Development of an Optical Fiber Sensor with a D-shaped Fiber Bragg Grating Integrated in a Loop-mirror Optical Fiber Laser as a High Sensitivity Refractometer

In this paper, we report a new type of refractometer based on a D-shaped fiber Bragg grating (FBG) integrated in a loop-mirror optical fiber laser. This proposed sensor is used in wavelength interrogation method, in which the D-shaped FBG is applied as a refractive index (RI) sensing probe and a mirror to select mode of laser. The D-shaped FBG is prepared by the removal of a portion of the fiber cladding covering the FBG by means of side-polishing technique. The D-shaped FBG sensing probe integrated in a loop-mirror optical fiber laser with saturated pump technique, the characteristics of sensing signals have been improved to obtain stable intensity, narrower bandwidth and higher optical signal-to-noise ratio compare to normal reflection configuration. The limit of detection (LOD) of this sensor can be achieved to 2.95 x 10-4 RIU in the refractive index (RI) range of 1.42-1.44. Accordingly, we believe that the proposed refractometer has a huge potential for applications in biochemical-sensing technique.

Excitation spectra of cubic perovskite titanates

We calculate excitation spectra of cubic perovskites ATiO3 (A = Ca, Sr, Ba, Pb). The calculations are performed within the time-dependent density functional theory, including local field effects. The theoretical calculations show that the perovskites have a plasmon mode at around 12 eV, which is not observed in experiments.

One-loop Form Factors for \(H\rightarrow \gamma^*\gamma^*\) in \(R_{\xi}\) Gauge

In this paper, we present general one-loop form factors for \(H\rightarrow \gamma^* \gamma^*\) in \(R_{\xi}\) gauge, considering all cases of two on-shell, one on-shell and two off-shell for final photons. The calculations are performed in standard model and in arbitrary beyond the standard models which charged scalar particles may be exchanged in one-loop diagrams. Analytic results for the form factors are shown in general forms which are expressed in terms of the Passarino-Veltman functions. We also confirm the results in previous computations which are available for the case of two on-shell photons. The \(\xi\)-independent of the result is also discussed. We find that numerical results are good stability with varying \(\xi=0,1\) and $\xi\rightarrow \infty\).

Molecular Dynamic Simulation of Zigzag Silicon Carbide Nanoribbon

The heating process of zigzag silicon carbide nanoribbon (SiCNR) is studied via molecular dynamics (MD) simulation. The initial model contained 10000 atoms is heating from 50K to 6000K to study the structural evolution of zigzag SiCNR. The melting point is defined at 4010K, the phase transition from solid to liquid exhibits the first-order type. The mechanism of structural evolution upon heating is studied based on the radiral distribution functions, coordination number, ring distributions, and angle distributions.

Light Scattering by Noble Metallic Nanoparticles for Performance of Compound Soalr Cells Enhancement

Light scattering by noble metallic nanoparticles are of interest for a variety of applications due to the large electromagnetic field enhancement that occurs in the vicinity of the metal surface, and the dependence of the resonance photon energy on the nanoparticle size, shape, local dielectric environment, and material. Here, the influences of electromagnetic scattering by Au and Ag nanoparticles placed atop compound solar cells on optical absorption and photocurrent generation were investigated based on the variation in the noble nanoparticle densities. The results indicated that the short-circuit current and power conversion efficiency were strongly affected by the density and material of the noble nanoparticles. The great improvement of 28% in power conversion efficiency can be obtained with Au nanoparticle density of 2\(\times\)108 cm-2. This improvement can be attributed to light scattering, light trapping, and surface roughness by noble nanoparticles. Furthermore, Au nanoparticles showed more efficient in solar cell power conversion efficiency improvement than Ag nanoparticles did although density of Au nanoparticle was lower than that of Ag nanoparticles.

Characteristics of Dye-doped Silica Nanoparticles- Based Random Lasers in the Air and Water

Random lasers based on dye-doped silica nanoparticles are attracted for biomedical applications due to their biocompatibility and high brightness. Several laser structures including silica powder and film have been reported. However, the dependence of lasing characteristics including lasing threshold and emission wavelength on the laser size and working environment have not been explored. Here, we demonstrate and compare the lasing characteristics of dye-doped silica random lasers in air and water. These lasers present in thin structures, the so-called microslices, with a thickness of 1 µm and various dimensions from 30 to 300 µm. It is found that the lasing threshold (Ith) decreases with increasing laser size such as for sample in the air and for sample in water, where A the sample surface area. For a similar size, the lasing threshold of the sample in water is about 3-8 times higher than that of the sample in the air. In addition, the lasing peak wavelength exhibits a red-shift with increasing laser size. In the air, a shift of 8 nm is recorded when the sample surface area increases from 21×103 to 169×103 µm2. Furthermore, for a similar size, the lasing wavelength of the sample in the air is also red-shifted (13 nm in average ) compared with that of the sample in water. Our finding provides useful information for the use of silica-based random lasers in bioimaging and biosensing applications.

Vibrational Dynamics of Pd-Ni-P Bulk Metallic Glasses

In the present paper, Phonon modes and elastic constant of three different concentrations of PdxNi1-xP (Pd64Ni16P20, Pd40Ni40P20 and Pd16Ni64P20) bulk metallic glass are calculated using (1) Hubbard-Beeby (HB) and (2) Takeno-Goda (TG) approach along with our well established local model potential. The Hartree (H), Farid et al (F) and Sarkar et al (S) local field correlation functions (LFCF) are employed to examine the effect of the screening function on the collective dynamics of Pd-Ni-P bulk metallic glasses. Results are also reported for phonon dispersion curve, propagation elastic wave and elastic properties viz: bulk modulus BT, modulus of rigidity G, Poisson’s ratio ξ, Young’s modulus Y, Debye temperature ƟD. However, the calculated elastic constants results agree well with other theoretical and available experimental data.

A proto-brown dwarf candidate in rho Ophiuchus

Brown dwarfs with masses below 0.075 solar masses are thought to form like low-mass stars (e.g., the Sun).However, it is still unclear how the physical formation processes occurin brown dwarfs at the ealiest stages (i.e., proto-brown dwarfs) of their formation.Up to date, only a few proto-brown dwarfs have been detected.The detection of proto-brown dwarfs offers us excellent benchmarks to studythe formation process of brown dwarfs, and thus understand their formation mechanism.In this paper, we present our identification of a proto-brown dwarf candidate in the star-forming regionrho Ophiuchus.The candidate shows a small-scale bipolar molecular outlfow that is similar to the outflows observed inother young brown dwarfs. The detection of this candidateprovides us with additional important implications for the formation mechanism of brown dwarfs.

Metamaterials for Improving Efficiency of Magnetic Resonant Wireless Power Transfer Applications

In this article, we investigate a compact metamaterial structure for enhancing a magnetic resonant wireless power transfer (WPT) system operated at 6.5 MHz. A thin magnetic metamaterial (MM) slab placed between the transmitter (Tx) and receiver (Rx) coil can improve WPT efficiency. The metamaterial unit cell is designed by a ten-turn spiral resonator (10T-SR) loaded with an external capacitor. The resonant frequency of MM unit cells can be easily controlled by changing the capacitor value. By using the optimization approach, we achieve a significant WPT efficiency improvement at a mid-range distance. The results showed an enhancement of the magnetic field in the WPT system when MM slab was present. This demonstrates the ability to amplify the evanescent wave of MM slab, thereby improving the WPT efficiency. The transmission coefficients of WPT system at 60 cm increased from 0.5 to 0.76 with MM slab, which corresponds to a 46% improvement.

An optimal segmentation method for processing medical image to detect the brain tumor

In the field of medical physics, detection of brain tumor from computed tomography (CT) or magnetic resonance (MRI) scans is a difficult task due to complexity of the brain hence it is one of the top priority goals of many recent researches. In this article, we describe a new method that combines four different steps including smoothing, Sobel edge detection, connected component, and finally region growing algorithms for locating and extracting the various lesions in the brain. The computational algorithm of the proposed method was implemented using Insight Toolkit (ITK). The analysis results indicate that the proposed method automatically and efficiently detected the tumor region from the CT or MRI image of the brain. It is very clear for physicians to separate the abnormal from the normal surrounding tissue to get a real identification of related areas; improving quality and accuracy of diagnosis, which would help to increase success possibility by early detection of tumor as well as reducing surgical planning time. This is an important step in correctly calculating the dose in radiation therapy later.