In this work, we considered mixtures of ethanol and water in the form of jets as samples for THz generation based on laser-induced filamentation. The dependence of the output energy of terahertz radiation on the concentration of ethanol in water was experimentally studied. It is shown that the energy grows linearly, which can be explained by an increase in the ionization energy due to the linear replacement of low-efficient charge carriers (water) with highly-efficient (ethanol). The dependence of the THz generation on the optical angle of incidence on the mixture jets was also demonstrated. The results of this study can be further used to create universal source of terahertz radiation.
A new nonlinear wave equation describing a propagation of a strong few-cycle optical pulse in isotropic dielectric media is used for an analysis of inertial polarization nonlinearity. The dependence of various inertial factors on the intensity, duration, and spectrum of radiation has been theoretically analyzed. Numerical simulation of few-cycle pulse propagation in fused silica illustrates some expected effects of nonlinear polarization inertia.
A nonlinear wave equation suitable for describing a propagation of a light pulse containing few oscillations of a
strong electric field in isotropic dielectric media is deduced. It describes non-resonant dispersion of linear refractive index
and non-inertial third-order non-linearity as well as inertia of dielectric non-linearity of electron nature, including
parts caused by energy state population dynamics and free electron motion.
The dependence of the conditions for the dominance of different physical factors in the self-action of few-cycle
optical pulses in dielectrics on the intensity, duration, and spectrum of radiation has been theoretically analyzed. It is
shown that the larger the pulse width and the central wavelength, the stronger the effect of plasma nonlinearity. For example,
for a quartz glass in the field of pulses with a duration of 10 fs and a central wavelength of 780 nm, this nonlinearity
mechanism is dominant at intensities exceeding 3 - 1013W/cm2.
In present paper we enhance the model of polarization response in field of extremely short pulse by a pseudoclassical description of multiphoton ionization. The system of material equations now includes a part related to a ionization nonlinearity of the optical material. We also obtain a new wave equation, which describes extremely short pulse propagation in tnmsparent dielectric when electromagnetic field intensity values approach to a boundary of dielectric destruction beginning. The equation is used for modeling computations, numerical analysis of pulse propagation. Also new expressions for media refraction index are derived from the equation.
The present paper is devoted to the introduction of enhanced model describing an interaction between laser radiation and dielectric medium. This model is based on our earlier researches, and contains a correct description of the dispersion of electrical field's third order nonlinear medium polarization response in a wide spectral range. We have accomplished this description by a pseudo-classical model of multi-photon ionization of optical medium particles (structural elements). A wave equation, describing wide- spectrum femtosecond pulse propagation in nonlinear medium with induced plasma non-linearity, is obtained.
In present paper we introduce a new model of interaction of laser radiation and dielectric medium. The model correctly describes the dispersion of third order nonlinear medium polarization response in a wide spectral range and is suitable for analysis of propagation of intensive extremely short laser pulses with a very wide spectrum. Also we include into this model a description of plasma-related effects, which are noticed when intensity of pulses increases high enough to initiate free electron generation process. A new wave equation, describing wide-spectrum femtosecond pulse propagation in nonlinear medium with induced plasma nonlinearity, is obtained.
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