International Journal of

The semi-classical model of atom-field interaction has been fully studied for some multilevel atoms, e.g. Vee, L, Cascade X , Y, and inverted Y and so on. This issue is developed into the full-quantum electrodynamics formalism, where the probe and coupling electromagnetic fields are quantized. In this article, we investigate the full-quantum model of absorption and dispersion spectrum of trapped four-levels inverted Y type atoms, interacting with a probe beam of photons as well as two-mode trapped coupling photons. It is shown that the measurement of the maximum of absorption of the probe field and its detuning gives us simply the number of two-mode coupling photons, individually. An experimental setup for this non-demolition photon counting method is proposed and the numbers of coupling photons are obtained analytically.

Detection of fuel adulteration in real time is the most important need of the world as it generates the hazardous effects on the environment, living and nonliving things. Various automotive users and fuel providers may mix kerosene in petrol and diesel. Adulterated fuel increases air pollution, as well as reduces the performance of vehicle engines. Such a malpractice in fuel is prevailing because vehicles do not have real time adulteration monitoring system. In this study, we propose evanescent wave optical fiber sensor, which is interfaced with peripheral interface controller (PIC) to detect fuel adulteration percentage by means of change in refractive index. A fuel sensor prototype is formulated and tested to detect adulteration percentage in petrol and diesel by kerosene. The sensor is useful as it has simple construction, real time operation, and safety handling with inflammable fuel for in-situ measurements. The sensors have detectable capacity of 5% contaminant in petrol and diesel using evanescent wave absorption technique. Other traditional techniques are able to detect presence of about more than 10 % of fuel adulteration only in the laboratory. PIC is used with a fuel sensor for incorporating an automation and sophistication in automotive display, so that it is more useful to layman.

In this paper, we report the numerical analysis of a photonic crystal fiber (PCF) for generating an efficient supercontinuum medium. For our computational studies, the core of the proposed structure is made up of As₂Se₃ and the cladding structure consists of an inner ring of holes made up As₂Se₃ and four outer rings of air holes in MgF₂. The proposed structure provides excellent nonlinear coefficient and dispersion optimization. For the analysis, finite difference frequency domain (FDFD) method is employed. Because of the high nonlinear refractive index of the chalcogenide glass and high difference between the refractive index of the core and the cladding, a small effective mode area of 0.68 μm² is obtained. The nonlinear coefficient is 14.98 W^-1m^-1 at the wavelength of 1.8 μm. Dispersion is almost flat from 1.6 μm up to 2.8 μm. The supercontinuum spectrum calculated ranges from 1 μm to 6 μm. The presented structure is appropriate for medical imaging, optical coherence tomography and optical communications

In this paper, a Y-shaped power splitter based on a two dimensional photonic crystal (PhC) for TE modes is designed and optimized. A triangular lattice of air holes is used for Y-shaped power divider. For analyzing these structures, plane wave expansion (PWE) and finite difference time domain (FDTD) methods are used. The simulation results show that more than 98% of the input power is transmitted to the outputs and the structure has just less than 2% reflected power. According to the simulation results this structure is suitable for high bandwidth optical integrated circuit at the 1550 nm wavelength.

To investigate the plasmonic effect in perovskite solar cells, the effect of depositing Au@SiO₂ nanoparticles on the top and the bottom of mesoporous TiO₂ layers was studied. First, Au@SiO₂ nanoparticles were synthesized. The particles were then deposited at the different interfaces of mesoporous TiO₂ layers. Although the two structures show approximately similar optical absorption, only cells with Au@SiO₂ nanoparticles deposited at the bottom of the mesoporous TiO₂ layers demonstrated an improved photocurrent performance compared to the reference cells. This structure shows a short-circuit current density (JSC) of 20.7 mA/cm² and open circuit voltage of 1081 mV. This enhancement may be attributed either to the interface surface engineering or plasmonic resonance of Au@SiO₂ nanoparticles depends to the NPs size and position.  

In this paper, a new structure is provided for the dispersion compensating photonic crystal fibers in order to broaden the chromatic dispersion and increase the dispersion compensating capability in a wide wavelength range. In the structure, putting elliptical holes in the first ring of the inner core clad of a dispersion compensating fiber of the hexagonal lattice, increases the wavelength range of the dispersion compensation, and causes this fiber to have the capability of dispersion compensation in the whole E to U telecommunication bands. In this fiber, the minimal dispersion will be -1006 ps/(nm.km) at the 1.68 μm wavelength and at the 1.55 μm wavelength the dispersion coefficient will be -710 ps/(nm.km). The simulations are all done using the finite difference time domain numerical method.

In this paper, we have investigated the dependence of the spectral entanglement and indistinguishability of photon pairs produced by the spontaneous parametric down-conversion (SPDC) procedure on the bandwidth of spectral filters used in the detection setup. The SPDC is a three-wave mixing process which occurs in a nonlinear crystal and generates entangled photon pairs and utilizes as one of the most useful resources in a variety of fields such as quantum computation, quantum cryptography, and quantum communication. The amount of the spectral entanglement and the indistinguishability of photon pairs are the two critical characteristics of the photon pairs determining their potential applications. The degree of the spectral entanglement of a quantum system, i.e. photon pairs, is determined by the entanglement entropy which is a measure of the system disorder. First, we derive the eigenvalue equation of reduced density operator of the signal and the idler photons in terms of the bandwidth of spectral filters. Then, by numerically solving the eigenvalue equation, we calculate the Schmidt coefficients for different values of the bandwidth of spectral filters. Finally, by calculating the entropy operator one can obtain the dependence of spectral entanglement of the photon pairs on filter bandwidth. The amount of indistinguishability of the photon pairs is measured by the visibility of the HOM diagram. Since the whole spectral information of the photon pairs exists in their two-photon mode function, using this function and the presented model we calculate the amount of indistinguishability by obtaining the visibility of the HOM diagram for different values of the bandwidth of the spectral filters. In this way, the dependence of the indistinguishability of the photon pairs on this quantity is reported.

In this article, the effect of plasmonic properties of metal nanoparticles with different shapes, and moreover, their plasmonic-photonic interaction, on solar cell performance were investigated and simulated. Because of low conversion efficiency and then high cost of solar cells, it is difficult to commercialize and replace them with conventional energy resources. But in recent years, the plasmonic solar cell has been very popular. In this study, it is shown that the enhancement of near-field electromagnetic waves severely affects the generation rate, which handles the carrier’s generation in the solar cell equations and causes alteration of the photocurrent. This means that by manipulating the plasmonic properties of nanoparticles (shape and density) and their interaction with photons in solar cell structure, distribution of electromagnetic fields will be altered. Hence, the optical power related to the poynting vector is changed. So, with the aim of improving the solar cell some important parameters such as alteration of nanoparticle shape and their inter-distance were investigated. Finally, a comparison between traditional solar cells and our improved structure was undertaken.

Since Amaranth (AM) is one of the dye compounds which is harmful to human’s life its removal from industrial waste water would reduce their environmental impact and health effect. Copper nanoparticle (CuNP) is a simple and eco-friendly material which can be used to remove this pollutant. In this paper, copper nanoparticles were synthesized, for removal of AM dye. The experiments were designed by response surface methodology with a modified cubic model to predict the variables. To investigate variables and interaction between them analysis of variance was used with high F-value (1.44), low P-value (<0.0409), non-significant lack of fit, the determination coefficient of 0.898 and the adequate precision of 7.25. Experimental and predicted values of the response illustrated a good correlation. The optimum parameters catalyst amount (0.14 w/w%), initial concentration (7.38 mg/l), reaction time (47.75 s) and pH (2.83) for the highest removal percentage of (96.10%) was attained.