Investigating the magnetic, electrical and structural behaviors of Au/MoS2@(NiFe2O4)x nanostructures as electromagnetic absorbers

   In this thesis morphology, structural and optical properties of three layers of ITO / Metal / NiO were investigated. NiO thin films were prepared by sputtering method in power of 100 w on the glass substrate which has thin films of ITO and metal on it. Metal thin films include two metals, silver and copper, which were deposited by thermal evaporation method. Two samples of ITO / Ag / NiO and ITO / Cu / NiO thin films were prepared which showed a weak crystaline peak on the Bragg plate (200) for Ag thin film and Bragg plate (111) for Cu thin film. The surface morphology of thin films displaied that the average size of NiO nanoparticles were about 14 nm and they had a uniform and regular growth. Also, optical studies indicate that the prepared three layers of ITO / Metal / NiO had good tra  arency of about 65% in the visible and infrared regions and absorption severely occurred in the ultraviolet region.

The non-exclusive cross-sectional area of bifurcations was measured in ALEPH, OPAL and DELPHI experiments. in thisنامهInterpretation Using these cross-sections, the bifurcation functions of these baryons are determined by fitting to the experimental data.  

The cavity which resonates on the continuous and wide of frequency range si- multaneously, without loss of ?nesse and build-up factor known as white light cavity (WLC). Such a cavity operates completely di?erent from the conventional Fabry- Perot cavity. One of the most considerable and interesting applications of white light cavity bandwidth is the production of optical switches with of a wide broad- band and enhancing the sensitivity of gravitational wave detectors which recently has been investigated in various scienti?c researches. In this thesis, the impact of atomic coherence and interference on white light generation by using a negative dispersive medium and tra  arent from Fabry-Perot cavity is investigated. This negative dis- persive medium is studied in di?erent models, such as the ladder-type three-level atomic system and cascade-type four-level atomic system. By driving non-resonant laser ?elds, the Hamiltonian of atomic system in the interaction picture is used to calculate the elements of the density matrix. In the steady state regime, the complex electric susceptibility of the atomic system is calculated up to ?rst order approxi- mation of the perturbation and initial conditions for making white light cavity is achieved. As shown that the white light cavity bandwidth in the three-level atomic system is increased to 40?1 and four-level in single band case to 103? and double band symmetric to 60?. This study can be used for designing and manufacturing of all- optical switches, gravitational wave detectors and sensors in optical communications and quantum information process.

Over the past several years, attention has been focused on Alternating crystal structures of various materials in physics and photonics. In this study, first the Alternating crystal structures (or photonic crystal) is introduced and the laws that is controlling the transmission of electromagnetic waves through the photonic crystal and the transfer matrix method are studied. Then the relationship of the transfer coefficient of the electromagnetic wave through the crystal layers is estimated and different structures of the dielectric layer alternation is studied. In order to improve the transfer coefficient of wave through the photon crystal and reduce the band gap energy, a metal nanoparticles composite and graphene layer is introduced and added to the structure and the results are studied. The results of the theoretical calculations that was performed in this study represente that the addition of a metal nanoparticles composite and the use of graphene monolayers in one-dimensional photonic crystal structure causes the destroy of band gap energy in the transmitted spectrum of the structure. This result can be used in the manufacture of photonic devices over a wide frequency range.

  Multi-Wave ‎Mixing ‎(MWM)‎ is one of the well-known phenomena in nonlinear optics that has been theoretically and ‎ experimentally ‎investigated‎ in recent years. The mentioned nonlinear phenomenon has a wide range of applications in nonlinear optics such as the production of short wavelength coherent radiation, nonlinear quantum ‎optics, t‎he optical image and quantum information science. In Four-wave mixing (FWM) process, three electromagnetic fields interact in a nonlinear optical system and generate electromagnetic field with a new frequency. FWM in the atomic media can be enhanced significantly via multi-photon atomic coherence effects, which are generated by the interaction of an atom with coherent electromagnetic fields. This enhanced FWM nonlinearity has been used in various multi-level systems, including ladder-type and double-?-type atomic systems, in order to generate correlated photon pairs. In this thesis, ‎the concept of the four-wave ‎mixing‎ and some of its applications is studied.‎ ‎ Then, the nonlinear FWM process in different media including cold atoms and ‎ asymmetric ‎double ‎quantum ‎wells ‎structures‎ is investigated and also‎ a brief overview of its applications is discussed‎. First, the time-dependent analysis of FWM based on resonant tunneling is investigated in an asymmetric semiconductor double quantum well structure. We analytically demonstrate that a highly efficient mixing wave is found to be induced by resonant tunneling in such a quantum well scheme with low-light pump wave intensities. Especially for small propagation distances, a significant enhancement of four-wave mixing conversion efficiency can be achieved. Moreover, in the multi-level atoms and under the suitable input-field conditions, strong interference effects between the input fields and the generated FWM fields can be induced and result in large amplification and deep attenuation of the output fields. Moreover, such an optical modulation from enhancement to suppression can be controlled by tuning the relative phase. ‎\\\\‎ keys ‎words: ‎Four ‎Wave ‎Mixing ‎(FWM), ‎Density ‎Matrix, ‎Multi-level ‎Systems.‎

  In thisstudy, nonlinear optical properties of core-shell nanoparticles and grapheneis investigated. Optical bistability as a consequence of Kerrnonlinearity has beenattracted lots of attention recently. Graphene monolayers due to their conductivitycan be applied as mirrors of Fabry-Perot cavity which is filled bycomposite of core-shell spherical nanoparticles. The controllable transition betweenoptical bistabilityand multistability in graphene/ composite of nanoparticles/ graphene structureforTE and TM polarizations is studied. It can be seen that the composite ofnanoparti-cles could enhance the nonlinearity response and optical bistability andmultistabilityof this structure considerably. The impact of various parameters such asFremi en-ergy of graphene, filing factor on the optical bistability behavior isstudied. Due tocontrollability of optical bistability, multistability and dualbistability of this struc-ture, it would find its application inall-optical communications as anoptical switchin terahertz range of frequency.

  1) In this research work, the magnetostriction is investigaterd by using Michelson laser interferometer. 2) Magnetostriction is a property of ferromagnetic materials that is defiend as the change in their dimensions due to the reorientation and rotation of the magnetic domains under the influence of an external magnetic field. 3) In fact, magnetostriction with Michelson interferometer uses two mirrors in a Michelson laser interferometer to obtain the interference pattern. 4) In the experimental set- up, on of the mirrors connected to the metal sample rod such as Fe, Al, Cu and Brass alloy, in to a coil, and is shifted by variation in the magnetic field, and this leads to the change in the interference pattern owning to the magnetostrictive effect.

  According to quantum theory the energy can exchange between physical system is quantized. Naturally, the study of the physical behavior of light can also follow this law. To consider the signature of the quantum nature of light from the theoretical perspective is required to quantize the electromagnetic field. The important field’s states are number states, coherent states and squeezed states. During the second half of twentieth century, field quantisation and field’s states were successfully detected and produced.  Keywords: Field Quantisation – Coherent States – Squeezed States

This research work reports results of a theoretical study of optical bistability behavior, where  is a typical feature of nonlinear effects, under an external static magnetic field from nanoparticles consisting of  magneto-optical shell and nonlinear metallic core. On the other hand, in this thesis, we study and compare  the magneto-optical properties of plasmonic nanoparticles with spherical and cylinderical geometry in the framework of dipole approximation, because the magneto-optical effect is widely used to manipulate light and  uch nanostructures with magneto-controllable optical bistability  are important to design of  optical nanoswitches, nanosensors.  The impact of the left circularly polarization (LCP) and right circularly polarization (RCP)   on the optical bistability and also the scattering efficiency is shown. In addition to  the influence of the MO effect on the bistable hysteresis and the threshold values, it is demonstrated the bistable behavior is strongly dependent on the incident polarization state.We also study the effect of locality and nonlocality on optical bistability when the core is described by a spatial dispersive dielectric function and the shell is a  magneto-optical material. To investigate the nonlocal effects we assume  the nonlocal response function i  ?(k,?). However, influence of the relevant parameters such as the incident wavelength, the volume fraction , the gyration parameter  g, LCP and RCP incident waves, and the environment on the optical bistability and the scattering coefficient is shown and discussed  

  ‎‎In this research work, the optical bistability, where a nonlinear optical system shows two different values of the local field intensity for one input intensity, in core-shell cylindrical nanoparticles is proposed and investigated within the quasistatic approximation. It is assumed that the core material of the nanoparticle is described by a spatial dispersive dielectric function or the nonlocal response function ‎?(k,?) ‎,coated with Kerr-type nonlinear shell which has a field-dependent permittivity. It is sown that the threshold values and hysteresis loop are adjustable which is important for design of optical bitable devices. However, the effect of the nonlocality, the permeability of the environment, the wavelength of the incoming light on the optical bistability behavior is studied and demonstrated.\\\\In addition to study the nonlocality and nonlocal effects, we investigate the absorption, the transmittance and reflection coefficients of a composite consisting of nanoparticles.   Finally, since graphene decorated nanomaterials can potentially be used in many applications, we study the role of graphene on the optical bistability by considering coated graphene monolayer on the core, shell and core and shell surfaces simultaneously of nanoparticle. It is shown that the optical bistable and the hysteretic behavior is strongly dependent on the Fermi energy of graphene and the carrier relaxation time in graphene

In this thesis, we have investigated transport properties of bilayer graphene lattice for two bernal and simple stacking states in the presence of gap parameter and bias voltages. Specially, electrical conductivity of this structure has been studied. For this purpose, a tight binding model Hamiltonian with a gap parameter describing on-site energy difference between two sublattices has been exploited. Moreover, the difference between on-site energies of two layers has been considered by applying a bias voltage.  

 investigation

A diffraction grating is a key element in optical spectroscopy and laser beam splitting. Production of such elements is a technologically complicated and expensive procedure. But the collection of ridges on the individual scales on the wings of a butterfly act as transmission diffraction gratings. Compound microscopes show such a micrometer periodical structure, but are not sufficient precise instrument to determine grating constant of butterfly in the range of 10-7 or 10-8 m. To determine grating constant one could use such instruments as SEM and TEM, but these are expensive.In this thesis, we first apply three methods to define grating constant of CENCO transmission gratings: 1) Diffraction grating spectroscopy, 2) Compound microscopy and 3) Diffraction of a He-Ne laser. Then we apply compound microscopy and laser diffraction methods to determine grating constant of butterfly. The results show that by laser diffraction one could precisely determine the grating constant of butterfly.This research was done using optical elements and instruments of Laboratory of Optics (2217) and research Laboratory of Laser (2218).Keywords: Diffraction, He-Ne laser, wings of butterfly, compound microscope, diffraction grating.

‎In this work‎, the transfer energy between molecules near a spherical multilayer nanoparticle and a coated-graphene nanoparticle is investigated.‎The process of energy transfer from a molecule which called donor to another molecule wich called acceptor has many applications in physics and biology.the most intresting example is the desig n of biosensors based on the energy transfer.‎The donor and acceptor molecules are considered as the point dipole in the vicinity of a plasmonic nanoparticle increases the extend of the energy transfer.‎The effect of parametrs such as the refractive index of the enviroument, the size of nanoparticle,the type of metal,the distance of molecules is shown. also, the influence of the graphene on the transfered energy from the donor molecule to the acceptor molecule is studied.

The alpha decay half-lives of superheavy nuclei (SHN) are investigated by employing a unified fission model (UFM) and Royer’s analytical formula .The good agreement with the experimental data indicates the UFM and the analytical formula are useful tools to investigate these ?-decays. A modified formula is proposed for determining the spontaneous fission half-lives based on Swiatecki’s formula. The spontaneous fission half lives for heavy and SHN in regions from Th to Fl are calculated systematically. Experimental data are well reproduced by the modified Swiatecki formula. The competition between ? decay and spontaneous fission is analyzed in detail and the decay modes are predicted for the unknown cases.

Channeling motion of charged particles in crstalline materials was considered first by Lindhard in 1965. In subsequent years, Kumakhov investigated in a simple form the channeling motion and radiation of relativistic light charged particles, such as electron and positrons, in crystalline materials. In this thesis, we consider from the classical and quantum points of view the dynamic of channeling motion of charged particles in crystals and resulting channeling radiation will be considered.

Based on the laws of 0in 0in 10pt" >Such spatial periodic structures are of two types: ‎ The first type is the macro undulator in a vacuum‎, ‎such as linear magnetic undulator‎. ‎The second one is called crystalline micro undulator (nano micro undulator)‎. ‎The theory of electromagnetic radiation produced by relativistic charged particles moving in nano structures, such as in Carbon nano-tubes is one of the newest areas of the Radiation Physics.   In this Master thesis, ‎the dynamic of motion of relativistic charged particles moving in nano crystalline structures, such as Carbon nano-tubes and produced electromagnetic radiation ‎will be considered. The periodic structure of the Carbon nano tubes will be considered in brief as a device for radiation production. ‎Then‎, ‎according to the periodic structure of the Carbon nanotubes‎, ‎the approximate inter atomic potential taking n into account the thermal vibrations of atoms will be calculated‎. ‎The dynamic of channeling motion will be studied in classical and quantum approximation.   ‎At the end‎, some features of the spectrum of produced radiation will be discussed‎.

In this thesis, the optical properties of the spherical plasmonic nanoparticles and nanoshells is investigated by using tht electromagnetic Maxwell equations. Since the multilayer nanoshells reveales tunable optical charachteristics due to the hybridization of the plasmons of the inner and outer surfaces and also the plasmon-exciton interaction, studying these particles are wothnoting and interesting. The light-velocity slowing factor and the group-velocity dispersion of the nanoshell system having concentric shells around a core consist of different materials such as dielecteric, metal and semiconductor has been studied. The effect of the some pivotal parameters such as size, surrounding medium and composition of shells/core on the slow light   and   the group-velocity dispersion have been demonstrated and analysed. Furtheromre, the transmission probablity, reflection probablity and absorption probablity of a hybride system consist of a composite with embeded spherical nanoparticles and nanoshells (two layer, three layer and four layer)   sandwiched between two metalic parrallel plates has been investigated.  

if rletivistic charged particles at some small angles equal to or smaller than Lyndhards angle with respect to atomic plane enter a crystal, while longitudinal motion in the crystal, in electric field due to potential between atomic planes will also have a transvrse oscillating motion. considering the oscillating motion as acceleratd motion, electromagnetic radiation that is called channeling radiation is emitted. many of channeled particles du to their scattering in collisions with crystal lattice, with increasing the energy of transverse oscillating motion higher than th potential-well depth between the atomic planes, leave the channeling mode.the transverse length with the particle until its transvrse energy is lower than the potential well depth is called dechanneling length. Dechanneling length of relativistic light charged particles in Silicon crystals based on solving the Fokker-Planck equation  will be discussed.  

In recent years, much attentions have been paid to the metal-semiconductor nanostructures due to their potential applications in science and technology, and also in enhancing the nanoscale sensors and optical devices. In addition, the exciton-plasmon interactions makes them a hot topic in the field of nanoscience and plasmonics. Interaction ‎between ‎noble ‎metal ‎plasmons ‎and ‎semiconductor ‎exciton‎s could lead to interesting nonlinear optical effects such as electromagnetically induced tra  arency (EIT) and slow light. Moreover, this phenomena would open a new route for designing new optical sensors and devices based on plasmon-exciton interaction. In this study, the electrodynamic of concentric cylindrical nanoshells in the framework of the Mie formalism has been investigated theoretically . By introducing the TE and TM modes in cylindrical geometry, the scattering coefficients for core-shell and multishell nanoparticles has been calculated. By considering an effective dielectric function for the system and using the Clausius-Mossoti relation, the group velocity in the medium has been formulated. Furthermore, the induced electromagnetic tra  arency in a system consisting of a dielectric slab doped with cylindrical nanoparticles sandwiched between two metallic parallel plates has been investigated.The influence of some key parameters such as the thickness of layers, the size and composition of nanoparticles and slabs on EIT has been shown and analyzed.