Showing 10 results for Optical Properties
M. Neghabi, A. Behjat, S.m.b. Ghorashi,
Volume 4, Issue 2 (6-2010)
Abstract
ZnS/metal/ZnS (ZMZ) nanomultilayer films with Au, Ag and Cu as a metal layer have been deposited on a glass substrate by thermal evaporation and then, were annealed in air at different temperatures from 100 to 300 ºC for one hour. Several analytical tools such as X-ray diffraction, four point probe and spectrophotometer were used to study the changes in structural, electrical and optical properties of the samples. XRD patterns show that the crystallinity of structures and also grain size of particles increases with increasing the annealing temperature. Improved electrical property (a sheet resistance of 7 Ω/sq for ZnS/Au/ZnS) and considerable improvement in the transmittance curves (86% maximum transmittance for ZnS/Au/ZnS) of the samples after heat treatment at 200ºC was observed. Also, the optical constants of the ZMZ multilayer samples were calculated from transmittance and reflectance measurements. The figure of merit was applied on the ZMZ coatings and the most suitable films and annealing temperature for the application as transparent conductive electrodes were determined.
K. Russel Raj, P. Murugakoothan,
Volume 5, Issue 1 (1-2011)
Abstract
Single crystals of nonlinear optical material bis (guanidinium) hydrogen phosphate monohydrate (G2HP) belonging to non centrosymmetric space group P 21c were successfully grown by the slow evaporation method. Optical transmittance and second harmonic generation of the grown crystals have been studied by UV-vis-NIR spectrum and Kurtz powder technique respectively. The transmittance of G2HP crystal has been used to calculate the refractive index (n), the extinction coefficient (k), reflectance (R) and both the real (εr) and imaginary (εi) components of the dielectric constant as a function of wavelength. The anisotropic mechanical behavior and dielectric response of G2HP has been analyzed.
F. Rahman, J. Podder, M. Ichimura,
Volume 5, Issue 2 (7-2011)
Abstract
Thin films of indium doped zinc sulfide (ZnS) for different indium (In) concentrations (x=0.0 - 0.8) were deposited onto glass substrate by spray pyrolysis method at 523K temperature. Aqueous solution of zinc acetate, indium chloride and thiorea were used to deposit the In-Zn-S film. The deposited thin films were characterized by Energy dispersive X-ray (EDX), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and by UVvisible spectroscopy. The XRD spectra of In-Zn- S revealed both the amorphous and polycrystalline property for different In concentration. The EDX showed a well stoichiometric result of different compositions of In in ZnS thin films. The granularity of irregular shape is observed in In doped ZnS thin films surface by scanning electron microscope. From the absorbance and transmittance data it is observed that the band gap energy is decreased from 3.75eV to 3.1eV with the increase of In concentration in ZnS.
Hojjat Amrollahi Bioki, Mahmood Borhani Zarandi,
Volume 5, Issue 2 (7-2011)
Abstract
Zinc Sulfide (ZnS) thin films were deposited on glass substrates at the pressure of 10-6 mbar by thermal resistor evaporation technique. The effects of annealing on the structural, optical properties of ZnS films were studied. Crystalline ZnS films have been analyzed by X-ray diffraction. Only cubic phase with the preferred (111) plane was found in ZnS films. Optical characteristics were studied as a function of annealing temperature and thickness in air. The results show that the energy band gap was found to be about 3.5 eV. It was observed that the energy gap decreases with the increase in the film thickness and increases with the increase in the annealing temperature.
Hamid Pashaei Adl, Samad Roshan Entezar,
Volume 6, Issue 1 (10-2012)
Abstract
In this paper, the optical properties of one dimensional fractal structures are investigated. We consider six typical fractal photonic structures: the symmetric dual cantor-like fractal structure, the asymmetric dual cantor-like fractal structure, the single cantor-like fractal structure, the symmetric dual golden-section fractal structure, the asymmetric dual golden-section fractal structure and the single golden-section fractal structure. By using the transfer matrix method the transmission spectra of these structures are simulated. The calculation results shows that the transmission spectrum of the symmetric dual cantor-like fractal structure is self-similar and the peak numbers in the transmission spectra of the SDGSFS also follow the principals of special fractal structures. It is also shown that in the symmetric dual golden-section fractal structure the localization of modes which appears within the stop band increases and getting closer to the middle of the gap by increasing the number of string.
Mina Eslamifar, Nastaran Mansour,
Volume 6, Issue 1 (10-2012)
Abstract
In this work, thermo-optical properties of gold nanoparticle colloids are studied using continuous wave (CW) laser irradiation at 532 nm. The nanoparticle colloids are fabricated by 18 ns pulsed laser ablation of pure gold plate in the distilled water. The formation of the nanoparticles has been evidenced by optical absorption spectra and transmission electron microscopy. The nonlinear optical properties of gold nanoparticles colloids are investigated by closed Z-scan under irradiation of a low power CW laser. It will be shown that the thermal lens model is in excellent agreement with the experimental results of samples. The aperture-limitted optical limiters based on the nonlinear refraction of colloidal solution are presented. The tunability of limiting threshold of optical limiters can be accomplished by engineering of the experimental geometry.
Dr. Esmaeil Shahriari, Dr. Mohammad Moradi, Dr. Mohsen Ghasemi Varnamkhasti,
Volume 9, Issue 2 (11-2015)
Abstract
In this research, Ag nanoparticles were prepared by using g-radiation at concentration of 5.18×10-3 M and irradiated at different doses. A green laser was employed as excited source for measuring nonlinear refractive index and absorption coefficient. The measurements were done by z-scan method for both, closed and open aperture at temperature room. We deduced that with growth of size of Ag nanoparticles, nonlinear refractive index increased while absorption coefficient of samples decreased
Tahereh Dirikvand, Mehdi Zadsar, Mina Neghabi, Jamshid Amighian,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >ta charset="UTF-8" >A green microcavity organic light-emitting diode combining an Al electrode (top mirror) with a distributed Bragg reflector (bottom mirror) was designed and fabricated to improve the quality factor (more than 51) and enable high reflectance and optimal electrical properties. Experimental results indicated a remarkable increase in electroluminescence and reduction of spectral width at half maximum. Distributed Bragg reflector (DBR) films were prepared at 550°C with a surface roughness of 0.25nm (root mean square: RMS). In addition, according to SiO2/TiO2 refractive indices, they obtained the highest reflection compared to all organic or inorganic DBR devices. The reflectance peak at 591 nm is 94.4% for five pairs of SiO2/TiO2 layers indicating good agreement with theoretical simulation samples. Microcavity Organic Light-Emitting Diode (OLED) with structure: 5 pairs of SiO2/TiO2/ITO(120nm) /MoO3(5nm) /MoO3:NPB(190nm) /NPB(10nm) /Alq3(35nm) /BCP(5nm) /LiF(0.7nm) /AL(200nm) has a quality factor of more than 51, high luminous (30%), remarkable increase in electro-luminescence (EL) and reduction of the spectral full width at half maximum of 10.93nm. This is an applied research that was obtained after detailed investigations on OLED microcavities and has a practical aspect to solving the problems of designing and manufacturing electrical and optical systems such as organic display screens. The innovative aspect of research in the technical knowledge of designing and manufacturing OLED microcavities and achieving an optimal structure using metal mirrors and Bragg reflectors to achieve coherent light output is a new and up-to-date issue that has not been done in Iran so far. As an essential step toward realizing organic lasers, the proposed approach can be used to produce new light sources.
Reihan Nejatipour, Mehrdad Dadsetani,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >In the density functional theory (DFT), optical properties of Sc2C(OH)2 monolayer are studied with and without silicon impurity. In the presence of silicon impurity, the structure and properties of this compound were changed from a semiconductor with a 0.57 eV band-gap to a topological insulator with a zero band-gap and a band inversion. With and without the silicon impurity, the spectral features in this compound originate from the electron transition from the p-Si and p-C to d-Sc and s-H, respectively. The values of optical constants are increased in the doped-structure with respect to the pure structure.
Bita Azemoodeh Afshar, Akbar Jafari, Rahim Naderali, Mir Maqsood Golzan,
Volume 16, Issue 2 (7-2022)
Abstract
In this study, we investigated the production of silver nanoparticles by pulsed Nd: YAG laser ablation with λ=532nm in distilled water. The sodium citrate used to control the size of nanoparticles (Nps). The sample containing Ag NPs was characterized by linear absorption spectroscopy (UV-Visible spectroscopy) and transmission electron microscopy (TEM observation). The behavior of nonlinear optical properties of silver nanoparticles was studied using the Z-Scan method at two optimum numbers of the laser pulses and four optimum laser energy densities. In the Z-Scan method, the nonlinear thermal properties of Ag NPs were investigated under exposure to nanosecond laser pulse at λ=532nm. They were gained by fitting theoretical and experimental data. The values of the nonlinear refractive index (n2) and the nonlinear absorption coefficient (β ) were compared concerning to two optimum numbers and four optimum energy densities. The results of the nonlinear refractive index showed a negative value for each sample, this means that samples act as a divergent lens, and the thermal self-defocusing effect can be the main factor of nonlinear behavior. Following the comparison of two quantities, n2 and β , we found that the nonlinear refractive index increased when the number of laser pulses light increased. In addition, the nonlinear absorption coefficient decreased when the number of laser pulses light increased. As a result, the application of these Ag NPs for optical switching devices was investigated, which demonstrated that the large Ag NPs are applicable tools for optical switching devices.
