This dissertation deals with nonclassical properties of radiation fields. Nonclassical properties are a required element of generating entanglement, and entanglement is the most valuable element in quantum information science. Entangled states can be generated from nonclassical states and play an essential role in quantum cryptography, quantum teleportation, and quantum computation. Using quantities that can be considered as nonclassical measures, such as quasi-probability distributions(P, Q and Wigner functions) and the Mandel Q-factor, we determine whether nonclassical states are generated or not in a given situation. Mathematically, nonclassical states can be generated by the photon creation operation applied to classical-like states, i.e., thermal and coherent states. Physically, they can be generated in a cavity system and in a linear optical system. Here we consider two cases. First, we study nonclassical properties of the states after the photon creation and annihilation operations on the thermal and coherent field states. Second, we determine the existence of degree of entanglement in a V-type three-level atomic system inside a resonant cavity.