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COURSE ANNOUNCEMENT
Spring Semester 2005
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ESc 541/ME 597:
LASER-MATERIALS INTERACTION
Course Content | Course Syllabus
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This course will provide graduate students and practicing engineers with an understanding of the physical processes accompanying laser interactions with matter under conditions typical for laser-materials processing. The course covers laser beam interaction with metals, dielectrics, semiconductors, polymers and biological tissue. Physical processes such as heat transfer, phase transitions, material removal, plasma formation, and synthesis of nanoclusters and nanocrystallyne films will be addressed. The course is designed to cover the gap between fundamental concepts and applications. A broad range of lasers (including CO2, excimer, Nd:YAG, Ti:sapphire, fiber, and diode lasers), operating in continuous wave, pulsed, and ultrashort pulsed regimes, will be described. Upon completion of the course the students will be apply to identify the laser systems and operating parameters that govern the effective use of a wide range of laser- materials processing technologies. |
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For more information on the course, please contact:
Dr. Vlad Semak |
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Esc 541
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Textbook: Laser Processing and Chemistry, D. Bauerle, Springer-Verlag, Berlin, (2000) Recommended literature: Laser Beam interactions with Materials, M. von Almen, Springer-Verlag, Berlin (1995), Instabilities in Laser-Matter Interaction, S. I. Anisimov and V. A. Khokhlov, CRC Press, Boca Raton, FL (1995), Industrial Lasers and Their Applications, J. T. Luxon and D. E. Parker, Prentice-Hall, Englewoods Cliffs, NJ (1985)
Course coverage: This course will provide graduate students and practicing engineers with an understanding of the physical processes accompanying laser interactions with matter under conditions typical for laser-materials processing. The course covers laser beam interaction with metals, dielectrics, semiconductors, polymers and biological tissue. Physical processes such as heat transfer, phase transitions, material removal, plasma formation, and synthesis of nanoclusters and nanocrystallyne films will be addressed. The course is designed to cover the gap between fundamental concepts and applications. A broad range of lasers (including CO2, excimer, Nd:YAG, Ti:sapphire, fiber, and diode lasers), operating in continuous wave, pulsed, and ultrashort pulsed regimes, will be described. Upon completion of the course the students will be apply to identify the laser systems and operating parameters that govern the effective use of a wide range of laser- materials processing technologies. Exams: There will be one midterm exam and a final exam. Both exams will be open book/notes. Term paper: A 10 page paper describing current research, engineering or business issues in laser-materials processing is expected during the course. Computer simulation project: A group project that simulates laser beam focusing and the thermal fields induced in a sample during laser-materials interactions will be performed at the end of the course under the supervision of the instructor. It is expected, but not required, that the students are familiar with some programming languages (C++, FORTRAN, BASIC, etc.).
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Course Content
Course Syllabus
Sections 1 and 2: The principles of laser operation and the propagation of a laser beam will be considered. The course will provide a detailed discussion of laser beam modes and related intensity distributions in different cross sections of the focused beam. Simple numerical codes will be presented to illustrate properties of Gaussian (TEM 00) and multimode beams. The effect of beam mode on materials processing will be described.
Section 3: Different types of lasers and the specifics of their applications for materials processing will be described.
Section 4: The main physical processes accompanying laser-materials interactions will be described. First we will consider the mechanism of laser radiation absorption for interactions on different time scales - faster and slower than the characteristic time of energy transition between electrons and lattice. Then the material heating and transfer of heat into the bulk will be described for strongly absorbing materials such as metals. Next, a physical model for melt front propagation will be discussed. Consideration of evaporation from a material surface will include description of the physical models corresponding to surface temperatures below and above the critical temperature of material. The role of evaporation in material removal will be discussed. Methods for calculating the evaporation rate and evaporation recoil at temperatures below the critical temperature will be provided. Generation of the near-surface plasma and its effect on the laser beam parameters will be considered for different beam intensities and pulse durations. Specifics of these physical processes will be discussed for strongly and weakly absorbing materials.
Section 5: The fundamentals of numerical solutions for equations governing laser-materials interactions will be described. Numerical examples simulating different processing conditions will be presented.
Section 6: This section will consider welding. First, conduction limited welding will be described. The influence of the melt flow, induced by the Marangoni effect, on the heat transfer in the weld pool will be considered. Transient keyhole welding will be described. Recently developed models describing the formation and dynamics of the keyhole will be presented. The effect of the melt flow generated at the front part of the transient keyhole on the weld pool oscillations and shape will be described. Steady state keyhole welding models will be considered and the processing conditions corresponding to transient and steady state keyhole modes will be determined. Examples of industrial implementation of laser welding will be presented.
Section 7: Laser Drilling. Interaction conditions corresponding to the transition from welding to drilling will be described and criteria defining the transition regime will be presented. The evaporation and hydrodynamic ejection dominated regimes of material removal will be described. Drilling with ultra-short laser pulses (femto- and pico-second) will be described. Examples of industrial implementation of laser drilling will be given.
Section 8: Cutting. The relation of cutting to welding and drilling and the conditions corresponding to welding-cutting transition will be given. Evaporation and hydrodynamic dominated material removal during cutting will be described. The effect of assist gas on laser cutting will be discussed and examples of industrial implementation of laser cutting will be provided.
Section 9: The physical and chemical processes accompanying the interaction of a laser beam with the organic materials will be described. Applications related to joining, cutting and ablating polymeric materials and biological tissue will be discussed.
Section 10: Computer simulation projects will include demonstration and discussion of the computer models for: laser beam propagation; thermal fields induced in strongly absorbing materials; welding and drilling of metals; and charring of polymeric materials.
A review of the course material will be conducted at the conclusion of the course.
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