Showing 4 results for Reflection
Dr. Saifollah Rasouli, Mr. Mohammad Yeganeh,
Volume 7, Issue 2 (8-2013)
Abstract
One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, production and applications of these types of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam from a plane wave of a He-Ne laser beam and a two-channel moiré based wavefront sensor is used to measure wavefront gradient of the vortex beam. In two different arrangements the vortex beam experience odd and even number of reflections, respectively, and from the moiré pattern deformations the topological charge of the vortex beam and its sign are determined.
Dr. Samad Roshan Entezar, Mrs Arezo Rashidi ,
Volume 8, Issue 2 (7-2014)
Abstract
In this paper, properties of reflection phase in one-dimensional quaternary photonic crystals combining dispersive meta-materials and positive index materials are investigated by transfer matrix method. Two omnidirectional band gaps are located in the band structure of considered structure. However, we limit our studies to the frequency range of the second wide band gap. We observe that the value of the reflection phase difference between TE and TM waves can be controlled by changing the incident angle and frequency. Also, the results show that the reflection phase difference in the second band gap increases by increasing the incident angle, and remains almost unchanged in a broad frequency band. Furthermore, at two points near to the edges of the gap the reflection phase difference keeps almost zero in spite of the change of incident angle. Based on these properties, phase compensators and omni-directionally synchronous reflectors and also polarizers can be designed.
Mandana Jalali, Hamid Nadgaran, Daniel Erni,
Volume 11, Issue 2 (8-2017)
Abstract
In this paper a novel anti-reflection (AR) coating based on silicon nano-bars is designed and its impact on the performance of crystalline silicon (c-Si) thin-film solar cells is extensively studied. Silicon nano-bars with optimized size and period are embedded on top of the active layer, under a 100nm Si3N4 layer. As a result of the proposed layer stack, an inhomogeneous intermediate layer with effective refractive index amid the two layers is formed and a graded refractive index AR coating is achieved, which has a substantial effect on broad, omnidirectional reduction of the reflection spectra. To validate our claim, the proposed structure as well as four conventional AR coatings are simulated and through the numerical analysis of both the spectral response of the reflection factor and the silicon active layer absorption spectra, it is shown that the proposed design outperforms conventional already existing AR coatings, and in addition provides a strong coupling of the incident light to the active layer, while improving the overall efficiency of the thin-film solar cell.
Sepideh Esmaeili Germezgholi, Behrooz Rezaei, Sohrab Ahmadi-Kandjani,
Volume 14, Issue 2 (12-2020)
Abstract
In this paper, a thin film silicon solar cell with anti-reflection coatings on front surface and the combination of periodic grating and photonic crystal on its back surface has been considered. The thickness and number of anti-reflection coatings, as well as the geometric and physical parameters of photonic crystal and grating are optimized to increase the optical absorption of solar cell. The simulations have been performed using the finite difference time domain method with Lumercial software. The results show that the optical absorption of solar cell has been increased significantly by utilizing the anti-reflection coatings, photonic crystal and grating.
