Showing 10 results for Nonlinear Optics
G. Aldea, H. Gutiérrez, J. M. Nunzi, G. C. Chitanu, M. Sylla, B. C. Simionescu,
Volume 1, Issue 1 (6-2007)
Abstract
Layer-by-layer (LBL) electrostatic assembly of poly-electrolytes is proving to be an increasingly rich and versatile technique for the formation of multilayered thin films with a wide range of electrical, magnetic, and optical properties. In the present work we synthesized a new nonlinear optical (NLO) maleic acid copolymer containing Disperse Red 1 moieties, built-up multilayer assemblies by alternate adsorption of poly (allylamine hydrochloride) (PAH) and maleic copolymer derivative, and carried out an investigation on their second harmonic generation (SHG) properties. The resulting multilayer assemblies exhibit SHG which arises from the non-centrosymmetric alignment of the chromophore in the copolymer. The SHG signal increases with the number of chromophore-containing polymer layers, up to 5 layers. Further assembly reduces the signal
R. P. Mildren,
Volume 1, Issue 1 (6-2007)
Abstract
Solid-state Raman lasers are known as important sources at normally difficult to access wavelengths, and our recent studies have shown that they also form the basis of a class of wavelength selectable lasers. This paper summarizes our recent studies in wavelength selectable Raman lasers in the visible (532-650 nm) and ultraviolet (266-321 nm).
S. Ghavami Sabouri, A. Khorsandi,
Volume 2, Issue 1 (2-2008)
Abstract
In this paper the Phase-Matching bandwidth, effective nonlinear coefficient and the walk-off angle within the effective bandwidth of the LiGa(SexS1-x)2 biaxial nonlinear crystals are calculated using the Genetic algorithm (GA). This calculation is held for all tree principle XY, YZ and XZ planes individually. The results are shown the accuracy of the applied algorithm is quite qualified.
Alireza Keshavarz, Zahra Abbasi, Mohsen Hatami,
Volume 6, Issue 1 (10-2012)
Abstract
Propagation of incoherently soliton pairs in photorefractive crystals under steady-state conditions is studied. These soliton states can be generated when the two mutually incoherent optical beams with the same polarization and wavelength incident on the biased photorefractive crystal. Such soliton pairs can exist in bright-bright, dark-dark, gray-gray as well as in bright-dark types. In this paper the stability against small perturbation in amplitude is investigated while they do not break up, and instead oscillates around the soliton solution. Results show that the bright-bright pairs can travel a longer distance without broadening in comparison with the other types. Finally the effect of self-deflection is simulated numerically.
H Pakarzadeh, K Nielsen, A. C Brunetti, K Rottwitt, A Zakery,
Volume 6, Issue 2 (10-2012)
Abstract
A polymethylmethacrylate (PMMA) microstructured polymer
optical fiber (mPOF) is fabricated and characterized. Using the cut-back
technique the fiber loss is measured which is higher than the step-index silica
fibers. Through a novel experimental scheme, the backward Stokes spectrum of
the fabricated mPOF is recorded over a range exceeding 3000 cm‑1
during the cut-back method and compared with that of step-index silica fiber.
Especially, the gain coefficient of the Raman peak at 2950 cm‑1
is directly measured, that is without comparing with other known material. The
results show a very good agreement with those obtained through other
experimental schemes.
Dr. Mohsen Hatami, Ms. Elham Yousefi,
Volume 7, Issue 2 (8-2013)
Abstract
In this study, a new numerical method is introduced to obtain the exact shape of output pulse in the chalcogenide fiber Bragg grating (FBG). A Gaussian pulse shape with 173 ps width is used as an input pulse for lunching to a 6.6 mm nonlinear FBG. Because of bistable and hysteresis nature of nonlinear FBG the time sequence of each portion of pulse is affected the shape of output pulse. So we divide the pulse to leading and trailing portion in time. By using bistability curve and Fourier transformation, the exact shape of output pulse is simulated. In comparison of non-unique solution for output pulse in the previous papers, the results of this study have an optional merit.
Dr Amin Ghadi, Prof Saeed Mirzanejhad,
Volume 10, Issue 1 (4-2016)
Abstract
In this paper, we numerically simulated a glass-based all-optical 1×N power splitter with eleven different configurations using soliton breakup in a nonlinear medium. It is shown that in addition to reconfigurability of the proposed splitter, its power splitting ratio is tunable up to some extent values too. Nonlinear semivectorial iterative finite difference beam propagation method (IFD-BPM) with inclusion of two photon absorption (TPA) effects is applied to simulate the soliton propagation at different mode power. It is shown that operation of the proposed splitter depends on input mode power and an all-optical reconfigurable-tunable functional device is designed with nonlinear optical (NLO) property of a simple structure.
Sohrab Behnia, Javid Ziaei, Mehdi Khodavirdizadeh,
Volume 11, Issue 2 (8-2017)
Abstract
The emergence of second-harmonic generation (SHG) is a pivotal issue to the development of nano-optical devices and interfaces. Here, we perform a classical analysis of the SHG dynamics with the aim of determining critical values of the electric field. The signals of the SHG process are nonlinear, so it seems reasonable that chaos theory can be a suitable tool to analyze their dynamics. For this purpose the bifurcation analysis and a new measure known as the scale index were employed. Obtained results show that the dynamics approaches from stable to self-pulsing and eventually to chaos through a period-doubling route. Moreover, the scale index can detect the critical strength of the electric field, where above it the SHG dynamics is chaotic.
Elham Yousefi, Mohsen Hatami, Amin Torabi Jahromi, Sajjad Dehghani,
Volume 13, Issue 2 (12-2019)
Abstract
In recent decades, fiber Bragg gratings (FBGs) have been very much considered for their many applications in optical communication systems, as well as due to their bistability and multi stability properties. In this paper, the formation of ternary stability (TS) in nonlinear chalcogenide fiber Bragg gratings (NCFBGs) is investigated via numerical simulations. Effective parameters on TS such as the FBG length, input wavelength and nonlinear property (or nonlinearity) on TS formation are introduced and studied. It is found that there exists a minimum length for each third order nonlinear coefficient that TS phenomena can be observed. Also, the threshold intensity for TS formation is calculated with respect to the length, input wavelength and third order nonlinearity. In addition, the relevance between the minimum length for TS formation and the third order nonlinearity in the range of chalcogenide nonlinearities are looked into. It is numerically confirmed that increasing the input wavelength (in a valid FBG input wavelength range) increases the TS formation threshold intensity, while decreases the needed FBG length. Because of using experimental values in this paper, it has valuable information about designing the all-optical device with three - level stability which makes NCFBG a suitable option for all-optical ternary switching and all-optical memory in the integrated optical circuits.
Mr. Moein Golestanifar, Dr. Mohammad Ali Haddad, Mr. Amir Namiq Hassan, Dr. Fatemeh Ostovari,
Volume 17, Issue 2 (6-2023)
Abstract
The spatial self-phase modulation (SSPM) method was used to study the nonlinear optical responses of hydraulic oil containing dispersed nanosheets of reduced graphene oxide (rGO), hydroxylated rGO (rGO-OH), and carboxylated rGO (rGO-COOH). The intensity-dependent number of observed symmetric diffraction rings was analyzed to estimate the samples' thermally induced nonlinear refractive indexes and lead to estimated thermo-optical coefficients. Based on the observed symmetric diffraction rings, the nonlinear refraction coefficient and thermo-optical coefficient of samples were estimated to be in the order of magnitude of 10-6 cm2/W and 10-2 K-1, respectively. The results indicated that the presence of rGO derivatives significantly enhanced the optical nonlinearity of hydraulic oil.
