In this paper, new structures of two-dimensional periodic photonic crystals in the form of dielectric rods with different geometric shapes, are presented. All photonic crystals presented in this paper are in a square lattice. Band structure and photonic band gap limitation graph of these structures are obtained by using numerical methods of plane wave expansion (PWE) for TE and TM modes. The simulation results for these structures show different photonic band gap widths and places for different structures and modes. تفاصيل المقالة

In this paper the effects of transmittance, dispersion angle and diffusion length on the quantum efficiency of solar cells (QESC) have been simulated and investigated. Optical path technic is used for simulation. The results show that base thickness, diffusion length, dispersion angle, number of optical confinement path and transmission angles have an extremely effects on the QESC. Simulation results show that for optical paths with and  QE can be achieved to 72% which is approximately 12% more than . The simulation results with grating in SC and reflecting about 100% at the end of the device show that QE increase to ٪47 with which is more than the results of device without grating. So the results show that the QESC increase with increasing the dispersion angle and diffusion length in the grating device. تفاصيل المقالة

In this paper, a photonic crystal waveguide with point defects and lattice constant perturbations of +5%, -5% are being investigated. Firstly waveguide structures with constant and specific parameters are being studied and photonic band gap diagrams for TE/TM modes are depicted; then pulse propagation in the frequencies available in the band gap are shown. After that, effects of parameters like refractive indicesand radius of the rods on the band gap diagram of TE/TMmodes are evaluated. It has beenshown that, by increasing the refractive indices and radius of the rods, band gap diagrams would be shifted to lower frequency amounts.  تفاصيل المقالة

In this paper, we present a switch based on coupling and resonance in the
graphene plate and rings operating at 10 THz. This structure consists of several layers of
Hexagonal Boron Nitride (hBN), SiO2 and P+Si, such that graphene plates and rings are
inside the hBN layer. The terahertz wave is incident from the upper part of the switch
and Surface Plasmons (SPs) are excited by the grating in the structure on the graphene
plate beneath the nano-aperture and moves towards the ports available on the left and
right of the switch. At first, at the certain applied voltage, the SPs cross the left port and
this port is ON. With the increase in voltage and the change in the chemical potential,
switching occurs and the SPs exit from the right and this port is ON while the left port
turns OFF. The extinction ratio in this structure is 18dB and the size of the structure is
1μm. Aforementioned benefits make this switch the best choice for using in integrated
optical circuits. تفاصيل المقالة

Abstract Plasmons in nanometer structures are caused by the interaction between electromagnetic waves and electrons on the metal surface. In this article, a comprehensive and detailed investigation of the effect of effective parameters on the performance of structured MIM waveguides (metal-insulator-metal) has been carried out. These structures are widely used in sensor applications based on refractive index changes or filters. This paper examines the impacts of altering factors like waveguide size, metal type, and insulation while also proposing novel structures with circular and square resonators,Then we simulated the structure of the MIM waveguide connected to the cavity of the T-shaped resonator for different values for the length L of the cavity, It is possible that this issue has a good use in filters and systems with high bandwidth to separate channels  . Also,the properties of surface plasmon polaritons emission were investigated in the case where a resonator is vertically connected to it. The transmission diagram had compared to the MIM waveguide without resonator. تفاصيل المقالة