ABSTRACT

Light Amplification by Stimulated Emission of Radiation (LASER) is an intense monochromatic source of electromagnetic radiation. It can generate coherent beam of photons having widely varying frequencies and intensities. It can be very small having the size of a micrometer; it can also be as large as the size of a football ground. Laser action needs three essential components: Cavity resonator, active medium and pumping mechanism. The cavity is confined within two mirrors which reflect the optical wave back and forth within the cavity to help buildup of energy. This provides optical feedback so that the amplified energy is fed back to help further amplification. The active medium should be filled with atoms or atomic systems with discrete quantized energy levels such that the population inversion can be established. Medium can be a pure atomic vapor or mixture of atoms like helium and neon, liquid like organic dye or a solid like a diode or crystal of ruby.