The intracavity frequency doubling of a simultaneous passively Q-switched mode-locked diode-pumped Nd^{3+} laser is studied with a polarized isotropic Cr^{4+}:YAG saturable absorber. A general recurrence formula for the mode-locked pulses under the Q-switched envelope at a fundamental wavelength has been reconstructed in order to analyze the temporal shape behaviour of a single Q-switched envelope with mode-locking pulse trains. This formula has been derived taking into account the impact of the intracavity frequency doubling and polarized Cr^{4+}:YAG saturable absorber (the Fresnel losses). The presented mathematical model essentially describes the self-induced anisotropy appearing in the polarized Cr^{4+}:YAG in the nonlinear stage of the giant pulse formation. For the anisotropic Nd^{3+}:YVO_4 active medium, the generated polarized waves are fixed through the lasing cycle. Second harmonic peak power, pulse width, pulse duration, shift pulse position of central mode and rotational angle as a function of the absorber initial transmission are estimated. The calculated numerical results are in good qualitative and quantitative agreement with the available experimental data reported in references.
A mathematical model for describing the polarization effect of the intracavity frequency-doubling of a simultaneous passively Q-switched and mode-locked diode-pumped Nd^{3+}-laser has been demonstrated. The generated polarized waves are assumed to be fixed through the lasing cycle. The maximum absorber initial transmission and the minimum mirror reflectivity values have been determined from the second threshold criterion. The calculated numerical results demonstrate the impact of the variation of the input laser parameters on the characteristics of the output laser pulses. The calculated results are in good agreement with the available experimental data reported in references.
Simulations of laser sheet scattering by microparticles, based on the generalized Lorenz-Mie theory for the case of numerous random spatial distributions of scattering particles, were done, using the novel computational time saving strategy. This type of scattering by particles immersed in a fluid flow and its recording on cameras, presents the essence of particle image velocimetry systems. The continuous and large change of the intensity of a scattered light falling on the camera causes the sequences of images of varying quality, which makes many of them useless. This paper shows how the problem could be alleviated by determining the angles of low relative standard deviation of scattered light intensity and using them for recording, as well as by avoiding the angles of high relative standard deviation of scattered light intensity.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.