Effect of two-color laser pulse duration on intense terahertz generation at different laser intensities

We study theoretically terahertz generation in two-color laser-gas interactions based on a transient photocurrent model. We show that terahertz generation depends on the laser pulse duration and intensity of the two-color laser field. Furthermore, the terahertz amplitude increases with an increase of the laser pulse duration at low laser intensity, but decreases with an increase of the laser pulse duration at high laser intensity. Our analysis shows that the ionization events play an important role in terahertz generation and the terahertz amplitude is determined by the superposition of contributions from individual ionization events.