Journal of Optoelectronical Nanostructures
Volume:7 Issue: 2, Spring 2022

A novel absorber based on a one-dimensional photonic crystal (PhC) is proposed by combining the absorption property of gold and graphene films. We designed two photonic crystals consisting of silicon and silicon dioxide layers with lattice constants 125 and 260 that alternate in one dimension. We placed a 125-nanometer-thick layer of graphene between the two photonic crystals and an 8-nanometer-thick layer of gold at the end of the second photonic crystal. When graphene is placed between two photonic crystals, a topological edge mode excitation creates a strong absorption enhancement. In this study, the absorbing spectrums and field distribution are analyzed by using the transfer matrix and the 2.5 dimensional variational finite difference time domain method (2.5 var.FDTD). The absorption spectrum for different angles was studied (θ=0 to 60), and more than 87 percent absorption can be maintained for θ =40°. The results of our studies will enhance the interaction between light and matter. Thus, opening up the possibility of their application for the absorption and modulation of light. Keywords: Photonic crystals, Absorber, Gold nanostructures,Graphene.

Optical logic gates are very important for all-optical communication systems. An all-optical majority gate will be proposed and designed in this paper. The proposed structure will be designed based on photonic crystal structures. The proposed structure works based on optical threshold switching which is realized using nonlinear resonant cavities. The nonlinear resonant cavities are created by adding a nonlinear defect made of doped glass that has a high Kerr coefficient. The proposed structure is simulated using Rsoft photonics CAD. The simulations are done using the finite difference time domain method. The proposed majority gate has 3 input ports and only one output port. The output port is ON, when at least two of the input ports are ON. The working wavelength of the proposed structure is 1550 nm. For the proposed all optical majority gate the ON/OFF contrast ratio and the bit rate are 19.5 dB and 500 GS/s respectively.

Using a photonic crystal array, an all-optical half-subtractor has been designed that consists of four resonant rings and some waveguides which connect two input ports to output ports. The silicon rods with a period of 0.631 μm are arranged in the form of a square. Concerning the four working states of the device, different radii of nonlinear rods inside the resonators have been chosen. This issue makes the different switching thresholds for the rings and results in the correct dropping operation for optical waves. Unlike the previous works, each bit is defined to one port, and the input ports have equal power. The maximum rise time and the contrast ratio of the presented circuit are 3.5 ps and 8.45 dB, respectively. The fast response and small size are the main advantages of the presented subtractor. The obtained results demonstrates that the designed device has an acceptable performance which is proper for optical applications.

Polymers are a very vast classification of materials that possess a lot of applications in various industries. For instance, they have application in structure modification of the perovskite solar cells (PSCs). Polymers’ application in perovskite solar cells can be divided into their usage as hole-transporting materials (HTMs) and the ultrathin interfaces between hole transporting materials and the perovskite layer. In the present research, we tried to highlight this application from the simulation perspective using SCAPS-1D software. For this purpose, this study investigates the effect of using different polymeric HTMs and interfaces from the photovoltaic parameters view. The total PSC structure was in the form of Au (Back contact)/ HTM/ polymeric Interface (if there are)/ CH3NH3PbI3 (absorber)/ TiO2 (Electron Transporting Material: ETM)/FTO (counter electrode). Results represented the best hole transporting material and interface as PEDOT:PSS and P3HT layers. The final efficiency was obtained at 18.77% with the optimal mentioned layers’ materials.

In this paper, we employed Raman spectroscopy to investigate Indium sulfide thin layer films deposited on glass substrates using the PVD method. The results showed that the bandwidth and Raman shift of different In2S3 thin films depended on the annealing temperature. In addition, the crystallization stage from tetragonal to cubic occurred at the excessive temperature range of 350-400 °C. The Raman spectroscopy of the In2S3 thin films before annealing and at 300 °C indicated the existence of β- In2S3 at 70, 166 and 281 cm-1 in the active modes of the spectra. New modes that were related to α-In2S3 appeared at 126, 244, and 266 cm-1 after thermal treatment at 400 °C for 30 and 60 min. Our results are in agreement with the phase transitions observed from the XRD analysis of In2S3 thin films. There are few reports about the Raman spectroscopy of In2S3 thin layer films deposited using vacuum thermal evaporation. In the present paper, the Raman spectra of In2S3 thin films with different thicknesses as well as the effects of temperature on their depositions in vacuum were examined.

Recently soliton propagation in few-mode fiber has been studied. In this paper, we used commercially few-mode fiber for investigating the soliton propagation. Three modes exist in this fiber, by considering polarization, we have six propagation modes. Initially, we calculate the propagation mode, effective cross-section, and dispersion for each mode then soliton propagation in fiber modes with respect to phase are simulated. The nonlinear effect causes XPM which affects propagation modes to each other. By various values of phase, the first maximum energy transfer between modes is calculated. We find minimum normalized length 0.66 which equal to a length of 23.3 meters of silica fiber for energy exchange. The energy exchange can be used as a basis for all-optical switching. Interestingly, these effects cause energy transfer between different modes and strongly depend on the phase difference. So, the results of this simulation can be used to design all-optical self-switches and all optical logic gates.