Journal of Optoelectronical Nanostructures
Volume:1 Issue: 3, Autumn 2016

Casimir entropy is an important aspect of casimir effect and at the nanoscale is visible. In this paper, we employ the path integral method to ýobtain aý ýgeneralý relation for casimir entropy and ýiýnternal energy of arbitrary shaped objects in the presence of two, three and four dimension scalar fields and ýtheý electromagnetic field. For this purpose, using Lagrangian and based on a perturbative approach, a series expansion in susceptibility function of the medium was obtained for the Casimir force between arbitrary shaped objects foliated in a scalar or vector fluctuating field in arbitrary dimensions. The finite temperature corrections are derived and using it, we obtain the casimir entropy and internal energy of two nano ýribýbons immersed in the scalar field and two nanospheres immersed in the scalar field and the electromagnetic field. The casimir entropy of two nanospheres immersed in the electromagnetic field ýbehave ýdifferentlyý in small interval of temperature variations.

The two-dimensional structure of graphene, consisting of an isotropic hexagonal lattice of carbon atoms, shows fascinating electronic properties, such as a gapless energy band and Dirac fermion behavior of electrons at fermi surface. Anisotropy can be induced in this structure by electrochemical pressure. In this article, by using tight-binding method, we review anisotropy effects in the electronic nanostructure of graphene in one direction. For this purpose, we just consider π states, which express electronic characteristics, and compare electronic band of π states with that of isotropic honeycomb lattice in graphene. As a result, by applying pressure or stretching in one direction, the gap will be created in the electronic band at the fermion surface, which can be useful for semiconducting nano devices. The isotropic graphene has a band structure with no energy gap. By applying electrochemical pressure in one direction, the translational symmetry can be broken, therefore an energy gap appears between the two bands.

Utilizing Boundary Integral Method (BIM), we investigate the spontaneous emission enhancement rate in the vicinity of plasmonic nanoparticles of elliptical cross section. These types of nanoparticles can considerably enhance molecules decay rate. One can easily adjust the spontaneous emission rate of the elliptical nanoparticle by altering the aspect ratio and the background refractive index. It is shown that the decay rate can be enhanced by two or three orders of magnitude for dipole distances below 10 nanometers. Also, the position of enhancement peaks is adjusted in the investigated spectral range (400-1000 nm) by changing the aspect ratio of the nanoparticle or the refractive index of background medium and nanoparticles material. To validate our result, we use BIM method to calculate light scattering by a circular gold nanowire and compare the results with those obtained from Mie theory. The results show a good agreement. Moreover, the BIM method is considerably faster that domain methods.

The group of 2D materials contains almost all the elements of the periodic table. In contrast to the graphene sheet, they are abundant, this creates a variety of electronic properties including metals, semimetals, insulators and semiconductors. Band gaps of these materials are direct or indirect by ranging from ultraviolet to infrared, for this reason, have received much attention for nanoelectronics, optoelectronics and flexible devices.
In this study, by a simple hydrothermal method, which is a bottom-up approach, molybdenum diselenide two-dimensional layers were synthesized. The samples were analyzed by X-ray diffraction spectroscopy, and the compound molybdenum diselenide was confirmed for the samples synthesized, and also with UV-visible spectroscopy (UV-Vis) to study the absorption spectrum and Fluorescence Spectroscopy of Fluorescence (PL) to investigate the properties of fluorescent, the nanoparticles were studied, and found that, by changing the concentration and time of hydrothermal process, the intensity of emission changes. Scanning electron micrographs indicate the size of 100 nanometers for particles synthesized.

In this paper, by using a quantum hydrodynamic plasma model which incorporates the important quantum statistical pressure and electron diffraction force, we present the corrected plasmon dispersion relation for graphene which includes a k quantum term arising from the collective electron density wave interference effects (which  is integer and constant and k is wave vector). The longitudinal plasmons are the electrostatic collective excitations of the solid electron gas. We have tried to use the quantum hydrodynamic model for studying of propagation of the electrostatic surface wave in single layer graphene, in the presence of an external and uniform magnetic field. The direction of magnetic field was selected in plane of graphene sheet. It shows the importance of quantum term from the collective electron density wave interference effects. By plotting the dispersion relation derived, it has been found that dispersion relation of surface modes depends significantly on these quantum effects (Bohm’s potential and statistical terms) and it should be taken into account in the case of magnetized or unmagnetized plasma; we have noticed successful description of the quantum hydrodynamic model. The quantum corrected hydrodynamic model can effectively describe the Plasmon dispersion spectrum in degenerate plasmas, since it takes into account the full picture of collective electron-wave interference via the quantum Bohm’s potential. By plotting the normalized dispersion relation, the behavior of two different wave types (lower- and higher- branches) was predicted. It was found that the lower-branch should not be propagated to the specific wave number (cut-off frequency). By drawing of the contour curve of the lower- and higher-branches modes, the areas that modes can be propagated were obtained. So, Quantum hydrodynamic model is an effective way to study the waves in various media.

In the present paper, the problem of light reflection from a birefringent medium and thin film is considered. First, the analytical equations governing the propagation of a plane and harmonic electromagnetic wave in an infinite, birefringent, linear, non-dispersive, non-absorbing, and non-magnetic medium is derived from Maxwell equations. Then, using phase matching condition and boundary conditions, the governing equations of reflection and transmission from a birefringent medium is obtained. Next, the reflection of s and p polarizations in incidence of s-polarized, p-polarized, and circularly polarized light on a plane surface is calculated using a massive computer code developed by the authors. Calculations show that the polarizations are mixed and converted to each other. On the other hand, dependence of reflection on azimuthal incidence angle is revealed. Then, the problem of interfering reflection from a birefringent thin film is regarded. The computer code calculates reflection of light from the film by considering the successive reflections and transmissions from the upper and lower surfaces of the film through two-reflection approach. Calculations show that, in reflection of white light from the film, a kind of banding is developed which is absent in isotropic films. Observation of reflection increase by increasing birefringent properties is another finding of the paper.

In this paper, the temperature dependence on optical absorption cross section of the core shell bimetallic nanoparticles (NPs) is investigated in quasi static approximation. Temperature dependence of the plasmon resonance is important issue because of recent applications of NPs of noble metal for heat treating of cancer and the computer chips. The effect of temperature on surface plasmon resonance and spectral properties of spherical core-shell NPs are studied by using the Drude Lorentz model. As temperatures increases, the spectrum can be expanded, and thus it causes to expand plasmon resonance absorption and a weak red shift in core-shell NPs. In addition, the temperature dependent absorption cross section of the material depends on the type, structure and geometry of the NPs. The high sensitivity of surface plasmon resonance peaks causes that core shell NPs be completely suitable for medical and optical biosensor applications.