Introduction to LASER

This course introduces LASER to senior undergraduate students, as well as first year postgraduate students. The objective is to provide a detailed account of the basic physics, including resonator physics, and the principle of operation of Lasers. Issues relevant to the design and output characteristics of the Lasers, and some specific laser systems would also be discussed. The course is ‘applied’ in nature, and could be taken by B.E/B.Tech IIIrd/ IVth Year, M.Sc IInd/ M.Tech. I Year. Working engineers/scientists/teachers, who did not have exposure to the subject earlier, would also find it very useful, if interested. The course would require a regular and serious study schedule on the part of the students (to understand the subject and do well). INTENDED AUDIENCE : IIIrd, IVth year B.Tech / M.Sc (Physics/ Electronics/ Electronic Sciences) students, and also M.Tech Ist Sem students, who had no previous exposure to Lasers in any course. PLUS Engineers working/ dealing with LasersPREREQUISITES : Basic undergraduate-level knowledge of Electromagnetics, Optics, and Atomic Physics/Modern Physics would be required. INDUSTRIES SUPPORT : Companies and R&D Laboratories working on Laser Applications, Optoelectronic and Optical Communication are expected to value this course.

Week 1:PART – I: Interaction of Radiation with Matter
General Introduction, Spontaneous and stimulated emissions, the Einstein coefficients
Week 2:Line shape function, Line-broadening mechanisms: Homogeneous and inhomogeneous broadening, natural-, Doppler- and collision broadening.
Week 3: PART – II: Scheme of Light Amplification
Rates of stimulated emission and absorption, condition for amplification by stimulated emission, the meta-stable state and laser action.
Week 4:3-level and 4-level pumping schemes. Laser Rate Equations: Two-, three- and four-level laser systems, condition for population inversion, gain saturation;
Week 5:Laser amplifiers, gain and bandwidth; Rare earth doped fiber amplifiers.
Week 6:PART – III:
Optical Resonators Plane mirror resonator: resonance frequencies, cavity loss, cavity lifetime and Q-factor;
Week 7: Spherical mirror resonators: Ray paths in the resonator, stable and unstable resonators,resonator stability condition
Week 8:Transverse modes of laser resonators. Hermite-Gauss modes of a spherical mirror resonator. Gaussian beams in laser resonators.
Week 9:PART – IV:
The Laser Laser Oscillations, Optical feedback, threshold condition, variation of laser power near threshold, optimum output coupling,
Week 10:Characteristics of the laser output, oscillation frequency, Mode selection, single-frequency lasers; Methods of pulsing lasers, Q-switching and mode-locking.
Week 11: PART – V: Some Laser Systems: Ruby, He-Ne, Nd:YAG, Fiber lasers
Week 12:Tunable lasers: The Ti Sapphire laser, Semiconductor lasers; Laser safety.