Showing 168 results for Photonic Crystal
Mohammad Noormohammadi, Mahmood Moradi, Abdollah Abbaspour Fathabadi, ,
year 20, Issue 0 (1-2014)
Abstract
Based on periodic anodization of aluminum, photonic crystals with photonic band gaps in the range of 625 and 740 nm were fabricated. Structural characteristic of prepared photonic crystal such as lattice constant can be well controlled by applying different voltage shapes. Optical measurement revealed that position of band gap depends on the lattice constant and consequently, the Bragg condition is satisfied. It was also found that the transmission light in photonic band gaps of the samples is lower than 2%.
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year 20, Issue 0 (1-2014)
Abstract
In this paper, the properties of linear/nonlinear transmission spectrum and filed distribution in 8-sery of one-dimensional Fibonacci photonic crystal structure with incident angle are investigated. On linear transmission, a resonant mode that shifts to higher frequencies with increasing of incident angled is observed. The filed distribution inside layers of the structure, for oblique incidents, becomes anisotropic. In the nonlinear transmission curves, around of the resonant frequency at different incident angles, the right to left and left to right transmission are different. This behaviour can be used to design all-optical diode (one-way transmission) from the structure.
Mr. Vahid Abedifar, Mr. Mohammad Mirjalili, Miss Elahe Faridchehr,
year 20, Issue 0 (1-2014)
Abstract
In photonic circuits, the substrate optical connections are usually realized by the Rib waveguides. The effective coupling between the slow light waveguides and the Rib waveguides is a major challenge which has been an interested research topic. Previously, several researches were conducted on the effective coupling while the incomplete coupling effects on the slow light propagation in the Photonic Crystal Waveguides (PCW) are not investigated so far. In this paper, an optimized structure of the ring-shape-hole PCW is utilized in order to investigate the effects of incomplete coupling on the slow light propagation. The simulation results show that a considerable portion of the propagation losses is caused by the incomplete coupling. On the other hand, the superposition of the waves reflected to the waveguide causes the irregular behavior of slow light. According to results, this phenomenon affects the calculation of the loss and the group index.
Mr Elyar Pourali, Prof. Mohammad Kazem Moravvej Farshi, Dr Majid Ebnali Heidari, Miss Zahra Mostashari Rad,
year 20, Issue 0 (1-2014)
Abstract
In this paper, using surface plasmon resonance effect, we demonstrate an optical OR gate. We have used gold and silver because of low losses of silver and gold in visible regime compared to other metals. The photonic crystal structure consists of a hexagonal lattice of iron nano rods, with a radius of r=50 nm and lattice constant of ɑ=200 nm, in a background of air. The designed optical gate, works in the wavelength of λ=0.65 μm with the TM (Hz,Ex,Ey) polarization. Simulation of this structure is done using the COMSOL software package.
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year 20, Issue 0 (1-2014)
Abstract
Abstract- Si based two dimensional photonic crystal consists of three nanoring resonator in panda configuration has been designed and investigated. A forward-dropped peak at 1550 nm proves that the proposed triple nano-ring resonator is a good channel drop filter,which makes it a good candidate for filter and dual channel nanomechanical sensor applications. It is realized that the symmetrical resonance output of this resonator enhance its suitability as a biosensor as this characteristic makes sensing multiple biomolecules.
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year 20, Issue 0 (1-2014)
Abstract
Abstract –Magnetic circular dichroism spectroscopy (MCD)is used in bio and solid magnetic materials. Ability of MCD in research and characterization of excited electronic states is so powerful while other spectroscopic methods are not efficient enough.Therefore in this research the transitions of magnetic photonic crystal with structure (TiO2/SiO2)6/Bi: YIG/(TiO2/SiO2)6 has been studied in the rang of 500 to700 by MCD. Which leads to recording of ⁶A_1g→4T_2g,⁶A_1g→4T_2g⁶,A_1g→4T_2gtransitions duo to field crystal transitions in 510,550,580,610, 680nm wavelength.
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year 20, Issue 0 (1-2014)
Abstract
Abstract- In this paper we try to describe and design of tunable microwave filter based on magnetic nanowires in magnetic photonic crystal. Use of magentic nanowires in tehse new structures yield to ability to control the ferromagentic resonance of the nanowires and then to use as microwave filters. Our theroretical results show the tunable microwave filetrs by the aid of external magentic field, which is very suitable in microwave devices.
Mrs Zahra Sadat Azizi, Dr Sayede Mehri Hamidi, Dr. Mohammad Mahdi Tehrancji,
year 20, Issue 0 (1-2014)
Abstract
Now days there is an interesting to producing narrow band pass filters by use of photonic crystals (PCs). There is two kinds of categories for PCs based on their radiant mode. Many plans for expansion and the restricted area to narrow wavelength photonic crystal bandwidth resonance mode are presented. To this end, we used the heterostructures PCs to create resonant modes. This design feature is the narrow width of the resonant modes, and you can adjust the distance and position of the resonant modes before and after construction of the building by changing the parameters of the emission angle of incident light.
Miss Mahshid Mokhtarnejad, Mr. Habib Tajali, Mr. Samad Roshan Entezar,
year 20, Issue 0 (1-2014)
Abstract
In this paper, the effect of incident angle on reflectivity and the active band gap of a one-dimensional resonant photonic crystal containing InGaAs/GaAs semiconductor quantum wells is discussed. The photonic crystal is excited by a strong external femtosecond pump pulse with a frequency close to the exciton resonance frequency. The results show that owing to the optical Stark effect and control of the exciton resonance frequency, the crystal band gap can be controlled. This band gap that is controlled by the Stark effect, can be useful to design optical switches and filters. Due to the small size of the introduced structure, it has the capacity to utilize in the optical integrated circuits and optical telecommunication systems.
Dr. Hassan Pakarzadeh,
year 20, Issue 0 (1-2014)
Abstract
In this paper, we investigate for the first time the parametric amplification in photonic crystal fibers (PCFs) with a continuously-decreasing zero-dispersion wavelength along their length. The use of these tapered fibers leads to the reduction of the length required for obtaining a high gain. Results show that although the gain is significantly increased, the gain bandwidth in such tapered PCFs is much narrower in comparison with that of un-tapered PCFs. Also, the gain flatness is quickly decreased with the increase of the input pump power.
Mr. Mohammadreza Hatami, Mrs. Roya Rajabi, Dr. Jamileh Seyedyazdi,
year 20, Issue 0 (1-2014)
Abstract
In this study considering refractive index dispersion and transfer matrix method, after optimization of the refractive index and thickness of the layers in a 1D photonic crystal in order to have a photonic band gap in the visible light region, we add a defect layer and made a photonic crystal with a symmetric structure and studied band gap and defect modes. The results show that considering refractive index dispersion for layers not only decrease the band gap, but also decrease the location and intensity of defect modes in the band gap. These findings are very important to consider in related applications.
Maliheh Hesamodini, Tahmineh Jalali, Fatemeh Parsaee,
year 20, Issue 0 (1-2014)
Abstract
In this paper, magnetic photonic crystals is investigated by their magneto-optical properties and interoducing defects to the structure. Physical relations and electromagnetic equations are proposed. A cavity-type 1-D magnetic photonic crystal which has a structure of (MG)4 (M) (GM)4 is simulated based on a finite element method and M is an active magnetic material and G is dielectric. Electric field profile is shown in optical regim and finally Faraday rotation is calculated and analyzed.
Dr Vahid Ahmadi, Alireza Mobini, Fatemeh Taghian,
year 20, Issue 0 (1-2014)
Abstract
In this paper we design InAs/GaAs QDs photodetector based on photonic crystal (PhC) slab for mid infrared (IR) range. The active layer is located in PhC cavity with resonant mode of 2.9μm. QDs dielectric function using Lorentz dispersion is inserted to Maxwell equations and then equations solved with 3 dimensional finite difference time domain method. Results show light-matter interaction at this mode and absorption spectrum for this mode with full width at half maximum of 0.87μm, increase up to 8 times compared with other wavelengths.
Farhad Mehdizadeh, Dr Mohammad Soroosh, Dr Hamed Alipour-Banaei,
year 20, Issue 0 (1-2014)
Abstract
In this paper we proposed an all-optical 3-Input NOR gate based on photonic crystals. In designing this gate we used three resonant rings. By employing the lattice constant of 625 nm, radius to lattice constant ratio equal to 0.265 and effective refractive index of 3.1, a fundamental crystal was obtained which is suitable for application in 1550 nm wavelength. By employing high intensity optical power into the device, based on Kerr effect the refractive index of the rods will be varied and the coupling of light into output will be controlled. The consistency of simulation results with the logical table of NOR gate confirms the suitable functionality of the device.
Abbas ۀhasempourardakani, Tahereh Kalantari, Hamid Nadgaran,
year 20, Issue 0 (1-2014)
Abstract
Abstract- In this paper, a one-dimensional photonic crystal composed of two defect layers with optical gain is considered. We place a nonlinear layer between two defect layers. Using the modified transfer matrix method, the effect of increasing the optical gain on the bistablity threshold is studied in both normal and oblique incidences. Our calculations show that the threshold of bistability decreases with increasing the optical gain. However, increasing the optical gain above a particular value leads to the enhancement of bistability threshold.
Somaye Rafiee, Dr. Majid Ghanaat Shoar,
year 20, Issue 0 (1-2014)
Abstract
Abstract- We study the potential of sub-wavelength spatial resolution of a two dimensional complex square-lattice photonic crystal (PC) consisting air holes immersed in the Ge medium. The band diagram calculations and the wave propagation studies are done utilizing the finite difference time domain method (FDTD) incorporating periodic and perfectly matched layer (PML) boundary conditions. In contrast to the common square PCs, photonic band structure shifts to the lower frequencies and the frequency corresponding to the effective negative refraction occurs in the second photonic band in near-infrared region, in our model system
Dr. Mehdi Zamani, Dr. Majid Ghanaatshoar,
year 20, Issue 0 (1-2014)
Abstract
Abstract- We have used a transfer matrix method (TMM) to introduce high performance reflection-type one dimensional magnetophotonic crystals (MPCs). In following, for practical purposes, the influence of the error in the thickness of individual layers on the operational parameters of the high-performance MPCs have also been considered. The results of the error analysis show that although the magneto-optical (MO) response of such high performance reflection-type MPC structures is affected by fabrication errors, their reflectance parameter is stable against nanometric thickness errors.
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year 20, Issue 0 (1-2014)
Abstract
Abstract- In this paper, wavelength, quality factor (Q) and confined mode distribution in the photonic crystal nanobeam cavity containing tapers with 4 air-holes nearby parabolic form narrowed nanocavity with couple of 9 air-holes mirrors are investigated. A high-Q mode was chosen to be created and enhanced by changing structural parameters of the nanobeam cavity. Variation of lattice constant and tapers, and number of air-holes in the mirrors offer improvements in the quality factors. The Q-values as high as 10410 are obtained by hiring couple of the tapers which their 4 air-holes centers have 25 nm reductions in positions. The results showed that the increasing in the Q-values occur as a consequence of more concentration of mode in the combined parabolic shape nanocavity and air-hole centers displaced tapers, and therefore reduction in diffraction and modal volumes.
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year 20, Issue 0 (1-2014)
Abstract
In this paper, confined modes in the photonic crystal nanobeam cavities containing air-holes taper is investigated which support small mode volume and high quality factor (Q). Computational results on this type of photonic crystal nanobeam structure demonstrate further increasing of the Q-value approximately 20550 in the fiber optics telecommunications wavelength range. The maximum Q-values obtained by combination of both nanocavity’s neighboring tapers and ends tapers plus carefully designed air-hole diameters and their non-periodic displacements within the tapered sections. Simulation in this paper is done using COMSOL Multiphysics software based upon the finite element method in the frequency domain.
Mrs Razieh Sanjari, Dr. Maryam Purmahyabadi,
year 20, Issue 0 (1-2014)
Abstract
One of most important problem in communication system is the control of the overall chromatic dispersion. In this article, a novel dispersion compensation photonic crystal fiber (DCPCF) with high negative dispersion is proposed. There are two concentric cores in the proposed DCPCF structure so that the outer core is formed by decreasing the size of the air-holes of the third ring and also additional air holes are incorporated between the air holes. The simulation results show the proposed structure for DCPCF has a very high negative chromatic dispersion of 11000ps/nm/km at 1.55μm wavelength. Also this DCPCF exhibits much less confinement loss in compare with the other DCPCFs-
