Showing 6 results for Dehghan
M. Erfani Jazi, M. Dehghan Baghi, M. Hajimahmodzadeh, M. Soltanolkotabim,
Volume 5, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 5, No 1, Winter-Spring 2011)
Abstract
In this paper, we report the experimental results of a pulsed flash lamped Nd:YAG laser at wavelength of 1064 nm and Qswitched by Cr4+:YAG solid state saturable absorber. We have obtained the output energy (E) and pulse-width ( p τ ) of this laser for various initial transmissions of this saturable absorber. Furthermore, the effect of reflectivity of the output coupler (R), diameter of the rod (d), and optical length of the cavity (l) on the laser output has been investigated. We have used the corner cube as a back mirror. We have obtained pulse-width 15ns with 31 mJ output energy. We have also analyzed this laser theoretically which agrees well with our corresponding experimental results.
Mrs Marzieh Nadafan, Prof. Rasoul Malekfar, Mrs. Zahra Dehghani,
Volume 8, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 8, No 2, Summer-Fall 2014)
Abstract
Polyurethane closed cell (PUCC)/SiO2 nanocomposites have been prepared by using in situ polymerization approach. The third-order optical nonlinearities of PUCC/SiO2 nanocomposites, dissolved in DMF are characterized by Z-scan technique at the measurement wavelength of 532 nm. The nonlinear refractive (NLR) indices and nonlinear absorption (NLA) coefficients of samples were calculated from closed and open aperture Z-scan in the order of 10-8 with negative sign and 10-5 , respectively. The origin of optical nonlinearity in this case may be attributed due to the presence of two photon absorption (TPA) effect. The synthesized samples were examined by optical microscopy, SEM imaging and Raman spectroscopy. All the results related to NLO properties, suggest that PUCC/SiO2 may be a promising candidate for the application to optical limiting in the visible region.
Dr. Abbas Behjat, Mehdi Dehghani, Fariba Tajabadi, Nima Taghavinia,
Volume 9, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 9, No 1, Winter-Spring 2015)
Abstract
Planar superstrate CuInS2 (CIS) solar cell devices are fabricated using totally solution-processed deposition methods. A titanium dioxide blocking layer and an In2S3 buffer layer are deposited by the spray pyrolysis method. A CIS2 absorber layer is deposited by the spin coating method using CIS ink prepared by a 1-butylamine solvent-based solution at room temperature. To obtain optimum annealing temperature, these layers are first annealed at 150°C and then annealed at 210°C, 250°C and 350°C respectively. The optimum annealing temperature of the layer is found to be 250°C, where 23 mA current density and 505 mV open circuit voltage are measured for the best fabricated solar cell sample.
Elham Yousefi, Mohsen Hatami, Sajjad Dehghani,
Volume 11, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 11, No 1, Winter-Spring 2017 2017)
Abstract
We solve the coupled mode equations governing the chalcogenide nonlinear fiber Bragg gratings (FBGs) numerically, and obtain the bistability characteristics. The characteristics of the chalcogenide nonlinear FBGs such as: switching threshold intensity, bistability interval and on-off switching ratio are studied. The effects of FBG length and its third order nonlinear refractive index on FBG characteristics are investigated. We obtain an interesting result that independent of the third order nonlinear refractive index; there exists an optimum FBG length of about 6 mm at which the on-off switching ratio becomes maximized. It is also found that by increasing the nonlinearity, the maximum value of on-off switching ratio decreases. The results of this paper can be mainly used for designing all-optical switches and memories.
Elham Yousefi, Mohsen Hatami, Amin Torabi Jahromi, Sajjad Dehghani,
Volume 13, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 13, No 2, Summer-Fall 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.
Nasrin Vahedi. G, Asghar Asgari, Gholamreza Dehghan,
Volume 16, Issue 2 (Summer-Fall 2022)
Abstract
Efforts to understand genetic diseases and mutations in biological systems are the most important driver of research development in medical and biomolecular sciences. Rapid, sensitive, accurate, and cost-effective biomolecule analysis is particularly important in diagnosis and treatment. The discovery of graphene as a new nanomaterial with a carbon structure with a single atom thickness due to its unique electronic, mechanical, thermal, and optical properties has opened a new topic in research in various biomedical sciences and the production of biosensors for biomolecule analysis. In this research, a biosensor based on a graphene field-effect transistor (GFET) is used to detect DNA with optimal accuracy and sensitivity, which can be a basis for making DNA detection tools. In the studied structure, using non-equilibrium Green function equations and Poisson equation, we study the electron transfer in graphene field-effect transistors. Then, by examining the interaction between nucleotide bases (C, G, A, T) and O6-carboxymethylguanine related to the colorectal cancer DNA sequence to detection of mutation will be identified by GFET, and their binding energy determined.
