From: [email protected]To: [email protected] Date: June,01, 2000 For everybody, who is interested in modern technological usages of lasers, Dr. M.Kitai suggests a course of lectures.If you need any further information about these course of lectures, please, contact with Dr. M.Kitai by E-mail: "[email protected]« The interaction of laser radiation with the matter and usage of these processes in the technology » Course of lectures by Senior Researcher of the Research Center for the Technological Lasers of Russian Academy of Sciences Dr. M.S.Kitai.
Topics of lectures.
1. The main effects of the action of laser radiation on the matter. The usage of these effects in technology. The typical parameters of the technological lasers. The ablation of the material (of the semiconductors, of the biological materials, of the dielectrics), the laser and the laser-chemical mode of ablation. The surface modification of the material (including the skin heating). The volumetric modification of the material (the generation of radicals into the volume, the volume heating). The laser deposition of the film on to the surface (the laser chemical vapor deposition, the laser electrolytic deposition), the influence of the temperature of the substrate and of the parameters of the diffusion. About the properties of the gas laser chemical reactions The typical parameters of the effects induced by the laser radiation (the linear resolution of the process, the depth of interaction, the typical energy thresholds)
2-3. Basic foundations of the theory of interaction of laser radiation with different materials. The basic equations used at the description. A. Absorption of the laser light by dielectrics. B . by semiconductors,
About influence of scattering of optical radiation by the biological tissue on the propagation of laser beam. Multiquantum character of absorption for the high intensity of radiation. The photochemical and thermo-chemical character of radiation action on a solid state. Conditions of ionization and radical generation under action of laser radiation. About the a heat effect of laser radiation. Propagation of heat initiated by the laser beam. Phase transitions in the solid states generated by this heating source. Mechanical phenomena caused by the influence of laser radiation on different substances. Basic equations describing phenomena, about which it is spoken in items. Solution of these equations in the elementary cases.
4. Photochemical ablation of polymers by UV excimer laser radiation. Typical parameters describing the polymer ablation UV excimer laser pulses. Effect of self-darkening of polymer (and bio-polymers) caused by photochemical reactions. The mechanics of material destruction under action of laser radiation. Usage of this effect in microelectronics. 5. Models of thermal ablation of polymers by the IR laser radiation. Distinction between photochemical and thermal mechanisms of ablation of these same materials. Distinction between main photochemical and thermo-chemical polymer reactions. Dependence of ablational characteristics from of the duration of laser pulse. The limitation of spatial resolution of ablation in several considered cases. The possible applications of this effect in microelectronics and biophysical studies. Ways of formation of the necessary shape of the laser beam for various lengths of waves.
6-7. Foundations of usage of laser radiation (lasers: excimer, Er, Ho, CO 2 , solid-state) in medicine. Role of water (obligatory component of all biological tissue) in the process of interaction with laser radiation, diffusion of water, evaporation and boiling of water under influence of the laser. Peculiarities of action of radiation for different wavelength of UV and IR ranges. About carbonisation of biological tissues. Generation of radicals in volume of biological tissues under laser irradiation. Nonlinear effects in the action of nano-second UV laser of pulses ÓÔ on the amino-acids. The influence of the temperature on the absorption of Er laser radiation. Medical aspects of usage of laser ablation in ophtalmology, in bone surgery, in surgery of cartilages etc. Laser coating of biologically compatible cover on to the metal substrates. 8. Treatment and ablation of HTSC films under action of laser radiation. Thermo-chemical reactions of HTSC and kinetics of these reactions. Different phase states of HTSC ceramics (ceramics of a high-temperature superconductor), movement of the phase front under influence of laser radiation. Generation of macroparticles of ceramics depending on parameters of laser radiation. 9. Peculiarities of action of femto-second of laser pulses on organic polymers and bio-polymers. Multi-quantum excitation of high-energy electronic states of molecules, ionization of molecules under action ultra-short laser pulses. The spectral characteristics of the value of multi-quantum absorption (characteristic sizes, difference from the spectra of linear absorption). The power aspects of action of ultra-short laser pulses on different materials. The value of absorbed energy in a case of linear and multi-photon absorption. The limiting spatial resolution of processes in the case of action of femtosecond of pulses - optical and power limits. Why the action of femtosecond laser pulse provides to the high quality of the treated surface? The process of laser liquid metal deposition under action of ultra-short laser pulses. 10 - 11. The action of laser radiation on different gases. Processes of transfer in gases, thermo-diffusion. Thermo-diffusional division of gas mixtures under laser heating. Methods of laser division of isotopes connected with distinction of their spectral characteristics. Heating of a gas mixtures with convertible chemical reaction, Instability of process, reduction of symmetry and instability at laser heating of a gas mixtures. Self-influence of laser radiation and self-focusing. Non-inertial and inertial nonlinearities acting on the propagation of laser radiation. Thermal and thermo-chemical nonlinearities. Process of self-focusing of the axial laser beam. The wave guide light propagation.
13. Laser oxidation and superficial treatment of metals. Kinetics of heterogeneous oxidation of metals. Kinetics of thermal treatment of metals. The diffusional limitation of oxidation of metals. Absorption of light by the system metal + oxide. The thermochemical instability, time of activation, the quasi-stationary stage. Localization and auto-sharpening of the temperature field. 14. Laser burning of metal. Concept of the burning. Semenov’s classical model of thermal explosion. About the laser heating of different metals. Dynamic modes of burning, diffusional limitation and auto generation mode of temperature of temperature oscillation into zone of burning. Features of processes under air blowing off of a zone of laser action.
15. Laser chemical vapor deposition (LCVD). Processes photochemical and pyrolytic LCVD. The dependence between the deposition rate and the diffusional "«barrier" of process. The deposition under action of moving laser beam, oscillation of the width of the metal track. Fields of applications of the process of LCVD. Reception of thin films of various structure, laser synthesis of powders.
16. Industrial equipment and developed installations of laser technology.
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