ABSTRACT
This chapter reveals the optics pertains of generation, amplification, propagation, detection, change, and modulation of light wave. It describes a very tiny portion of the electromagnetic spectrum responsible for vision and Measurement techniques based on light fall into the subject of optical metrology. Bessel beams propagate over a considerable distance without diffraction. They also has a "healing" property in that they exhibit self-reconstruction after encountering. The magnitude and sign of the topological charge of the vortex beam can be determined from the interference pattern of the beam with a plane or a spherical reference wave and the diffractionless solutions of the Helmholtz wave equation in the form of Bessel functions constitute Bessel beams. A laser beam propagates as a nearly unidirectional wave with little divergence and with finite cross-section. A plane wave propagates in a particular direction, whereas a spherical wave is not unidirectional that is a phase-singular beam embedded in a Gaussian beam.
