Nader Daneshfar; Ali Bahari; Milad Jalilian
Abstract
A B S T R A C TIn this paper, optical bistability in a Fabry-Pérot optical cavity filled with semiconductor quantum dots coupled to graphene-coated metal nanospheres is investigated due to the outstanding optical properties of graphene, such as its strong nonlinear optical response and strong ...
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A B S T R A C TIn this paper, optical bistability in a Fabry-Pérot optical cavity filled with semiconductor quantum dots coupled to graphene-coated metal nanospheres is investigated due to the outstanding optical properties of graphene, such as its strong nonlinear optical response and strong light-graphene interaction, which have numerous potential applications in optoelectronic devices. In a hybrid molecule made of a semiconductor quantum dot coupled to a graphene-coated nanoparticle structure, the quantum dot is considered as an atomic system, and the Hamiltonian of the system is written under the electric dipole and rotating wave approximations. Then, the dynamic equations of the system are written in the density matrix approach, and Maxwell's equation is used to describe the propagation of the probe field inside the cavity to achieve optical bistability. By solving the density matrix equations in the steady state, and also by applying boundary conditions, the relationship between the incident field and the transmitted field is obtained, which can be used to investigate the output intensity in terms of the input intensity. It should be noted that quantum dot-metal nanoparticle hybrid structures have been of interest in recent years due to their ability to enhance plasmon-exciton interactions; therefore, the addition of graphene coating allows for greater tunability. The effect of nanoparticle size, number density of hybrid molecules, and intensity transmission on optical bistability and its hysteretic behavior is investigated.
Fatemeh Moslemi; Behnam Kazempour
Abstract
In this work, the effect of optical axis orientation on the transmission intensity of a terahertz filter in a magneto photonic crystal is studied. The transmission spectrum of the proposed structure with symmetric arrangement of (AB)7 InAs (BA)7 for both s and p polarizations is calculated using the ...
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In this work, the effect of optical axis orientation on the transmission intensity of a terahertz filter in a magneto photonic crystal is studied. The transmission spectrum of the proposed structure with symmetric arrangement of (AB)7 InAs (BA)7 for both s and p polarizations is calculated using the 4×4 transfer matrix method where A, B layers are the common dielectric materials and InAs defect layer is an anisotropic semiconductor. The presence of defect layer will be cause to appear a defect mode (filter) inside the photonic band gap of the structure. The results show that band gap width and frequency location of the filter are independent of the changes of the optical axis angle but the dependence of transmission intensity on the optical axis direction it is possible to realization of Malus law of the proposed structure in the terahertz frequency range for both s and p polarizations. The trend of transmission intensity changes of the THz filter with the optical axis angle in the s (p) polarization has the opposite behavior to the p (s) polarization and the coupling of modes occurs at 450 optical axis angle. Also, The simultaneous effects of temperature and magnetic field intensity on the frequency localization and the filter transmission intensity in the range of changes in the optical axis angle have been investigated. The proposed structure can be used as a new polarizer in the terahertz frequency range.
Habib Khalilpour; Hosein Ghaforyan
Abstract
Human blood, as a liquid, can be the target of laser radiation most of the time during laser surgeries. In this case, the bubbles grow under the influence of the energy received by the liquid from the laser. In this work, for the first time, using the real Gilmore model for a compressible liquid, the ...
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Human blood, as a liquid, can be the target of laser radiation most of the time during laser surgeries. In this case, the bubbles grow under the influence of the energy received by the liquid from the laser. In this work, for the first time, using the real Gilmore model for a compressible liquid, the dynamics of a single spherical bubble induced by laser in human blood and the oscillations of a bubble inside the blood are numerically investigated. For comparison with a similar liquid, the results will be compared with ordinary water. The numerical results show that when the base liquid is blood, the radius of oscillation as well as the number of oscillations of the bubble decreases. The bubble wall moves at a much slower speed than water.
mojtaba gholami
Abstract
In this study, lithium‑ion migration and the role of point defects in monoclinic Li₂TiO₃ were investigated using density functional theory (DFT). The crystal structure of Li₂TiO₃ in the C2/m space group was optimized, and electronic structure calculations showed that the pristine compound exhibits ...
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In this study, lithium‑ion migration and the role of point defects in monoclinic Li₂TiO₃ were investigated using density functional theory (DFT). The crystal structure of Li₂TiO₃ in the C2/m space group was optimized, and electronic structure calculations showed that the pristine compound exhibits semiconducting behavior with a direct band gap of about 2.90 eV. The valence band is dominated by O 2p orbitals, while the conduction band originates from Ti 3d states.To investigate the influence of defects on lithium diffusion, several point defects, including a single lithium vacancy (VLi), a double lithium vacancy (V₂Li), and a lithium–oxygen vacancy complex (VLi+VO), were introduced. The calculated band structures and partial density of states (PDOS) reveal that these defects produce localized states near the Fermi level, enhancing electronic conductivity. Defect formation energies were also calculated to evaluate the stability of the defective configurations.Lithium‑ion migration was studied using the nudged elastic band (NEB) method to identify diffusion pathways. Three migration paths were obtained with activation energy barriers of approximately 0.886, 1.09, and 1.20 eV. Transition state analysis indicates that migration barriers are mainly controlled by the local Li–O coordination environment, while Li–Ti interactions play a secondary role by influencing diffusion channel width. Charge density difference analysis shows that charge redistribution around oxygen atoms affects transition state stability.Overall, the results show that lattice geometry and defect engineering control lithium‑ion migration in Li₂TiO₃ and guide the design of lithium‑based materials with improved ionic transport
Ali Raheli
Abstract
Poisson-Gaussian mixed noise removal in optical sensor images is considered one of the major challenges in digital imaging, machine vision, and photon-limited optical systems due to its heterogeneous statistical nature and the signal-dependent characteristics of part of the noise. In this study, a deep ...
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Poisson-Gaussian mixed noise removal in optical sensor images is considered one of the major challenges in digital imaging, machine vision, and photon-limited optical systems due to its heterogeneous statistical nature and the signal-dependent characteristics of part of the noise. In this study, a deep convolutional neural network (DnCNN) based on a residual learning strategy was developed for image restoration and denoising. The proposed architecture, incorporating batch normalization layers and the Adam optimization algorithm, exhibited favorable stability and convergence during the training process.The simulation results and both quantitative and qualitative evaluations demonstrated that the proposed network outperformed conventional denoising methods in suppressing mixed Poisson-Gaussian noise and restoring image information. In addition to improving image quality assessment metrics, the proposed method showed a high capability for preserving high-frequency structures, edge details, and photometric features. Furthermore, the performance analysis of the model under different noise levels indicated its stability, satisfactory generalization capability, and robust performance under low-light and high-noise imaging conditions. The findings of this study indicate that the DnCNN-based approach effectively removes mixed noise while preventing image blurring and loss of sharpness, thereby enabling more accurate recovery of photometric and structural information. Therefore, the proposed approach can serve as an efficient computational framework for low-light imaging systems and for scientific and industrial applications based on optical sensors.