Laser Radiation Interaction with Solids

Two Phase Flow, Phase Change and Numerical Modeling, 2011

Heat and Mass Transfer, 2003

Recently, lasers are being increasingly used in the industry owing to their precision and low cost. Material is heated and evaporated during laser and material interaction due to the absorption of laser beams by the material. In this study, a 3-D Laser heating model including evaporation has been solved using the electronkinetic theory approach. The basis in examining the problem using the kinetic theory approach is to describe the heat conduction through electron-phonon and molecule-phonon collisions. The problem is solved by using the electron-kinetic theory approach in such a way that heat conduction is taken into account until the material is heated to its melting temperature and non-conduction limited heat transfer is considered after the melting temperature is reached. Non-conduction limited heat transfer through the phase change process is resulted from vacancy-molecule collisions. A numerical scheme is introduced to solve the governing equation, owing to the fact that the energy equation resulted is in the form of integro-differential equation. Four different materials, namely iron, nickel, tantalum and titanium are chosen in this study determine the material response to laser pulse heating. For each material, time dependent temperature distribution through the depth of the material and on the surface of the material is computed and analyzed for four different materials.

Infrared Physics & Technology, 2008

This paper is a description of the analytical model developed to study the temperature distributions in solid materials heated by pow-12 erful laser pulses. The calculations are based on a three-dimensional model of heat diffusion in solids using the integral transform 13 method. Our model takes into account the one-, two-, three-and four-photon absorption. Specific results are presented for an application 14 of the model to a InSb sample heated with a pulsed CO 2 laser. The results indicate that (i) the two-, three-photon absorption does pro-15 duce detectable temperature variation but the four-photon absorption may produce detectable variation only at very high laser beam 16 intensity; (ii) the surface absorption coefficient does play a very important role in temperature distribution; (iii) the field temperature 17 depends on the duration of the pulse. 18

Journal of Materials Processing Technology, 2004

A model of energy exchange, based on the finite element method is specially developed to determine the thermal field for semi-transparent polymers irradiated by laser. Our model, which uses the finite element method, allows to define the laser and specific structure characteristics in terms of density of power, speed and shape of the spotlight, material coefficient absorption, etc. The model has been experimentally validated by measuring the thermal response induced by the laser source. The experimental part of the study has been performed using a semiconductor laser diode source and an infrared thermography camera.

Contemporary Materials, 2010

In this article we present our physical model for interaction of laser radiation with metals and alloys through structural changes, melting and vaporizing. We describe the interaction of laser radiation with materials, kinetic process of energy transmitting from free electrons to the crystal lattice and propagation of heat and the processing zone. We consider influence of optical and thermal properties over exploring process as they change with temperature and in the presence of mixtures.

Optical Materials, 2011

Modeling of optical and electro-optical devices requires the implementation of properties of these device materials over a broad temperature range. The accurate evaluation of temperature is essential for the calculation of optical, thermo-optical, elasto-optical and gain characteristics of solid-state laser materials. Among thermally induced effects in optical materials one finds that thermal focus escalates with pump power as well as does its induced aberration. Derived in this paper is a closed form solution to the problems of nonlinear heat transfer and stress field, resulting in expressions for the local temperature, stress and strain, refractive index, trajectories of propagating rays, optical path difference, thermal lensing, tilt and third order aberrations, induced birefringence and depolarization. In the analysis the temperature dependent coefficients were best fitted to existing experimental data. Calculations are presented for some thermally-induced optical effects in the temperature range of 77-770 K. It is found that for large heat deposition rates the use of the nonlinear solution is uniquely necessary to accurately assess the thermal and optical characteristics, that high pumping loads require cryogenic cooling to maintain reasonably low thermal lensing and that thermally induced dioptric power quadratic dependence on the heat level. Finally, it is found that the disk configuration suffers the least adverse thermo-optical effects.

Optics & Laser Technology, 2008

The heating of solid surfaces using consecutive laser pulses is studied and the temperature field inside slabs with different thermal properties is predicted. A Gaussian beam intensity distribution is assumed at the irradiated surface and axisymmetric heating situation is accommodated in the numerical simulations. The materials selected include titanium, stainless steel, tantalum, nickel, and aluminum. A control volume approach is introduced to discretize the governing equation of heat transfer. It is found that temperature rise in the early heating period is higher than that in the later heating period. The temperature difference between two consecutive pulses is higher in the heating cycle than that corresponding to the cooling cycle of the consecutive pulses. r

This paper presents a new method of real-time measuring technology to investigate the thermo- physical process of laser-material interaction during laser non-melting surface processing. In the thickness direction of the specimen, the temperature distribution was measured with Thermovision Infrared System in real-time. The dynamic micro-deformation of the specimen was studied using laser beam reflex amplifier system. Experiment results display the thermo-physical process of laser- material interaction and lay a foundation of further researching on the process of laser processing.

Nowadays technological developments, the use of lasers in production is increasing and plays an important role due to low cost and high accuracy. The heat transfer, over the course of laser-metal interplay, has a great importance in metal forming. In this study, different types of materials were investigated in order to designate the temperature distributions inside material and on the material surface versus the thermodynamic properties of the material used and then the temperature distributions obtained from the analysis were compared each other. In addition, the heat transfer is occurring during the interaction of the laser power of 1.1010 W/m2 and 5.1010 W/m2 with laser power intensity in two main groups using different materials these are steel, nickel, tantalum and titanium, and numerical results are obtained using the finite-difference method. In the first step, a solution is obtained by electron kinetic theory according to the basic heat transfer. In the second step, since heat convection is formed after material has reached the melting point. Using electron kinetic theory model for convection solutions have been obtained. Moreover, the temperature distribution that occurs during the laser metal interaction was studied by variation of the time chart and the material depth. As a result of the study, material's surface at the correct temperature of liquid phase change material and increased depth in the direction perpendicular to the electro-kinetic theory approach is further demonstrated by the decrease in the first manner and then remains constant in exponential phase change temperature. In addition to this the analysis results, the substrate temperature increases, the change in phase in the material becomes smaller and smaller.

Journal of Optoelectronics and Advanced Materials

This study presents theoretical and experimental results on the laser irradiation of some metals (titanium, nickel, aluminium, copper, steel), using an Nd:YAG laser. The theoretical study involves the solving of heat equation for half-infinite targets. The determination of the temperature at the surface of the irradiated material allows quantitative estimations regarding the induced thermo deformation and the involved phase transition, in our case, the melting. The confrontation with experience is achieved through the comparison of the thermo deformation sizes and obtained craters and of the others related parameters with the direct microscopically measurements. The calculated values are in proper correlation with the experimental ones, the observed differences having as major cause the insufficiently precise knowledge of the involved physical values of observables, at high reached temperatures on the irradiated surfaces.