Study of terahertz generation via the interaction of two-color ultra-short laser pulses with water vapor plasmas

In this work, using a two dimensional particle in cell-Monte Carlo collision simulation scheme, the Terahertz (THz) generation process via the interaction of a two-color ultra-short laser pulses with the water vapor gas (H2O) is examined. The background gas pressure and various laser parameters, e.g., its pulse shape, duration, and waist, are varied, and their effects on the temporal variation of the generated current density, THz electric field, and THz spectral intensity are studied. It is shown that the best pulse shape generating the THz signal radiation with the highest intensity is a trapezoidal pulse. Moreover, the intensity of generated THz radiation is increased at the higher pulse durations and waists. In addition, at the higher water vapor gas pressures, the time to peak of the generated current density is shifted to the earlier moments. Finally, it is observed that, for the laser pulses with the intensities of about 8 × 1013 W/cm2, the water vapor triatomic molecules are a proper source for the THz radiation generation under the illumination of high power ultra-short two-color laser pulses.<p></p>