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Chapter I Brief Introduction...
like telescopes, microscopes, interferometers, etc. Moreover, the study of
various optical phenomena, for example, diffraction, interference, dispersion,
polarizations, etc. has added either new branches or new dimensions to
optics.
Optics, the study of light, is usually divided into three fields, each of
which employs different method of theoretical treatment, these are (1)
geometrical optics (2) physical optics and (3) quantum optics.
The geometrical optics is treated by the method of light rays. The
physical optics is concerned with the nature of light and involves primarily the
theory of waves. Whereas, the quantum optics deals with the interaction of
light with the atomic entities of matter and which for an exact mathematical
treatment needs quantum mechanic [1].
Later on, the new fields like magneto-optics and electro-optics were
developed .The optical phenomena, which depends on an applied magnetic
field are called magneto-optics and, similarly, which depends on applied
electric field are called electro- optics. Nowadays, extended fields of optics,
for instant, singular optics, non-imagining optics, non-linear optics, statistical
otpics, etc, are available.
An optical vortex or phase singularity is a zero of an optical field- a
point of zero intensity. The research into the properties of vortices has begun
after the comprehensive study by Nye and Berry [2], which is known as
“Singular Optics”. Light can be twisted like a corkscrew around its axis of
travel and because of this; the light waves at the axis itself cancel each other
out. When projected on to a flat surface, an optical vortex looks like a ring of
2