Study Of Casimir Effect In Different Micro Cavities

The emergence of quantum theory has profoundly altered our conception of space. Quantum theory says that the space is filled vacuum field fluctuations. One of the most surprising predictions of modern quantum theory is that the vacuum of space is not empty. In fact, quantum theory predicts that the vacuum teems with virtual particles in and out of existence. Although initially a curiosity, it was quickly realized that these vacuum fluctuations had measurable consequences in microscopic physics, for example the radiative corrections in subatomic physics, the spontaneous emission processes and Lamb shift in atomic physics.The best evidence for vacuum fluctuations of the electromagnetic fields is Casimir effect that exhibits attractive forces between two perfectly conducting parallel plates in the vacuum. The force was predicted by H. B. G. Casimir in 1948 and soon confirmed experimentally by Lamoreaux and by Mohideen et al. In 2009, the research team of Harvard University confirmed the presence of Casimir repulsion in the experiment. Their experiment shows that the appropriate choice of materials optical properties can be converted attractive Casimir into Casimir repulsion.The other vacuum quantum effect is the process of photons creation from the vacuum due to the motion of the cavity mirrors or due to time-dependent properties of materials, commonly referred to as dynamical Casimir effect. The phenomenon was theoretically predicted by Moore in 1970. In 2011, Wilson and coworkers reported about the successful experiment on photon creation using DCE effect in superconductive circuit.The study is mainly in the following two aspects. Firstly, we studied the system consists of a non-stationary cavity and an ensemble of two-level atoms at finite temperature under resonance conditions. Due to strengthened coupling, rotating wave approximation is no longer applicable. Therefore we investigated strengthened coupling effect and thermal effect on dynamical Casimir effect and collective excitation effect under counter-rotating wave approximation. We described the model of the system and derived Hamiltonian and master equation with counter-rotating wave approximation. After that, we calculated the number of photons and the number of excitons at finite temperature with counter-rotating wave approximation. Compared with the condition of rotating-wave approximation, the created photons and the created excitons increased obviously at different temperatures and different total coupling strengths. The numerical results show that counter-rotating wave terms enhance dynamical Casimir effect and collective excitation effect at finite temperatures. Secondly, we calculated the Casimir force between a perfect plane mirror and a semitransparent plane mirror in a cavity under vacuum state and squeezed vacuum state. We obtain the analysis expression of the Casimir force, which shows that the interaction of the two walls in this system is attractive. The value of the Casimir force varies with the cavity size and the amplitude of the field reflectivity.