Abstract:
The objective of this thesis is to explore the effects of the quantum coherence
towards the precise control of the manipulation of the interaction between the atomic
or molecular systems and the electromagnetic fields. This leads to the maneuvering
of the optical response of the medium. More precisely, the present study is devoted
to the coherence phenomena designated for the manipulation of dispersion together
with absorption in an anisotropic as well as an isotropic medium. Such a control is
attributed to the quantum interference created by the control field. Many novel optical
phenomena such as electromagnetically induced transparency, coherent population
trapping, lasing without inversion, saturated absorption techniques, enhancement of
refractive index, manipulation of group velocity etc. are consequences of the quantum
interference and coherence. Coherence can also be generated by vacuum that arises
due to the quantum interference between the spontaneous emission pathways. The
present study deals with the application-oriented aspects of the these novel optical
phenomena. Further, besides the manipulation of linear response, quantum coherence
plays a vital role for the control of nonlinear response, as well. Several nonlinear
phenomena such as saturable and reverse saturable absorption along with the optical
bistability have been explored. The theoretical investigations have been done in the
framework of semiclassical picture of the light-matter interaction, while the dynamics
of the constituents of the medium is studied using density matrix formalism.
