Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 7 Articles
Various applications require an antenna to provide coverage in the azimuthal plane while still retaining a\nlow profile. Transformation Optics method can be used to provide novel solutions to fulfill this objective. In this paper,\nthe design of dielectric superstrate inspired from Transformation Optics has been reported which completely reorients\nthe electromagnetic waves emanating from a directive antenna in the azimuthal plane. The physical space is modeled\nusing a virtual space composed of two opposed quarter circles. It is shown analytically that a dielectric-only solution\ncan be obtained from the transformation relations. Use of shift and compression factors has been applied to the\nmaterial parameter profile to achieve the reorientation. A full wave solution has been presented which reorients\nthe radiation pattern of a classical patch antenna in the azimuthal plane. The solution can be fabricated from isotropic\ndielectric materials....
A miniature fiber-optic Fabry-Perot interferometer (MOFPI) fabricated by splicing a\nhollow silica tube (HST) with inner diameter of 4 m to the end of a single-mode fiber is investigated\nand experimentally demonstrated. The theoretical relationship between the free spectrum range and\nthe length of HST is verified by fabricating several MOFPIs with different lengths. We characterize\nthe MOFPIs for temperature, liquid refractive index, and strain. Experimental results show that the\nsensitivities of the temperature, liquid refractive index, and strain are 16.42 pm...
Defects produced during selective laser sintering\n(SLS) are difficult to non-destructively detect after\nbuild completion without the use of X-ray-based\nmethods. Overcoming this issue by assessing integrity\non a layer-by-layer basis has become an area of\nsignificant interest for users of SLS apparatus.\nOptical coherence tomography (OCT) is used in\nthis study to detect surface texture and sub-surface\npowder, which is un-melted/insufficiently sintered,\nis known to be a common cause of poor part\nintegrity and would prevent the use of SLS where\napplications dictate assurance of defect-free parts.\nTo demonstrate the capability of the instrument and\nassociated data-processing algorithms, samples were\nbuilt with graduated porosities which were embedded\nin fully dense regions in order to simulate defective\nregions. Simulated in situ measurements were then\ncorrelated with the process parameters used to\ngenerate variable density regions. Using this method,\nit is possible to detect loose powder and differentiate\nbetween densities of �±5% at a sub-surface depth\nof approximately 300 �¼m. In order to demonstrate\nthe value of OCT as a surface-profiling technique,\nsurface texture datasets are compared with focus...
A narrow linewidth laser configuration based on distributed feedback fiber lasers\n(DFB-FL) with eight wavelengths in the international telecommunication union (ITU) grid is\npresented and realized. In this laser configuration, eight phase-shifted gratings in series are\nbidirectionally pumped by two 980-nm laser diodes (LDs). The final laser output with over 10-mW\npower for each wavelength can be obtained, and the maximum power difference within eight\nwavelengths is 1.2 dB. The laser configuration with multiple wavelengths and uniform power outputs\ncan be very useful in large scaled optical fiber hydrophone fields....
Possessing a variety of remarkable optical, electronic, and mechanical properties, graphene has emerged as an attractive material\nfor a myriad of optoelectronic applications. The wonderful optical properties of graphene afford multiple functions of graphene\nbased polarizers, modulators, transistors, and photodetectors. So far, the main focus has been on graphene based photonics and\noptoelectronics devices. Due to the linear band structure allowing interband optical transitions at all photon energies, graphene\nhas remarkably large third-order optical susceptibility x(3), which is only weakly dependent on the wavelength in the nearinfrared\nfrequency range.The graphene-assisted four-wave mixing (FWM)based wavelength conversions have been experimentally\ndemonstrated. So, we believe that the potential applications of graphene also lie in nonlinear optical signal processing, where the\ncombination of its unique large x(3) nonlinearities and dispersionless over the wavelength can be fully exploited. In this review\narticle,we give a brief overviewof our recent progress in graphene-assisted nonlinear optical device and their applications, including\ndegenerate FWM based wavelength conversion of quadrature phase-shift keying (QPSK) signal, phase conjugated wavelength\nconversion by degenerate FWM and transparent wavelength conversion by nondegenerate FWM, two-input and three-input highbase\noptical computing, and high-speed gate-tunable terahertz coherent perfect absorption (CPA) using a split-ring graphene...
The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD\npattern shows that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. Raman\nspectra reveal that Bi2O3 segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the\nfilm was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary\nwere interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the\nbreakdown voltage reduced to 5.34V....
The feasibility of polarization-maintaining photonic crystal fibre (PM-PCF) strategy for acoustooptic modulation using all-fibre\nSagnac interferometer is demonstrated. The principal constraint to apply the strategy is defined by a linear laser acoustooptic\nmodulator (AOM) for 1550 nm. The intensity of incident acoustic waves over the PM-PCF loop segment affected the signal\ninterference transmission; here, modulation by birefringence variation around 7.6 Ã?â?? 10âË?â??4 Ã?± Ã?â?ni\nwas observed. It is discovered\nthat, through mathematical analysis, two operation points in the spectrum, T\nSI\n(Ã?»), operate in a linear region, and expressions for\nspectral gain and sensibility are also discovered. AOM has a bandwidth from 0.1 Hz to 20 kHz, and its dynamic range is from 0.0\nto 43.5 dB....
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