In this paper, using the Optical Emission Spectroscopy technique, the physical properties of a fabricated pulsed DBD plasma jet are studied. Ar/N 2 gaseous mixture is taken as operational gas, and Ar contribution in Ar/N 2 mixture is varied from 75 to 95%. Through the optical emission spectra analysis of the pulsed DBD plasma jet, the rotational, vibrational and excitation temperatures and density of electrons in plasma medium of the pulsed plasma jet are obtained. It is seen that, at the wavelength of 750.38 nm, the radiation intensity from the Ar 4p ? 4 s transition increases at the higher Ar contributions in Ar/N 2 mixture. It is found that, for 95% of Ar presence in the mixture, the emission intensities from argon and molecular nitrogen are higher, and the emission line intensities will increase nonlinearly. In addition, it is observed that the quenching of Ar * by N 2 results in the higher intensities of N 2 excited molecules. Moreover, at the higher percentages of Ar in Ar/N 2 mixture, while all the plasma temperatures are increased, the plasma electron density is reduced.

In this work, using a two-dimensional Particle In Cell-Monte Carlo Collision simulation method, a comparative study is performed on the influences of different types of atomic and molecular gases at various background gas pressures on the generation of broadband and intense Terahertz (THz) radiation via the application of two-color laser pulses. These two modes are focused into Argon (Ar), Xenon (Xe), Nitrogen (N2), Oxygen (O2), and air as the background gaseous media and the plasma channel is created. It is observed that the THz radiation emission dramatically changes due to the propagation effects. A wider THz pulse is emitted from the formed plasma channel at the higher gas pressures. The significant effects of the propagation features of the emitted THz pulse on its energy at the longer lengths of the plasma channel are observed.

In this work, using a two dimensional particle in cell-Monte Carlo collision simulation scheme, interaction of two-color ultra-short laser pulses with the molecular hydrogen gas (H2) is examined. The operational laser parameters, i.e., its pulse shape, duration, and waist, are changed and, their effects on the density and kinetic energy of generated electrons, THz electric field, intensity, and spectrum are studied. It is seen that the best pulse shape generating the THz signal radiation with the highest intensity is a trapezoidal pulse, and the intensity of generated THz radiation is increased at the higher pulse durations and waists. For all the operational laser parameters, the maximum value of emitted THz signal frequency always remains lower than 5 THz. The intensity of applied laser pulses is taken about 1014 w/cm2, and it is observed that while a small portion of the gaseous media gets ionized, the radiated THz signal is significant.

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.

In this paper a theoretical model for transient behaviour analysis of the discharge current pulse in the transversely excited atmospheric pressure CO2 laser with dielectric corona pre-ionization is presented. The laser discharge tube is modelled by a non-linear distributed RLC electric circuit. The transmission line method is applied to the non-linear distributed circuit and it is approximated by a lumped non-linear RLC circuit. By this method the governing partial differential equations are reduced to a system of ordinary differential equations. The governing ordinary differential equations of the lumped non-linear RC electric circuit are solved numerically. On the basis of this model the pre-ionization and main discharge energies are evaluated. Our theoretical results are in good agreement with the published experimental observations.