Transformation of THz spectra emitted from dual-frequency femtosecond pulse interaction in gases

Experimental and theoretical study of the mechanisms affecting the spectral form of the pulsed THz emission generated due to the interaction between a bichromatic laser field and a gaseous medium is presented. The influence of a photoionization process and Raman rotational molecular transitions on the THz spectrum is discussed. Typical spectral modifications of THz emission are tracked down and linked to the duration of the two-color laser pump pulse.