Ali Rostami, Samiye Matloub, Mohammad Kazem Moravvej-Farshi,
Volume 3, Issue 1 (3-2009)
Abstract
In this work, using perturbation technique we have developed an approximate analytic model for evaluating the band structure of a 2-D octagonal photonic quasicrystal (PQC). Although numerical techniques are being used for evaluating such band structures, developing a numerical model to the best of our knowledge this work is the first instance of reporting helps to understand the physical properties of the structure more easily. Use of perturbation technique can be beneficial in approximating the photonic band structures, in PQCs made with low-dielectric contrast materials, with high accuracy. To the best of our knowledge this work is the first instance of reporting the development of such an analytic model for octagonal PQCs. In addition, we have studied the effect of variations in the dielectric contrast on the photonic band structure.
Phd Student Neda Asili Firouzabadi , Dr Mohammad Kazem Tavassoly,
Volume 15, Issue 2 (7-2021)
Abstract
Recalling that the rotating wave approximation (RWA) is only valid in the weak coupling regimes, our purpose is to study the Hamiltonian dynamics of the interaction between various configurations of a three-level atom of Lambda, V, or Ladder-type distinctly with a two-mode radiation quantized field, while the RWA is not considered. Generally, this prevents one to achieve an analytical solution. Moreover, as we will show, using the perturbation theory analytical solution can be successfully obtained. According to our considerations, the contribution of counter rotating terms (CRTs) within the ordinary Hamiltonian is equivalent to arriving at some intermixed intensity-dependent atom-field coupling as functions of the two modes of the field, i.e., f(n_1, n_2). At last, via evaluating the time-dependent atom–field state vector, the effects of CRTs on a few nonclassical properties of the state of the system as atomic population inversion and photon statistics are numerically studied. It is observed that, the presence of CRTs in the Hamiltonian dynamics destroys the clear patterns of collapse-revival phenomena in the time behavior of the evaluated quantities.
