Keywords (Extracted from title, table of contents and abstract of thesis)
quantum studies, micromaser, quantum phase fluctuations, twophoton micromaser, onephoton micromaser, quantum phase properties, cavity eigenmodes, inject atomic coherence 
Abstract The oneatom maser or micromaser has been a system of fundamental interest in quantum optics. It provides an experimental realization of the JaynesCummings model. As compared to the ordinary laser, field inside a micromaser exhibits a number of interesting features. In this thesis, we consider the problem of quantum phase fluctuations of the field generated in one and twophoton micromaser. In a onephoton micromaser, we discuss the effect of cooperative atomic interactions, cavity losses, and pump fluctuations on quantum phase properties of the field. We consider, initial coherent state of the radiation field and atoms initially in the excited and coherent superposition of their atomic states, respectively. We find that quantum phase properties of the field in a micromaser are highly sensitive to twoatom events and cavity losses. Both contribute to the randomization of the well defined phase structure associated with the initial coherent state. However, the approach towards the randomization is quite different in the two cases. We also find that the fluctuations, associated with the random injection of the atoms, affect the phase structure of the coherent state. Next, we study the quantum phase properties of the field in a twophoton micromaser, including the effects of the finite detuning of the intermediate level. For initial coherent state of the cavity field and atoms initially in their excited state multipeak phase structure appears which eventually leads to the randomization of the cavity field phase. However, the approach towards the randomization depends upon the detuning. If the atoms are injected in a coherent superposition of their upper and lower atomic states then the phase distribution evolves into twopeak structure. For initial thermal state and atoms in polarized state, cavity field acquires some phase. We also consider the effect of the finite Q of the cavity and random injection of the atoms in our system. Finally, we discuss the effects of spatial mode function in a onephoton micromaser in the presence of twoatom events. It is shown that twoatom events allow us a possibility to study the effects of different cavity eigenmodes in a micromaser. We find that squeezing properties of the radiation field depend upon the parity (odd or even) and order (lower or higher) of cavity eigenmodes. For example, squeezing can be obtained for oddorder cavity eigenmodes which completely vanishes for evenorder modes. Our results also show that effects similar to selfinduced transparency which are studied in JaynesCummings model with atomic motion are never obtained in a micromaser in the presence of twoatom events.
