is studied. It is shown that due to dispersion effects the amplitude of the response THz field varies periodically with the travelled distance. These spatial variations manifest themselves in the angular spectra of THz emission and, as a result, the integral efficiency of the THz emission depends significantly on the medium geometry. The origin of such behavior is in the variation of the relative phase of ω and 2ω components of the laser field. The THz intensity dependence on the relative phase between the fundamental and the second harmonics for two gases (Ne and Ar), two seed lasers (Ti:Sa and Cr:F) and two angles between the polarization of two-color laser field components (0 and π/2) is investigated quantum-mechanically, and it is confirmed that the optimal phase for the THz generation is π/2 for all described cases.