Showing 8 results for Dispersion
H. Nadgaran, M. Sabaeian,
Volume 2, Issue 1 (2-2008)
Abstract
In this work the effects of heat generation on the modes of Yb:Glass double clad fiber laser were investigated. The thermal dispersion and thermally-induced birefringence were considered when the gain medium becomes an anisotropic medium. The results showed considerable modifications of laser modes profiles, in particular for transfer magnetic (TM) and transfer electric (TE) modes which their polarization vectors possess radial and azimuthal components.
A.k Gautam, V Mishra,
Volume 5, Issue 1 (1-2011)
Abstract
In this Article dispersion characteristic of conventional optical waveguide with helical winding at core – cladding interface has been obtained. The model dispersion characteristics of optical waveguide with helical winding at core-cladding interface have been obtained for five different pitch angles. This paper includes dispersion characteristics of optical waveguide with helical winding, and compression of dispersion characteristics of optical waveguide with helical winding at core-cladding interface for five different pitch angles. Boundary conditions have been used to obtain the dispersion characteristics and these conditions have been utilized to get the model Eigen values equation. From these Eigen value equations dispersion curve are obtained and plotted for modified optical waveguide for particular values of the pitch angle of the winding and the result has been compared.
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. Hassan Pakarzadeh, Ms. Masoume Bagheri,
Volume 9, Issue 2 (11-2015)
Abstract
In this paper, the gain spectrum and the saturation behavior of one-pump fiber optical parametric amplifiers (1-P FOPAs) are investigated by taking into account the fourth-order dispersion coefficient b4 in the analysis. The results show that it is necessary to consider b4 in the analysis when the wavelength difference between the signal and pump waves is large enough and/or whenever the pump wavelength approaches to the zero-dispersion wavelength (ZDW) of the fiber. Also, it is shown that by increasing the value of b4, the gain value is increased and the saturation power is decreased. Finally, the simulation results are compared with the available experimental data and a very good agreement is obtained.
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
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.
Mr Saeed Ranjbar, Dr. Abbas Azarian,
Volume 15, Issue 2 (7-2021)
Abstract
In this article, the optical properties of silver cubic-shape nanostructures (SCNs) were analyzed by employing the discrete dipole approximation (DDA) in aqueous media. The absorption, dispersion and extinction cross-sections of these nanostructures were calculated based on the wavelength change of the incident light in the visible and near infrared region. Moreover, the height change, wavelength and full width at half maximum (FWHM) of extinction cross-section peaks (from plasmon resonances) based on the size of nanoparticles and the environment dielectric constant were surveyed. The results showed that only two peak modes, named dipole peak and quadrupole peak, exist in this spectrum, such as spherical particles.
