Showing 242 results for Type of Study: Research
Mojgan Momeni-Demneh, Ali Mahdifar, Rasoul Roknizadeh,
Volume 16, Issue 1 (1-2022)
Abstract
ABSTRACT—One of the nonlinear optical phenomena which arise out of a χ(3) nonlinearity, is the intensity dependence of the refractive index. In this paper, we describe this phenomenon based on the nonlinear coherent states approach. We show that the deformed two-dimensional oscillator algebra can be used to describe this nonlinear optical system. Then, we construct the nonlinear coherent states for this nonlinear optical system and study their quantum statistical properties. Finally, we find that by changing nonlinearity of the media, it is possible to control the nonclassical properties of the system.
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.
Batul Nasrabadi, Mohammad Ismail Zibaii, Seyedeh Mahshad Hosseini,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >Optogenetics is an advanced optical tool in neuroscience research. However, light stimulation in optogenetic experiments may also affect neural function by generating heat. In this paper, the effect of increasing the temperature of the brain tissue was studied during light stimulation. The Hodgkin-Huxley model and the hippocampal pyramidal cell model have been used to investigate the effect of temperature on spike neurons. The modeling results show that irradiation of brain tissue by pulsed laser with a frequency of 40 Hz, the duty cycle of 90% and wavelength of 593 nm at a distance of 10 μm from the tip of the fiber, for 60 seconds with a power of 1 and 40 mW leads to the temperature change from 37 °C to 39 °C. The obtained results show that the laser intensity decreases to zero at a distance of 1 mm from the tip of a fiber, which is absorbed by the tissue and causes a temperature rise of 2 °C that can increase the spike rate of neurons by 16.6%.
Shadi Davoudi, Somayeh Mehrabian,
Volume 16, Issue 1 (1-2022)
Abstract
In this study, the self-guiding of an ultrashort laser pulse through air is investigated. Therefore, the terms of self-focusing, plasma defocusing and the pulse energy depletion due to the ionization, are considered in the wave equation. Then the laser pulse spot size equation is obtained using the source-dependent expansion method. Our results show that the laser pulse self-guiding occurs for the first twenty Rayleigh lengths. However, the laser pulse undergoes diffraction as it propagates further along the z axis. Moreover, it is seen that the back of the laser pulse is diffracted the most owing to the fact that the plasma is formed as the laser pulse propagates through air. It is also shown that the spot size variations affect the temporal and spatial profiles of the laser intensity, the laser pulse power and the ionization process.
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.
Ehsan Naghizadeh Alamdari, Mostafa Sahrai, Reza Kheradmand, Mansour Eslami,
Volume 16, Issue 1 (1-2022)
Abstract
Cavity Solitons (CSs) in an injected broad-area semiconductor laser with intracavity saturable absorber exhibit phase noise free and high-contrast intensity oscillations in period-one dynamical state. The continuous-wave periodic intensity oscillation of the CSs has a frequency well beyond the relaxation oscillation frequency and can be regarded as a photonic microwave source. Here we numerically investigate the effect of linewidth enhancement factor on the dynamical characteristics of CSs in the period-one regime. We show that in a fixed injection amplitude, it has a key role in shifting the oscillation frequencies of the period-one CSs and that its effects strongly depend on the cavity detuning value.
Hoda Sadat Lotfipour, Majid Khodabandeh, Zahra Bagheri, Hassan Sobhani,
Volume 16, Issue 2 (7-2022)
Abstract
This paper describes the second-order coherence degree of photons produced in SPDC. First, the nonlinear BBO crystal generates the twin correlated signal and idler photons in the experimental setup. Then, g2 (0) is obtained experimentally via Hanbury Brown-Twiss set-up for investigation of the light source nature. The results show this value is less than 1 which verifies the generated photons are in the heralded single photon (HSP) regime.
Iman Rahmani, Majid Ghanaatshoar,
Volume 16, Issue 2 (7-2022)
Abstract
ta charset="UTF-8" >We investigate the Cu2FeSnS4 (CFTS) thin film. The raw materials of this thin film are copper, iron and tin, which are mixed in the form of tablets and then are deposited on a glass substrate through the process of pulsed laser deposition (PLD). The produced metallic thin films are then sulfurized to carry out the process of merging the element sulfur in the thin films and forming CFTS structure. We investigate the influence of sulfurization temperature and the laser pulse energy in the PLD process on the deposited CFTS thin films. The X-ray diffraction (XRD), Raman and UV-Vis analyses’ results show that by decrease in sulfurization temperature from 600 °C to 550 °C the crystal quality of the thin films is improved, which is realized by increase in volume and quality of the CFTS phase. On the other hand, the results confirm that the laser fluence is a decisive factor which should be taken into account to achieve an optimized structure.
Jafar Bakhtiar Shohani, Morteza Hajimahmoodzadeh, Hamidreza Fallah,
Volume 16, Issue 2 (7-2022)
Abstract
In this paper, we investigate the usage of machine learning in the detection and recognition of double stars. To do this, numerous images including one star and double stars are simulated. Then, 100 terms of Zernike expansion with random coefficients are considered as aberrations to impose on the aforementioned images. Also, a telescope with a specific aperture is simulated. In this work, two kinds of intensity are used, one is in-focus and the other is out-of-focus of the telescope. After these simulations, a convolutional neural network (CNN) is configured and designed and its input is simulated intensity patterns. After learning the network, we could recognize double stars at severe turbulence without needing phase correction with a very high accuracy level of more than 98%.
Zoha Ameri, Fazel Jahangiri,
Volume 16, Issue 2 (7-2022)
Abstract
Using terahertz waves for intra-body communications between nanomachines is associated with dissipation during propagation, of which scattering is one of the most important effects. In this paper, scattering path loss with two different assumptions of air-enclosed and tissue-enclosed in subcutaneous fat is calculated and compared. The results show that for TM polarization, air-enclosed assumption gives smaller and greater scattering loss for frequencies less and bigger than 0.26 THz. The greatest difference between air-enclosed and tissue-enclosed results is observed for TE polarization at the approximate frequency of 0.4 THz.
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.
Arash Tirandaz,
Volume 16, Issue 2 (7-2022)
Abstract
A generalized Born-Markov master equation for describing inelastic tunneling under non-equilibrium interaction is recommended. Rate equations are extracted and analyzed for reaching maximization in tunneling rates. Possible rooms for reviving quantum coherence despite the role of the environment have been surveyed. The scheme extended in this article can provide a general framework for the analysis of quantum tunneling in different realms of quantum optics and quantum biology. It is shown how the non-equilibrium character of the system-environment interaction may strengthen the chance of predominance probability of occurrence of inelastic tunneling against elastic tunneling despite the usual expectation.
Zohre Mahmoudi Meimand, Omid Hamidi, Ali Reza Bahrampour,
Volume 16, Issue 2 (7-2022)
Abstract
ta charset="UTF-8" >In This paper a ground-state cooling method for bad optomechanical systems is proposed. Previous authors show that an optical cavity with equal loss and gain has a parity-time reversal (PT) symmetry. We introduced an optomechanical cavity coupled to the two modes of a PT symmetry and a passive optical cavity. A quarter-wave plate provides linear mixing interaction between the PT symmetry and passive cavities. In this study, our proposed system improved the cooling rate by utilizing two effects: energy localization and quantum interference. These two impacts increase the cooling rate while the system is red or blue-detuned. It is demonstrated that optomechanical cooling occurs in both the bad-cavity limit and the weak optomechanical coupling regime. These innovations can be attained by parameter management of the system.
Shakiba Mosavat Shahreza, Seyed Ayoob Moosavi, Hossein Saghafifar,
Volume 16, Issue 2 (7-2022)
Abstract
In this paper, Laguerre-Gaussian beams are produced by Computer Generated Hologram (CGH) on Spatial Light Modulator (SLM). The realization of CGH on SLM is simulated by the scalar diffraction theory. At first, Laguerre-Gaussian beam generation process is simulated by diffraction of laser light from phase and amplitude fork gratings in two types: blazed and binary grating and the results are compared. The higher efficiency is obtained for the blazed phase grating in the first order which is more important in our study. Recorded data from the experiment shows a good agreement with simulation results. In order to evaluate the topological charge of the generated Laguerre-Gaussian beam, the Mach-Zehnder interferometer setup is used.
Sarang Medhekar, Puja Sharma, Man Mohan Gupta, Nilaksha Ghosh,
Volume 16, Issue 2 (7-2022)
Abstract
In this paper, a structure is proposed using ring resonator created on 2D photonic crystal (PC) that acts as an add-drop filter (ADF) in all-optical communication systems. The same structure can also act as refractive index (RI) and temperature sensor. The structure is made up of a hexagonal lattice of air holes in a dielectric slab of silicon with the refractive index of 3.46. The band diagram of the considered structure is obtained using plane wave expansion (PWE) method, and optical propagation through it is simulated using finite difference time domain (FDTD) method. The computational analysis is performed on different structural and physical parameters. Transmission efficiency, quality factor and bandwidth are investigated by varying (i) lattice constant (ii) radius of holes of different parts of the structure and (iii) refractive index of different parts of the structure. The chosen parameters result in operating wavelength around 1550 nm. The designed ADF has a footprint of only 68µm2 and a dropping efficiency of 100%. The sensitivity of the structure is determined by determining shifts in the resonance wavelength as a function of the RI of the holes/slab. The designed structure exhibits desirable features like (i) narrow bandwidth of 1.5 nm, (ii) high-quality factor of 1033, (iii) low detection limit of 3.6´10-4 RIU, (iv) high RI sensitivity of 407 nm/RIU, and (v) high temperature sensitivity of 104 pm/K.
Nasrin Vahedi. G, Asghar Asgari, Gholamreza Dehghan,
Volume 16, Issue 2 (7-2022)
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.
Ramin Zohrabi, Abdolrahman Namdar, Sohrab Ahmadi-Kandjani, Babak Olyaeefar,
Volume 16, Issue 2 (7-2022)
Abstract
This article examines the impact of graded-index reflectors (GIRs) constructed from cholesteric liquid crystals (CLCs) on the modification of escape-cone loss and the improvement of luminescent solar concentrator (LSC) efficiency. GIRs are comprised of a structure in which the refractive index changes gradually with a spatial function. In this study, the LSC is a planar optical waveguide made of Poly (methyl methacrylate) (PMMA) with dimensions of 5×5×0.5 cm³ and contains CH₃NH₃PbBr₃ perovskite material as a fluorophore. Two types of GIRs are employed at the bottom of the LSC: periodic and quasi-periodic GIRs. Periodic reflectors (PRs) have a refractive index matrix that gradually changes with a periodic sinusoidal function, while the refractive index matrix of the quasi-periodic reflectors (QPRs) gradually changes with a chirped sinusoidal function. To analyze the models of the study, Monte-Carlo and Finite-Difference Time-Domain (FDTD) methods were utilized in conjunction with experimental results. The results indicated that the reflection band of a PR exhibited the maximum overlap (lowest escape cone) with the dye emission spectrum when the mirror's reflection band underwent a redshift of 20 nm compared to the dye emission spectrum. On the other hand, the QPR generated a broader reflection band, resulting in complete overlap and higher efficiency. Moreover, GIRs enhanced sunlight absorption in the LSC by reflecting transmitted solar photons through it. The optical efficiency (OE) of the LSC increased by 12% (33%) once a periodic (quasi-periodic) reflector is utilized. Furthermore, GIRs reduced escape cone loss, thereby increasing reabsorption, and subsequently, the system selected a lower optimal concentration to minimize reabsorption losses.
Tarek Al-Saeed,
Volume 17, Issue 1 (1-2023)
Abstract
In this work we applied a Bessel beam (BB) to a layer of turbid medium. We applied the Monte Carlo simulation. This work emulates a tissue under surgery by a Bessel beam. Actually, the BB introduces less divergence. Thus it will be good for surgery. On the other part this is done by Monte Carlo simulation. Upon simulation we got family of curves to characterize absorption, reflection and scattering of this layer. Where we got numerical values of absorption, transmission and reflection of this layer. The curves are for layer thickness that varies along with varying scattering coefficient, absorption coefficient and anisotropy factor.
Mahsa Khadem Sadigh,
Volume 17, Issue 1 (1-2023)
Abstract
Xanthene and its derivatives are important in medical diagnosis and laser technology. In this work, spectral features of fluorescein disodium were investigated in different environments with different polarity characteristics. Hence, the absorption and fluorescence spectra of this molecule were studied in different environments. Our results show that spectral features of fluorescein disodium depend strongly on substituents in its structure and molecular interactions. To investigate the contribution of various molecular interactions on the spectral behavior of the used sample, the linear solvation energy relationship concept is used. Moreover, the dipole moment variations from ground to excited states were estimated using molecular spectral features in different solvent media. According to the results, the dipole moment value in the excited state is higher than that in the ground state.
Farshad Khoshnood, Mohammad Sabaeian,
Volume 17, Issue 1 (1-2023)
Abstract
The authors report on the impact of electrode doping on the optical and electrical properties of argon flash lamps. In this work, the lamps are made using borosilicate glass tubes with an outer diameter of 6 mm and a discharge distance of 35 mm. In the construction of the lamps, five types of tungsten electrodes doped with thorium at two different percentages, cerium, lanthanum as well as pure tungsten are used. Properties such as threshold voltage, light intensity, tube temperature, and flash time profile at various argon pressures are measured. The results indicated that, first, the threshold voltage is a linear function of gas pressure inside the tube. Second, the lamp with 1.7%-2.2% thorium doped tungsten cathode showed a lower threshold voltage, higher light intensity, and lower temperature rise at continuous wave operation. These characteristics of electrodes doped with thorium make them an appropriate option for use in the fabrication of argon flash lamps.
