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Results 401 - 450 of 2550
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Kocaman Serdar - - 2012
We demonstrate chip-scale flat-top filters at near-IR wavelengths using negative index photonic crystal based Mach-Zehnder interferometers. Supported by full three-dimensional numerical simulations, we experimentally demonstrate a new approach for engineering high-pass, low-pass, bandpass, and band-reject filters, based on designing the photonic band diagram both within the bandgap frequency region and ...
Chau B Nelson - - 2012
Scarring of the kidney is a major public health concern, directly promoting loss of kidney function. To understand the role of microRNA (miRNA) in the progression of kidney scarring in response to injury, we investigated changes in miRNA expression in two kidney fibrosis models and identified 24 commonly up-regulated miRNAs. ...
Pelc J S - - 2012
We present a device for two-stage frequency upconversion of single-photon-level signals in the 1.55 μm telecom band to the green spectral region with low excess noise, suitable for detection by low-timing-jitter silicon single-photon avalanche photodiodes (APDs). We achieve a net conversion efficiency of 87% and a system timing jitter below ...
Xiao Yong-Liang - - 2012
System geometrical calibration is a challenging task in fringe-reflection 3D measurement because the fringe displayed on the LCD screen does not lie within the camera's field of view. Commonly, a flat mirror with markers can accomplish system geometrical calibration. However, the position of the markers must be precisely located by ...
Mannucci Pier Mannuccio - - 2012
Patients with hemophilia now have a life expectancy very close to that of the unaffected male population and, hence, are at risk of developing the classic age-related morbidities, i.e., cardiovascular diseases. The peculiarity of the management of these diseases in hemophilia is that antithrombotic drugs impinge on the already compromised ...
Okusaga O - - 2012
Rayleigh scattering in optical fibers has the potential to degrade the performance of low-noise opto-electronic systems. In this Letter, we measure the Rayleigh gain spectrum of optical fibers. Our data show the gain bandwidth and the offset frequency of the Rayleigh gain peak. Both the gain bandwidth and the peak ...
Zou Xihua - - 2012
We propose and experimentally demonstrate a photonic approach to the measurement of the time-difference-of-arrival (TDOA) and the angle-of-arrival (AOA) of a microwave signal. In the proposed system, the TDOA and the AOA are equivalently converted into a phase shift between two replicas of a microwave signal received at two cascaded ...
Bernhardt Birgitta - - 2012
We present the first (to our best knowledge) femtosecond enhancement cavity in the visible wavelength range for ultraviolet frequency comb generation. The cavity is seeded at 518 nm by a frequency-doubled Yb fiber laser and operates at a peak intensity of 1.2×10<sup>13</sup>  W/cm<sup>2</sup>. High harmonics of up to the ninth order ...
Kumkar Sören - - 2012
We generate broadband pulses covering the Yb: and Tm:silica amplification ranges with a passively phase-locked front end based on Er:fiber technology. Full spectral coherence of the octave-spanning output from highly nonlinear germanosilicate bulk fibers is demonstrated. Seeding of a high-power Tm:fiber generates pulses with a clean spectral shape and a ...
El Ketara Mohamed - - 2012
We report on the observation of self-induced nonlinear spin-orbit interaction of light driven by Kerr orientational optical nonlinearities in liquid crystals. It consists of the self-induced spin-to-orbital nonlinear conversion for the angular momentum of light. The optical angular momentum conversion is driven by the creation of a topological liquid crystal ...
Lisman John J Department of Biology, Brandeis University, Waltham, Massachusetts 02454, USA. - - 2012
Long-term potentiation (LTP) of synaptic strength occurs during learning and can last for long periods, making it a probable mechanism for memory storage. LTP induction results in calcium entry, which activates calcium/calmodulin-dependent protein kinase II (CaMKII). CaMKII subsequently translocates to the synapse, where it binds to NMDA-type glutamate receptors and ...
Xiao Zhe - - 2012
In this Letter, we propose general optimization methods to design broadband high-efficiency grating couplers for planar waveguides. We attribute the coupling bandwidth to the mismatch of effective indices between the diffracted beam and the actual grating structure around the operation wavelength for fiber to waveguide excitation. The coupling bandwidth formula ...
Preda Cristina Elena - - 2012
Self-Q-switched operation of the all-fiber laser using erbium and samarium fibers in the cavity is realized experimentally. This passively Q-switched all-fiber laser produces very stable pulses with energy of 142 nJ and duration of 450 ns. The experimental results were well reproduced by the results obtained through the numerical integration of a ...
Xie Changqing - - 2012
In this Letter, we report a significant step forward in the design of single-optical-element optics for two-dimensional (2D) hard X-ray differential-interference-contrast (DIC) imaging based on modified photon sieves (MPSs). MPSs were obtained by a modified optic, i.e., combining two overlaid binary gratings and a photon sieve through two logical XOR ...
Shi Chunmeng - - 2012
A recent report from Urano et al. described the development of near-infrared (NIR) probes for cancer detection using chemical bioconjugation of targeting agents. Here, I highlight an alternative strategy to develop cancer-selective NIR imaging and theranostic agents without chemical conjugation.
Brown Graeme - - 2012
We report the fabrication of high-strength (>30  dB) first order Bragg-grating waveguides in borosilicate glass substrates using ultrafast laser inscription. The cross section of each waveguide was controlled using the well known multiscan fabrication technique, where the desired waveguide cross section is constructed by scanning the sample through the laser focus ...
Luo Lian-Wee - - 2012
We demonstrate power insensitive silicon microring resonators without the need for active feedback control. The passive control of the resonance is achieved by utilizing the compensation of two counteracting processes, free carrier dispersion blueshift and thermo-optic redshift. In the fabricated devices, the resonant wavelength shifts less than one resonance linewidth ...
Sun Zhijun - - 2012
The effect of absorption enhancement with metallic nanoparticles on solar cell surfaces is often confused with various optical processes. In this work, the effective absorption rates in the active materials of solar cells are explicitly calculated including all possible factors. The results show that, although the total absorption is highly ...
Huang R - - 2012
Strong white electroluminescence (EL) from SiN-based devices containing Si nanodots with a density of more than 4.6×10<sup>12</sup>/cm<sup>2</sup> was investigated. The white EL illustrates enhanced light emission with increasing applied voltage and can be divided into two components, a dominant peak at ∼710  nm and weak one at ∼550  nm, which are close ...
Chen Weibin - - 2012
Owing to a geometric phase effect, an isosceles triangular aperture etched into thin metal film leads to constructive or destructive interference of surface plasmons excited at the two equal sides under linearly polarized illumination. Through appropriate spatial arrangement of an array of triangles, a highly confined focal spot beyond the ...
Restrepo John F - - 2012
We present an automatic procedure for 3D tracking of micrometer-sized particles with high-NA digital lensless holographic microscopy. The method uses a two-feature approach to search for the best focal planes and to distinguish particles from artifacts or other elements on the reconstructed stream of the holograms. A set of reconstructed ...
Chen Y F - - 2012
We explore the operation of spontaneous mode locking in a diode-pumped Nd:SrGdGa<sub>3</sub>O<sub>7</sub> disordered crystal laser. The first- and second-order autocorrelations are simultaneously performed to evaluate the temporal characteristics. An 80 GHz pulse train with a pulse duration as short as 616 fs is observed. The maximum output power is 415 ...
Kim Se-Heon - - 2012
A photonic crystal (PhC) nanocavity formed in an optically very thick slab can support reasonably high-Q modes for lasing. Experimentally, we demonstrate room-temperature pulsed lasing operation from the PhC dipole mode emitting at 1324 nm, which is fabricated in an InGaAsP slab with thickness (T) of 606 nm. Numerical simulation ...
Yang Li - - 2012
We propose a fiber structure based on a single-mode-multimode-single-mode one. A theoretical analysis model based on leaky mode expansion along with a new concept of leaky mode interference is presented to facilitate and enlighten the analysis for the leaky structure. Then we focus on transmission characteristics of the structure in ...
Zolot A M - - 2012
We demonstrate a dual-comb spectrometer using stabilized frequency combs spanning 177 to 220 THz (1360 to 1690 nm) in the near infrared. Comb-tooth-resolved measurements of amplitude and phase generate over 4×10<sup>5</sup> individually resolved spectral elements at 100 MHz point spacing and kilohertz-level resolution and accuracy. The signal-to-noise ratio is 100 to 3000 per ...
Maysonnave J - - 2012
We used a terahertz (THz) quantum cascade laser (QCL) as an integrated injection seeded source and amplifier for THz time-domain spectroscopy. A THz input pulse is generated inside a QCL by illuminating the laser facet with a near-IR pulse from a femtosecond laser and amplified using gain switching. The THz ...
Tringham Elizabeth - - 2012
Absence seizures are a common seizure type in children with genetic generalized epilepsy and are characterized by a temporary loss of awareness, arrest of physical activity, and accompanying spike-and-wave discharges on an electroencephalogram. They arise from abnormal, hypersynchronous neuronal firing in brain thalamocortical circuits. Currently available therapeutic agents are only ...
Forestier Nicole - - 2012
More than 180 million people worldwide are infected with the chronic hepatitis C virus (HCV), a major cause of liver cirrhosis, and its life-threatening complications including liver failure, portal hypertension and hepatocellular carcinoma. For patients infected with HCV genotype 1, the chances of a sustained virologic response (SVR) with the ...
Yin Yongkai - - 2012
The measurement accuracy of fringe projection profilometry (FPP) largely depends on the calibration procedure. A more reliable calibration approach based on the stereo vision model of the FPP scheme in conjunction with the bundle adjustment strategy is presented. It can adjust the coordinates of benchmarks and thereby estimate the scheme ...
Zaccaria Remo Proietti - - 2012
We report on the possibility of realizing a radial mode on a metallic conical structure by means of a linearly polarized incident wave. This result is utilized for observing surface plasmon polaritons adiabatic compression on a tapered conical nanostructure. The ingredients for radial mode generation are described in terms of ...
Zhu Z H - - 2012
We proposed and fabricated a nanofilm half-wave plate consisting of periodic arrays of orthogonally coupled slit-hole resonator structures in Au film. Experimental results reveal that 95.2% of energy of the incident linearly polarized light is converted to the perpendicular polarization direction after reflection from the nanostructure. The wave plate is ...
Ossikovski Razvigor - - 2012
The manuscript proposes a novel virtual experiment nondepolarizing estimate, as an alternative to the Cloude sum decomposition estimate, to be used in the extraction of the elementary polarization properties of a medium from its experimentally determined Mueller matrix. The estimate results from the minimization of a least squares estimator based ...
Westerveld Wouter J - - 2012
Recently there has been growing interest in sensing by means of optical microring resonators in photonic integrated circuits that are fabricated in silicon-on-insulator (SOI) technology. Taillaert et al. [Proc. SPIE 6619, 661914 (2007)] proposed the use of a silicon-waveguide-based ring resonator as a strain gauge. However, the strong lateral confinement ...
Yeh Yunhae - - 2012
In order to implement a fiber-optic Fabry-Perot tunable filter with a simple configuration, a concave mirror is made at the end of the optical fiber. The concave mirror is fabricated by attaching a thin polycarbonate (PC) film on the fiber end, pressing the PC film with a fiber ball to ...
Duan Qianqian - - 2012
A quantum cutting mechanism for the sublinear near-IR power dependence property in Tb<sup>3+</sup>-Yb<sup>3+</sup> codoped NaYF<sub>4</sub> powders were investigated both experimentally and theoretically. The slopes of Yb<sup>3+</sup> luminescence intensity versus excitation power were fitted to be between 0.5 and 1. We have developed a quantum cutting rate equation model to explain ...
Battiato Alfio - - 2012
We present the results of variable-angle spectroscopic ellipsometry and transmittance measurements to determine the variation of the complex refractive index of ion-implanted single-crystal diamond. An increase is found in both real and imaginary parts at increasing damage densities. The index depth variation is determined in the whole wavelength range between ...
Kozlov Victor V - - 2012
We theoretically investigate the polarization properties of Raman amplifiers based on silicon-on-insulator waveguides, and show that it is possible to realize a waveguide Raman polarizer. The Raman polarizer is a special type of Raman amplifier with the property of producing an amplified and highly repolarized beam when it is fed ...
Bradke Frank F Axonal Growth and Regeneration, German Center for Neurodegenerative Disease, Ludwig-Erhard-Allee 2, 53175 Bonn, - - 2012
The assembly of a new growth cone is a prerequisite for axon regeneration after injury. Creation of a new growth cone involves multiple processes, including calcium signalling, restructuring of the cytoskeleton, transport of materials, local translation of messenger RNAs and the insertion of new membrane and cell surface molecules. In ...
Safrani Avner - - 2012
We developed an ultrahigh-resolution full-field optical coherence tomography (FF-OCT) microscope that is based on the spatial, rather than the temporal, coherence gating. The microscope is capable of observing three-dimensional microbiological structures as small as 0.4 μm×0.4 μm×1.0 μm (xyz) using quasi-monochromatic light and a liquid crystal retarder. Unlike traditional FF-OCT systems, this microscope ...
Richter Sören - - 2012
We investigate the role of self-trapped excitons (STEs) and defects in the formation of femtosecond laser pulse induced nanogratings (NGs) in fused silica. Our experiments reveal strongly enhanced NG formation for pulse separations up to the STE lifetime. In addition, the absorption spectra show that the weaker cumulative action of ...
Zeuner J M - - 2012
We report on the experimental demonstration of negative coupling constants between defect guides in a waveguide lattice. We find that coupling can only be negative if the defects are negative and an odd number of lattice sites is between the defect guides.
Gao Chunqing - - 2012
A fiber laser resonantly pumped 1.645 μm passively Q-switched Er:YAG laser is reported. Graphene on a silicon carbide was used as the saturable absorber for the Q-switching. The pulse energy of the 1.645 μm Q-switched Er:YAG laser was 7.05 μJ, with a pulse repetition rate of 35.6 kHz and an ...
Su Rongtao - - 2012
We report on active coherent beam combining of two single-frequency nanosecond fiber amplifiers by using stochastic parallel gradient descent algorithm. Each fiber amplifier produces an average power of more than 100 W by using three-stage cascaded amplification. The two laser beams are actively phase-locked with a total average power of 215.8 W, ...
Menzel Christoph - - 2012
Most left-handed metamaterials cannot be described by local effective permittivity or permeability tensors in the visible or near-infrared due to the mesoscopic size of the respective unit cells and the related strong spatial dispersion. We lift this problem and propose a metamaterial exhibiting artificial magnetism that does not suffer from ...
Wei Tao - - 2012
This Letter proposes an optical fiber radio frequency (RF) Mach-Zehnder interferometer (MZI) for sensing applications. An RF modulated laser source is injected into an optical fiber RF-MZI and collected by a photodiode. The interference pattern is observed in the RF domain by sweeping the frequency using a network analyzer. The ...
Courtial Johannes - - 2012
Building on recent work on windows that can be modeled as interfaces between materials with a complex ray-optical refractive-index ratio, we define here objects and images at complex positions. We give an example of an optical component that performs imaging between real and complex object and image positions.
Lin Shyh-Tsong - - 2012
This Letter introduces a polarization phase-shifting Newton interferometer that can be utilized for plane optical surface measurements, a setup constructed to realize the interferometer, and the experimental results from the use of the setup. The results confirm not only the validity but also the feasibility of the interferometer.
Daniault L - - 2012
We experimentally investigate the impact of spectral phase mismatch on the coherent beam combining of two femtosecond fiber chirped-pulse amplifiers. By measuring the differential spectral phase, both linear and nonlinear contributions are identified. An accumulated nonlinear phase as high as 6 rad has been measured, for which a combination efficiency ...
Lauzardo Michael M University of Florida, College of Medicine, 1600 SW Archer Road, PO Box 100486, Gainesville, FL 32610-0486, - - 2012
In terms of human suffering, tuberculosis has a huge impact on global society, making it arguably the most important infectious disease in history. Despite the devastating impact on society, the tools to fight tuberculosis are very limited. Current standard therapy has been used for over 40 years and threats, such ...
Eftekhari Fatemeh - - 2012
In this Letter, we demonstrate the efficacy of hollow core photonic crystal fibers (HCPCFs) as a surface-enhanced Raman spectroscopy (SERS) platform for investigating the ligand exchange process on the surface of gold nanoparticles. Raman measurements carried out using this platform show the capability to monitor minute amounts of surface ligands ...
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