Unit 1
Review of some basic concepts and principle of laser.
Introduction to light and its properties: Reflection, refraction, interference, diffraction and polarization. Photometry – calculation of solid angle. Brewster’s law. Snell’s law and, its analysis.
Introduction to LASERS: Interaction of radiation with matter – induced absorption, spontaneous emission, stimulated emission. Einstein’s co-efficient (derivation). Active material. Population inversion – concept and discussion about different techniques. Resonant cavity.
Unit 2
Properties of LASERS
Gain mechanism, threshold condition for PI (derivation), emission broadening – line width, derivation of FWHM natural emission line width as deduced by quantum mechanics – additional broadening process: collision broadening, broadening due to dephasing collision, amorphous crystal broadening, Doppler broadening in laser and broadening in gases due to isotope shifts. Saturation intensity of laser, condition to attain saturation intensity.
Properties – coherency, intensity, directionality, monochromaticity and focussibility. LASER transition – role of electrons in LASER transition, levels of LASER action: 2 level, 3 level and 4 level laser system.
Unit 3
Types of LASERS
Solid state LASER: (i) Ruby LASER – principle, construction, working and application. (ii) Neodymium (Nd) LASERS. gas LASER: (i) He-Ne LASER – principle, construction, working and application. (i) CO2 LASER – principle, construction, working and application.
Liquid chemical and dye LASERS. Semiconductor LASER: Principle, characteristics, semiconductor diode LASERS, homo-junction and hetero-junction LASERS, high power semi conductor diode LASERS.
Applications in Communication field:
LASER communications: Principle, construction, types, modes of propagation, degradation of signal, analogue communication system, digital transmission, fiber optic communication.
Applications of LASERS in other fields:
Holography: Principle, types, intensity distribution, applications. laser induced fusion. Harmonic generation. LASER spectroscopy. LASERS in industry: Drilling, cutting and welding. Lasers in medicine: Dermatology, cardiology, dentistry and ophthalmology.
