In order to optically pump pulsed solid-state lasers like Nd: YAG laser, one needs a power supply that basically contains a trigger circuit, a main discharge circuit and a simmer circuit. These circuits must be synchronized by a command. In this communication we will present the synchronization circuit of the system. This circuit is a quartz oscillator known for its good frequency stability, followed by a frequency divider in order to have different repetition rates of the laser. We will also present the simmer circuit which was modelled using a voltage multiplier and a switch mode power supply. The same circuits were also simulated by using Pspice software, thus giving results in good agreement with those of modelling. Experimental proof of modelling has been obtained through the successful use of the command and simmer circuits to control the main discharge into a flash lamp operated at both 1 and 10 Hz frequencies.

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In this paper, we study the oxidation process during the heating of a titanium metallic surface by a Nd-YAG fiber pulsed laser beam under air environment. For this, we adopted an approach that considers a three-dimensional heat diffusion model coupled with an oxidation parabolic law (oxidation kinetics). The heat diffusion equation solved numerically, gives the temperature field. The oxide film growth is simulated by implementing a dynamic mesh technique. We developed computational procedures UDFs (User Defined Function) running interactively with the Fluent fluid dynamics software [ that implements the finite volume method. These UDFs are developed to insert the oxidation law, the temperature field, the specific boundary conditions and the mesh deformation into the calculation.

In lasers, the use of diffracting apertures involves many effects and applications. This goes from the selection of only one eigenmode to oscillate inside the resonator, often called the fundamental mode, the discrimination of the opposite travelling waves within ring resonators, to the control of the beam parameters like diffraction losses, the phase shift and the angular divergence. However, diffraction upon the aperture edge shifts along the optical axis the diffracted beam waist from the position where it would occur for a non apertured bcam. The determination of the axial position of the beam waist is important insofar as it indicates the adequate position, inside the resonator, for small amplifying or absorbing media. Realizing that there is no effective treatment of this issue anywhere in literature, we attempt, in this work, to establish formulae which give the axial position for the effective waist of a diffracted beam by one aperture. This position will be expressed as a function of the beam parameters as well as those of the aperture.