Showing 26 results for Photonic Crystal
A. Gharavi, H. Karimi-Alavijeh, E. Sarailou, M.–a. Baghban, G.–m. Parsanasab,
Volume 2, Issue 1 (2-2008)
Abstract
In this paper, we have reported the fabrication of two-dimensional photonic crystals, using a direct writing method in azo polymers. Periodic structures have been fabricated using the interference patterns of two coherent laser beams. The frequency response of the initial one-dimensional structure shows an attenuation of 19.3dB at 1554nm. The twodimensional structure shows 8.3dB and 11.3dB of attenuation at 1554nm in two perpendicular main axes of the structure. The diffraction pattern shows the characteristic rectangular pattern.
Faramarz E. Seraji, F. Asghari,
Volume 3, Issue 1 (3-2009)
Abstract
In this paper, we present a comparative numerical analysis to determine the refractive index of photonic crystal fibers (PCFs) by using FDFD method and used the results to evaluate the confinement losses of PCFs by considering the effects of air-hole rings in the cladding.
It is shown that by increasing the wavelength, the imaginary part of refraction index rises, resulting in increase of confinement losses nearly by order of 10. In lower wavelengths over the range of 0.2 to 1 μm, these losses were shown to be negligible. The obtained results show that as the number of air-hole ring in the cladding increases, the confinement losses over wavelengths would reduce. To show the effect of air-hole rings on confinement losses in PCFs, the FDFD method yielded accurate results that agree well with results of FEM method and source–model technique reported by others.
H. Pakarzadeh, A. Zakery,
Volume 4, Issue 1 (1-2010)
Abstract
In this paper, by including Raman scattering in the coupled-mode equations, the scalar modulation instability in photonic crystal fibers is investigated. The evolution of the pump, Stokes and anti-Stokes waves along the fiber as well as the conversion efficiency for two cases, with and without Raman effect, are studied. The effect of anti-Stokes seed and the pump depletion on the evolution of Stokes wave is also considered. Moreover, the parametric gain when it is affected by Raman gain is dealt with. The results show that it is important to take into account Raman scattering, especially for wide-bandwidth parametric amplifiers which results in an asymmetric spectrum and more amplification of the Stokes wave.
A. Namdar, R. Talebzadeh, K. Jamshidi-Ghaleh,
Volume 5, Issue 2 (7-2011)
Abstract
We perform a theoretical investigation on the Goos-Häenchen shift (the lateral shift) in one-dimensional photonic crystals (1DPCs) containing left-handed (LH) metamaterials. The effect was studied by use of a Gaussian beam. We show that the giant lateral displacement is due to the localization of the electromagnetic wave which can be both positive and negative depending on the incidence angle of Gaussian beam that can be excited the forward and backward surface states, respectively. Dependence of beam width on the incidence angle of beam and thickness of air layer for both backward and forward surface states are studied in this paper. We also find that the weak lossy in LH layers of 1DPCs may affect these shifts. These giant negative and positive lateral shifts are smaller than that of the lossless structure.
S.s. Mishra, Vinod Kumar Singh,
Volume 5, Issue 2 (7-2011)
Abstract
A novel design of Dual-Core Photonic Crystal Fiber (DC-PCF) with silica-air microstructures is proposed in this paper. Nonlinearity and confinement loss of DC-PCF are evaluated by using a Full-Vectorial Finite Element Method (FV-FEM) successfully. By optimizing the geometry of three ring DC-PCFs, a high nonlinearity (52w-1km-1) and low confinement loss (0.001dB/km) can be achieved at 1.55μm wavelength when diameter to pitch ratio (d/Λ) is 0.70.
Mojtaba Sadeghi, Saeed Olyaee, Fahimeh Taghipour,
Volume 6, Issue 1 (10-2012)
Abstract
In this paper, a fractal photonic crystal fiber (F-PCF) based on the 1st iteration of Koch fractal configuration for optical communication systems is presented. Complex structure of fractal shape is build up through replication of a base shape. Nowadays, fractal shapes are used widely in antenna topics and its usage in PCF has not been investigated yet. The purpose of this research is to compare normal photonic crystal fibers (N-PCFs) with F-PCFs through the simulation and optimization procedure based on the finite element method (FEM). The effective mode index of the fundamental mode is found for different PCF structures. In addition, dispersion properties of F-PCF are numerically calculated and compared with N-PCF.
Mr. Farshid Koohi-Kamali, Dr. Majid Ebnali-Heidari, Mohammad Kazem Moravvej-Farshi,
Volume 6, Issue 2 (10-2012)
Abstract
We report the results of our study on the role of microfluidic infiltration technique in improving the coupling characteristics of dual-core photonic crystal fiber (PCF) couplers. Using the finite element method (FEM), we evaluate the effective mode area, dispersion and coupling parameters of an infiltrated dual-core PCF. We use these parameters to design a compact and reconfigurable coupler by solving a set of coupled generalized nonlinear Schrödinger equations. This approach allows one to obtain wavelength-flattened dispersion characteristics with bandwidth of in the ITU region, and large walk-off length simply by choosing a suitable infiltrated refractive index. We also demonstrate that under certain conditions one can observe a pulse break-up effect to generate pulse trains with high repetition rate.
Dr. Samad Roshan Entezar,
Volume 7, Issue 1 (6-2013)
Abstract
The performance of a polarizing beam splitter based
on the one-dimensional photonic crystals (1D-PCs), is theoretically investigated.
The polarizing beam splitter consists of a symmetric stack of the low-index quarter-wave
plates and the high-index half-wave plates with a central defect layer of air. The
linear transmission properties of the polarizing beam splitter are numerically
simulated by the transfer matrix method. The results show that the wavelength
of the polarizing beam splitter can be tuned by adjusting the thickness of the defect
layer of air and the incident angle of light due to the resonant couple of the evanescent
waves localized at the interfaces between neighboring layers.
Dr. Majid Ghanaat Shoar, Dr. Somayeh Rafiee Dastjerdi, Dr. Kaveh Delfanazaric,
Volume 8, Issue 1 (1-2014)
Abstract
We study the focusing properties of a two dimensional complex square-lattice photonic crystal (PC) comprising air holes immersed in Ge medium. The finite difference time domain (FDTD) method is utilized to calculate the dispersion band diagram and to simulate the image formation incorporating the perfectly matched layer (PML) boundary condition. In contrast to the common square PCs with the same air filling factor, the frequency corresponding to the effective negative refraction occurs in the second photonic band and the spatial image resolution is improved.
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.
Dr Vahid Ahmadi, Mr Saeed Pahlavan,
Volume 10, Issue 1 (4-2016)
Abstract
Photonic crystal design procedure for negative refraction has so far been based on trial and error. In this paper, for the first time, a novel and systematic design procedure based on physical and mathematical properties of photonic crystals is proposed to design crystal equi-frequency contours (EFCs) to produce negative refraction. The EFC design is performed by the help of rectangular stair-case (RSC) photonic crystals. The RSC crystal is then converted to more common structures like pillar crystals by matching Fourier coefficients of periodic electric permittivity. Methods to design common crystals which have approximately equal Fourier components to the RSC crystal are also discussed. The proposed procedure can be used to design metamaterials without the difficulties of large trial and error. The devised procedure can also be applied in designing other structures involving photonic crystals.
Dr. Mahmoud Nikoufard, Mohsen Hatami,
Volume 10, Issue 2 (11-2016)
Abstract
A photonic crystal-based TE to TM polarization converter for integrated optical communication is proposed in this paper. The photonic crystal consists of air circular-holes in slab waveguide. The radius of holes are determined to be 291nm having lattice constant of 640nm using the gap map and band diagram. The polarization converter is composed of an InGaAsP triangular-shaped waveguide on SiO2 substrate. At first, the bandgap wavelengths of two-dimensional structure are determined using finite difference method and then polarization conversion length, polarization conversion efficiency and rotation are determined as a function of the ratio of height to width of the triangle waveguide. The simulation results show a minimum conversion length of 750nm with a conversion efficiency of about 90% could be obtained.
Dr. Savarimuthu Robinson, Dr. Krishnan Vijaya Shanthi,
Volume 10, Issue 2 (11-2016)
Abstract
In this paper, homogeneous, wavelength shift biosensor is designed for sensing the protein concentration using two dimensional Photonic Crystal Ring Resonator (PCRR). The sensor is designed to monitor the protein concentration from 0% to 100%. The proposed sensor is composed of periodic Si rods embedded in an air host with a circular PCRR that is placed between the inline quasi waveguides. It is observed that the resonant wavelength of the sensor is shifted (0.9 nm) to higher wavelength while increasing the protein concentration (5%) as the protein has a unique refractive index for each level. With this underlying principle, the performance of the sensor is analyzed for different protein concentration.
Mahmood Seifouri, Mohammad Reza Alizadeh,
Volume 12, Issue 1 (1-2018)
Abstract
In this paper, we report the numerical analysis of a photonic crystal fiber (PCF) for generating an efficient supercontinuum medium. For our computational studies, the core of the proposed structure is made up of As2Se3 and the cladding structure consists of an inner ring of holes made up As2Se3 and four outer rings of air holes in MgF2. The proposed structure provides excellent nonlinear coefficient and dispersion optimization. For the analysis, finite difference frequency domain (FDFD) method is employed. Because of the high nonlinear refractive index of the chalcogenide glass and high difference between the refractive index of the core and the cladding, a small effective mode area of 0.68 μm2 is obtained. The nonlinear coefficient is 14.98 W-1m-1 at the wavelength of 1.8 μm. Dispersion is almost flat from 1.6 μm up to 2.8 μm. The supercontinuum spectrum calculated ranges from 1 μm to 6 μm. The presented structure is appropriate for medical imaging, optical coherence tomography and optical communications
Mohammad Danaie, Ruhollah Nasiri Far, Abbas Dideban,
Volume 12, Issue 1 (1-2018)
Abstract
In this paper, a Y-shaped power splitter based on a two dimensional photonic crystal (PhC) for TE modes is designed and optimized. A triangular lattice of air holes is used for Y-shaped power divider. For analyzing these structures, plane wave expansion (PWE) and finite difference time domain (FDTD) methods are used. The simulation results show that more than 98% of the input power is transmitted to the outputs and the structure has just less than 2% reflected power. According to the simulation results this structure is suitable for high bandwidth optical integrated circuit at the 1550 nm wavelength.
Esmat Jafari, Mohammad Ali Mansouri-Birjandi,
Volume 12, Issue 2 (12-2018)
Abstract
In this paper, a new structure is provided for the dispersion compensating photonic crystal fibers in order to broaden the chromatic dispersion and increase the dispersion compensating capability in a wide wavelength range. In the structure, putting elliptical holes in the first ring of the inner core clad of a dispersion compensating fiber of the hexagonal lattice, increases the wavelength range of the dispersion compensation, and causes this fiber to have the capability of dispersion compensation in the whole E to U telecommunication bands. In this fiber, the minimal dispersion will be -1006 ps/(nm.km) at the 1.68 μm wavelength and at the 1.55 μm wavelength the dispersion coefficient will be -710 ps/(nm.km). The simulations are all done using the finite difference time domain numerical method.
Aghil Shaverdi, Mohammad Soroosh, Ehsan Namjoo,
Volume 12, Issue 2 (12-2018)
Abstract
In this paper, a channel drop ring resonator filter based on two dimensional photonic crystal is proposed which is suitable for all optical communication systems. The multilayer of silicon rods in the center of resonant ring enables one to adjust resonant wavelength of the ring and enhance power coupling efficiency between ring and waveguide. Refractive index and radius of multilayer rods inside the ring are important factors which help one to enhance the desired output parameters. The proposed structure is capable of presenting high quality factor near 1937 in conjunction with 0.8 nm pass band. The high coupling efficiency 99% is another advantage of the proposed filter.
Maryam Soltani, Alireza Keshavarz, Gholamreza Honarasa, Reza Ghayoor,
Volume 13, Issue 1 (1-2019)
Abstract
In a ring laser gyroscope, due to the rotation and the Sagnac effect, a phase difference between the two counter-propagating beams is generated. In this device, the higher phase difference between these two beams causes the better the interference pattern detection, and thus the sensitivity is increased. In this paper, the effect of inserting a dielectric-graphene photonic crystal inside a ring laser gyroscope on the interference pattern and the sensitivity of the device are studied and simulated using ABCD propagation matrix method. Results show that dielectric-graphene photonic crystal has a high transmission and therefore high efficiency in the wavelength of ring laser gyroscope. So it is a suitable choice to use in the ring laser gyroscope. Also, a comparison between ring laser gyroscope with and without dielectric-graphene photonic crystal shows that when the dielectric-graphene photonic crystal is in the system it is possible to build gyroscope with smaller lengths and high sensitivity.
Fatemeh Hadadan, Mohammad Soroosh,
Volume 13, Issue 2 (12-2019)
Abstract
In this paper, we proposed an all optical 4-to-2 encoder that has 4 input and 3 output ports. This device generates a 2 bit binary code based on which input port is active. We used nonlinear photonic crystal ring resonators along with optical power splitter for realizing the proposed encoder. In this device the switching rate and area are obtained about 333 GHz and 612µm2 respectively.
Sajjad Moshfe, Mohammad Kazem Moravvej-Farshi, Kambiz Abedi,
Volume 14, Issue 1 (1-2020)
Abstract
We present the procedure for designing a high speed and low power all-optical analog to digital converter (AO-ADC), by integrating InGaAsP semiconductor optical amplifier (SOA) with InP based photonic crystal (PhC) drop filters. The self-phase modulation in the SOA can shift the frequency of the Gaussian input pulse. The two output PhC based drop filters are designed to appropriately code the frequency-shifted analog signals by the SOA, converting them to four desired digital output levels. Our numerical results show that in an appropriately designed AO-ADC, the center wavelength (1572 nm) of an amplitude modulated Gaussian pulse of 1.8 ps width and 1.56 pJ energy can be shifted by 6.7 nm, by the SOA, and then be quantized and coded to four digital levels (00, 01, 10, and 11). The two point-defect PhC drop filters, compensating the effect of the frequency shift by SOA, minimize the AO-ADC integral and differential nonlinearity errors.
