Search Results
Results 351 - 400 of 2549
< 3 4 5 6 7 8 9 10 11 12 13 >
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 ...
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 ...
Naether U - - 2012
We investigate experimentally the light evolution inside a two-dimensional finite periodic array of weakly coupled optical waveguides with a disordered boundary. For a completely localized initial condition away from the surface, we find that the disordered boundary induces an asymptotic localization in the bulk, centered around the initial position of ...
Boppel Sebastian - - 2012
We demonstrate the principle applicability of antenna-coupled complementary metal oxide semiconductor (CMOS) field-effect transistor arrays as cameras for real-time coherent imaging at 591.4 GHz. By scanning a few detectors across the image plane, we synthesize a focal-plane array of 100×100 pixels with an active area of 20×20  mm<sup>2</sup>, which is applied ...
Fu Hao - - 2012
We explore the laser spot position (LSP) dependence of photothermal mode cooling in a microcantilever-based Fabry-Perot cavity. Experiments on photothermal cooling demonstrate that the direction of photothermal backaction on the first two cantilever modes is LSP dependent, which can be either parallel or antiparallel. A theoretical analysis of this LSP-dependent ...
Tan Qing - - 2012
We propose here an application to sensing of annular aperture arrays (AAA). We theoretically investigate the optical properties of the reflective AAA device when illuminated in-plane. The cavity presents almost perfect absorption due to the waveguide mode resonance with strong field localization in the aperture. Additionally, the reflective cavity is ...
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.
Lehmann Peter - - 2012
In this Letter, the transfer characteristics of rectangular periodic phase objects are studied. It turns out that there are significant differences compared to amplitude objects. The imaging of an amplitude object can be understood as a linear process, whereas phase objects behave nonlinearly. It is shown that under certain conditions ...
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 ...
Eilenberger Falk - - 2012
We show experimentally that the recently proposed iterative shadowgraphic method can be applied to in-line digital holography, provided a suitable regularization step is introduced. We show that the method correctly solves the "twin-image" problem using just two samples of the intensity field scattered by a phase object. Field retrieval accuracy ...
Yi Xiaoke - - 2012
A new technique to realize an array of multiple true-time-delay elements, which can be independently and continuously tuned, is reported. It is based on a WDM parallel signal processing approach in conjunction with a diffraction-based Fourier-domain optical signal processor. Programmable linear optical phase transfer functions are realized to obtain different ...
Balsells José María Garrido - - 2012
In this paper, the performance of the variable weight multiple pulse-position modulation (MPPM) coding technique in an atmospheric optical communication environment under gamma-gamma optical scintillation is analyzed, proposing a closed-form expression for the average bit error rate (BER). This study is based on a hyperexponential fitting of the conditional BER ...
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 ...
Salter P S - - 2012
We demonstrate an improved method for fabricating optical waveguides in bulk materials by means of femtosecond laser writing. We use an LC spatial light modulator (SLM) to shape the beam focus by generating adaptive slit illumination in the pupil of the objective lens. A diffraction grating is applied in a ...
Abedin Kazi S - - 2012
We demonstrate a single-frequency Brillouin distributed feedback laser (DFB). The DFB laser cavity was a 12.4 cm long fiber Bragg grating with a π-phase shift offset from the grating center. It exhibited a threshold of 30 mW and conversion efficiency from pump to Stokes wave as high as 27%. Higher-order ...
Kuzmin V L - - 2012
For a one-elastic-constant model of nematic liquid crystal the optical theorem is shown to produce an explicit relationship between the scattering length of extraordinary wave mode and magnetic coherence length. The Monte Carlo simulation of coherent backscattering is performed accounting for the long-range orientational fluctuations and scattering length anisotropy; the ...
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 ...
Lamrini Samir - - 2012
We report on the high-energy laser operation of an Ho:YAG oscillator resonantly pumped by a GaSb-based laser diode stack at 1.9 μm. The output energy was extracted from a compact plano-concave acousto-optically Q-switched resonator optimized for low repetition rates. Operating at 100 Hz, pulse energies exceeding 30 mJ at a ...
Kim Shin Ae - - 2012
We propose an intrinsic optical method for in vivo neural recording using optic fiber-based surface plasmon resonance (SPR) phenomena. The fiber-based SPR method is electrical artifact free, labeling free, and feasible for a portable system compared with conventional in vivo neural recording systems. We simultaneously detected SPR signals and electrical ...
Wang Pengfei - - 2012
In this Letter, the fabrication and characterization of a microsphere resonator from the semiconductor germanium is demonstrated. Whispering gallery modes are excited in a 46 μm diameter germanium microsphere resonator using evanescent coupling from a tapered silica optical fiber with a waist diameter of 2 μm. Resonances with Q factors ...
Kim Jongki - - 2012
Highly efficient Bessel-like beam generation was achieved based on a new all-fiber method that implements Fourier transformation of a micro annular aperture along a concatenated composite optical fiber. The beam showed unique characteristics of tilted washboard optical potential in the transverse plane and sustained a nondiffracting length over 400 μm ...
Marchev Georgi - - 2012
A 21.4 mm long noncritically cut CdSiP<sub>2</sub> crystal, pumped by 8 ns pulses at 1064 nm in a double-pass configuration for pump, signal, and idler, generated 523 μJ, 5.8 ns idler pulses at 6.125 μm. The average power of 52.3 mW at the repetition rate of 100 Hz is the ...
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 ...
Kumar Arunandan - - 2012
Improved outcoupling efficiency of organic light emitting diodes (OLEDs) is demonstrated by incorporating a nanostructured indium tin oxide (NSITO) film between a conducting anode and a glass substrate. NSITO film was fabricated using rf-sputtering at oblique angle (85°). Significant reduction in refractive index and improved transmission of NSITO film was ...
Xu Lin - - 2012
At room temperature, highly efficient, doubly resonant periodically poled MgO-doped congruent LiNbO<sub>3</sub> crystal optical parametric oscillators (OPO) pumped at 1.9 μm have been realized for the first time to our knowledge. A 2.9 W, 2 kHz acousto-optic Q-switched homemade Tm:YLF laser served as a pump source. A 900 mW mid-infrared ...
Pedrini Giancarlo - - 2012
We describe a method where the wavefront emitted by a self-luminous object is superimposed to its filtered counterpart by using a Mach-Zehnder interferometer. The amplitude and phase of the resulting interference pattern is used for digital three-dimensional imaging. Experimental results are presented.
Sun Biao - - 2012
We propose and demonstrate a low-threshold single-wavelength all-fiber laser generating cylindrical vector beams using a few-mode fiber Bragg grating. Both radially and azimuthally polarized beams have been generated with very good modal symmetry and polarization purity higher than 94%. The radially and azimuthally polarized modes can be switched by simply ...
Huang Jie - - 2012
This paper proposes an actively mode-locked fiber ring laser for sensing applications. Mode-locking of the laser is achieved by driving an electro-optic amplitude modulator at an RF corresponding to the fundamental beat frequency between the longitudinal modes. The change of the cavity length produces a frequency comb around the beat ...
Naether U - - 2012
We study the gradual transition from one-dimensional (1D) to two-dimensional (2D) Anderson localization upon transformation of the dimensionality of disordered waveguide arrays. An effective transition from a 1D to a 2D system is achieved by increasing the number of rows forming the arrays. We observe that, for a given disorder ...
Yaroslavsky Anna N - - 2012
Because of low optical contrast in the visible spectral range, accurate detection of basal cell carcinomas (BCC) remains a challenging problem. In this letter, we experimentally demonstrate that reflectance confocal imaging in the vicinity of 1300 nm can be used for the detection of BCC without exogenous contrast agents. We ...
Gerhard Christoph - - 2012
In this Letter, we report on the near-surface modification of fused silica by applying a hydrogenous atmospheric pressure plasma jet at ambient temperature. A significant decrease in UV-transmission due to this plasma treatment was observed. By the use of secondary ion mass spectroscopy, the composition of the plasma-modified glass surface ...
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 ...
Crasto Tristan D - - 2012
We report the observation, first to our knowledge, of optical waveguiding found beneath trenches etched in congruent lithium niobate using the recently reported etching during the indiffusion of Ti process. Observations of multi-mode and single-mode guiding at visible wavelengths and preliminary measurements of waveguide insertion losses are presented.
Eckerle Michael - - 2012
A diode-pumped actively Q-switched and actively mode-locked Tm<sup>3+</sup>-doped double-clad silicate fiber laser is reported providing up to 5 W of average output power at ~60 kHz Q-switch envelope repetition rate and ∼8  μJ subpulses with up to 2.4 kW peak power. Using this source as a pump laser for supercontinuum generation ...
Park Hyunkyu - - 2012
A highly disordered GaN nanostructure was grown by using hydride vapor phase epitaxy on an Si(100) substrate, and its diffuse reflectivity was measured in the 200-1200 nm spectral range by using an integrating sphere. A modified multiple-scattering-based model successfully explained the spectral distribution of diffuse reflectivity of this highly disordered ...
Saleh Khaldoun - - 2012
Nonlinear phenomena occurring in an optical fiber ring resonator featuring ultrahigh Q factor are experimentally studied. The laser is locked onto the resonator, and the optical power induced in the resonator is controlled. The onset of the first stimulated Brillouin scattering wave occurs at an optical input power as low ...
Feiyue Mao - - 2012
The aerosol lidar ratio is a key parameter for the retrieval of aerosol optical properties from elastic lidar, which changes largely for aerosols with different chemical and physical properties. We proposed a method for retrieving the aerosol lidar ratio profile by combining simultaneous ground- and space-based elastic lidars. The method ...
Ding W - - 2012
We report frequency conversion experiments in silicon-on-insulator (SOI) directional couplers. We demonstrate that the evanescent coupling between two subwavelength SOI waveguides is strongly dispersive and significantly modifies modulational instability (MI) spectra through the coupling induced group velocity dispersion (GVD). As the separation between two 380-nm-wide silicon photonic wires decreases, the ...
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 ...
< 3 4 5 6 7 8 9 10 11 12 13 >