[en] In this paper, which is the third part of a work devoted to modelling high-power CO₂ lasers, the kinetic and fluid-dynamic model of the investigated device is presented. The kinetic model takes into account intermode vibrational exchange and vibrational-energy transfer among different molecular species CO₂, n reduced to a single equation coupled to kinetic and discharge equations via gas flow velocity in the discharge chamber. Effects of temperature, density and velocity variations in the flowing mixture on laser small signal gain have been investigated by using a numerical code based on the above theoretical model. Profiles of sustainer current, small signal gain and fluid-dynamic parameters in the discharge chamber have been obtained. The output power has been calculated by using a simplified model for the optical cavity. Finally, numerical and experimental results are compared

[en] The authors have studied some kinetic, fluid-dynamic and electrical problems arising in the numerical modelling of a cw TE high power CO₂ laser operating with N₂ and H(e) additives. The effects of temperature, density and velocity in the flowing mixture on the small signal gain of the device have been investigated. (author)

[en] In the present paper a general model of plasma instabilities in high-power e-beam sustained CO₂ laser amplifiers is illustrated. This model improves the Nighan-Haas one by allowing explicitly for the various degrees of vibrational freedom and taking into account the stabilizing effect of the laser field intensity. Two numerical codes, which have been used to calculate the steady-state plasma properties needed to carry out the stability analysis, are also presented. The model has been used to test the degree of thermal and ionic instability of an EDCL device using four-component gas mixture (CO₂-N₂-He-CO)

[en] The general theory of photoacoustic signals is adapted to the detection of liquid crystals' thermal parameters. The thermal-diffusion length to optical-absorption length ratio is given as a simple function of the phase, while the sample to gas effusivity ratio is given as a simple function of phase and normalized amplitude. A method allowing the determination of each thermal parameter separately is presented. Since it does not require strong thermal gradients in the sample, it is particularly well suited to the study of pretransitional effects in liquid crystals

[en] The experimental validation of a mathematical model of the temperature field generated by the laser irradiation of a sample is shown. The test was performed on water, a material with well-known thermodynamic parameters. The experimental data were obtained by means of holographic interferometry. The validated model, in connection with the microholographic method, can be used to determine the thermodynamic properties of different materials

[en] A comparison is presented between transport coefficients of electrons in CO², N², CO and laser mixtures, obtained by a conventional solution of the Boltzmann equation and Monte Carlo simulations. The results show discrepancies which call partly into question some applications which are currently done of the conventional theory. However, the agreement is generally good. (author)

[en] Temperature profiles related to the laser irradiation of the epiphysis area of Rana esclulenta are reported. Experimental results are compared to theoretical ones

[en] A mathematical model is presented for the computation of intensity of radiation in biological tissues irradiated by laser. The time-indipendent transport radiative equation is solved in terms of a Neumann series. Each term of the series is associated with a different order of magnitude of the internal-scattering effect. The importance of these effects has been recognized during the irradiation by ion-argon and ND: YAG laser used as coagulating or cutting instruments in surgery applications. Agreement is found with the single-scattering picture