WorldWideScience

Sample records for bragg angle

  1. X-ray diffraction at Bragg angles around π/2

    International Nuclear Information System (INIS)

    X-ray diffraction at Bragg angles around π/2 is studied from the theoretical and experimental points of view. The proposed corrections to the dynamical theory in the θβ ≅ π/2 cases, has been reviewed showing the equivalence between two formalisms leading to a corrected expression for the dependence of the angular parameter y with the angle of incidence. An expression for y valid in the conventional and θ β ≅ π/2 cases has been obtained. A general expression for Bragg law and for energy resolution after a Bragg diffraction was also deduced. (author)

  2. Angle dependent Fiber Bragg grating inscription in microstructured polymer optical fibers

    DEFF Research Database (Denmark)

    Bundalo, Ivan-Lazar; Nielsen, Kristian; Bang, Ole

    2015-01-01

    We report on an incidence angle influence on inscription of the Fiber Bragg Gratings in Polymethyl methacrylate (PMMA) microstructured polymer optical fibers. We have shown experimentally that there is a strong preference of certain angles, labeled Gamma K, over the other ones. Angles close...

  3. Bragg prism monochromator and analyser for super ultra-small angle neutron scattering studies

    Indian Academy of Sciences (India)

    Apoorva G Wagh; Sohrab Abbas; Markus Strobl; Wolfgang Treimer

    2008-11-01

    We have designed, fabricated and operated a novel Bragg prism monochromator–analyser combination. With a judicious choice of the Bragg reflection, its asymmetry and the apex angle of the silicon single crystal prism, the monochromator has produced a neutron beam with sub-arcsec collimation. A Bragg prism analyser with the opposite asymmetry has been tailored to accept a still sharper angular profile. With this optimized monochromator–analyser pair, we have attained the narrowest and sharpest neutron angular profile to date. At this facility, we have recorded the first SUSANS spectra spanning wave vector transfers ∼ 10−6 Å-1 to characterize samples containing agglomerates up to tens of micrometres in size.

  4. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

    Science.gov (United States)

    Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

    2016-06-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks.

  5. Fused-silica sandwiched three-port grating under second Bragg angle incidence

    Science.gov (United States)

    Li, Hongtao; Wang, Bo; Pei, Hao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-05-01

    The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

  6. Efficiency enhancement and angle-dependent color change in see-through organic photovoltaics using distributed Bragg reflectors

    Science.gov (United States)

    Dong, Wan Jae; Lo, Nhat-Truong; Jung, Gwan Ho; Ham, Juyoung; Lee, Jong-Lam

    2016-03-01

    A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs.

  7. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

    OpenAIRE

    Shiwei Shu; Yawen Zhan; Chris Lee; Jian Lu; Yang Yang Li

    2016-01-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-se...

  8. Are Bragg Peaks Gaussian?

    OpenAIRE

    Hammouda, Boualem

    2014-01-01

    It is common practice to assume that Bragg scattering peaks have Gaussian shape. The Gaussian shape function is used to perform most instrumental smearing corrections. Using Monte Carlo ray tracing simulation, the resolution of a realistic small-angle neutron scattering (SANS) instrument is generated reliably. Including a single-crystal sample with large d-spacing, Bragg peaks are produced. Bragg peaks contain contributions from the resolution function and from spread in the sample structure....

  9. Gratings' rotation angle tolerance for diode lasers with external cavity formed by volume Bragg grating%体布拉格光栅外腔半导体激光器的光栅旋转角度容差

    Institute of Scientific and Technical Information of China (English)

    李志永; 谭荣清; 徐程; 李琳; 刘世明; 赵志龙; 黄伟

    2013-01-01

    采用步进电机控制光栅角度,对φ200 μm和φ600 μm圆柱透镜准直的体布拉格光栅(VBG)外腔单管C封装半导体激光器进行了系统研究.实验结果表明:激光二极管(LD)驱动电流越大,准直效果越好,VBG的角度调整容差越小;快轴方向的准直效果越好,慢轴方向的光栅调节角度容差越大;对于衍射效率28%、厚1.4 mm的光栅,LD快轴发散角为7.3 mrad时,快轴方向的角度容差不大于3.2 mrad,慢轴方向的角度容差较快轴大约一个数量级.%For high power linewidth-narrowed diode lasers, it's important to study rotation angle tolerance of the volume Bragg grating (VBG) for narrowing the spectral linewidth of two dimensional diode laser stacks. The diode laser with the VBG' s external cavity and C-mounted modules is collimated by Φ200 μm and Φ600μm cylindrical lens separately in the paper. The VBG's angle tolerance is acquired by two stepper motors. According to the research, more accuracy is needed for the VBG's adjustment with higher driving current and better beam collimation. If the laser diode is collimated better in fast axis direction, rotation angle tolerance in slow axis direction will be bigger. When a VBG with a diffraction efficiency of 28% and thickness of 1. 4 mm is used to lock the wavelength of a laser diode with a fast axis divergence angle of 7. 3 mrad, the grating's rotation angle tolerance is no more than 3. 2 mrad in the fast axis direction and that for the slow axis direction is one order of magnitude bigger.

  10. Bragg grating rogue wave

    CERN Document Server

    Degasperis, Antonio; Aceves, Alejandro B

    2015-01-01

    We derive the rogue wave solution of the classical massive Thirring model, that describes nonlinear optical pulse propagation in Bragg gratings. Combining electromagnetically induced transparency with Bragg scattering four-wave mixing, may lead to extreme waves at extremely low powers.

  11. Fiber Bragg grating sensors

    NARCIS (Netherlands)

    Cheng, L.K.; Nieuwland, R.A.; Toet, P.M.; Agovic, K.

    2010-01-01

    A brief overview of fiber Bragg grating based sensor technology from sensor head, read out unit and commercial applications is given. Fiber Bragg grating based sensor systems are becoming mature rapidly. Components for commercial pressure sensors and temperature sensors are available and slowly gett

  12. Bragg gratings in Topas

    DEFF Research Database (Denmark)

    Zhang, C.; Webb, D.J.; Kalli, K.;

    We report for the first time fibre Bragg grating inscription in microstructured optical fibre fabricated from Topas® cyclic olefin copolymer. The temperature sensitivity of the grating was studied revealing a positive Bragg wavelength shift of approximately 0.8 nmK-1,the largest sensitivity yet...

  13. Bragg grating rogue wave

    Energy Technology Data Exchange (ETDEWEB)

    Degasperis, Antonio [Dipartimento di Fisica, “Sapienza” Università di Roma, P.le A. Moro 2, 00185 Roma (Italy); Wabnitz, Stefan, E-mail: stefan.wabnitz@unibs.it [Dipartimento di Ingegneria dell' Informazione, Università degli Studi di Brescia and INO-CNR, via Branze 38, 25123 Brescia (Italy); Aceves, Alejandro B. [Southern Methodist University, Dallas (United States)

    2015-06-12

    We derive the rogue wave solution of the classical massive Thirring model, that describes nonlinear optical pulse propagation in Bragg gratings. Combining electromagnetically induced transparency with Bragg scattering four-wave mixing may lead to extreme waves at extremely low powers.

  14. Birefringent Bragg Gratings in Highly-Nonlinear Photonic Crystal Fiber

    Institute of Scientific and Technical Information of China (English)

    Kevin Cook; John Canning; John Holdsworth

    2008-01-01

    Efficient writing of Bragg gratings in 12-ring highly-nonlinear photonic crystal fibers is described. Experimental and numerical investigations are performed to reveal the optimum angle for coupling UV writing light to the core. Furthermore, we show that the formation of a strongly briefringent grating is at a particular angle of orientation.

  15. Supersymmetric Bragg gratings

    CERN Document Server

    Longhi, Stefano

    2015-01-01

    The supersymmetric (SUSY) structure of coupled-mode equations that describe scattering of optical waves in one-dimensional Bragg gratings is highlighted. This property can find applications to the synthesis of special Bragg filters and distributed-feedback (DFB) optical cavities. In particular, multiple SUSY (Darboux-Crum) transformations can be used to synthesize DFB filters with any desired number of resonances at target frequencies. As an example, we describe the design of a DFB structure with a set of equally-spaced resonances, i.e. a frequency comb transmission filter.

  16. Supersymmetric Bragg gratings

    International Nuclear Information System (INIS)

    The supersymmetric (SUSY) structure of coupled-mode equations that describe scattering of optical waves in one-dimensional Bragg gratings is highlighted. This property can find applications to the synthesis of special Bragg filters and distributed-feedback (DFB) optical cavities. In particular, multiple SUSY (Darboux–Crum) transformations can be used to synthesize DFB filters with any desired number of resonances at target frequencies. As an example, we describe the design of a DFB structure with a set of equally-spaced resonances, i.e. a frequency comb transmission filter. (paper)

  17. Simultaneous 2D Strain Sensing Using Polymer Planar Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Manuel Rosenberger

    2015-02-01

    Full Text Available We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain.

  18. UV writing of advanced Bragg gratings in optical waveguides

    DEFF Research Database (Denmark)

    Jensen, Jesper Bo Damm

    2002-01-01

    were then translated into a polarizer angle profile and the Bragg grating were written using a pulsed excimer laser. Only optical fibers were used in this part of the thesis. The high quality planar waveguides used during the study were produced in the cleanroom facility at the Microelectronic Center...

  19. Fiber Bragg grating based tunable sensitivity goniometer

    Science.gov (United States)

    Padma, Srivani; Umesh, Sharath; Pant, Shweta; Srinivas, Talabattula; Asokan, Sundarrajan

    2016-03-01

    Goniometer has found extensive usage in diverse applications, primary being medical field in which it is employed for obtaining the range of motion of joints during physical therapy. It is imperative to have a dynamic system to measure the range of motion which will aid for a progressive therapeutic treatment. Hence in the present study, a novel goniometer for real time dynamic angle measurement between two surfaces with the aid of a Fiber Bragg Grating sensor is proposed. The angular rotation between the two surfaces will be identified by the two arms of the Fiber Bragg Grating Goniometer (FBGG), which is translated to the rotation of the shaft which holds these arms together. A cantilever beam is fixed onto the base plate whose free end is connected to the rotating shaft. The rotating shaft will actuate a mechanism which will pull the free end of the cantilever resulting in strain variation over the cantilever beam. The strain variation on the cantilever beam is measured by the Fiber Bragg Grating sensor bonded over it. Further, the proposed FBGG facilitates tunable sensitivity by the discs of varying diameters on the rotating shaft. Tunable sensitivity of the FBGG is realised by the movement of these discs by varying circumferential arc lengths for the same angular movement, which will actuate the pull on the cantilever beam. As per the requirement of the application in terms of resolution and range of angular measurement, individual mode of sensitivity may be selected.

  20. Development of variable-magnification X-ray Bragg optics.

    Science.gov (United States)

    Hirano, Keiichi; Yamashita, Yoshiki; Takahashi, Yumiko; Sugiyama, Hiroshi

    2015-07-01

    A novel X-ray Bragg optics is proposed for variable-magnification of an X-ray beam. This X-ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X-ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X-ray diffraction. The feasibility of the variable-magnification X-ray Bragg optics was verified at the vertical-wiggler beamline BL-14B of the Photon Factory. For X-ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M ≥ 1.0), X-ray images of a nylon mesh were observed with an air-cooled X-ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption-contrast but also edge-contrast due to Fresnel diffraction was observed in the magnified images.

  1. Flexible nanofiber-coupled hybrid plasmonic Bragg grating.

    Science.gov (United States)

    Liu, Sheng; Zhou, Linjie; Xu, Jian; Wang, Xinyi; Chen, Jianping

    2016-05-01

    We report a hybrid plasmonic Bragg grating composed of a nanofiber coupled with orthogonally oriented metal strips. Numerical simulations are performed to study the transmission and reflection spectra of the grating. It shows that the TM polarization has much stronger Bragg reflection due to the excitation of hybrid plasmonic modes. The dependence of reflection peaks on several key device parameters is analyzed. Light propagation simulation further reveals that both fundamental and first-order TM modes are excited upon Bragg reflection, leading to two separate peaks in the spectrum. We implement the prototype device by attaching a nanofiber onto the surface of an array of sub-micrometer-wide metal strips. The main reflection peak is measured to have a 3-dB bandwidth of 15 nm and out-of-band rejection of more than 30 dB. The effects of nanofiber radius, alignment angle and coupling length on the device performance are also experimentally investigated. PMID:27137547

  2. Fiber Bragg distributed chemical sensor

    NARCIS (Netherlands)

    Boersma, A.; Cheng, L.K.; Jansen, T.H.

    2010-01-01

    A distributed chemical sensor is developed by coating multiple Bragg gratings in a fibre with chemical selective responsive coatings. The optical response of the coated grating is optimised and the recoat process is very reproducible.

  3. MEMS Bragg grating force sensor

    DEFF Research Database (Denmark)

    Reck, Kasper; Thomsen, Erik Vilain; Hansen, Ole

    2011-01-01

    We present modeling, design, fabrication and characterization of a new type of all-optical frequency modulated MEMS force sensor based on a mechanically amplified double clamped waveguide beam structure with integrated Bragg grating. The sensor is ideally suited for force measurements in harsh...... environments and for remote and distributed sensing and has a measured sensitivity of -14 nm/N, which is several times higher than what is obtained in conventional fiber Bragg grating force sensors. © 2011 Optical Society of America....

  4. Multiple Bragg reflection by a thick mosaic crystal.

    Science.gov (United States)

    Wuttke, Joachim

    2014-09-01

    Symmetric Bragg-case reflections from a thick, ideally imperfect, crystal slab are studied mostly by analytical means. The scattering transfer function of a thin mosaic layer is derived and brought into a form that allows for analytical approximations or easy quadrature. The Darwin-Hamilton equations are generalized, lifting the restriction of wavevectors to a two-dimensional scattering plane. A multireflection expansion shows that wavevector diffusion can be studied independently of the real-space coordinate. Combining analytical arguments and Monte Carlo simulations, multiple Bragg reflections are found to result in a minor correction of the reflected intensity, a moderate broadening of the reflected azimuth angle distribution, a considerable modification of the polar angle distribution, and a noticeable shift and distortion of rocking curves.

  5. Polymer optical fiber bragg grating sensors

    DEFF Research Database (Denmark)

    Stefani, Alessio; Yuan, Scott Wu; Andresen, Søren;

    2010-01-01

    Fiber-optical accelerometers based on polymer optical fiber Bragg gratings are reported. We have written fiber Bragg gratings for 1550 nm and 850 nm operations, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

  6. Development of tilted fibre Bragg gratings using highly coherent 255 nm radiation

    Indian Academy of Sciences (India)

    O Prakash; J Kumar; R Mahakud; U Kumbhkar; S V Nakhe; S K Dixit

    2014-02-01

    This paper reports the study on development of tilted fibre Bragg gratings using highly coherent 255 nm radiation, obtained from the second harmonic generation (SHG) of copper vapour laser (CVL). The transmission and reflection spectra of the tilted fibre Bragg gratings (TFBG) were studied for the tilt angles of 0° (normal FBG), 1°, 3° and 4° between the fibre axis and the interference fringe plane. It was observed that as the angle of fibre axis and phase mask increased, the main Bragg peak shifted towards the higher wavelength and transmission dip decreased. The transmission dip of the cladding mode first increased and then decreased after reaching a maximum with the increase in the tilt angle.

  7. Formularization and simulation of Bragg selectivity of readout signals in angular-multiplexing holographic data storage.

    Science.gov (United States)

    Ide, Tatsuro

    2016-04-01

    Bragg selectivity of readout signals in angular-multiplexing holographic data storage was investigated. The effects of degrading factors, namely, volume change, refractive-index change, and positional change (tilt and rotation) of a hologram, and the effects of compensating variables, namely, wavelength shift and reference-beam-angle shift, on Bragg selectivity were evaluated. Deviation of wave vectors of recovered pixels of a hologram from the Bragg condition under degrading factors and compensating variables, namely, Bragg mismatch, Δσ, was mathematically derived. Approximating Δσ by using the first-order Maclaurin series with respect to degrading factors and compensating variables revealed their effects on Bragg selectivity. The extent to which wavelength and angle of reference beam should be shifted to compensate for the degrading factors were determined. Then, readout images were simulated under multiple degrading factors and compensating variables. These simulated images were found to agree well with the experimentally obtained ones, which reveals the validity of the formalization of Bragg selectivity. PMID:27139671

  8. Fiber Bragg Grating Based Thermometry

    OpenAIRE

    Ahmed, Zeeshan; Filla, James; Guthrie, William; Quintavalle, John

    2016-01-01

    In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined m...

  9. Fate of the Peak Effect in a Type-II Superconductor: Multicriticality in the Bragg-Glass Transition

    OpenAIRE

    Park, S R; S.M. CHOI; Dender, D. C.; Lynn, J. W.; Ling, X. S.

    2003-01-01

    We have used small-angle-neutron-scattering (SANS) and ac magnetic susceptibility to investigate the global magnetic field H vs temperature T phase diagram of a single crystal Nb in which a first-order transition of Bragg-glass melting (disordering), a peak effect, and surface superconductivity are all observable. It was found that the disappearance of the peak effect is directly related to a multicritical behavior in the Bragg-glass transition. Four characteristic phase boundary lines have b...

  10. Effects of dispersion and absorption in resonant Bragg diffraction of x-rays.

    Science.gov (United States)

    Lovesey, S W; Scagnoli, V; Dobrynin, A N; Joly, Y; Collins, S P

    2014-03-26

    Resonant diffraction of x-rays by crystals with anisotropic optical properties is investigated theoretically, to assess how the intensity of a Bragg spot is influenced by effects related to dispersion (birefringence) and absorption (dichroism). Starting from an exact but opaque expression, simple analytic results are found to expose how intensity depends on dispersion and absorption in the primary and secondary beams and, also, the azimuthal angle (rotation of the crystal about the Bragg wavevector). If not the full story for a given application, our results are more than adequate to explore consequences of dispersion and absorption in the intensity of a Bragg spot. Results are evaluated for antiferromagnetic copper oxide, and low quartz. For CuO, one of our results reproduces all salient features of a previously published simulation of the azimuthal-angle dependence of a magnetic Bragg peak. It is transparent in our analytic result that dispersion and absorption effects alone cannot reproduce published experimental data. Available data for the azimuthal-angle dependence of space-group forbidden reflections (0,0, l), with l ≠ 3n, of low quartz depart from symmetry imposed by the triad axis of rotation symmetry. The observed asymmetry can be induced by dispersion and absorption even though absorption coefficients are constant, independent of the azimuthal angle, in this class of reflections.

  11. Degradation of the Bragg peak due to inhomogeneities.

    Science.gov (United States)

    Urie, M; Goitein, M; Holley, W R; Chen, G T

    1986-01-01

    The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles.

  12. Degradation of the Bragg peak due to inhomogeneities.

    Science.gov (United States)

    Urie, M; Goitein, M; Holley, W R; Chen, G T

    1986-01-01

    The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles. PMID:3952143

  13. Fiber Bragg Grating Based Thermometry

    CERN Document Server

    Ahmed, Zeeshan; Guthrie, William; Quintavalle, John

    2016-01-01

    In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining the peak center fitting and by thermal aging of polyimide coated fibers.

  14. Cascaded Bragg scattering in fiber optics.

    Science.gov (United States)

    Xu, Y Q; Erkintalo, M; Genty, G; Murdoch, S G

    2013-01-15

    We report on a theoretical and experimental study of cascaded Bragg scattering in fiber optics. We show that the usual energy-momentum conservation of Bragg scattering can be considerably relaxed via cascade-induced phase-matching. Experimentally we demonstrate frequency translation over six- and 11-fold cascades, in excellent agreement with derived phase-matching conditions.

  15. Omnidirectional mirror based on Bragg stacks with a periodic gain-loss modulation

    Energy Technology Data Exchange (ETDEWEB)

    Manzanares-Martinez, Jesus; Ham-Rodriguez, Carlos Ivan [Departamento de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83000 (Mexico); Moctezuma-Enriquez, Damian, E-mail: foxonicos@gmail.com [Centro de Investigacion en Materiales Avanzados (CIMAV), Miguel de Cervantes 120, Chihuahua 31109 (Mexico); Manzanares-Martinez, Betsabe [Departamento de Fisica, Universidad de Sonora, Blvd. Luis Encinas y Rosales, Hermosillo, Sonora 83000 (Mexico)

    2014-01-15

    In this work we demonstrate that a Bragg Stack with a periodic gain-loss modulation can function as an Omnidirectional Mirror (OM) with complete reflection at any angle of incidence irrespective of the light polarization. The Bragg Stack is composed by the periodic variation of two layers with the same value of the real part of the refractive index (n{sub r}) and a periodic modulation in the imaginary part (n{sub i}). The origin of the band gaps is due to the interference of complex waves with propagating and evanescent fields in each layer. It is found that the band gaps are wider as the contrast n{sub i}/n{sub r} increases. We have found the ambient conditions to obtain an OM considering an auxiliary medium n{sup ′} external to the Bragg Stack.

  16. Determination of the polarization of Bragg-reflected gamma rays by means of the Mössbauer effect

    DEFF Research Database (Denmark)

    Olsen, J.

    1969-01-01

    Recoil-free 14.4 keV gamma rays from 57Fe are reflected from an aluminium single crystal. By measurements of the intensities of the peaks in the Mössbauer spectra the polarization at different Bragg angles is determined.......Recoil-free 14.4 keV gamma rays from 57Fe are reflected from an aluminium single crystal. By measurements of the intensities of the peaks in the Mössbauer spectra the polarization at different Bragg angles is determined....

  17. Reflectivity and Braggs Wavelength in FBG

    Directory of Open Access Journals (Sweden)

    Dinesh Arora

    2011-12-01

    Full Text Available We have presented an analytical model of splitters based on Fiber Bragg grating used to detect a Bragg wavelength from the number of wavelengths which are traveling in an optical fiber. The number of grids and grating length can be used as a wavelength shifter.This paper presents experimental results that are used to show the effect of number of grids and the length of the grating on the Bragg wavelength and reflectivity of Fiber Bragg Grating (FBG. The pitch of grating is directly proportional to the grating length and inversely proportional to number of grids. When the grating length is fixed and the number of grids is increased, the Bragg wavelength decreases and reflectivity increases. This increase in reflectivity is very small. Further when the number of grids was kept constant and the grating length was increased the Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. In our model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.

  18. Hyperbolic Metamaterials with Bragg Polaritons

    Science.gov (United States)

    Sedov, Evgeny S.; Iorsh, I. V.; Arakelian, S. M.; Alodjants, A. P.; Kavokin, Alexey

    2015-06-01

    We propose a novel mechanism for designing quantum hyperbolic metamaterials with the use of semiconductor Bragg mirrors containing periodically arranged quantum wells. The hyperbolic dispersion of exciton-polariton modes is realized near the top of the first allowed photonic miniband in such a structure which leads to the formation of exciton-polariton X waves. Exciton-light coupling provides a resonant nonlinearity which leads to nontrivial topologic solutions. We predict the formation of low amplitude spatially localized oscillatory structures: oscillons described by kink shaped solutions of the effective Ginzburg-Landau-Higgs equation. The oscillons have direct analogies in gravitational theory. We discuss implementation of exciton-polariton Higgs fields for the Schrödinger cat state generation.

  19. Strain imaging by Bragg edge neutron transmission

    CERN Document Server

    Santisteban, J R; Fitzpatrick, M E; Steuwer, A; Withers, P J; Daymond, M R; Johnson, M W; Rhodes, N; Schooneveld, E M

    2002-01-01

    The Bragg edges appearing in the transmitted time-of-flight spectra of polycrystalline materials have been recorded using a two-dimensional array of detectors. Subsequent analysis has enabled maps of the elastic strain to be produced.

  20. Mode characteristics of hollow core Bragg fiber

    Institute of Scientific and Technical Information of China (English)

    Minning Ji; Zhidong Shi; Qiang Guo

    2005-01-01

    Analytical expression to calculate propagation constant and mode field of the hollow core Bragg fiber is derived. Numerical results are presented. It is shown that the fundamental mode of the hollow core Bragg fiber is circularly symmetric TE01 mode with no polarization degeneracy, while the higher order mode may be HE11, TM01, or TE02 etc.. This property is different from conventional optical fiber that its fundamental mode is the linearly polarized HE11 mode and is polarization degeneracy.

  1. Bragg diffraction of fermions at optical potentials

    International Nuclear Information System (INIS)

    This thesis describes the Bragg diffraction of ultracold fermions at an optical potential. A moving optical lattice was created, by overlaying two slightly detuned lasers. Atoms can be diffracted at this lattice if the detuning fulfills the Bragg condition for resting atoms. This Bragg diffraction is analyzed systematically in this thesis. To this end Rabi oscillations between the diffraction states were driven, as well in the weakly interacting Bragg regime, as in the strongly interacting Kapitza-Dirac regime. Simulations, based on a driven two-, respectively multilevel-system describe the observed effects rather well. Furthermore, the temporal evolution of the diffracted states in the magnetic trapping potential was studied. The anharmonicity of the trap in use and the scattering cross section for p-wave collisions in a 6Li system was determined from the movement of these states. Moreover the momentum distribution of the fermions was measured with Bragg spectroscopy and first signs of Fermi degeneracy were found. Finally an interferometer with fermions was build, exhibiting a coherence time of more than 100 μs. With this, the possibility for measurement and manipulation of ultracold fermions with Bragg diffraction could bee shown. (orig.)

  2. Reflectivity and Braggs Wavelength in FBG

    Directory of Open Access Journals (Sweden)

    Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason

    2011-12-01

    Full Text Available We have presented an analytical model of splitters based on Fiber Bragg Grating used to detect a Braggwavelength from the number of wavelengths which are traveling in an optical fiber. The number of gridsand grating length can be used as a wavelength shifter. This paper presents experimental results that areused to show the effect of number of grids, the length of the grating on the Bragg wavelength andreflectivity of Fiber Bragg Grating (FBG. The pitch of grating is directly proportional to the grating lengthand inversely proportional to number of grids. When the grating length is fixed and the number of grids isincreased, the Bragg wavelength decreases resulting in increased reflectivity. This increased reflectivity isvery small. Further when the number of grids is kept constant and the grating length is increased theBragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. Inour model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.

  3. Fiber Bragg Grating Filter High Temperature Sensors

    Science.gov (United States)

    Lyons, Donald R.; Brass, Eric D.; Pencil, Eric (Technical Monitor)

    2001-01-01

    We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.

  4. Pure Bending Characteristic of Tilted Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    Bo Liu; Yin-Ping Miao; Hai-Bin Zhou; Qi-Da Zhao

    2008-01-01

    a novel structure of the pure macro-bending sensor based on the tilted fiber Bragg grating (TFBG) is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.

  5. Results from a Bragg Curve Spectrometer

    International Nuclear Information System (INIS)

    The Bragg Curve Spectrometer (BCS) is an ionization chamber long enough to stop particles of interest. Particles enter through the cathode window and leave an ionization track parallel to the electric field. The ionization electrons drift through a Frisch grid and are collected on an anode. The anode current, as a function of time, is split and used as input for two amplifiers, one with a long integration time constant for energy measurement, and one with a short time constant to pick off the maximum ionization or Bragg peak. The Bragg peak, which is proportional to the nuclear charge, is used for particle identification. We have constructed and tested several versions of the BCS. The results are described

  6. POLICRYPS-based electrically switchable Bragg reflector.

    Science.gov (United States)

    De Sio, Luciano; Tabiryan, Nelson; Bunning, Timothy J

    2015-12-14

    The formation and characterization of a switchable volume reflective element fabricated from a polymer liquid crystal (LC) polymer slice (POLICRYPS) structure by holographic photopolymerization at high temperature (65 °C) using a photosensitive/nematic liquid crystal prepolymer mixture is reported. The submicron Bragg structure formed consists of periodic continuous polymeric walls separated by periodic LC channels. The phase separated NLC self-aligns in a homeotropic alignment between the polymer walls as indicated by polarizing optical microscopy analysis (Maltese cross). The resulting periodic grating structure results in a Bragg reflection notch upon illumination with white light due to the periodic variation in refractive index. Electro-optical experiments realized through in-plane electrodes and temperature experiments confirm that the multilayer structure acts as a Bragg mirror whose reflection efficiency can be controlled by either a small (~3V/µm) electric field or temperature. PMID:26699059

  7. Characteristics of Smart Concrete with Fiber Optical Bragg Grating Sensor

    Institute of Scientific and Technical Information of China (English)

    XIN Si-jin; JIANG De-sheng; LIANG Lei; Luo Pei; ZUO Jun; NAN Qiu-ming; CHEN Da-xiong

    2004-01-01

    Based on the advantages of the fiber Bragg grating sensing technology, this paper presents a principle of a novel smart concrete with fiber optical Bragg grating sensor, analyses the theory and characteristics,illustrates the key technology and method to make the fiber Bragg grating sensor for the smart concrete, and proves the feasibility with experiments. The results indicate that the smart concrete with fiber Bragg grating sensors is feasible in the structure monitoring and damage diagnosing in the long run.

  8. X-ray Raman scattering with Bragg diffraction in a La-based superlattice

    OpenAIRE

    André, Jean-Michel; Jonnard, Philippe; Bonnelle, Christiane; O. Filatova, E.; Michaelsen, C.; Wiesmann, J

    2005-01-01

    11 pages The non-dispersed soft x-ray emission from a La/B4C periodic multilayer irradiated by monochromatic x-rays has been measured as a function of the incident photon energy in the 125-200 eV range for different scattering angles. We have observed a scattered intensity peak at incident energies which shift towards the low-energy side as the value of the scattering angle increases. These observations are interpreted as Raman scattering by the 5p level of lanthanum assisted by Bragg diff...

  9. Efficient iterative technique for designing bragg gratings

    DEFF Research Database (Denmark)

    Plougmann, Nikolai; Kristensen, Martin

    2004-01-01

    We present a new iterative method for designing Bragg gratings based on the Levenberg-Marquardt method of minimizing a chi-squared merit function. It is effective for designing both weak and strong gratings and is particularly well suited for unchirped gratings....

  10. Superwide-angle acoustic propagations above the critical angles of the Snell law in liquid—solid superlattice

    Science.gov (United States)

    Zhang, Sai; Zhang, Yu; Gao, Xiao-Wei

    2014-12-01

    In this paper, superwide-angle acoustic propagations above the critical angles of the Snell law in liquid—solid superlattice are investigated. Incident waves above the critical angles of the Snell law usually inevitably induce total reflection. However, incident waves with big oblique angles through the liquid—solid superlattice will produce a superwide angle transmission in a certain frequency range so that total reflection does not occur. Together with the simulation by finite element analysis, theoretical analysis by using transfer matrix method suggests the Bragg scattering of the Lamb waves as the physical mechanism of acoustic wave super-propagation far beyond the critical angle. Incident angle, filling fraction, and material thickness have significant influences on propagation. Superwide-angle propagation phenomenon may have potential applications in nondestructive evaluation of layered structures and controlling of energy flux.

  11. Bragg diffraction from magnetic materials

    DEFF Research Database (Denmark)

    Lebech, B.

    2002-01-01

    -ray scattering when studying crystalline properties of matter. In addition, neutrons possess magnetic moments of the same order of magnitude as the atomic magnetic moments in elements and this makes neutrons highly suited for studies of the order and interactions between the magnetic moments in magnetic...... materials. This will be illustrated by reviewing the ordered magnetic structures found in some simple elements and in some chemically more complex systems containing several magnetic elements. The different scattering techniques (two- and three-axis neutron scattering, small angle neutron scattering...

  12. Utilization of monolayer MoS2 in Bragg stacks and metamaterial structures as broadband absorbers

    Science.gov (United States)

    Mukherjee, Bablu; Simsek, Ergun

    2016-06-01

    We numerically study the possibility of using atomically thin transition metal dichalcogenides (TMDs) for applications requiring broadband absorption in the visible range of the electromagnetic spectrum. We demonstrate that when monolayer TMDs are positioned into a finite-period of multilayer Bragg stack geometry, they make broadband, wide-angle, almost polarization-independent absorbers. In our study, we consider molybdenum disulfide (MoS2) and silicon dioxide (SiO2) as semiconducting and dielectric thin film of alternate high- and low- index films, respectively. By optimizing the thickness of the SiO2 film, we find that monolayer MoS2 based Bragg stacks can absorb 94.7% of the incident energy in the visible (350-700 nm). Similar structures can be engineered to make perfect reflectors for saturable absorption applications. We also demonstrate that bandwidth of metamaterial absorbers can be expanded using monolayer TMDs.

  13. Stationary Light Pulses without Bragg Gratings

    CERN Document Server

    Lin, Yen-Wei; Peters, Thorsten; Liao, Wen-Te; Cho, Hung-Wen; Guan, Pei-Chen; Yu, Ite A

    2008-01-01

    The underlying mechanism of the stationary light pulse (SLP) was identified as a band gap being created by a Bragg grating formed by two counter-propagating coupling fields of similar wavelength. Here we present a more general view of the formation of SLPs, namely several balanced four-wave mixing processes sharing the same ground-state coherence. Utilizing this new concept we report the first experimental observation of a bichromatic SLP at wavelengths for which no Bragg grating can be established. We also demonstrate the production of a SLP directly from a propagating light pulse without prior storage. Being easily controlled externally makes SLPs a very versatile tool for low-light-level nonlinear optics and quantum information manipulation.

  14. Ground effects on magnetooptic Bragg cells

    Institute of Scientific and Technical Information of China (English)

    WEN Feng; WU BaoJian; QIU Kun

    2008-01-01

    Propagation equation of magnetostatic waves in an arbitrarily magnetized yttrium-iron-garnet/gadolinium-gallium-garnet waveguide coated with perfect metal planes is obtained using the method of the surface magnetic permeability. And ground effects on magnetooptic Bragg cells are investigated with the magnetooptic coupled-mode theory. Theoretical analysis indicates that, diffraction efficiency of guided optical waves can be improved by adjusting the spacing of the metal plane from the ferrite film, and ground effects on the diffraction efficiency will be enhanced using an appropriately tilted bias magnetic field. In the metal clad waveguide system, the magnetostatic wave frequency at which the diffraction efficiency peak is obtained corresponds to the "zero-dispersion" point. Performance of RF spectrum analyzers in this system can also be improved by comparing with the case of the sandwich waveguide. Therefore, magnetooptic Bragg cells with the metal clad waveguide are potential applications to the microwave communication and optical signal processing.

  15. Fort Bragg Embraces Groundbreaking Heat Pump Technology

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2013-03-01

    The U.S. Army’s Fort Bragg partnered with the Department of Energy (DOE) to develop and implement solutions to build new, low-energy buildings that are at least 50% below Standard 90.1-2007 of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), the American National Standards Institute (ANSI), and the Illuminating Engineering Society of North America (IESNA) as part of DOE’s Commercial Building Partnerships (CBP) Program.

  16. Sampled phase-shift fiber Bragg gratings

    Institute of Scientific and Technical Information of China (English)

    Xu Wang(王旭); Chongxiu Yu(余重秀); Zhihui Yu(于志辉); Qiang Wu(吴强)

    2004-01-01

    A phase-shift fiber Bragg grating (FBG) with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands. The sampled noire fiber gratings are analyzed by Fourier transform theory first, and then simulation and experiment are performed, the results show that transmission peaks are opened in every reflective channel, the spectrum shape of every channel is identical.It can be used to fabricate multi-wavelength distributed feedback (DFB) fiber laser.

  17. Control of Angular Intervals for Angle-Multiplexed Holographic Memory

    Science.gov (United States)

    Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

    2009-03-01

    In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

  18. Extraction of polychromatic thermal neutrons by Bragg diffraction to use for prompt gamma neutron activation analysis

    International Nuclear Information System (INIS)

    Extraction method of thermal neutron beam by Bragg diffraction is investigated. A thermal neutron beam is used for the Prompt Gamma Neutron Activation Analysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic beam including all orders of diffraction is obtained by setting a pair of pyrolytic graphite crystals with a Bragg angle of 45 deg. on a horizontal white beam line. Diffracted neutron flux at the sample position is calculated by considering the integrated reflectivity and mosaic spread of crystals. Due to the divergence effect, the mosaic spread of crystals is optimized to give the maximum and flat flux at the sample position. An experiment has been performed to verify the reflectivities for high order diffractions from pyrolytic graphite. When the focusing technique of bending the crystals is adopted, a design value of 1.0x108 n/cm2s is expected at the sample position. Hence Bragg diffraction is a promising method of extracting thermal neutrons for PGNAA

  19. Investigation of omnidirectional reflection band in ZnTe/ZnSe distributed Bragg reflector

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ying-Shin [Department of Electrical Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China); Hu, Sheng-Yao [Department of Digital Technology Design, Tungfang Design University, Kaohsiung 82941, Taiwan (China); Lee, Yueh-Chien, E-mail: jacklee@mail.tnu.edu.tw [Department of Electronic Engineering, Tungnan University, New Taipei City 22202, Taiwan (China); Chang, Chung-Cheng; Tiong, Kwong-Kau [Department of Electrical Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China); Shen, Ji-Lin [Department of Physics, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Chou, Wu-Ching [Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2015-11-15

    We report the characteristics of reflectance spectra of the 15- and 20-period ZnTe/ZnSe distributed Bragg reflector grown on GaAs (001) substrates by molecular beam epitaxy. The reflectance spectra measured at various incident angles and polarizations were investigated by the theoretical curves simulated using transfer matrix method. The wavelength variation of the refractive indices described by Sellmeier equation and random thickness model were also considered for the interpretation of the experimentally observed curves. An omnidirectional reflection range defined from the edge of incident-angle-dependent reflection band with TE and TM polarizations is about 15 nm, and is consistent with the observed experimental curves. The results showed that the selected ZnTe and ZnSe materials are suitable for constructing multilayer structures having omnidirectional reflection band. - Highlights: • ZnTe/ZnSe distributed Bragg reflector grown by molecular beam epitaxy. • The reflectance spectra are measured at various incidence angles and polarizations. • The theoretical curves are considered by Sellmeier and random thickness models. • An observed omnidirectional reflection range in ZnTe/ZnSe DBR is about 15 nm.

  20. Fiber Bragg Grating Sensors for Harsh Environments

    Directory of Open Access Journals (Sweden)

    Stephen J. Mihailov

    2012-02-01

    Full Text Available Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments.

  1. Spatially Resolved Analysis of Bragg Selectivity

    Directory of Open Access Journals (Sweden)

    Tina Sabel

    2015-11-01

    Full Text Available This paper targets an inherent control of optical shrinkage in photosensitive polymers, contributing by means of spatially resolved analysis of volume holographic phase gratings. Point by point scanning of the local material response to the Gaussian intensity distribution of the recording beams is accomplished. Derived information on the local grating period and grating slant is evaluated by mapping of optical shrinkage in the lateral plane as well as through the depth of the layer. The influence of recording intensity, exposure duration and the material viscosity on the Bragg selectivity is investigated.

  2. Longitudinal coupling effect in microfiber Bragg gratings

    Science.gov (United States)

    Zhao, Ping; Zhang, Jihua; Wang, Guanghui; Jiang, Meng; Ping Shum, Perry; Zhang, Xinliang

    2012-10-01

    We theoretically present longitudinal coupling effect (LCE) in air-cladding microfiber Bragg gratings (MFBGs). Distinct from conventional weakly-guiding optical fibers, large longitudinal electric field (Ez) exists in wavelength-scale microfibers. Due to LCE, MFBG reflectivity can be reduced by more than 30% within the band-gap and the full width at half maximum (FWHM) is obviously narrowed. This theoretical analytical work is instructive to precisely design and fabricate MFBGs that are promising in the areas of optical sensing and nanophotonics.

  3. Thermal annealing of tilted fiber Bragg gratings

    Science.gov (United States)

    González-Vila, Á.; Rodríguez-Cobo, L.; Mégret, P.; Caucheteur, C.; López-Higuera, J. M.

    2016-05-01

    We report a practical study of the thermal decay of cladding mode resonances in tilted fiber Bragg gratings, establishing an analogy with the "power law" evolution previously observed on uniform gratings. We examine how this process contributes to a great thermal stability, even improving it by means of a second cycle slightly increasing the annealing temperature. In addition, we show an improvement of the grating spectrum after annealing, with respect to the one just after inscription, which suggests the application of this method to be employed to improve saturation issues during the photo-inscription process.

  4. Fiber Bragg grating hydrophone with high sensitivity

    Institute of Scientific and Technical Information of China (English)

    Wentao Zhang; Yuliang Liu; Fang Li

    2008-01-01

    A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure,a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressuresensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young's modulus of the diaphragm is higher, a flatter frequency response will be obtained.

  5. Optical fibre Bragg grating recorded in TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, I.P.; Yuan, Scott Wu; Stefani, Alessio;

    2011-01-01

    A report is presented on the inscription of a fibre Bragg grating into a microstructured polymer optical fibre fabricated from TOPAS cyclic olefin copolymer. This material offers two important advantages over poly (methyl methacrylate), which up to now has formed the basis for polymer fibre Bragg...

  6. Status of the OCS Bragg-Spectrometer for SODART

    DEFF Research Database (Denmark)

    Wiebicke, H.J.; Halm, I.; Christensen, Finn Erland;

    1998-01-01

    OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented.......OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented....

  7. Fano resonances in integrated silicon Bragg reflectors for sensing applications.

    Science.gov (United States)

    Chang, Chia-Ming; Solgaard, Olav

    2013-11-01

    We investigate theoretically and experimentally Fano resonances in integrated silicon Bragg reflectors. These asymmetric resonances are obtained by interference between light reflected from the Bragg waveguide and from the end facet. The Bragg reflectors were designed and modeled using the 1D transfer matrix method, and they were fabricated in standard silicon wafers using a CMOS-compatible process. The results show that the shape and asymmetry of the Fano resonances depend on the relative phase of the reflected light from the Bragg reflectors and end facet. This phase relationship can be controlled to optimize the lineshapes for sensing applications. Temperature sensing in these integrated Bragg reflectors are experimentally demonstrated with a temperature sensitivity of 77 pm/°C based on the thermo-optic effect of silicon. PMID:24216944

  8. Composite cure monitoring with Bragg grating sensors

    Science.gov (United States)

    Slattery, Kerry T.; Corona-Bittick, Kelli; Dorr, Donald J.

    1998-03-01

    Residual stress is induced in fiber composite materials during the cure process because the thermal expansion coefficient of the fiber is generally much lower than that of the polymer matrix. The two materials are 'locked' together at the cure temperature. Then, as they cool, the matrix attempts to contract more than the fiber leading to tension in the matrix and compression in the fiber. This can lead to the formation of microcracks parallel to the fibers in thick composite piles or yarns. The magnitude of residual stress can be reduced by modifying the cure cycle; however, optimizing the cure cycle requires a complete understanding of the state of cure throughout the composite. This is a complex problem -- especially in thick composites. Pilot studies have been performed placing Bragg gratin sensors in glass fabric preforms and monitoring the response of the grating during resin infusion and cure. The typical response shows the initial thermal expansion of the Bragg grating, a rapid contraction of the grating as the resin gels, slower contraction during cure, and thermal contraction at the composite thermal expansion coefficient during cool down. This data is then sued with micromechanical models of the fiber/matrix interaction during cure to establish material parameters for cure simulation. Once verified, these cure simulation methods will be used to optimize tooling design and cure cycles in composite components.

  9. Oblique incidence properties of locally resonant sonic materials with resonance and Bragg scattering effects

    Institute of Scientific and Technical Information of China (English)

    Yuan Bo; Wen Ji-Hong; Wen Xi-Sen

    2013-01-01

    A locally resonant sonic material (LRSM) is an elastic matrix containing a periodic arrangement of identical local resonators (LRs),which can reflect strongly near their natural frequencies,where the wavelength in the matrix is still much larger than the structural periodicity.Due to the periodic arrangement,an LRSM can also display a Bragg scattering effect,which is a characteristic of phononic crystals.A specific LRSM which possesses both local resonance and Bragg scattering effects is presented.Via the layered-multiple-scattering theory,the complex band structure and the transmittance of such LRSM are discussed in detail.Through the analysis of the refraction behavior at the boundary of the composite,we find that the transmittance performance of an LRSM for oblique incidence depends on the refraction of its boundary and the transmission behaviors of different wave modes inside the composite.As a result,it is better to use some low-speed materials (compared with the speed of waves in surrounding medium) as the LRSM matrix for designing sound blocking materials in underwater applications,since their acoustic properties are more robust to the incident angle.Finally,a gapcoupled LRSM with a broad sub-wavelength transmission gap is studied,whose acoustic performance is insensitive to the angle of incidence.

  10. Bragg-case limited projection topography study of surface damage in diamond-crystal plates

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Y; Krasnicki, S; Macrander, A T; Chu, Y S; Maj, J [Advanced Photon Source, Argonne National Laboratory, Argonne (United States)

    2005-05-21

    To characterize diamond monochromators for synchrotron radiation beamlines, images for a region 25 {mu}m below the surface were obtained. Topographical images of a Bragg-diffracted beam having a scattering angle (twice the Bragg angle) of 90 deg. were obtained from asymmetric reflections with a CCD area detector. A 25 {mu}m incident slit was used to section the sample topographically. Patchwork images for the full surface area, but limited in depth to the slit size, were assembled from microbeam images. The small extinction depths provided by the asymmetric reflection geometry, namely, 2.8 {mu}m and 3.5 {mu}m for ideal diamond crystals set for the (224) and (044) reflections, respectively, permitted data analyses for a region near the surface. The diamonds were synthetic type Ib (yellowish due to nitrogen impurities). They were in the shape of plates sized 6 x 5 mm and were 0.5 mm thick. Measurements were made using monochromatic bending magnet radiation at the Advanced Photon Source at 12.04 keV and 13.90 keV. Data obtained before and after chemical etching demonstrate that damage visible as contrast from saw grooves is largely removed by etching. Dislocation etch pits were observed after etching for the (111) surface but not for the (100) surface.

  11. Wake monochromator in asymmetric and symmetric Bragg and Laue geometry for self-seeding the European X-ray FEL

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni; Serkez, Svitozar; Tolkiehn, Martin [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2013-01-15

    We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging beamline at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (sigma polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to {pi}/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom.

  12. Research of fiber Bragg grating geophone based on cantilever beam

    Science.gov (United States)

    Wang, Liang; Chen, Shao-hua; Tao, Guo; Lu, Gui-wu; Zhao, Kun

    2009-07-01

    Along with the development of seismic exploration, the demand of frequency, dynamic range, precision and resolution ration is increased. However, the traditional geophone has disadvantages of narrower bandwidth, lower dynamic range and resolution, and cannot meet the new needs of seismic exploration. Geophone technology is a choke point, which constrains the development of petroleum prospecting in recent years. Fiber Bragg Grating seism demodulation technology is the newest kind of seism demodulation technology. The sensing probe of the Fiber Bragg Grating geophone is made up of Fiber Bragg Gating. The information which it collects is embodied by wavelength. The modulation-demodulation is accomplished by Fiber Bragg Gating geophone directly. In this paper, we design different size Fiber Bragg Grating geophones based on the transmission properties of Fiber Bragg Grating and cantilever beam method. Beryllium bronze and stainless steel are chosen as the elastic beam and shell materials, respectively. The parameters such as response function and sensitivity are given theoretically. In addition, we have simulated the transmission characteristics of Fiber Bragg Grating geophone by virtue of finite element analysis. The influences of wavelength, mass block, fiber length on the characteristics of geophones are discussed in detail, and finally the appropriate structural parameters are presented.

  13. Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave

    Science.gov (United States)

    Wen, Biyang; Li, Ke

    2016-08-01

    Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity.

  14. Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave.

    Science.gov (United States)

    Wen, Biyang; Li, Ke

    2016-01-01

    Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity. PMID:27531469

  15. A ballistic motion disrupted by Bragg reflections

    CERN Document Server

    Clark, Jeremy Thane

    2012-01-01

    I study a Lindblad dynamics modeling a quantum test particle in a Dirac comb that collides with particles from a background gas. The main result is a homogenization theorem in a semi-classical limiting regime involving large mass for the test particle and a rescaling for the strength and period of the Dirac comb. Over the time interval considered, the particle would exhibit essentially ballistic motion if either the singular periodic potential or the kicks from the gas were removed. However, the particle behaves diffusively when both sources of forcing are present. The conversion of the motion from ballistic to diffusive is generated by occasional Bragg reflections that result when the test particle's momentum is driven through a collision near an element of the half-spaced reciprocal lattice of the Dirac comb.

  16. Solgel grating waveguides for distributed Bragg reflector lasers.

    Science.gov (United States)

    Fardad, M A; Luo, H; Beregovski, Y; Fallahi, M

    1999-04-01

    Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated. PMID:18071539

  17. Dispersion blue-shift in an aperiodic Bragg reflection waveguide

    CERN Document Server

    Fesenko, Volodymyr I

    2016-01-01

    A particular feature of an aperiodic design of cladding of Bragg reflection waveguides to demonstrate a dispersion blue-shift is elucidated. It is made on the basis of a comparative study of dispersion characteristics of both periodic and aperiodic configurations of Bragg mirrors in the waveguide system, wherein for the aperiodic configuration three procedures for layers alternating, namely Fibonacci, Thue-Morse and Kolakoski substitutional rules are considered. It was found out that, in a Bragg reflection waveguide with any considered aperiodic cladding, dispersion curves of guided modes appear to be shifted to shorter wavelengths compared to the periodic configuration regardless of the modes polarization.

  18. Modeling Component-based Bragg gratings Application: tunable lasers

    Directory of Open Access Journals (Sweden)

    Hedara Rachida

    2011-09-01

    Full Text Available The principal function of a grating Bragg is filtering, which can be used in optical fibers based component and active or passive semi conductors based component, as well as telecommunication systems. Their ideal use is with lasers with fiber, amplifiers with fiber or Laser diodes. In this work, we are going to show the principal results obtained during the analysis of various types of grating Bragg by the method of the coupled modes. We then present the operation of DBR are tunable. The use of Bragg gratings in a laser provides single-mode sources, agile wavelength. The use of sampled grating increases the tuning range.

  19. Resonantly enhanced Bragg-scattering spectroscopy of an atomic transition

    Science.gov (United States)

    Yang, Xudong; Qiao, Cuifang; Li, Chuanliang; Chen, Fenghua

    2016-07-01

    A novel resonantly enhanced Bragg-scattering (REBS) spectroscopy from a population difference grating (PDG) is reported. The PDG is formed by a standing-wave (SW) pump field, which periodically modulates the space population distributions of two levels in the 87Rb D1 line. Then, a probe beam, having identical frequency and orthogonal polarization with the SW pump field, is Bragg-scattered by the PDG. The research achievement shows that the Bragg-scattered light is strongest at an atomic transition, and forms an REBS spectrum with a high signal-to-noise ratio and sub-natural linewidth. The observed REBS can be applied in precise frequency measurements.

  20. Dispersion blue-shift in an aperiodic Bragg reflection waveguide

    Science.gov (United States)

    Fesenko, Volodymyr I.; Tuz, Vladimir R.

    2016-04-01

    A particular feature of an aperiodic design of cladding of Bragg reflection waveguides to demonstrate a dispersion blue-shift is elucidated. It is made on the basis of a comparative study of dispersion characteristics of both periodic and aperiodic configurations of Bragg mirrors in the waveguide system, wherein for the aperiodic configuration three procedures for layers alternating, namely Fibonacci, Thue-Morse and Kolakoski substitutional rules are considered. It was found out that, in a Bragg reflection waveguide with any considered aperiodic cladding, dispersion curves of guided modes appear to be shifted to shorter wavelengths compared to the periodic configuration regardless of the modes polarization.

  1. Thermally tunable integrated planar Bragg-grating stabilized diode laser

    Science.gov (United States)

    Lynch, S. G.; Gates, J. C.; Berry, S. A.; Holmes, C.; Smith, P. G. R.

    2015-03-01

    A pair of external cavity diode lasers are fabricated using an integrated planar Bragg grating. The planar waveguide and Bragg reflector is UV-written within a glass-on-silicon chip. Intensity isolated, continuous wavelength tuning at > 1kHz modulation rate is acheived using micro-heating elements fabricated directly over the Bragg grating. Low RIN (<140dB) and low linewidth (δν ~ 200 kHz) operation is found using a heterodyne measurement. We demonstrate the lasers operating in phase-locked loop configuration where one laser is frequency-offset locked to the other.

  2. Controlling the Multiport Nature of Bragg Diffraction in Atom Interferometry

    CERN Document Server

    Parker, Richard H; Estey, Brian; Zhong, Weicheng; Huang, Eric; Müller, Holger

    2016-01-01

    Bragg diffraction has been used in atom interferometers because it allows signal enhancement through multiphoton momentum transfer and suppression of systematics by not changing the internal state of atoms. Its multi-port nature, however, can lead to parasitic interferometers, allows for intensity-dependent phase shifts in the primary interferometers, and distorts the ellipses used for phase extraction. We study and suppress these unwanted effects. Specifically, phase extraction by ellipse fitting and the resulting systematic phase shifts are calculated by Monte Carlo simulations. Phase shifts arising from the thermal motion of the atoms are controlled by spatial selection of atoms and an appropriate choice of Bragg intensity. In these simulations, we found that Gaussian Bragg pulse shapes yield the smallest systematic shifts. Parasitic interferometers are suppressed by a "magic" Bragg pulse duration. The sensitivity of the apparatus was improved by the addition of AC Stark shift compensation, which permits d...

  3. Observation of sub-Bragg diffraction of waves in crystals

    CERN Document Server

    Huisman, Simon R; Hartsuiker, Alex; Woldering, Léon A; Mosk, Allard P; Vos, Willem L

    2011-01-01

    We investigate the diffraction conditions and associated formation of stopgaps for waves in crystals with different Bravais lattices. We identify a prominent stopgap in high-symmetry directions that occurs at a frequency below the ubiquitous first-order Bragg condition. This sub-Bragg diffraction condition is demonstrated by reflectance spectroscopy on two-dimensional photonic crystals with a centred rectangular lattice, revealing prominent diffraction peaks for both the sub-Bragg and first-order Bragg condition. These results have implications for wave propagation in 2 of the 5 two-dimensional Bravais lattices and 7 out of 14 three-dimensional Bravais lattices, such as centred rectangular, triangular, hexagonal and body-centred cubic.

  4. Bragg Reflection of Waves by Different Shapes of Artificial Bars

    Institute of Scientific and Technical Information of China (English)

    许泰文; 张宪国; 蔡立宏

    2002-01-01

    Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificialbars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are placed discretely on theseabed for measurement of the Bragg reflection. A series of experimental conditions including the number of bars, the pe-riodic bar spacing, the water depth and various wave conditions are tested. Key parameters influencing the Bragg reso-nances are investigated. The experimental data are compared with the values from both theoretical and numerical models.Some key parameters have proved to be effective in describing the primary resonances. Predictive equations of the charac-teristics for the Bragg reflection are proposed in this paper.

  5. Bragg-Fresnel optics: New field of applications

    Energy Technology Data Exchange (ETDEWEB)

    Snigirev, A. [ESRF, Grenoble (France)

    1997-02-01

    Bragg-Fresnel Optics shows excellent compatibility with the third generation synchrotron radiation sources such as ESRF and is capable of obtaining monochromatic submicron focal spots with 10{sup 8}-10{sup 9} photons/sec in an energy bandwidth of 10{sup -4}-10{sup -6} and in a photon energy range between 2-100 keV. New types of Bragg-Fresnel lenses like modified, ion implanted, bent and acoustically modulated were tested. Microprobe techniques like microdiffraction and microfluorescence based on Bragg-Fresnel optics were realised at the ESRF beamlines. Excellent parameters of the X-ray beam at the ESRF in terms of low emittance and quite small angular source size allow for Bragg-Fresnel optics to occupy new fields of applications such as high resolution diffraction, holography, interferometry and phase contrast imaging.

  6. Time/Wavelength Fiber Bragg Grating Multiplexing Sensor Array

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A novel time/wavelength-multiplexed fiber Bragg grating sensor array is presented. This type of sensor array has the advantages of more points for multi-point measurement, simple structure and low cost.

  7. Structural Health Monitoring Using Fiber Bragg Grating Sensor Matrix Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Fiber Bragg Grating had been identified as very important elements, especially for strain measurements in smart structures. In many applications, arrays of FBG...

  8. The localized surface plasmon resonances based on a Bragg reflector

    Science.gov (United States)

    Wang, Jie; Liu, Yumin; Yu, Zhongyuan; Ye, Chunwei; Lv, Hongbo; Shu, Changgan

    2014-09-01

    In this paper, we present the theoretical analysis on how the wavelength of the localized surface plasmon resonances of gold nanoparticle can lead shift for the resonance wavelength. In our results, we calculate the scattering cross-section, the absorption cross-section and the field enhancement due to the nanoparticle. Numerical simulation were done using the finite element method (FEM). The work that we do here is different from the previous work because we use the Bragg reflector as a substrate. The Bragg reflector has a property of high reflectivity in some certain frequency bandwidth because of its periodic structure. The coherence interference of the Bragg reflector contributes to the plasmon resonances and results in some special character for a wide variety application, from sensing to photovoltaic. The periodic number of the Bragg reflector substrate and shapes of the nanoparticles are also discussed that result in a shift of the resonance wavelength.

  9. Technical textiles with embedded fibre Bragg grating sensors

    Science.gov (United States)

    Bilro, L.; Cunha, H.; Pinto, J. L.; Nogueira, R. N.

    2009-10-01

    The characterization of fiber Bragg grating (FBG) sensors integrated on 2D and 3D mesh structures is presented. Several materials and configurations were tested, namely cork, foams, PVC, hexagonal 3D. Sensors were embedded between two substrates using textile lamination technique. Every sample was subjected to temperature variations and mechanical deformations. Through Bragg wavelength monitoring, thermal, deformation and pressure performance were evaluated. These results provide significant information to the conception of smart textiles.

  10. Fibre Bragg Grating Components for Filtering, Switching and Lasing

    OpenAIRE

    Yu, Zhangwei

    2008-01-01

    Fibre Bragg gratings (FBGs) are key components for a vast number of applications in optical communication systems, microwave photonics systems, and optical sensors, etc. The main topic of this thesis is fibre Bragg grating fabrication and applications in direct microwave optical filtering, high speed switching and switchable dual-wavelength fibre lasers. First, a brief overview is given about the photosensitivity in optical fibre, basic FBG fabrication techniques, the popular coupled-mode the...

  11. Photonic scanning receiver using an electrically tuned fiber Bragg grating.

    Science.gov (United States)

    Rugeland, P; Yu, Z; Sterner, C; Tarasenko, O; Tengstrand, G; Margulis, W

    2009-12-15

    A 5-cm-long electrically tuned fiber Bragg grating is used to filter a microwave signal on an optical carrier at 1.55 mum. A chirped distributed-feedback structure is employed, with a transmission bandwidth of 54 MHz and relative optical carrier rejection of >30 dB for rf frequencies >2 GHz. The rapid monotonic sweep of the Bragg wavelength is translated into a fast-frequency sweep for rf analysis. PMID:20016616

  12. Multipoint sensor based on fiber Bragg gratings

    Energy Technology Data Exchange (ETDEWEB)

    Mendez-Zepeda, O; Munoz-Aguirre, S; Beltran-Perez, G; Castillo-Mixcoatl, J, E-mail: mezeos9@yahoo.com [Facultad de Ciencias FIsico-Matematicas, BUAP Av. San Claudio y Rio Verde, Col. San Manuel, CU. C.P. 72570, Puebla, Puebla (Mexico)

    2011-01-01

    In some control and industrial measurement systems of physical variables (pressure, temperature, flow, etc) it is necessary one system and one sensor to control each process. On the other hand, there are systems such as PLC (Programmable Logic Control), which can process several signals simultaneously. However it is still necessary to use one sensor for each variable. Therefore, in the present work the use of a multipoint sensor to solve such problem has been proposed. The sensor consists of an optical fiber laser with two Fabry-Perot cavities constructed using fiber Bragg gratings (FBG). In the same system is possible to measure changes in two variables by detecting the intermodal separation frequency of each cavity and evaluate their amplitudes. The intermodal separation frequency depends on each cavity length. The sensor signals are monitored through an oscilloscope or a PCI card and after that acquired by PC, where they are analyzed and displayed. Results of the evaluation of the intermodal frequency separation peak amplitude behavior with FBG stretching are presented.

  13. Writing Bragg Gratings in Multicore Fibers.

    Science.gov (United States)

    Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

    2016-01-01

    Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

  14. Dynamic fiber Bragg grating sensing method

    Science.gov (United States)

    Ho, Siu Chun Michael; Ren, Liang; Li, Hongnan; Song, Gangbing

    2016-02-01

    The measurement of high frequency vibrations is important in many scientific and engineering problems. This paper presents a novel, cost effective method using fiber optic fiber Bragg gratings (FBGs) for the measurement of high frequency vibrations. The method uses wavelength matched FBG sensors, with the first sensor acting as a transmission filter and the second sensor acting as the sensing portion. Energy fluctuations in the reflection spectrum of the second FBG due to wavelength mismatch between the sensors are captured by a photodiode. An in-depth analysis of the optical circuit is provided to predict the behavior of the method as well as identify ways to optimize the method. Simple demonstrations of the method were performed with the FBG sensing system installed on a piezoelectric transducer and on a wind turbine blade. Vibrations were measured with sampling frequencies up to 1 MHz for demonstrative purposes. The sensing method can be multiplexed for use with multiple sensors, and with care, can be retrofitted to work with FBG sensors already installed on a structure.

  15. Perception of perspective angles

    NARCIS (Netherlands)

    Erkelens, C.J.

    2015-01-01

    We perceive perspective angles, that is, angles that have an orientation in depth, differently from what they are in physical space. Extreme examples are angles between rails of a railway line or between lane dividers of a long and straight road. In this study, subjects judged perspective angles bet

  16. Fiber Bragg gratings in heterogeneous multicore fiber for directional bending sensing

    Science.gov (United States)

    Zhang, Hailiang; Wu, Zhifang; Shum, Perry Ping; Wang, Ruoxu; Quyen Dinh, Xuan; Fu, Songnian; Tong, Weijun; Tang, Ming

    2016-08-01

    We present the fabrication of fiber Bragg gratings (FBGs) in a trench-assisted heterogeneous multicore fiber (MCF). Two obviously different Bragg reflection peaks are obtained due to the slight difference of refractive indices between the center core and the outer cores. To investigate the reflections of the two FBGs simultaneously, only a segment of multimode fiber is inserted between the lead-in single mode fiber and the MCF. The experimental results confirm that the curvature sensitivity of the FBG in the outer core is a sinusoidal function of the bending orientation angle. The maximum linear curvature sensitivity is about 0.128 nm/m‑1. The cross sensitivity to temperature or externally applied axial strain can be eliminated by discriminating the different responses of FBGs inscribed in outer cores and the center core. Thus this MCF with FBGs can be utilized as a directional bending sensor. Moreover, the proposed sensor offers several advantages, such as low cost and flexibility in fabrication.

  17. First order Bragg grating filters in silicon on insulator waveguides

    Science.gov (United States)

    Waugh, Peter Michael

    2008-08-01

    The subject of this project is the design; analysis, fabrication and characterisation of first order Bragg Grating optical filters in Silicon-on-Insulator (SOI) planar waveguides. It is envisaged that this work will result in the possibility of Bragg Grating filters for use in Silicon Photonics. It is the purpose of the work to create as far as is possible flat surface waveguides so as to facilitate Thermo-Optic tuning and also the incorporation into rib-waveguide Silicon Photonics. The spectral response of the shallow Bragg Gratings was modelled using Coupled Mode Theory (CMT) by way of RSoft Gratingmod TM. Also the effect of having a Bragg Grating with alternate layers of refractive index of 1.5 and 3.5 was simulated in order to verify that Silica and Silicon layered Bragg Gratings could be viable. A series of Bragg Gratings were patterned on 1.5 micron SOI at Philips in Eindhoven, Holland to investigate the variation of grating parameters with a) the period of the gratings b) the mark to space ratio of the gratings and c) the length of the region converted to Bragg Gratings (i.e. the number of grating period repetitions). One set of gratings were thermally oxidised at Philips in Eindhoven and another set were ion implanted with Oxygen ions at the Ion Beam Facility, University of Surrey, England. The gratings were tested and found to give transmission minima at approximately 1540 nanometres and both methods of creating flat surfaces were found to give similar minima. Atomic Force Microscopy was applied to the grating area of the as-implanted samples in the Advanced Technology Institute, University of Surrey, which were found to have surface undulations in the order of 60 nanometres.

  18. Variable Depth Bragg Peak Method for Single Event Effects Testing

    Science.gov (United States)

    Buchner, S.; Kanyogoro, N.; Foster, C.; O'Neill, P.

    2011-01-01

    Traditionally, accelerator SEE testing is accomplished by removing the tops of packages so that the IC chips are accessible to heavy ions. However, ICs in some advanced packages cannot be de-lidded so a different approach is used that involves grinding and/or chemically etching away part of the package and the chip from the back side. The parts are then tested from the back side with ions having sufficient range to reach the sensitive volume. More recently, the entire silicon substrate in an SOI/SRAM was removed, making it possible to use low-energy ions with shorter ranges. Where removal of part of the package is not possible, facilities at Michigan State, NASA Space Radiation Laboratory, GANIL (France) and GSI (Germany) offer high-energy heavy ions with long ranges so that the ions can reach the devices' sensitive volumes without much change in the LET. Unfortunately, a run will typically involve only one ion species having a single energy and LET due to the long time it takes to tune a new energy. The Variable Depth Bragg Peak (VDBP) method is similar to the above method in that it involves the use of high-energy heavy ions that are able to pass through the packaging material and reach the device, obviating the need to remove the package. However, the method provides a broad range of LETs from a single ion by inserting degraders in the beam that modify the ion energy and, therefore, the LET. The crux of the method involves establishing a fiduciary point for degrader thickness, i.e., where the Bragg peak is located precisely at the sensitive volume in the device, for which the measured SEU cross-section and the ion LET are both also maxima and can be calculated using a Monte-Carlo program, TRIM. Once the fiduciary point has been established, calibrated high density polyethylene (HDPE) degraders are inserted into or removed from the beam to vary the ion LET at the device in a known manner. After each change of degrader thickness, the SEU cross-section is measured

  19. A double focusing SAXS camera with µm focal spot based on a circular bragg-fresnel lens

    OpenAIRE

    Snigirev, A.; Snigireva, I.; Riekel, C.; Miller, A.; Wess, L.; Wess, T.

    1993-01-01

    A 2D focusing SAXS camera has been build based on a circular Bragg-Fresnel lens. The camera has been tested at the Microfocus beamline at the European Synchrotron Radiation Facility. An undulator was used as radiation source. The focused beam size at the sample position of about 1,5*2µm2 and intensity of about 109 photons/s was obtained at a wavelength of 1.24A (10keV). A Molecular Dynamics image plate was used to detect the low-angle diffraction pattern. For native turkey leg tendon collagen...

  20. Simultaneous high bit-rate format and mode conversion with a single tilted apodized few-mode fiber Bragg grating

    Science.gov (United States)

    Gao, Ya; Sun, Junqiang; Sima, Chaotan

    2016-10-01

    We propose an all-optical approach for simultaneous high bit-rate return-to-zero (RZ) to non-return-to-zero (NRZ) format and LP01 to LP11 mode conversion using a weakly tilted apodized few-mode fiber Bragg grating (TA-FM-FBG) with specific linear spectral response. The grating apodization profile is designed by utilizing an efficient inverse scattering algorithm and the maximum refractive index modulation is adjusted based on the grating tilt angle, according to Coupled-Mode Theory. The temporal performance and operation bandwidth of the converter are discussed. The approach provides potential favorable device for the connection of various communication systems.

  1. A Soft X-ray Beam-splitting Multilayer Optic for the NASA GEMS Bragg Reflection Polarimeter

    OpenAIRE

    Allured, Ryan; Fernandez-Perea, Monica; Soufli, Regina; Alameda, Jennifer B.; Pivovaroff, Michael J.; Gullikson, Eric M.; Kaaret, Philip

    2013-01-01

    A soft X-ray, beam-splitting, multilayer optic has been developed for the Bragg Reflection Polarimeter (BRP) on the NASA Gravity and Extreme Magnetism Small Explorer Mission (GEMS). The optic is designed to reflect 0.5 keV X-rays through a 90 degree angle to the BRP detector, and transmit 2-10 keV X-rays to the primary polarimeter. The transmission requirement prevents the use of a thick substrate, so a 2 micron thick polyimide membrane was used. Atomic force microscopy has shown the membrane...

  2. Fabrication and optical characterization of Bragg resonance luminescence porous silicon

    Science.gov (United States)

    Park, Mi-Ae; Sohn, Honglae

    2016-01-01

    The synthesis and characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and strong narrow visible photoluminescence (PL) prepared from highly doped n-type silicon wafers through the electrochemical etching are reported. BRL PS showing the luminescence at 702 nm with an excitation wavelength of 400 nm was prepared by applying the current of 360 mA cm-2 for 1.6 s and 75 mA cm-2 for 3.6 s with 50 repeats in etching solution of 1:1 volume mixture of absolute ethanol and aqueous 48% HF. BRL PS exhibited sharp PL peak which reached full width at half maximum of 14 nm, originated from the result of Bragg resonance in PS multilayer. The sharp PL peak at 702 nm of BRL PS is the second-order transmitted luminescence peak by Bragg resonance phenomenon. The simultaneous measurement of reflectivity and luminescence in the BRL PS under an exposure to a vapor flux of acetone showed that a narrow transmitted luminescence based on Bragg resonance in BRL PS quenched as well as the red-shifted by 37 nm of reflection wavelength was observed. A dramatic quenching PL of BRL PS compare to that of the monolayer PS, is probably due to the Bragg resonance effect on luminescence.

  3. Electrically controlled Bragg resonances of an ambichiral electro-optic structure: oblique incidence

    CERN Document Server

    Dixit, Mukul

    2007-01-01

    The Pockels effect can increase the effective birefringence of ambichiral, electro--optic rejection filters made of materials with a $\\bar{4}2m$ point group symmetry, when a dc electric field is applied parallel to the axis of nonhomogeneity. The reflectances and the transmittances of such an ambichiral structure for obliquely incident plane waves is solvable through a boundary-value problem that is formulated using the frequency-domain Maxwell equations, the constitutive equations that contain the Pockels effect, and standard algebraic techniques for handling 4x4 matrix ordinary differential equations. The Bragg resonance peaks, for different circular-polarized-incidence conditions, blueshift as the angle of incidence increases. These blueshifts are unaffected by the sign of the dc electric field.

  4. Multifrequency Magneto-optic Bragg Diffraction and Radio Frequency Signal Parallel Processing

    Institute of Scientific and Technical Information of China (English)

    SHANG Dan; WU Bao-jian; QIU Kun

    2008-01-01

    Magneto-optic(MO) coupling of guided optical waves with microwave magnetostatic waves(MSWs) simultaneously excited by multiple radio frequency(RF) signals can lead to multifrequency diffraction effects and then parallel processing of RF signals can be realized by using of the characteristics that diffraction efficiencies(Des) are approximately in direct proportion to RF signals intensities and diffraction angles are related to frequencies of the corresponding RF signals within linear MO interaction region. In this paper, studied is the multifrequency MO Bragg diffraction in first-order MO interaction approximation, and obtained was the approximate analytical expression for principle diffraction efficiency(PDE). Also, put forward was a parallel imaging method of relative intensity of RF signals based on single-frequency diffraction. By calculation and analysis, it is shown that the relative error is not more than 0.3 dB for the case of three RF signals within the frequency space of 60 MHz.

  5. Sensitivity Distribution Properties of a Phase-Shifted Fiber Bragg Grating Sensor to Ultrasonic Waves

    Directory of Open Access Journals (Sweden)

    Qi Wu

    2014-01-01

    Full Text Available In this research, the sensitivity distribution properties of a phase-shifted fiber Bragg grating (PS-FBG to ultrasonic waves were investigated employing the surface attachment method. A careful consideration was taken and examined by experimental results to explain that the distances and angles between the sensor and ultrasonic source influence not only the amplitudes, but also the initial phases, waveforms, and spectra of detected signals. Furthermore, factors, including the attachment method and the material’s geometric dimensions, were also discussed. Although these results were obtained based on PS-FBG, they are also applicable to a normal FBG sensor or even an optical fiber sensor, due to the identical physical changes induced by ultrasonic waves in all three. Thus, these results are useful for applications of optical fiber sensors in non-destructive testing and structural health monitoring.

  6. A novel oil level monitoring sensor based on string tilted fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    JIANG Qi

    2011-01-01

    In this paper, we present a novel oil level monitoring sensor based on string tilted fiber Bragg grating (TFBG). The mea- surement range and sensitivity of oil level monitoring can be modulated via changing the length and number of string tilted fiber gratings. The transmission spectrum of string TFBGs immersed in oil changes obviously with the oil level variation. Experiments are conducted on three 2 crn-length serial TFBGs with the same tilted angle of 10°. A sensitivity of 3.28 dB/cm in the string TFBG sensor is achieved with good linearity by means of TFBG spectrum characteristic with peak-low value. The cladding mode transmission power and the amplitude of high order cladding mode resonance are nearly linear to the oil level variation. This kind of sensor is insensitive to temperature and attributed to be employed in extremely harsh environ- ment oil monitoring.

  7. Temperature Compensation for Double Fiber Bragg Grating Sensors

    Institute of Scientific and Technical Information of China (English)

    WANG Chun-cheng; LIU Jia; ZHENG Jian-bang

    2006-01-01

    A novel double fiber Bragg grating(FBG) strain sensor configuration is presented. Temperature compensation method is based on double FBG moored on a rhombus frame. Through the theoretical analysis,the relation between relative shift of Bragg wavelength and the strain applied on the sensor is obtained,and the analytical expression of strain sensitivity coefficient is also given. The experiment results show that:in the strain range of 0~0.8 mm,the relation between the relative shift of Bragg wavelength and applied strain is linear,and the dispersion of double FBG wavelength at the range of -25 ℃~60 ℃ is 0~0.002 nm. The strain sensitivity of the displacement sensor configuration is 0.171 nm/με,and is nearly twice than that of single FC sensor.

  8. A plating method for metal coating of fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    Yulong Li; Hua Zhang; Yan Feng; Gang Peng

    2009-01-01

    We present a method for metal coating optical fiber and in-fiber Bragg grating. The technology process which is based on electroless plating and electroplating method is described in detail. The fiber is firstly coated with a thin copper or nickel plate with electroless plating method. Then, a thicker nickel plate is coated on the surface of the conductive layer. Under the optimum conditions, the surfaces of chemical plating and electroplating coatings are all smooth and compact. There is no visible defect found in the cross-section. Using this two-step metallization method, the in-fiber Bragg grating can be well protected and its thermal sensitivity can be enhanced. After the metallization process, the fiber sensor is successfully embedded in the 42CrMo steel by brazing method. Thus a smart metal structure is achieved. The embedding results show that the plating method for metallization protection of in-fiber Bragg grating is effective.

  9. Damage behaviors of fiber Bragg grating sensor in fabrication

    Science.gov (United States)

    Tang, Liqun; Sang, Dengfeng; Chen, Jinming; Yang, Bao; Liu, Yiping

    2008-11-01

    It is has been noted that for fiber Bragg grating sensor (FBGS), the tensile strengths of fiber Bragg grating sensors (FBGSs) were decreased after the gratings were written, which may reduce the sensor's measurement range obviously. In this paper, we focused on the damage behaviours of FBGS after fabrication experimentally. Firstly, the tensile tests were carried to measure the tensile strengths of naked optical fiber, decoated optical fiber and optical fiber with Bragg gratings to learn deduction of the tensile strength of optical fiber in the cases respectively. Further, the microscope photography was used to observe the surfaces of optical fiber with or without exposure of excimer laser. The main conclusion is that the UV pulse is the main contribution to reduce the strength remarkably, and the mechanical decoating method also can induce the surface damage on the optical fiber.

  10. High sensitivity fiber Bragg grating pressure difference sensor

    Institute of Scientific and Technical Information of China (English)

    Haiwei Fu(傅海威); Junmei Fu(傅君眉); Xueguang Qiao(乔学光)

    2004-01-01

    Based on the effect of fiber Bragg grating (FBG) pressure difference sensitivity enhancement by encapsulating the FBG with uniform strength beam and metal bellows, a FBG pressure difference sensor is proposed, and its mechanism is also discussed. The relationship between Bragg wavelength and the pressure difference is derived, and the expression of the pressure difference sensitivity coefficient is also given. It is indicated that there is good linear relation between the Bragg wavelength shift and the pressure difference of the sensor. The theoretical and experimental pressure difference sensitivity coefficients are 38.67 and 37.6 nm/MPa, which are 12890 and 12533 times of that of the bare FBG, respectively. The pressure difference sensitivity and dynamic range can be easily changed by changing the size, Young's modulus, and Poisson's ratio of the beam and the bellows.

  11. Applications of distributed fiber Bragg grating sensors in civil engineering

    Science.gov (United States)

    Nellen, Philipp M.; Broennimann, Rolf; Sennhauser, Urs J.; Askins, Charles G.; Putnam, Martin A.

    1995-09-01

    We report on civil engineering applications of wavelength multiplexed optical-fiber Bragg grating arrays produced directly on the draw tower for testing and surveying advanced structures and material like carbon fiber reinforced concrete elements and prestressing tendons. We equipped a 6 m X 0.9 m X 0.5 m concrete cantilever beam reinforced with carbon fiber lamellas with fiber Bragg grating sensors. Static and dynamic strain levels up to 1500 micrometers /m were measured with a Michelson interferometer used as Fourier spectrometer with resolutions of about 10 micrometers /m for all sensors. Comparative measurements with electrical resistance strain gauges were in good agreement with the fiber optic results. We used the fiber sensors in two different arrangements: some Bragg grating array elements measured the local strain while others were configured in an extensometric way to measure moderate strain over 0.1-1 m.

  12. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

    Science.gov (United States)

    Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

    2014-10-15

    We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated. PMID:25361125

  13. BRAGG-PEAK LOCATION EMPLOYING A MAXIMUM-ENTROPY FORMALISM

    OpenAIRE

    Lehmann, M.; Robinson, T.; Wilkins, S.

    1986-01-01

    The maximum entropy method has been tried on simulated data from a small 2-dimensional position-sensitive detector. Constraints were introduced to account for smoothness and the fact that only one peak was found within the frame of the recording. Analysis of a large number of weak Bragg peaks with I/σ(I) < 9 and of different size and background showed the method to give virtually bias-free results. The computing time is sufficiently low to allow real time use on measurements of a single Bragg...

  14. Bragg gratings in index-guiding photonic crystal fibres

    DEFF Research Database (Denmark)

    Riishede, Jesper; Hougaard, Kristian G.; Libori, S.E. Barkou;

    2002-01-01

    A numerical investigation of coupling coefficients of Bragg-gratings in index-guiding photonic crystal fibres is presented. It is shown that index-guiding photonic crystal fibres have larger coupling coefficients for fibres with small core areas than step-index fibres.......A numerical investigation of coupling coefficients of Bragg-gratings in index-guiding photonic crystal fibres is presented. It is shown that index-guiding photonic crystal fibres have larger coupling coefficients for fibres with small core areas than step-index fibres....

  15. Temperature sensor based on dual fiber Bragg gratings

    OpenAIRE

    Ekestam, Henrik; Larsson, Jim

    2015-01-01

    The objective of the project was to examine if it was possible to develop a low-cost temperature sensor using dual fiber Bragg gratings (FBGs). The intention was to use one FBG as a reference and let the other FBG function as the sensor. The study shows that it is possible to characterize the temperature sensitivity of each FBG and use the reference to sweep over the applicable spectrum to find the Bragg-wavelength of the sensor. This could be done measuring only the total intensity instead o...

  16. New cobweb-structure hollow Bragg optical fibers

    Institute of Scientific and Technical Information of China (English)

    YU Rong-jin; ZHANG Yong-qiang; ZHANG Bing; WANG Chao-ran; WU Chang-qi

    2007-01-01

    A new type of Bragg fibers,i.e. hollow-core cobweb-structured optical fibers,which can be used to the low-loss transmission from visible to near infrared region (0.65 μm-1.55 μm),terahertz wave (200 μm-480 μm) and circular-polarization-maintaining single-mode transmission are investigated. Results show that the hollow-core cobweb-structured fibers have less loss than other hollow-core Bragg fibers. The fibers can be constituted by using the plastics or glasses with large absorption losses.

  17. Bragg grating chemical sensor with hydrogel as sensitive element

    Institute of Scientific and Technical Information of China (English)

    Xiaomei Liu(刘小梅); Shilie Zheng(郑史烈); Xianmin Zhang(章献民); Jun Cong(丛军); Kangsheng Chen(陈抗生); Jian Xu(徐坚)

    2004-01-01

    A novel fiber Bragg grating (FBG) based chemical sensor using hydrogel, a swellable polymer, as sensitive element is demonstrated. The sensing mechanism relies on the shift of Bragg wavelength due to the stress resulted from volume change of sensitive swellable hydrogel responding to the change of external environment. A polyacrylamide hydrogel fiber grating chemical sensor is made, and the experiments on its sensitivity to the salinity are performed. The sensitivity is low due to the less stress from the shrinking or swelling of hydrogels. Reducing the cross diameter of the grating through etching with hydrofluoric acid can greatly improve the sensitivity of the sensor.

  18. A novel optical filter of fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    LI; Xiaolu; JIANG; Yuesong

    2006-01-01

    A theory of a novel optical filter of drawing the fiber Bragg grating by the heated elastic sheet is advanced. Based on the heat conduction equation, a set of functions of temperature and thermal expansion on the heated elastic sheet are calculated. And the most displacement of the heated elastic sheet is also described. Finally the expression of the reflected Bragg wavelength deviation in terms of the thermal power density of heat-source is deduced. The physics feasibility of these conclusions mentioned above is proved. It is a potential value for the novel optical filter to research.

  19. Laser sensor with Bragg gratings of fiber optics to physics parameter measuring

    International Nuclear Information System (INIS)

    We present the operation of a fiber laser sensor made by an Erbium Doped Fiber pumped at 980nm, an 4.23 km passive fiber and two fiber Bragg gratings placed at the ends of the laser cavity. Under normal conditions, the Bragg gratings have different reflection wavelengths and laser emission is not generated. The two Bragg gratings can be placed at the same reflection wavelength when the Bragg grating with the lowest reflective wavelength increases their temperature which can be used as a sensor element. The laser generation thus shows that the Bragg grating is increasing their temperature. We used a Peltier cell for to change gradually the temperature. (Author)

  20. Crystal clear the autobiographies of Sir Lawrence and Lady Bragg

    CERN Document Server

    Thomson, Patience

    2015-01-01

    The main body of this book contains the hitherto unpublished autobiographies of both William Lawrence Bragg, an innovative scientist who won the Nobel Prize for Physics in 1915, and his wife, Alice, a Mayor of Cambridge and National Chairman of Marriage Guidance. Their autobiographies give unusual insights into the lives and times of two distinguished people and the real personalities behind their public appearance.

  1. The Wavelength Shifting and Temperature Athermalization of Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    Yu; e; Kong

    2003-01-01

    The wavelength shifting properties and the temperature athermalization technology of fiber Bragg grating (FBG) were studied in this paper, and then two different athermalization methods were introduced. The research shows that FBG with athermalization by applying the substrate with negative coefficient of thermal expansion is effective and can be used in many fields.

  2. Dynamic gate algorithm for multimode fiber Bragg grating sensor systems

    DEFF Research Database (Denmark)

    Ganziy, Denis; Jespersen, O.; Woyessa, Getinet;

    2015-01-01

    -to-noise ratio and different peak shapes. Our simulations and experiments demonstrate that the DGA method is fast and robust with better stability and accuracy than conventional algorithms. This makes it very attractive for future implementation in sensing systems, especially based on multimode fiber Bragg...

  3. High Sensitivity Polymer Optical Fiber-Bragg-Grating-Based Accelerometer

    DEFF Research Database (Denmark)

    Stefani, Alessio; Andresen, Søren; Yuan, Wu;

    2012-01-01

    We report on the fabrication and characterization of the first accelerometer based on a polymer optical fiber Bragg grating (FBG) for operation at both 850 and 1550 nm. The devices have a flat frequency response over a 1-kHz bandwidth and a resonance frequency of about 3 kHz. The response is line...

  4. Monolithic integrated optic fiber Bragg grating sensor interrogator

    Science.gov (United States)

    Mendoza, Edgar A.; Esterkin, Yan; Kempen, Cornelia; Sun, Songjian

    2010-04-01

    Fiber Bragg gratings (FBGs) are a mature sensing technology that has gained rapid acceptance in civil, aerospace, chemical and petrochemical, medicine, aviation and automotive industries. Fiber Bragg grating sensors can be use for a variety of measurements including strain, stress, vibration, acoustics, acceleration, pressure, temperature, moisture, and corrosion distributed at multiple locations within the structure using a single fiber element. The most prominent advantages of FBGs are: small size and light weight, multiple FBG transducers on a single fiber, and immunity to radio frequency interference. A major disadvantage of FBG technology is that conventional state-of-the-art fiber Bragg grating interrogation systems are typically bulky, heavy, and costly bench top instruments that are assembled from off-the-shelf fiber optic and optical components integrated with a signal electronics board into an instrument console. Based on the need for a compact FBG interrogation system, this paper describes recent progress towards the development of a miniature fiber Bragg grating sensor interrogator (FBG-TransceiverTM) system based on multi-channel monolithic integrated optic sensor microchip technology. The integrated optic microchip technology enables the monolithic integration of all of the functionalities, both passive and active, of conventional bench top FBG sensor interrogators systems, packaged in a miniaturized, low power operation, 2-cm x 5-cm small form factor (SFF) package suitable for the long-term structural health monitoring in applications where size, weight, and power are critical for operation.

  5. Compact Bragg Gratings for Long-Range Surface Plasmon Polaritons

    DEFF Research Database (Denmark)

    Boltasseva, Alexandra; Bozhevolnyi, Sergey I; Nikolajsen, Thomas;

    2006-01-01

    By introducing periodic thickness-modulation of thin metal stripes embedded in a dielectric, we realize compact and efficient Bragg gratings for long-range surface plasmon polaritons (LR-SPPs) operating around 1550 nm. We measure reflection and transmission spectra of the gratings having different...

  6. Growth and characterization of nitride-based distributed Bragg reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, Carsten; Dartsch, Heiko; Aschenbrenner, Timo; Figge, Stephan; Hommel, Detlef [Section Semiconductor Epitaxy, Institute of Solid State Physics, University of Bremen (Germany)

    2011-08-15

    We report on a systematic study concerning the realization of nitride-based distributed Bragg reflectors (DBRs) for opto-electronic applications in the near-UV to visible spectral range. Different material combinations are used in order to find an optimized trade-off concerning peak reflectivity, stop band width, and strain state of the Bragg mirrors. For the high refractive index material GaN is used in all cases, while for the low index material a layer of either AlGaN or AlInN, respectively, or a AlN/(In)GaN short-period superlattice (SL) is employed. The best peak reflectivity of 97% at a wavelength of 495 nm is achieved for a lattice matched Bragg reflector based on the GaN/AlInN material combination. Transmission electron microscopy image of a 30-fold distributed Bragg reflector consisting of AlInN (dark) and GaN (bright) layers. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Ultrafast Laser Fabrication of Bragg Waveguides in GLS Chalcogenide Glass

    Directory of Open Access Journals (Sweden)

    McMillen Ben

    2013-11-01

    Full Text Available We present work on the fabrication of Bragg waveguides in gallium-lanthanum-sulfide chalcogenide glass using an ultrafast laser. Waveguides were written with a single pass while modulating the writing beam. The spatial and temporal profile of the writing beam was ontrolled during waveguide fabrication in order to control the shape and size of the waveguide cross-section.

  8. Optimization of Apodized Chirped Fiber Bragg Grating for Dispersion Compensation

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Multiwavelength chirped fiber Bragg grating (MCFBG) is a more valuable approach to chromatic dispersion compensation. And adjusting the structure of FBG will optimize the performance of dispersion compensator in 8×10Gb/s DWDM network, which is proved by simulating calculation.

  9. Rational solitons in deep nonlinear optical Bragg grating

    NARCIS (Netherlands)

    Alatas, H.; Iskandar, A.A.; Tjia, M.O.; Valkering, T.P.

    2006-01-01

    We have examined the rational solitons in the Generalized Coupled Mode model for a deep nonlinear Bragg grating. These solitons are the degenerate forms of the ordinary solitons and appear at the transition lines in the parameter plane. A simple formulation is presented for the investigation of the

  10. Southern high-latitude Digisonde observations of ionosphere E-region Bragg scatter during intense lacuna conditions

    Directory of Open Access Journals (Sweden)

    D. P. Monselesan

    2004-09-01

    Full Text Available During summer months at solar cycle minimum, F-region lacuna and slant-Es conditions (SEC are common features of daytime ionograms recorded around local magnetic noon at Casey, Antarctica. Digisonde measurements of drift velocity height profiles show that the occurrence of lacuna prevents the determination of F-region drift velocities and also affects E-region drift velocity measurements. Unique E-region spectral features revealed as intervals of Bragg scatter superimposed on typical background E-region reflection were observed in Digisonde Doppler spectra during intense lacuna conditions. Daytime E-region Doppler spectra recorded at carrier frequencies from 1.5 to 2.7MHz, below the E-region critical frequency foE, have two side-peaks corresponding to Bragg scatter at approximately ±1-2Hz symmetrically located on each side of a central-peak corresponding to near-zenith total reflections. Angle-of-arrival information and ray-tracing simulations show that echo returns are coming from oblique directions most likely resulting from direct backscatter from just below the total reflection height for each sounding frequency. The Bragg backscatter events are shown to manifest during polar lacuna conditions, and to affect the determination of E-region background drift velocities, and as such must be considered when using standard Doppler-sorted interferometry (DSI techniques to estimate ionospheric drift velocities. Given the Doppler and spatial separation of the echoes determined from high-resolution Doppler measurements, we are able to estimate the Bragg scatter phase velocity independently from the bulk E-region motion. The phase velocity coincides with the ExB direction derived from in situ fluxgate magnetometer records. When ionospheric refraction is considered, the phase velocity amplitudes deduced from DSI are comparable to the ion-acoustic speed expected in the E-region. We briefly consider the plausibility that these

  11. Calculation of shear angles in holographic gratings recorded in bleached silver-halide emulsions

    OpenAIRE

    Beléndez Vázquez, Augusto; Pascual Villalobos, Inmaculada; Fuentes Rosillo, Rosa; Fimia Gil, Antonio

    1993-01-01

    Shearing phenomena in holographic gratings formed in bleached silver-halide emulsions due to chemical processing are evaluated. These effects are introduced because of the inability of emulsion-thickness changes to explain the anomalous detuning of the peak diffraction efficiency from the expected Bragg condition. Experimental results obtained with transmission and reflection gratings are presented and discussed considering shearing effects, and the values of the shear angles calculated from ...

  12. Wavelength-specific forward scattering of light by Bragg-reflective iridocytes in giant clams.

    Science.gov (United States)

    Ghoshal, Amitabh; Eck, Elizabeth; Gordon, Michael; Morse, Daniel E

    2016-07-01

    A surprising recent discovery revealed that the brightly reflective cells ('iridocytes') in the epithelia of giant clams actually send the majority of incident photons 'forward' into the tissue. While the intracellular Bragg reflectors in these cells are responsible for their colourful back reflection, Mie scattering produces the forward scattering, thus illuminating a dense population of endosymbiotic, photosynthetic microalgae. We now present a detailed micro-spectrophotometric characterization of the Bragg stacks in the iridocytes in live tissue to obtain the refractive index of the high-index layers (1.39 to 1.58, average 1.44 ± 0.04), the thicknesses of the high- and low-index layers (50-150 nm), and the numbers of pairs of layers (2-11) that participate in the observed spectral reflection. Based on these measurements, we performed electromagnetic simulations to better understand the optical behaviour of the iridocytes. The results open a deeper understanding of the optical behaviour of these cells, with the counterintuitive discovery that specific combinations of iridocyte diameter and Bragg-lamellar spacing can produce back reflection of the same colour that is also scattered forward, in preference to other wavelengths that are scattered at higher angles. We find for all values of size and wavelength investigated that more than 90% of the incident energy is carried by the photons that are scattered in the forward direction; while this forward scattering from each iridocyte shows very narrow angular dispersion (ca ±6°), the multiplicative scattering from a layer of ca 20 iridocytes broadens this dispersion to a cone of approximately ±90°. This understanding of the complex biophotonic dynamics enhances our comprehension of the physiologically, ecologically and evolutionarily significant light environment inside the giant clam, which is diffuse and nearly white at small tissue depths and downwelling, relatively monochromatic, and can be the same colour as

  13. XFEL OSCILLATOR SIMULATION INCLUDING ANGLE-DEPENDENT CRYSTAL REFLECTIVITY

    Energy Technology Data Exchange (ETDEWEB)

    Fawley, William; Lindberg, Ryan; Kim, K-J; Shvyd' ko, Yuri

    2010-08-23

    The oscillator package within the GINGER FEL simulation code has now been extended to include angle-dependent reflectivity properties of Bragg crystals. Previously, the package was modified to include frequencydependent reflectivity in order to model x-ray FEL oscillators from start-up from shot noise through to saturation. We present a summary of the algorithms used for modeling the crystal reflectivity and radiation propagation outside the undulator, discussing various numerical issues relevant to the domain of high Fresnel number and efficient Hankel transforms. We give some sample XFEL-O simulation results obtained with the angle-dependent reflectivity model, with particular attention directed to the longitudinal and transverse coherence of the radiation output.

  14. Angle resolved electron energy loss spectroscopy on graphite

    Science.gov (United States)

    Diebold, U.; Preisinger, A.; Schattschneider, P.; Varga, P.

    We report on angle resolved electron energy loss spectroscopy (EELS) in reflection mode with low primary energy on a graphite single crystal. Measurements with primary electron energy of 175 eV have been performed in off-Bragg-reflex geometry in two different directions within the (0001) surface plane of the graphite single crystal. In addition, EELS measurements in specular reflection mode with different primary energies and angles of incidence were done in order to distinguish between surface and bulk plasmon losses. The energy losses and the transferred momenta of the losses have been analyzed. The results are compared with the loss functions for bulk and surface excitations calculated from the dielectric function ɛ(ω, q) obtained from TEELS-data (EELS in transmission mode) [Springer Tracts Mod. Phys. 54 (1970) 77].

  15. Reading Angles in Maps

    Science.gov (United States)

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections…

  16. Ionoacoustic characterization of the proton Bragg peak with submillimeter accuracy

    Energy Technology Data Exchange (ETDEWEB)

    Assmann, W., E-mail: walter.assmann@lmu.de; Reinhardt, S.; Lehrack, S.; Edlich, A.; Thirolf, P. G.; Parodi, K. [Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, Garching 85748 (Germany); Kellnberger, S.; Omar, M.; Ntziachristos, V. [Institute for Biological and Medical Imaging, Technische Universität München and Helmholtz Zentrum München, Ingolstädter Landstrasse 1, Neuherberg 85764 (Germany); Moser, M.; Dollinger, G. [Institute for Applied Physics and Measurement Technology, Universität der Bundeswehr, Werner-Heisenberg-Weg 39, Neubiberg 85577 (Germany)

    2015-02-15

    Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams in tissue (ionoacoustics). Aim of this work was to study experimentally the achievable position resolution of ionoacoustics under idealized conditions using high frequency ultrasonic transducers and a specifically selected probing beam. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity and length. The acoustic signal of single proton pulses was measured by different PZT-based ultrasound detectors (3.5 and 10 MHz central frequencies). The proton dose distribution in water was calculated by Geant4 and used as input for simulation of the generated acoustic wave by the matlab toolbox k-WAVE. Results: In measurements from this study, a clear signal of the Bragg peak was observed for an energy deposition as low as 10{sup 12} eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Bragg peak position measurements were reproducible within ±30 μm and agreed with Geant4 simulations to better than 100 μm. The ionoacoustic signal pattern allowed for a detailed analysis of the Bragg peak and could be well reproduced by k-WAVE simulations. Conclusions: The authors have studied the ionoacoustic signal of the Bragg peak in experiments using a 20 MeV proton beam with its correspondingly localized energy deposition, demonstrating submillimeter position resolution and providing a deep insight in the correlation between the acoustic signal and Bragg peak shape. These results, together with earlier experiments and new simulations (including the results in this study) at higher energies, suggest ionoacoustics as a technique for range verification in particle therapy at locations, where the tumor can be localized by ultrasound

  17. Distribution of Micronuclei in Human Fibroblasts across the Bragg Curve of Light and Heavy Ions

    Science.gov (United States)

    Hada, M.; Lacy, S.; Gridley, D. S.; Rusek, A.; Cucinotta, F. A.; Wu, H.

    2007-01-01

    The space environment consists of energetic particles of varying mass and energy, and understanding the :biological Bragg curve" is essential in optimizing shielding effectiveness against space radiation induced biological impacts. The "biological Bragg curve" is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. Previously, we studied the induction of micronuclei (MN) across the Bragg curve of energetic Fe and Si ions, and observed no increased yield of MN at the location of the Bragg peak. However, the ratio of mono- to bi-nucleated cells, which indicates inhibition of cell progression, was found higher at the Bragg peak location in comparison to the plateau region of the Bragg curve. Here, we report the induction of MN in normal human fibroblast cells across the Bragg curve of incident protons generated at Loma Linda University. Similar to Si and Fe ions, the ratio of mono- to bi-nucleated cells showed a clear spike as the protons reached the Bragg peak. Unlike the two heavy ions, however, the MN yield also increased at the Bragg peak location. These results confirm the hypothesis that severely damaged cells at the Bragg peak of heavy, but not light ions are more likely to go through reproductive death and not be evaluated for micronuclei.

  18. Neutron beam instruments at the Bragg Institute, phase 2

    International Nuclear Information System (INIS)

    Full text: On 12 May 2009, the Minister for Innovation, Industry, Science and Research announced funding for the NBI2 Program as part of the Super Science - Future Industry initiative. The budget for the NBI2 Program is $37 million and it is scheduled to be completed within four years (1 July 2009 - 30 June 2013). The project builds on the previous successful Neutron Beam Instruments Project (2000-2007), which funded the original suite of 8 instruments, along with 2 subsequent instruments funded in other ways. NBI2 will feature a new split cold neutron guide (CG-2) with two end positions, three new instruments (a second small-angle neutron scattering machine, a high-resolution back-scattering spectrometer and a neutron radiography/tomography/imaging station) along with a substantial suite of sample-environment apparatus. On 27-28 August 2009, the Bragg Institute organised a NBI2 scoping workshop in which the key parameters of the new neutron instruments, guides and sample environments were defined [1]. The case for a second SANS machine rests on the overwhelming interest and demand from the domestic community in soft matter, structural biology, materials science, magnetism and superconductivity. A second SANS instrument will have many similarities with QUOKKA but it will be geared towards excelling in measuring a wider range of object sizes simultaneously, i.e. within a single experimental setting, enabled by a time-of-flight operation mode. This is very important for kinetic measurements, which is an emerging technique and essential in various science areas. Another key design feature will be the development of sophisticated sample environment techniques such as high magnetic fields and polarisation analysis along with the appropriate data analysis methods. The back-scattering spectrometer will open up spectroscopic studies at lower energies (longer times) than on the Pelican time-of-flight spectrometer, doubling the dynamic range in energy that can be accessed at

  19. Temperature effects in concrete structures measured with fibre Bragg grating

    Science.gov (United States)

    Silva, Jean C.; Martelli, Cicero; Penner, Elisabeth; Kalinowski, Hypolito J.

    2004-06-01

    We analyze the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure is instrumented with two fiber Bragg gratings (FBG) sensors. One of them is used to measure vibration and another one is used to measure temperature inside of the cantilever beam, while the beam is exposed to fire. The temperature in the cantilever beam increased until 150°C and a reduction in the strength of concrete can be observed through the modal analysis. A fiber Bragg grating interrogation system, based on tunable filter method, is used for the static and dynamic measurements during the experiments. That system has low cost and it is easy to assemble and maintain when compared to other available instruments.

  20. Processing of Signals from Fiber Bragg Gratings Using Unbalanced Interferometers

    Science.gov (United States)

    Adamovsky, Grigory; Juergens, Jeff; Floyd, Bertram

    2005-01-01

    Fiber Bragg gratings (FBG) have become preferred sensory structures in fiber optic sensing system. High sensitivity, embedability, and multiplexing capabilities make FBGs superior to other sensor configurations. The main feature of FBGs is that they respond in the wavelength domain with the wavelength of the returned signal as the indicator of the measured parameter. The wavelength is then converted to optical intensity by a photodetector to detect corresponding changes in intensity. This wavelength-to-intensity conversion is a crucial part in any FBG-based sensing system. Among the various types of wavelength-to-intensity converters, unbalanced interferometers are especially attractive because of their small weight and volume, lack of moving parts, easy integration, and good stability. In this paper we investigate the applicability of unbalanced interferometers to analyze signals reflected from Bragg gratings. Analytical and experimental data are presented.

  1. Andreev-Bragg Reflection from an Amperian Superconductor

    Science.gov (United States)

    Baireuther, P.; Hyart, T.; Tarasinski, B.; Beenakker, C. W. J.

    2015-08-01

    We show how an electrical measurement can detect the pairing of electrons on the same side of the Fermi surface (Amperian pairing), recently proposed by Patrick Lee for the pseudogap phase of high-Tc cuprate superconductors. Bragg scattering from the pair-density wave introduces odd multiples of 2 kF momentum shifts when an electron incident from a normal metal is Andreev reflected as a hole. These Andreev-Bragg reflections can be detected in a three-terminal device, containing a ballistic Y junction between normal leads (1, 2) and the superconductor. The cross-conductance d I1/d V2 has the opposite sign for Amperian pairing than it has either in the normal state or for the usual BCS pairing.

  2. Magneto-Optic Field Coupling in Optical Fiber Bragg Gratings

    Science.gov (United States)

    Carman, Gregory P. (Inventor); Mohanchandra, Panduranga K. (Inventor); Emmons, Michael C. (Inventor); Richards, William Lance (Inventor)

    2016-01-01

    The invention is a magneto-optic coupled magnetic sensor that comprises a standard optical fiber Bragg grating system. The system includes an optical fiber with at least one Bragg grating therein. The optical fiber has at least an inner core and a cladding that surrounds the inner core. The optical fiber is part of an optical system that includes an interrogation device that provides a light wave through the optical fiber and a system to determine the change in the index of refraction of the optical fiber. The cladding of the optical fiber comprises at least a portion of which is made up of ferromagnetic particles so that the ferromagnetic particles are subject to the light wave provided by the interrogation system. When a magnetic field is present, the ferromagnetic particles change the optical properties of the sensor directly.

  3. Localized topological states in Bragg multihelicoidal fibers with twist defects

    Science.gov (United States)

    Alexeyev, C. N.; Lapin, B. P.; Milione, G.; Yavorsky, M. A.

    2016-06-01

    We have studied the influence of a twist defect in multihelicoidal Bragg fibers on the emerging of localized defect modes. We have shown that if such a fiber is excited with a Gaussian beam this leads to the appearance of a defect-localized topological state, whose topological charge coincides with the order of rotational symmetry of the fiber's refractive index. We have shown that this effect has a pronounced crossover behavior. We have also formulated a principle of creating the systems that can nestle defect-localized topologically charged modes. According to this principle, such systems have to possess topological activity, that is, the ability to change the topological charge of the incoming field, and operate in the Bragg regime.

  4. Andreev-Bragg Reflection from an Amperian Superconductor.

    Science.gov (United States)

    Baireuther, P; Hyart, T; Tarasinski, B; Beenakker, C W J

    2015-08-28

    We show how an electrical measurement can detect the pairing of electrons on the same side of the Fermi surface (Amperian pairing), recently proposed by Patrick Lee for the pseudogap phase of high-Tc cuprate superconductors. Bragg scattering from the pair-density wave introduces odd multiples of 2k(F) momentum shifts when an electron incident from a normal metal is Andreev reflected as a hole. These Andreev-Bragg reflections can be detected in a three-terminal device, containing a ballistic Y junction between normal leads (1, 2) and the superconductor. The cross-conductance dI1/dV2 has the opposite sign for Amperian pairing than it has either in the normal state or for the usual BCS pairing.

  5. Self-aligned Coupled Waveguide Distributed Bragg Reflector Lasers

    Institute of Scientific and Technical Information of China (English)

    LIU Guoli; WANG Wei; ZHU Hongliang; ZHANG Jingyuan; HU Xiaohua; LU Yu; ZHANG Jing

    2002-01-01

    A novel self-aligned coupled waveguide (SACW) multi-quantum-well (MQW) distributed Bragg reflector (DBR) laser is proposed and demonstrated for the first time. By selectively removing the MQW layer and leaving the low SCH/SACW layer the Bragg grating is partially formed on this layer. By optimizing the thickness of the low SCH/SACW layer, a~80% coupling efficiency between the MQW gain region and the passive region are obtained. The typical threshold current of the SACW DBR laser is 39 mA, the slope efficiency can reach to 0.2 mW/mA and the output power is more than 20 mW with a more than 30dB side mode suppression ratio.

  6. Planar Bragg Grating Sensors—Fabrication and Applications: A Review

    Directory of Open Access Journals (Sweden)

    I. J. G. Sparrow

    2009-01-01

    Full Text Available We discuss the background and technology of planar Bragg grating sensors, reviewing their development and describing the latest developments. The physical operating principles are discussed, relating device operation to user requirements. Recent performance of such devices includes a planar Bragg grating sensor design which allows refractive index resolution of 1.9×10−6 RIU and temperature resolution of 0.03∘C. This sensor design is incorporated into industrialised applications allowing the sensor to be used for real time sensing in intrinsically safe, high-pressure pipelines, or for insertion probe applications such as fermentation. Initial data demonstrating the ability to identify solvents and monitor long term industrial processes is presented. A brief review of the technology used to fabricate the sensors is given along with examples of the flexibility afforded by the technique.

  7. Microwave Magneto-Optic Bragg Modulators with Rectangular MSFVW Pulses

    Institute of Scientific and Technical Information of China (English)

    Cheng-You Luo; Bao-Jian Wu; Kun Qiu

    2009-01-01

    Microwave magneto-optic (MO) modu- lators can directly transform radio frequency (RF) signals into optical data through the Bragg diffraction of guided optical waves (GOWs) induced by microwave magneto-static waves (MSWs). According to the MO coupled-mode theory, the modulation of continuous GOWs by a rectangular magneto-static-forward- volume-wave (MSFVW) pulse in MO film waveguide is studied in the small signal case and the modulated optical pulse at the output is analyzed by means of an analytical form, which is dependent on the instantaneous diffraction intensity determined by the overlap of rectangular MSFVW pulse and light beam aperture. On the basis of it, the characteristics of MSFVW-based MO modulators can be explained well for the case of rectangular pulse modulation. It is also shown that the line codes of optical data generated by MO Bragg modulators can be controlled by adjusting the duty factor of modulating pulse signals.

  8. Boron-doped superlattices and Bragg mirrors in diamond

    OpenAIRE

    Fiori, Alexandre; Bousquet, Jessica; Eon, David; Omnès, Franck; Bellet-Amalric, E.; Bustarret, Etienne

    2014-01-01

    International audience A periodic modulation of the boron doping level of single crystal diamond multilayers over more than three orders of magnitude during epitaxial growth by microwave plasma-enhanced chemical vapor deposition is shown to yield Bragg mirrors in the visible. The thicknesses and doping level of the individual layers were controlled by in situ spectroscopic ellipsometry, enabling to tune the reflec-tance peak to the wavelength range of diamond color centers, such as NV 0 or...

  9. Photonic crystal distributed feedback fiber lasers with Bragg gratings

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2000-01-01

    Two new types of optical fibers, where air-holes are running down their length, are considered for making fiber lasers with Bragg gratings. The mode areas for pump and signal in these fiber lasers may be either larger or smaller compared to the corresponding mode areas for fiber lasers based on...... standard step index fibers. This makes possible realization of fiber lasers with a low pump threshold (small mode area), and fiber lasers suitable for high-power applications (large mode area)...

  10. Moiré Fibre Bragg Grating Written on Strained Fibres

    Institute of Scientific and Technical Information of China (English)

    孙磊; 冯新焕; 刘艳格; 张伟刚; 袁树忠; 开桂云; 董孝义

    2004-01-01

    Moiré fibre Bragg gratings are made in a single mode fibre and a polarization-maintaining fibre respectively, using an excimer KrF laser and a phase mask. Two gratings are written at the same location of the optical fibre. The wavelength spacing can be finely tuned from 0 to 1.86nm by straining the optical fibre during UV illumination.

  11. DESIGN AND SIMULATION OF FIBER BRAGG GRATING BASED SENSORS

    OpenAIRE

    MOHAMED M. SALEH; RIADH K. A. Al-ANI; ILHAM K. ONEES

    2014-01-01

    In this paper the temperature and strain sensing principle of FBG based sensors are design & simulated by using Optigrating software. Simulation tools provide valuable help in optimizing the design parameters.From the graphical simulations, it can be concluded that there is a linear relationship between the Bragg wavelength shift and the temperature as well as the strain change. Also different values of grating period due to increasing the value of shifted wavelength.

  12. Highly reproducible Bragg grating acousto-ultrasonic contact transducers

    Science.gov (United States)

    Saxena, Indu Fiesler; Guzman, Narciso; Lieberman, Robert A.

    2014-09-01

    Fiber optic acousto-ultrasonic transducers offer numerous applications as embedded sensors for impact and damage detection in industrial and aerospace applications as well as non-destructive evaluation. Superficial contact transducers with a sheet of fiber optic Bragg gratings has been demonstrated for guided wave ultrasound based measurements. It is reported here that this method of measurement provides highly reproducible guided ultrasound data of the test composite component, despite the optical fiber transducers not being permanently embedded in it.

  13. Fiber Bragg Gratings Embedded in 3D-Printed Scaffolds

    CERN Document Server

    Liacouras, Peter; Choudhry, Khazar; Strouse, G F; Ahmed, Zeeshan

    2015-01-01

    In recent years there has been considerable interest in utilizing embedded fiber optic based sensors for fabricating smart materials. One of the primary motivations is to provide real-time information on the structural integrity of the material so as to enable proactive actions that prevent catastrophic failure. In this preliminary study we have examined the impact of embedding on the temperature-dependent response of fiber Bragg gratings.

  14. Bragg optics computer codes for neutron scattering instrument design

    Energy Technology Data Exchange (ETDEWEB)

    Popovici, M.; Yelon, W.B.; Berliner, R.R. [Missouri Univ. Research Reactor, Columbia, MO (United States); Stoica, A.D. [Institute of Physics and Technology of Materials, Bucharest (Romania)

    1997-09-01

    Computer codes for neutron crystal spectrometer design, optimization and experiment planning are described. Phase space distributions, linewidths and absolute intensities are calculated by matrix methods in an extension of the Cooper-Nathans resolution function formalism. For modeling the Bragg reflection on bent crystals the lamellar approximation is used. Optimization is done by satisfying conditions of focusing in scattering and in real space, and by numerically maximizing figures of merit. Examples for three-axis and two-axis spectrometers are given.

  15. Trial analysis of swine's periodontal ligament with Bragg grating sensors

    Science.gov (United States)

    Menegotto, G. F.; Grabarski, L.; Kalinowski, H. J.; Simões, J. A.

    2009-10-01

    In this work it is reported the measurement of the differential strain between the dental and bone tissues under effect of an applied load. Slices of swine mandible, containing the premolar tooth, are cut and measured in fresh condition. The strain is measured using fibre Bragg grating sensors glued to both tissues. In the measured range the results show a linear behaviour and confirm the importance of the periodontal ligament in the load transfer mechanism.

  16. Simulation of Novel Tunable Nonlinear Chirped Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-min; YU Zhong-yuan; ZHANG Xiao-guang; YU Li; YANG Bo-jun

    2003-01-01

    A novel tunable chirped fiber Bragg grating technology is proposed and simulated numerically by Matlab. If we adhere a uniform fiber grating with super magnetostrictive film and expose them in a non-uniform magnetic field, the period of the grating can be changed with the strain imposed on it by the magnetostrictive effect .The chirped characteristics can be tuned by changing the magnetic filed which is very flexible in designing.

  17. Large-momentum-transfer Bragg interferometer with strontium atoms

    CERN Document Server

    Mazzoni, T; Del Aguila, R; Salvi, L; Poli, N; Tino, G M

    2015-01-01

    We report on the first atom interferometer based on Bragg diffraction in a fountain of alkaline-earth atoms, namely $^{88}$Sr. We demonstrate large momentum transfer to the atoms up to eight photon recoils and the use of the interferometer as a gravimeter with a sensitivity $\\delta g/g=4\\times 10^{-8}$. Thanks to the special characteristics of strontium atoms for precision measurements, this result opens a new way for experiments in fundamental and applied physics.

  18. A high sensitive fiber Bragg grating cryogenic temperature sensor

    Institute of Scientific and Technical Information of China (English)

    Kuo Li; Zhen'an Zhou; Aichun Liu

    2009-01-01

    At cryogenic temperature, a fiber Bragg grating (FBG) temperature sensor with controllable sensitivity and variable measurement range is demonstrated by using bimetal configuration. In experiments, sensitivities of -51.2, -86.4, and -520 pm/K are achieved by varying the lengths of the metals. Measurement ranges of 293 - 290.5, 283 - 280.5, and 259 - 256.5 K are achieved by shortening the distance of the gap among the metals.

  19. Fiber Bragg grating pressure sensor with enhanced sensitivity

    Institute of Scientific and Technical Information of China (English)

    Wentao Zhang; Lihui Liu; Fang Li; Yuliang Liu

    2007-01-01

    @@ A novel fiber Bragg grating (FBG) pressure sensor with the enhanced sensitivity has been demonstrated. A piston-like diaphragm with a hard core in the center is used to enhance the sensitivity. Both the theoretical analysis and the experimental result show that the radius of the hard core has significant effect on the pressure sensitivity. When the radius of the hard core is 1.5 mm, a pressure sensitivity of 7.23 nm/MPa has been achieved.

  20. Fiber Bragg Grating Pressure Sensor Based on Corrugated Diaphragm

    Institute of Scientific and Technical Information of China (English)

    FU Hai-wei; FU Jun-mei; QIAO Xue-guang

    2004-01-01

    A kind of fiber Bragg grating pressure sensor based on corrugated diaphragm is proposed. The relationship between the central wavelength of reflective wave of FBG and pressure is given, and the expression of the pressure sensitivity coefficient is also given. Within the range from results agree with the theoretical analysis. It is indicated that the expected pressure sensitivity of the sensor can be obtained by optimizing the size and mechanical parameters of the corrugated diaphragm.

  1. Micro-displacement sensors based on plastic photonic bandgap Bragg fibers

    CERN Document Server

    Qu, H; Bergeron, F; Olesik, J; Skorobogatiy, M

    2013-01-01

    We demonstrate an amplitude-based micro-displacement sensor that uses a plastic photonic bandgap Bragg fiber with one end coated with a silver layer. The reflection intensity of the Bragg fiber is characterized in response to different displacements (or bending curvatures). We note that the Bragg reflector of the fiber acts as an efficient mode stripper for the wavelengths near the edge of the fiber bandgap, which makes the sensor extremely sensitive to bending or displacements at these wavelengths. Besides, by comparison of the Bragg fiber sensor to a sensor based on a regular multimode fiber with similar outer diameter and length, we find that the Bragg fiber sensor is more sensitive to bending due to presence of mode stripper in the form of the multilayer reflector. Experimental results show that the minimum detection limit of the Bragg fiber sensor can be smaller than 5 um for displacement sensing.

  2. Angles as probabilities

    CERN Document Server

    Feldman, David V

    2008-01-01

    We use a probabilistic interpretation of solid angles to generalize the well-known fact that the inner angles of a triangle sum to 180 degrees. For the 3-dimensional case, we show that the sum of the solid inner vertex angles of a tetrahedron T, divided by 2*pi, gives the probability that an orthogonal projection of T onto a random 2-plane is a triangle. More generally, it is shown that the sum of the (solid) inner vertex angles of an n-simplex S, normalized by the area of the unit (n-1)-hemisphere, gives the probability that an orthogonal projection of S onto a random hyperplane is an (n-1)-simplex. Applications to more general polytopes are treated briefly, as is the related Perles-Shephard proof of the classical Gram-Euler relations.

  3. Phase angle measurement techniques

    Energy Technology Data Exchange (ETDEWEB)

    Madge, R.; Fischer, D.

    1996-01-01

    Real-time measure of the power transfer across a transmission line was discussed. Phase angle measurement techniques, algorithms and applications relevant to power utilities were assessed. Phase-based applications compute the voltage angle difference between two stations, thereby allowing for power transfer calculations and power system control applications. A list of phase angle measurement applications was provided. It includes frequency measurement, state estimation, adaptive relaying, power system control, system restoration, real power flow monitoring and stability assessment, reactive power requirements monitoring, HVDC modulation, subsynchronous resonance, sequence of event recording, and loss reduction and fault location. The optimum timing requirement was determined for each application. Among the timing systems available today, the Global Positioning System (GPS), supported by powerful computers and other custom hardware, is the only tool that can provide the accuracy and coverage needed by today`s power system applications. Commercially available equipment for phase angle measurements was also reviewed. 30 refs., 32 tabs., 5 figs.

  4. A Method to Discriminate Strain and Temperature in Fiber Bragg Grating Sensors

    OpenAIRE

    Chalapati, Madhan T; Pattnaik, PK; Selvarajan, A; T. Srinivas

    2005-01-01

    A significant limitation to the applications of fiber Bragg gratings (FBG) sensors is the sensitivity of the Bragg wavelength to both temperature and strain, complicating the independent measurement of these paremeters. In this letter, we explore a new method to discriminate strain and temperature in FBG sensors, which utilises the additioanl wavelength dependent phase introduced by Fiber Bragg grating written on sensing arm of Mach Zehnder Interferometer (MZI). The intensity variations of th...

  5. Influence of Non-uniform Temperature Field on Spectra of Fibre Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yan; HE Xing-Fang; YUAN Jie; YIN Li-Qun; FANG Xiao-Yong; CAO Mao-Sheng

    2009-01-01

    We simulate the spectrum characteristics of fibre Bragg grating (FBG) with non-uniform temperature using the transmission matrix method, and the results are analysed. It is found that firstly the modulated coefficient of average refractive index is a very important parameter that influences the spectrum characteristic of the fibre Bragg grating, and secondly the spectrum curves are different in different temperature fields at the same parameter. Hence, we can determine the metrical temperature by analysing the spectrum of fibre Bragg grating.

  6. Fabrication of High Quality Broadband Type IIA Chirped Fiber Bragg Gratings

    Institute of Scientific and Technical Information of China (English)

    SANG Xin-zhu; YU Chong-xiu; YAN Bin-bin; MA Jian-xin; LU Nai-guang

    2006-01-01

    Chirped fiber Bragg gratings have found many applications in optical communication and sensing systems. High quality filters based on chirped fiber Bragg gratings with reflection bandwidth of 2.6 and 32nm and high reflectivity are demonstrated experimentally with 2 and 4cm long phase masks, respectively. These filters with flat reflection band and high reflectivity are achieved by writing type IIA chirped Bragg gratings.

  7. Bragg scattering as a probe of atomic wave functions and quantum phase transitions in optical lattices.

    Science.gov (United States)

    Miyake, Hirokazu; Siviloglou, Georgios A; Puentes, Graciana; Pritchard, David E; Ketterle, Wolfgang; Weld, David M

    2011-10-21

    We have observed Bragg scattering of photons from quantum degenerate ^{87}Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wave function whose position and momentum width is Heisenberg limited. The spatial coherence of the wave function leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence. PMID:22107532

  8. Spectral characteristics of draw-tower step-chirped fiber Bragg gratings

    Science.gov (United States)

    Idrisov, Ravil F.; Varzhel, Sergey V.; Kulikov, Andrey V.; Meshkovskiy, Igor K.; Rothhardt, Manfred; Becker, Martin; Schuster, Kay; Bartelt, Hartmut

    2016-06-01

    This paper presents research results on the spectral properties of step-chirped fiber Bragg grating arrays written during the fiber drawing process into a birefringent optical fiber with an elliptical stress cladding. The dependences of resonance shift of the step-chirped fiber Bragg grating on bending, on applied tensile stress and on temperature have been investigated. A usage of such step-chirped fiber Bragg gratings in fiber-optic sensing elements creation has been considered.

  9. Electric field dependent Electroreflectance of GaAs/AlGaAs multiple quantum well Bragg structure at second quantum state

    Science.gov (United States)

    Nakarmi, Mim; Shakya, Naresh; Chaldyshev, Vladimir

    Electroreflectance Spectroscopy was employed to study the effect of electric field on the excitonic transitions in a GaAs/AlGaAs multiple quantum well (MQW) Bragg structure. The sample used in this experiment consists of 60 periods of quantum well structures with GaAs well layer (~13 nm) and AlGaAs barrier layer (~94 nm), grown by molecular beam expitaxy on a semi-insulating GaAs substrate. The sample structure was designed to coincide the Bragg resonance peak with the x(e2-hh2) exciton transitions. We observed a significant enhancement of excitonic feature around the x(e2-hh2) exciton transition due to the double resonance along with the sharp features of x(e1-hh1) and x(e1-lh1) ground state exciton transitions by tuning the angle of incidence of the light. We will present the results on electric field dependent electroreflectance measurements of this structure and discuss the effect of electric field on the first and second energy states.

  10. Measurement of fragment production DDX of 72 and 144 MeV 12C beam induced reaction on carbon using Bragg Curve Counter

    International Nuclear Information System (INIS)

    Double differential cross section (DDX) data of fragment production for 72 (6 MeV/nucleon) and 144 MeV (12 MeV/nucleon) 12C beam induced reaction on carbon were measured using a Bragg Curve Counter (BCC). The DDX data were obtained for fragments of He, Li, Be, B, C, N and O at 30 degree emission angle. Theoretical calculation using PHITS code with QMD+GEM model represents the DDX well except for components from reactions of direct process and α particle clustering process. (author)

  11. Study of the magnetic order in a Co/Cr multilayer by magnetic Bragg diffraction at the Co 2p resonance

    Energy Technology Data Exchange (ETDEWEB)

    Mirone, Alessandro E-mail: mirone@lure.u-psud.fr; Sacchi, Maurizio; Dudzik, Esther; Duerr, Hermann; Laan, Gerrit van der; Vaures, Annie; Petroff, Frederic

    2000-08-01

    We have measured the resonant scattering from an antiferromagnetic Co/Cr multilayer at photon energies close to the cobalt 2p{yields}3d transitions. The cobalt dielectric tensor has an anisotropic component, enhanced by resonance, which depends on the magnetic order and follows its modulation inside the sample. We have studied the vertical distribution of this component through the dependence of the reflectivity on the scattering angle. Using s-polarized light, we have observed the signature of the cobalt-cobalt antiferromagnetic coupling as an half-integer-order Bragg peak. Experimental results have been analyzed by numerical simulation.

  12. Characteristics of AlN/GaN nanowire Bragg mirror grown on (001) silicon by molecular beam epitaxy

    KAUST Repository

    Heo, Junseok

    2013-10-01

    GaN nanowires containing AlN/GaN distributed Bragg reflector (DBR) heterostructures have been grown on (001) silicon substrate by molecular beam epitaxy. A peak reflectance of 70% with normal incidence at 560 nm is derived from angle resolved reflectance measurements on the as-grown nanowire DBR array. The measured peak reflectance wavelength is significantly blue-shifted from the ideal calculated value. The discrepancy is explained by investigating the reflectance of the nanoscale DBRs with a finite difference time domain technique. Ensemble nanowire microcavities with In0.3Ga 0.7N nanowires clad by AlN/GaN DBRs have also been characterized. Room temperature emission from the microcavity exhibits considerable linewidth narrowing compared to that measured for unclad In0.3Ga0.7N nanowires. The resonant emission is characterized by a peak wavelength and linewidth of 575 nm and 39 nm, respectively. © 2013 AIP Publishing LLC.

  13. A Soft X-ray Beam-splitting Multilayer Optic for the NASA GEMS Bragg Reflection Polarimeter

    CERN Document Server

    Allured, Ryan; Soufli, Regina; Alameda, Jennifer B; Pivovaroff, Michael J; Gullikson, Eric M; Kaaret, Philip

    2013-01-01

    A soft X-ray, beam-splitting, multilayer optic has been developed for the Bragg Reflection Polarimeter (BRP) on the NASA Gravity and Extreme Magnetism Small Explorer Mission (GEMS). The optic is designed to reflect 0.5 keV X-rays through a 90 degree angle to the BRP detector, and transmit 2-10 keV X-rays to the primary polarimeter. The transmission requirement prevents the use of a thick substrate, so a 2 micron thick polyimide membrane was used. Atomic force microscopy has shown the membrane to possess high spatial frequency roughness less than 0.2 nm rms, permitting adequate X-ray reflectance. A multilayer thin film was especially developed and deposited via magnetron sputtering with reflectance and transmission properties that satisfy the BRP requirements and with near-zero stress. Reflectance and transmission measurements of BRP prototype elements closely match theoretical predictions, both before and after rigorous environmental testing.

  14. Angles in hyperbolic lattices

    DEFF Research Database (Denmark)

    Södergren, Carl Anders; Risager, Morten S.

    2015-01-01

    It is well known that the angles in a lattice acting on hyperbolic n -space become equidistributed. In this paper we determine a formula for the pair correlation density for angles in such hyperbolic lattices. Using this formula we determine, among other things, the asymptotic behavior...... of the density function in both the small and large variable limits. This extends earlier results by Boca, Pasol, Popa and Zaharescu and Kelmer and Kontorovich in dimension 2 to general dimension n . Our proofs use the decay of matrix coefficients together with a number of careful estimates, and lead...

  15. OPTIMIZATION OF INTRAGRATING SENSING USING FIBER BRAGG GRATING

    OpenAIRE

    B.B.PADHY; HAFTAY ABADI GEBRU; SANDIPAN M.NALAWADE

    2011-01-01

    Linearly Chirped Fiber Bragg Gratings (FBGs) have been optimized and investigated for intragrating sensing. The side lobes have been suppressed using Gaussian apodization while maintaining the peak reflectivity and the bandwidth of the reflected signal. We have achieved a chirp rate of 0.5 to 2 nm/mm for intragrating sensing.Average thermal sensitivity of 11.55 pm/ oC is obtained which is higher than uniform FBGs. We have achieved novel characteristics of linearly chirped FBGs under the effec...

  16. OPTIMIZATION OF INTRAGRATING SENSING USING FIBER BRAGG GRATING

    Directory of Open Access Journals (Sweden)

    B.B.PADHY

    2011-01-01

    Full Text Available Linearly Chirped Fiber Bragg Gratings (FBGs have been optimized and investigated for intragrating sensing. The side lobes have been suppressed using Gaussian apodization while maintaining the peak reflectivity and the bandwidth of the reflected signal. We have achieved a chirp rate of 0.5 to 2 nm/mm for intragrating sensing.Average thermal sensitivity of 11.55 pm/ oC is obtained which is higher than uniform FBGs. We have achieved novel characteristics of linearly chirped FBGs under the effect of non-monotonic physical parameter distribution fields for excellent spectral response profile for intragrating sensing.

  17. On-Chip Silicon Waveguide Bragg Grating Photonic Temperature Sensor

    CERN Document Server

    Klimov, Nikolai N; Berger, Michaela; Ahmed, Zeeshan

    2015-01-01

    Resistance thermometry is a time-tested method for taking temperature measurements. In recent years fundamental limits to resistance-based approaches spurred considerable interest in developing photonic temperature sensors as a viable alternative. In this study we demonstrate that our photonic thermometer, which consists of a silicon waveguide integrated with a Bragg grating, can be used to measure temperature changes over the range from 5 C to 160 C with a combined expanded uncertainty [k = 2 ; 95% confidence level] of 1.25 degree C. The computational modeling of the sensor predicts the resonance wavelength and effective refractive index within 4% of the measured value.

  18. Bragg x-ray survey spectrometer for ITER.

    Science.gov (United States)

    Varshney, S K; Barnsley, R; O'Mullane, M G; Jakhar, S

    2012-10-01

    Several potential impurity ions in the ITER plasmas will lead to loss of confined energy through line and continuum emission. For real time monitoring of impurities, a seven channel Bragg x-ray spectrometer (XRCS survey) is considered. This paper presents design and analysis of the spectrometer, including x-ray tracing by the Shadow-XOP code, sensitivity calculations for reference H-mode plasma and neutronics assessment. The XRCS survey performance analysis shows that the ITER measurement requirements of impurity monitoring in 10 ms integration time at the minimum levels for low-Z to high-Z impurity ions can largely be met.

  19. Humidity insensitive TOPAS polymer fiber Bragg grating sensor

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Khan, Lutul; Webb, David J.;

    2011-01-01

    We report the first experimental demonstration of a humidity insensitive polymer optical fiber Bragg grating (FBG), as well as the first FBG recorded in a TOPAS polymer optical fiber in the important low loss 850nm spectral region. For the demonstration we have fabricated FBGs with resonance...... wavelength around 850 nm and 1550 nm in single-mode microstructured polymer optical fibers made of TOPAS and the conventional poly (methyl methacrylate) (PMMA). Characterization of the FBGs shows that the TOPAS FBG is more than 50 times less sensitive to humidity than the conventional PMMA FBG in both...

  20. Bragg-Berry mirrors: reflective broadband q-plates.

    Science.gov (United States)

    Rafayelyan, Mushegh; Brasselet, Etienne

    2016-09-01

    We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and, consequently, foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies. PMID:27607950

  1. Microfiber-Based Bragg Gratings for Sensing Applications: A Review

    Directory of Open Access Journals (Sweden)

    Jun-Long Kou

    2012-06-01

    Full Text Available Microfiber-based Bragg gratings (MFBGs are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI, temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated.

  2. Structural Health Monitoring of Bridges with Fiber Bragg Grating Sensors

    Directory of Open Access Journals (Sweden)

    Francisco Navarro-Henríquez

    2014-11-01

    Systems with fiber optic sensors FBG (Fiber Bragg Grating are consolidated in the Structural Health Monitoring (SMH of bridges, Nondestructive Testing (NDT static and dynamic measurements of deformation, displacement, deflection, temperature and vibration. This article provides a brief introduction to the technology and the fundamentals of fiber optic sensors, also present comparative advantages over its traditional counterpart is presented. Their characteristics are described and measurement graphics are presented as an application example of the FBG sensors. Finally, some key aspects to consider for proper use in the field are mentioned.

  3. Bragg x-ray survey spectrometer for ITER

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, S. K.; Jakhar, S. [ITER-India, Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India); Barnsley, R. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); O' Mullane, M. G. [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2012-10-15

    Several potential impurity ions in the ITER plasmas will lead to loss of confined energy through line and continuum emission. For real time monitoring of impurities, a seven channel Bragg x-ray spectrometer (XRCS survey) is considered. This paper presents design and analysis of the spectrometer, including x-ray tracing by the Shadow-XOP code, sensitivity calculations for reference H-mode plasma and neutronics assessment. The XRCS survey performance analysis shows that the ITER measurement requirements of impurity monitoring in 10 ms integration time at the minimum levels for low-Z to high-Z impurity ions can largely be met.

  4. Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

    Institute of Scientific and Technical Information of China (English)

    LI Lin; LI Yong-da; LIU Wen-li; LU Bin; JU Guo-xian; ZHANG Yong-ming; HAO Yong-qin; SU Wei; ZHONG Jing-chang

    2004-01-01

    Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.

  5. Ultrafast laser inscribed fiber Bragg gratings for sensing applications

    Science.gov (United States)

    Mihailov, Stephen J.

    2016-05-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on femtosecond infrared laser-material processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This tutorial paper will present a review of some of the more recent developments.

  6. Application of the Transmission Bragg Gratings for Vibration Monitoring

    CERN Document Server

    Tikhonov, E A

    2010-01-01

    It is shown that the optical-electronic system consisted of the transmission Bragg grating, a laser and the intermediate sensitive to the vibrations mirror can detect the vibrations, when touched by them laser beam scan will exceed the angular divergence of the beam. The mathematical model of the sensor of the vibrations presented in the form of Taylor series describes the system response taking into account the operating point, in particular, describes the effect of the doubling of the modulation frequency response relative to the frequency of acting vibrations.

  7. Underwater Acoustic Sensors Based on Fiber Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Giuseppe Parente

    2009-06-01

    Full Text Available We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating.

  8. Supercontinuum generation in a Bragg fiber:a novel proposal

    Institute of Scientific and Technical Information of China (English)

    Bishnu P.Pal; Sonali Dasgupta; M.R.Shenoy; Alexej Sysoliatin

    2006-01-01

    @@ We propose a silica-core dispersion-decreasing Bragg fiber (DDBF) of mode effective area as large as 55 μm2 for supercontinuum (SC) generation at the pump wavelength of 1 060 nm.Using a fast and simple matrix method to model propagation in the DDBF,we have presented a general criterion to obtain the shortest length of the DDBF that would result in a broad SC spectrum.The proposed DDBF design should be amenable for reproducible fabrication through the well-developed MCVD fiber manufacturing technology and the concept has potential for realization as a practical device.

  9. Bragg-Berry mirrors: reflective broadband q-plates

    CERN Document Server

    Rafayelyan, Mushegh

    2016-01-01

    We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and consequently foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies.

  10. Dynamic gate algorithm for multimode fiber Bragg grating sensor systems.

    Science.gov (United States)

    Ganziy, D; Jespersen, O; Woyessa, G; Rose, B; Bang, O

    2015-06-20

    We propose a novel dynamic gate algorithm (DGA) for precise and accurate peak detection. The algorithm uses a threshold-determined detection window and center of gravity algorithm with bias compensation. We analyze the wavelength fit resolution of the DGA for different values of the signal-to-noise ratio and different peak shapes. Our simulations and experiments demonstrate that the DGA method is fast and robust with better stability and accuracy than conventional algorithms. This makes it very attractive for future implementation in sensing systems, especially based on multimode fiber Bragg gratings. PMID:26193010

  11. The quadriceps angle

    DEFF Research Database (Denmark)

    Miles, James Edward; Frederiksen, Jane V.; Jensen, Bente Rona;

    2012-01-01

    : Pelvic limbs from red foxes (Vulpes vulpes). METHODS: Q angles were measured on hip dysplasia (HD) and whole limb (WL) view radiographs of each limb between the acetabular rim, mid-point (Q1: patellar center, Q2: femoral trochlea), and tibial tuberosity. Errors of 0.5-2.0 mm at measurement landmarks...

  12. Dynamic strain measurement of hydraulic system pipeline using fibre Bragg grating sensors

    Directory of Open Access Journals (Sweden)

    Qiang Wang

    2016-04-01

    Full Text Available Fatigue failure is a serious problem in hydraulic piping systems installed in the machinery and equipment working in harsh operational conditions. To alleviate this problem, health monitoring of pipes can be conducted by measuring and analysing vibration-induced strain. Fibre Bragg grating is considered as a promising sensing approach for dynamic load monitoring. In this article, dynamic strain measurements based on fibre Bragg grating sensors for small-bore metal pipes have been investigated. The quasi-distributed strain sensing of fibre Bragg grating sensors is introduced. Two comparison experiments were carried out under vibration and impact loads among the methods of electrical strain gauge, piezoelectric accelerometer and fibre Bragg grating sensor. Experimental results indicate that fibre Bragg grating sensor possesses an outstanding ability to resist electromagnetic interference compared with strain gauge. The natural frequency measurement results, captured by fibre Bragg grating sensor, agree well with the modal analysis results obtained from finite element analysis. In addition, the attached fibre Bragg grating sensor brings a smaller impact on the dynamic characteristics of the measured pipe than the accelerometer due to its small size and lightweight. Fibre Bragg grating sensors have great potential for the quasi-distributed measurement of dynamic strain for the dynamic characteristic research and health monitoring of hydraulic system pipeline.

  13. Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

    OpenAIRE

    Zheng WenJun; Fei GuangTao; Wang Biao; Zhang Li

    2009-01-01

    Abstract We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR) using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature.

  14. Numerical Simulation of Bragg Reflection Based on Linear Waves Propagation over A Series of Rectangular Seabed

    Institute of Scientific and Technical Information of China (English)

    Chih-Chung WEN; Li-Hung TSAI

    2008-01-01

    A numerical model, Evolution Equation of Mild-Slope Equation (EEMSE) developed by Hsu et al. (2003), was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters of the Bragg reflection including the peak coefficient of primary Bragg reflection, its corresponding relative wavelength, and the bandwidth, have shown to be effective in describing the characteristics of the primary Bragg reflection. The characteristics of the Bragg reflection were investigated under the various conditions comprising number, height, and spacing interval of a series of rectangular seabed. The results reveal that the peak of Bragg reflection increases with the increase of rectangular seabed height and number, the bandwidth and the shift value of the Bragg reflection depend on the increase of the rectangular seabed height as well as the decrease of rectangular seabed number, and the relative rectangular seabed spacing in the rang of 3 and 4 could produce higher Bragg reflection. Finally, a correlative and regressive analysis is performed by use of the calculated data. Based on the results of the analysis, empirical equations were established. Our study results can provide an appropriate choice of a series of rectangular seabed field for a practical design.

  15. Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

    Directory of Open Access Journals (Sweden)

    Zheng WenJun

    2009-01-01

    Full Text Available Abstract We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature.

  16. Simultaneous demodulation of polarization mode coupling and fiber Bragg grating within a polarization maintaining fiber

    Science.gov (United States)

    Zhao, Yanshuang; Liu, Yanlei; Zhang, Jianzhong; Yang, Jun; Canning, John; Peng, G. D.; Chen, Yujin; Yuan, Libo

    2015-09-01

    We propose a simultaneous demodulation scheme of polarization mode coupling and fiber Bragg grating in a polarization maintaining fiber based on a white light interferometer. A polarization maintaining fiber with two inscribed fiber Bragg gratings is used to demonstrate the feasibility.

  17. Embedding silica and polymer fibre Bragg gratings (FBG) in plastic 3D-printed sensing patches

    DEFF Research Database (Denmark)

    Zubel, Michal G.; Sugden, Kate; Webb, David J.;

    2016-01-01

    This paper reports the first demonstration of a silica fibre Bragg grating (SOFBG) embedded in an FDM 3-D printed housing to yield a dual grating temperature-compensated strain sensor. We also report the first ever integration of polymer fibre Bragg grating (POFBG) within a 3-D printed sensing...

  18. Optical Properties of High Sensitivity Fiber Bragg Grating on Temperature Sensor

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper, the spectrum shift properties of the center reflection wavelength detected to be based on the FBG sensor with ambient temperature change. The basic theoretical methods and numerical simulation for the spectral properties of uniform Bragg grating is analyzed by using coupling mode theory which is optical properties of high sensitivity fiber Bragg grating on temperature sensor in accordance with experiment.

  19. Discourse on the Characterization of Waveguide Distributed Bragg Reflectors for Application to Nonlinear Optics

    Science.gov (United States)

    Grieco, Andrew Lewis

    Precise characterization of waveguide parameters is necessary for the successful design of nonlinear photonic devices. This dissertation contains a description of methods for the experimental characterization of distributed Bragg reflectors for use in nonlinear optics and other applications. The general coupled-mode theory of Bragg reflection arising from a periodic dielectric perturbation is developed from Maxwell's equations. This theory is then applied to develop a method of characterizing the fundamental parameters that describe Bragg reflection by comparing the spectral response of Bragg reflector resonators. This method is also extended to characterize linear loss in waveguides. A model of nonlinear effects in Bragg reflector resonators manifesting in bistability is also developed, as this phenomenon can be detrimental to the characterization method. Specific recommendations are made regarding waveguide fabrication and experimental design to reduce sources of experimental error.

  20. Multilayer Bragg Fresnel zone plate for coherent HHG radiation

    Energy Technology Data Exchange (ETDEWEB)

    Spaeth, Christian; Schmidt, Juergen [Fakultaet fuer Physik, Ludwig Maximilians Universitaet Muenchen, Garching (Germany); Hofstetter, Michael [Max Planck Institut fuer Quantenoptik, Garching (Germany); Krausz, Ferenc; Kleineberg, Ulf [Fakultaet fuer Physik, Ludwig Maximilians Universitaet Muenchen, Garching (Germany); Max Planck Institut fuer Quantenoptik, Garching (Germany)

    2010-07-01

    Coherent diffractive imaging in the (soft) X-ray regime is an emerging new lens-less X-ray microscopy technique with the future potential of molecular or even atomic resolution, because it is ultimately limited by the wavelength of the illuminating radiation and not by the imaging quality of the X-ray lens. However, this technique depends on the availability of coherent x-ray sources as well as optics for spectral filtering and focusing. We describe the development fabrication and testing of a reflective multilayer Bragg Fresnel phase zone plate for focusing coherent XUV radiation at 13 nm wavelength from a High Harmonic Generation source. This X-ray optical device serves for spectral filtering as well as sub-micron focusing of the HH spectrum in a single element for largely reduced losses. Large zone plate structures (conventional, spiral) matching the HH beam size are recorded by e-beam lithography in ultrathin HSQ e-beam resist and over-coated with a reflective Mo/Si multilayer by ion beam deposition. By accurately matching the groove depth of the diffractive structure to odd multiples of the quarter Bragg wavelength, the total diffraction efficiency can be improved by a factor of 4 theoretically compared to amplitude structures.

  1. A simple Bragg detector design for AMS and IBA applications

    Energy Technology Data Exchange (ETDEWEB)

    Müller, Arnold Milenko; Döbeli, Max; Seiler, Martin; Synal, Hans-Arno

    2015-08-01

    A new compact Bragg type gas ionization chamber (GIC) has been built for use as particle counter in AMS and IBA applications. The detector stands out due to its simple concept, which does not include a Frisch grid. Test experiments have been performed with ions in the mass range from He to Th and energies ranging from 30 keV to 2.5 MeV, in order to find optimal measurement conditions and to characterize the detector performance. For projectiles heavier than Al at energies below 2.5 MeV the obtained energy resolution is comparable with that of a state-of-the-art GIC with Frisch grid and clearly outperforms solid state detectors. Additionally the operation of this simplified Bragg GIC in the electron multiplication mode was investigated for the first time, which allows the detection of radiocarbon ions at energies below 50 keV with an energy resolution of the order of 10 keV.

  2. Muscular condition monitoring system using fiber bragg grating sensors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Heon Young; Lee, Jin Hyuk; Kim, Dae Hyun [Seoul National University of Technology, Seoul (Korea, Republic of)

    2014-10-15

    Fiber optic sensors (FOS) have advantages such as electromagnetic interference (EMI) immunity, corrosion resistance and multiplexing capability. For these reasons, they are widely used in various condition monitoring systems (CMS). This study investigated a muscular condition monitoring system using fiber optic sensors (FOS). Generally, sensors for monitoring the condition of the human body are based on electro-magnetic devices. However, such an electrical system has several weaknesses, including the potential for electro-magnetic interference and distortion. Fiber Bragg grating (FBG) sensors overcome these weaknesses, along with simplifying the devices and increasing user convenience. To measure the level of muscle contraction and relaxation, which indicates the muscle condition, a belt-shaped FBG sensor module that makes it possible to monitor the movement of muscles in the radial and circumferential directions was fabricated in this study. In addition, a uniaxial tensile test was carried out in order to evaluate the applicability of this FBG sensor module. Based on the experimental results, a relationship was observed between the tensile stress and Bragg wavelength of the FBG sensors, which revealed the possibility of fabricating a muscular condition monitoring system based on FBG sensors.

  3. Self-consistent electrodynamic scattering in the symmetric Bragg case

    International Nuclear Information System (INIS)

    We have analyzed the symmetric Bragg case, introducing a model of self consistent scattering for two elliptically polarized beams. The crystal is taken as a set of mathematical planes, each of them defined by a surface density of dipoles. We have considered the mesofield and the epifield differently from that of the Ewald's theory and, we assumed a plane of dipoles and the associated fields as a self consistent scattering unit. The exact analytical treatment when applied to any two neighbouring planes, results in a general and self consistent Bragg's equation, in terms of the amplitude and phase variations. The generalized solution for the set of N planes was obtained after introducing an absorption factor in the incident radiation, in two ways: (i) the analytical one, through a rule of field similarity, which says that the incidence occurs in both faces of the all crystal planes and also, through a matricial development with the Chebyshev polynomials; (ii) using the numerical solution we calculated, iteratively, the reflectivity, the reflection phase, the transmissivity, the transmission phase and the energy. The results are showed through reflection and transmission curves, which are characteristics as from kinematical as dynamical theories. The conservation of the energy results from the Ewald's self consistency principle is used. In the absorption case, the results show that it is not the only cause for the asymmetric form in the reflection curves. The model contains basic elements for a unified, microscope, self consistent, vectorial and exact formulation for interpretating the X ray diffraction in perfect crystals. (author)

  4. The lateral angle revisited

    DEFF Research Database (Denmark)

    Morgan, Jeannie; Lynnerup, Niels; Hoppa, R.D.

    2013-01-01

    measurements taken from computed tomography (CT) scans. Previous reports have observed that the lateral angle size in females is significantly larger than in males. The method was applied to an independent series of 77 postmortem CT scans (42 males, 35 females) to validate its accuracy and reliability...... method appears to be of minimal practical use in forensic anthropology and archeology. © 2013 American Academy of Forensic Sciences....

  5. Why are angles misperceived?

    OpenAIRE

    Nundy, Surajit; Lotto, Beau; Coppola, David; Shimpi, Amita; Purves, Dale

    2000-01-01

    Although it has long been apparent that observers tend to overestimate the magnitude of acute angles and underestimate obtuse ones, there is no consensus about why such distortions are seen. Geometrical modeling combined with psychophysical testing of human subjects indicates that these misperceptions are the result of an empirical strategy that resolves the inherent ambiguity of angular stimuli by generating percepts of the past significance of the stimulus rather than the geometry of its re...

  6. Cerebellopontine angle Hodgkin's disease

    International Nuclear Information System (INIS)

    Intracranial Hodgkin's disease is a rare site of involvement, and even more rare is its presentation as a cerebellopontine angle mass. It can be difficult to diagnose especially when recurrent tumors occur because both CT and lumbar puncture have been shown to have a relatively low yield. Gadolinium-enhanced MRI is more sensitive. It is concluded that while the imaging findings can be non-specific, the rapid response to therapy (steroids) may provide a clue to diagnosis. Copyright (1999) Blackwell Science Pty Ltd

  7. Critical angle laser refractometer

    International Nuclear Information System (INIS)

    A simple laser refractometer based on the detection of the critical angle for liquids is presented. The calibrated refractometer presents up to 0.000 11 of uncertainty when the refractive index is in the range between 1.300 00 and 1.340 00. The experimental setup is easy to construct and the material needed is available at most optics laboratories. The calibration method is simple and can be used in other devices. The refractive index measurements in aqueous solutions of sodium chloride were carried out to test the device and a linear dependence between the refractive index and the salt concentration was found

  8. Microwave Bragg-scattering zone-axis-pattern analysis

    CERN Document Server

    Fraundorf, P; Garver, W; Freeman, M; Proctor, D

    2013-01-01

    Louis deBroglie's connection between momentum and spatial-frequency vectors is perhaps most viscerally-experienced via the real-time access that electron-diffraction provides to transverse slices of a crystal's reciprocal lattice. The classic introductory (and/or advanced) physics lab-experiment on microwave Bragg-scattering can with a bit of re-arrangement also give students access to "zone-axis-pattern" slices through the 3D spatial-frequency (i.e. reciprocal) lattice of a ball-bearing crystal. In this paper we show how data from the standard experimental set up can be used to generate zone-axis-patterns oriented down the crystal rotation-axis. This may be used to give students direct experience with crystal shape-transforms (which help to explain anomalous peaks), as well as to the complementary relation between non-Cartesian basis-vectors in direct and reciprocal (co-vector) space.

  9. Wavefront distortion optimized with volume Bragg gratings in photothermorefractive glass.

    Science.gov (United States)

    Gao, Fan; Zhang, Xiang; Sun, Xiaojie; Yuan, Xiao

    2016-03-15

    The wavefront characteristics in 2D angular filtering on the basis of two orthogonal transmitting volume Bragg gratings (VBGs) is presented. The experimental results show that middle-high frequency wavefront distortions are efficiently suppressed with VBGs. The peak-valley value of the beam at a wavelength of 1053 nm reduces from 2.075λ to 0.209λ, and the root mean square value reduces from 0.207λ to 0.041λ. The wavefront power spectrum density shows that the wavefront distribution of the beam in medium and high frequencies is corrected by the VBGs. Additionally, the far-field distribution and focusing properties of the beam are improved. The beam Strehl ratio increases from 0.43 to 0.96, and the encircled energy improves from 95% energy at 4.01 mrad to 95% energy at 1.26 mrad. PMID:26977639

  10. Fiber Bragg grating demodulation through innovative numerical procedures

    Science.gov (United States)

    Dinardo, Giuseppe; Vacca, Gaetano

    2016-01-01

    The aim of this article is to introduce an innovative algorithm for the calculation of the shift of the maximum reflectivity wavelength of a Fiber Bragg Grating experiencing an applied strain. An accurate and precise evaluation of the FBG spectrum displacement is crucial for determining the amount of the physical quantity inducing such perturbations. The proposed method is based on the Fast Fourier Transform based Cross Correlation function. Such method is compared to Least Squares Fitting (LSF) and the centroid algorithms, pointing out remarkable improvements in accuracy, precision, and time consumption performance. In addition, a further improvement of the proposed algorithm is introduced. It consists in an iteratively performed Cross Correlation algorithm. It has been proved that such improvement leads to estimations characterized by better accuracy and precision, thanks also to a considerable reduction of the peak-locking effect due to the FBG spectral resolution.

  11. Bragg diffraction and the Iron crust of Neutron Stars

    CERN Document Server

    Llanes-Estrada, Felipe J

    2009-01-01

    If neutron stars have a thin atomic crystalline-iron crust, they must diffract X-rays of appropriate wavelength. So that the diffracted beam is visible from Earth, the illuminating source must be very intense and near the reflecting star. An example is a binary system with two neutron stars, one of them inert, the other an X-ray pulsar, in close orbit. The observable to be searched for is a secondary peak added (quasi-) periodically to the main X-ray pulse. The distinguishing feature of this secondary is that it appears at wavelengths related by simple integer numbers, lambda, lambda/2, lambda/3... lambda/n because of Bragg's diffraction law.

  12. A fast response temperature sensor based on fiber Bragg grating

    International Nuclear Information System (INIS)

    Aimed at the requirement for a fast-response expendable ocean temperature sensor, this paper presents a new design scheme for an optic fiber sensor. Ocean temperature sensors require high sensitivity and high response speed, which must be up to milliseconds. The fiber Bragg grating (FBG) temperature sensor with high sensitivity has been declared in the last decade, but its response speed has been rarely reported. In this paper, a method is proposed which is to package an FBG with a metal tube. The response time of this sensor is 48.6 ms, which is an order of magnitude greater than that of an ordinary optical fiber temperature sensor. Temperature sensitivity is 27.6 pm/°C and the linearity is up to 0.9999. In addition, the sensor can be less than 15 mm. It offers a new way to detect ocean temperature. (paper)

  13. Open pit slope deformation monitoring by fiber Bragg grating sensors

    Science.gov (United States)

    Xu, Guoquan; Xiong, Daiyu; Duan, Yun; Cao, Xiaoshuang

    2015-01-01

    With microstrain resolution and the capability to sample at rates of 2000 Hz or higher, fiber Bragg grating (FBG) strain sensor offers exciting new possibilities for in situ deformation monitoring induced by blasting load in an open pit slope. Here, we are developing a new technology for measuring deformation in real time on the microstrain in an open pit slope during the blasting. A fiber optically instrumented rock mass strain sensor measured strain at 100-cm intervals along a two anchor rock bolt grouted in the slope intact rock mass. In field testing, a number of transient signals have been observed, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new insight into the slope stability and blasting cumulative effects. Therefore, FBG sensors are a useful tool for measuring in situ strain in intact rock masses.

  14. A Magnetostrictive Composite-Fiber Bragg Grating Sensor

    Science.gov (United States)

    Quintero, Sully M. M.; Braga, Arthur M. B.; Weber, Hans I.; Bruno, Antonio C.; Araújo, Jefferson F. D. F.

    2010-01-01

    This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor. PMID:22163644

  15. A Magnetostrictive Composite-Fiber Bragg Grating Sensor

    Directory of Open Access Journals (Sweden)

    Jefferson F. D. F. Araújo

    2010-08-01

    Full Text Available This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 µm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor

  16. Dynamic and static strain gauge using superimposed fiber Bragg gratings

    International Nuclear Information System (INIS)

    This paper demonstrates a simple and fast interrogation method for the dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to decrease nonequidistant space of generated a sensing pulse train in a time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A four times increase in the interrogation speed of dynamic strain, by generating a 2 kHz optical sensing pulse train from a 500 Hz scanning frequency, is demonstrated experimentally. The interrogation uncertainty and total harmonic distortion characterization of superimposed FBGs are tested and less than 4 pm standard deviation is obtained. (paper)

  17. Femtosecond soliton diode on heterojunction Bragg-grating structure

    CERN Document Server

    Deng, Zhigui; Li, Hongji; Fu, Shenhe; Liu, Yikun; Xiang, Ying; Li, Yongyao

    2016-01-01

    We numerically propose a scheme for realizing an all-optical femtosecond soliton diode based on a tailored heterojunction Bragg grating, which is designed by two spatially asymmetric chirped cholesteric liquid crystals. Our simulations demonstrate that with the consideration of optical nonlinearity, not only the femtosecond diode effect with nonreciprocal transmission ratio up to 120 can be achieved, but also the optical pulse evolving into soliton which maintains its shape during propagation through the sample is observed. Further, the influence of pulse width and the carrier wavelength to the femtosecond diode effect is also discussed in detail. Our demonstrations might suggest a new direction for experimentally realizing the femtosecond soliton diode based on the cholesteric liquid crystals.

  18. Remote (250 km Fiber Bragg Grating Multiplexing System

    Directory of Open Access Journals (Sweden)

    Manuel Lopez-Amo

    2011-09-01

    Full Text Available We propose and demonstrate two ultra-long range fiber Bragg grating (FBG sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system.

  19. Fiber Bragg grating (FBG) sensors used in coal mines

    Science.gov (United States)

    Wang, Jinyu; Liu, Tongyu; Song, Guangdong; Xie, Hongjing; Li, Lianqing; Deng, Xiaolin; Gong, Zhijie

    2014-06-01

    The fiber Bragg grating (FBG) strain sensors were used for on-line monitoring of the stress variation of the lined wall in the gateway retained along the goaf of No. 3203 coal mining face in Dongtan Mine. The results showed that the FBG strain sensor with the wide measuring range could measure the stress variation accurately during the support process of the gateway retained along the goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect the micro-seismic signal. The signals were well received and analyzed to determine the location and energy level of the source of the micro-seismic event warning. The FBG sensors and detecting system show a significant potential for micro-seismic detection and geological disasters detection.

  20. Compact Single-Mode Distributed Bragg Reflector Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    XUE Yi-Yuan; AN Hong-Lin; FU Li-Bin; LIN Xiang-Zhi; LIU Hong-Du

    2000-01-01

    A compact single-mode distributed Bragg reflector (DBR) fiber laser with narrow spectral linewidth is investigated. Firstly, based on our theoretical analysis the single longitudinal mode operation domain is obtained. Then, a single-mode DBR fiber laser of 7.9cm long with master oscillator power amplifier (MOPA) configuration is designed and constructed to operate in the single-mode domain. The fiber laser is pumped by a semiconductor laser at 975.5nm. The master oscillator operates at 1556.91 nm with a cw output power of 1.43mW for a pump power of 55.35 mW. Its slope efficiency is 2.7% and the spectral linewidth is less than 1.2MHz (instrument resolution limited). With the MOPA configuration the laser output power and slope efficiency are increased to 7.8mW and 16.9%, respectively.

  1. Direct UV-written planar Bragg grating sensors

    International Nuclear Information System (INIS)

    Integrated photonics is a proven platform for physical and chemical sensing. It offers miniaturised solutions that are suited for use in extreme environments, including strong EM-fields, EM-pulses and contact with flammable materials, often far exceeding electronic sensors in this regard. This review looks into direct UV-written planar Bragg grating technology and its application to integrated photonic sensors. The platform has been demonstrated widely for measurement of physical properties such as temperature, pressure and strain. In addition, by using an evanescent interaction, refractive index can be measured allowing for chemical and biochemical detection. Further to this, the platform has recently been utilised in quantum information processing, where quantum gate operations and single photon detection has been shown. (topical review)

  2. High-sensitivity temperature sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

    Institute of Scientific and Technical Information of China (English)

    Xusheng Cheng; Weiwei Qiu; Wenxuan Wu; Yanhua Luo; Xiujie Tian; Qijin Zhang; Bing Zhu

    2011-01-01

    @@ A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.%A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.

  3. Fabrication of Dual-Wavelength Fiber Bragg Grating with a Longitudinal Stretch

    Institute of Scientific and Technical Information of China (English)

    JIANG Li; ZHANG Dong-sheng; ZHANG Wei-gang; KAI Gui-yun; DONG Xiao-yi

    2006-01-01

    A method of fabricating dual-wavelength fiber Bragg grating with a uniform phase mask is demonstrated.Theoretical analysis and numerical simulation using Matrix method arc given.The moving exposing technique is adopted.Good control over the grating's reflectivity and the separation of the two Bragg wavelengths is enabled by adjusting the stretch,the length of the grating,and the exposure.A grating with two equal transmission peaks of 19.5 dB is obtained by using this method,and the separation of the two Bragg wavelengths is 0.78 nm.

  4. Compressive and tensile strain sensing using a polymer planar Bragg grating.

    Science.gov (United States)

    Rosenberger, M; Hessler, S; Belle, S; Schmauss, B; Hellmann, R

    2014-03-10

    A polymer planar Bragg grating sensor is used for measuring both mechanical compressive and tensile strain. The planar waveguide with integrated Bragg grating is fabricated in bulk Polymethylmethacrylate in a single writing step using combined amplitude and phase mask technique. After butt coupling of a single-mode optical fiber the planar structure can be applied for measuring both mechanical tensile and compressive strain alongside the integrated waveguide without the need of further modifications. In this respect, we particularly report for the first time compressive strain measurements using a polymer Bragg grating. Furthermore, the sensitivity of the sensor against tensile and compressive strain, its reproducibility and hysteresis are investigated and discussed.

  5. New imaging using pulsed neutron sources imaging of crystalline structural information by Bragg edge transmission spectroscopy

    International Nuclear Information System (INIS)

    Neutron imaging at a pulsed neutron source can simultaneously give position-dependent neutron transmission spectra of a material. 'Bragg edge' transmission pattern appears at low energy region of the spectrum. Since the Bragg edge transmission spectrum includes various crystalline structural information, e.g., crystal structure, crystalline phase, crystallographic texture, crystallite size and strain, the pulsed neutron imaging using a two-dimensional area detector can non-destructively visualize such the information over the wide area of a material. In this article, principles, features and experimental examples of the Bragg edge transmission imaging that is expected as a new analysis tool for materials science are presented. (author)

  6. Resonant THz sensor for paper quality monitoring using THz fiber Bragg gratings

    CERN Document Server

    Yan, Guofeng; Mikulic, Predrag; Bock, Wojtek J; Skorobogatiy, Maksim

    2013-01-01

    We report fabrication of THz fiber Bragg gratings (TFBG) using CO2 laser inscription on subwavelength step-index polymer fibers. A fiber Bragg grating with 48 periods features a ~4 GHz-wide stop band and ~15 dB transmission loss in the middle of a stop band. The potential of such gratings in design of resonant sensor for monitoring of paper quality is demonstrated. Experimental spectral sensitivity of the TFBG-based paper thickness sensor was found to be ~ -0.67 GHz / 10 um. A 3D electromagnetic model of a Bragg grating was used to explain experimental findings.

  7. Variable angle correlation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y K [Univ. of California, Berkeley, CA (United States)

    1994-05-01

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with {sup 13}C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

  8. Miniature fiber Bragg grating sensor interrogator (FBG-Transceiver) system

    Science.gov (United States)

    Mendoza, Edgar A.; Kempen, Cornelia; Lopatin, Craig

    2007-04-01

    This paper describes recent progress conducted towards the development of a miniature fiber Bragg grating sensor interrogator (FBG-Transceiver TM) system based on multi-channel integrated optic sensor (InOSense TM) microchip technology. The hybrid InOSense TM microchip technology enables the integration of all of the functionalities, both passive and active, of conventional bench top FBG sensor interrogator systems, packaged in a miniaturized, low power operation, 2-cm x 5-cm package suitable for the long-term structural health monitoring in applications where size, weight, and power are critical for operation. The FBG-Transceiver system uses active optoelectronic components monolithically integrated to the InOSense TM microchip, a microprocessor controlled signal processing electronics board capable of processing the FBG sensors signals related to stress-strain and temperature as well as vibration and acoustics. The FBG-Transceiver TM system represents a new, reliable, highly robust technology that can be used to accurately monitor the status of an array of distributed fiber optic Bragg grating sensors installed in critical infrastructures. Its miniature package, low power operation, and state-of-the-art data communications architecture, all at a very affordable price makes it a very attractive solution for a large number of SHM/NDI applications in aerospace, naval and maritime industry, civil structures like bridges, buildings and dams, the oil and chemical industry, and for homeland security applications. The miniature, cost-efficient FBG-Transceiver TM system is poised to revolutionize the field of structural health monitoring and nondestructive inspection market. The sponsor of this program is NAVAIR under a DOD SBIR contract.

  9. Angle-deviation optical profilometer

    Institute of Scientific and Technical Information of China (English)

    Chen-Tai Tan; Yuan-Sheng Chan; Zhen-Chin Lin; Ming-Hung Chiu

    2011-01-01

    @@ We propose a new optical profilometer for three-dimensional (3D) surface profile measurement in real time.The deviation angle is based on geometrical optics and is proportional to the apex angle of a test plate.Measuring the reflectivity of a parallelogram prism allows detection of the deviation angle when the beam is incident at the nearby critical angle. The reflectivity is inversely proportional to the deviation angle and proportional to the apex angle and surface height. We use a charge-coupled device (CCD) camera at the image plane to capture the reflectivity profile and obtain the 3D surface profile directly.%We propose a new optical profilometer for three-dimensional (3D) surface profile measurement in real time.The deviation angle is based on geometrical optics and is proportional to the apex angle of a test plate.Measuring the refiectivity of a parallelogram prism allows detection of the deviation angle when the beam is incident at the nearby critical angle. The refiectivity is inversely proportional to the deviation angle and proportional to the apex angle and surface height. We use a charge-coupled device (CCD) camera at the image plane to capture the refiectivity profile and obtain the 3D surface profile directly.

  10. Tunable channel drop filters consisting of a tilted Bragg grating and a mode sorting polymer waveguide.

    Science.gov (United States)

    Park, Tae-Hyun; Shin, Jin-Soo; Huang, Guanghao; Chu, Woo-Sung; Oh, Min-Cheol

    2016-03-21

    Optical wavelength filters with large tuning range and narrow bandwidth are crucial for enhancing the capability of WDM communication systems. A polymeric tunable filter for C-band, comprising a tilted Bragg grating and a mode sorting waveguide junction is proposed in this work. For dropping a certain wavelength signal, the tilted Bragg grating reflects an odd mode into an even mode and then the reflected even mode propagates towards an output port of the asymmetric Y-junction due to the mode sorting. Consequently, the output port is separated from the input port, which is not possible in an ordinary Bragg reflector. The tilted Bragg reflector with an odd-even mode coupling efficiency of 61% exhibited a maximum reflectivity of 95% for a grating of 6 mm. A linear wavelength tuning of over 10 nm was achieved for an applied thermal power of 312 mW.

  11. High Power Compact Single-Frequency Volume Bragg Er-Doped Fiber Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is based on successful results of Phase I project where it was shown that the use of volume Bragg gratings in PTR glass as selectors of transverse and...

  12. Development of a Fibre Bragg Grating Sensor for Rock Deformation Monitoring

    Science.gov (United States)

    Kanopoulos, Patrick Paskalis

    This thesis examines the theoretical and experimental performance of a fibre Bragg grating sensor for static and dynamic strain measurement in hard rock. A literature review focuses on the fundamental theory of fibre Bragg gratings, various physical demodulation schemes used to interrogate Bragg sensors with an emphasis on charge coupled device spectrometry, as well as the aliasing behaviour of Bragg gratings as sensors. A coupled numerical-analytical analysis is conducted on various sensor configurations designed for borehole deployment in order to establish the response of the strain sensors under various strain conditions. The findings of an experimental investigation of two sensors subjected to uniaxial strain within a grout and a rock specimen are presented. The experimental data confirm the feasibility of using the proposed sensor as a part of an integrated optical strain sensing network.

  13. Analysis of Sampled Fiber Bragg Grating Based on the Photonic Crystal Theory

    Institute of Scientific and Technical Information of China (English)

    ZHU Dan-dan

    2009-01-01

    One of the most basic characteristics of photonic crystal is frequency band gap.When defects are introduced into the periodic photonic crystal,a number of defect modes appear in the stop band.In this paper,we exploit transfer matrix method based on photonic crystal theory,and assume the sampled fiber Bragg grating as one-dimensional dual photonic crystal with a large size defect.Characteristics of the sampled fiber Bragg grating are analyzed.Experimental results show that the sampled fiber Bragg grating has many reflective peaks.Its reflectivity,center wavelength,reflective peak intervals and band width all change with the grating parameters,including grating length,duty ratio of the material with high dielectric constant,and index modulation depth and period.Results agree with the conventional couple mode theory which can be used when analyzing other characteristics of the sampled fiber Bragg grating or applying it into practice.

  14. Study on Dual Bragg Wavelength Fiber Grating and Its Tuning Scheme

    Institute of Scientific and Technical Information of China (English)

    Dong Xingfa; Fu Shenggui; Zhang Hao; Kai Guiyun; Dong Xiaoyi

    2003-01-01

    Because of package, a single FBG has dual Bragg wavelength. One is sensitive to stress and the other is sensitive to temperature. By using the special mechanism, the wavelengths can be tuned by stress and temperature respectively.

  15. Fiber Bragg Grating (FBG) sensors as flatness and mechanical stretching sensors

    Science.gov (United States)

    Abbaneo, D.; Abbas, M.; Abbrescia, M.; Abdelalim, A. A.; Abi Akl, M.; Aboamer, O.; Acosta, D.; Ahmad, A.; Ahmed, W.; Ahmed, W.; Aleksandrov, A.; Aly, R.; Altieri, P.; Asawatangtrakuldee, C.; Aspell, P.; Assran, Y.; Awan, I.; Bally, S.; Ban, Y.; Banerjee, S.; Barashko, V.; Barria, P.; Bencze, G.; Beni, N.; Benussi, L.; Bhopatkar, V.; Bianco, S.; Bos, J.; Bouhali, O.; Braghieri, A.; Braibant, S.; Buontempo, S.; Calabria, C.; Caponero, M.; Caputo, C.; Cassese, F.; Castaneda, A.; Cauwenbergh, S.; Cavallo, F. R.; Celik, A.; Choi, M.; Choi, S.; Christiansen, J.; Cimmino, A.; Colafranceschi, S.; Colaleo, A.; Conde Garcia, A.; Czellar, S.; Dabrowski, M. M.; De Lentdecker, G.; De Oliveira, R.; De Robertis, G.; Dildick, S.; Dorney, B.; Elmetenawee, W.; Endroczi, G.; Errico, F.; Fenyvesi, A.; Ferry, S.; Furic, I.; Giacomelli, P.; Gilmore, J.; Golovtsov, V.; Guiducci, L.; Guilloux, F.; Gutierrez, A.; Hadjiiska, R. M.; Hassan, A.; Hauser, J.; Hoepfner, K.; Hohlmann, M.; Hoorani, H.; Iaydjiev, P.; Jeng, Y. G.; Kamon, T.; Karchin, P.; Korytov, A.; Krutelyov, S.; Kumar, A.; Kim, H.; Lee, J.; Lenzi, T.; Litov, L.; Loddo, F.; Madorsky, A.; Maerschalk, T.; Maggi, M.; Magnani, A.; Mal, P. K.; Mandal, K.; Marchioro, A.; Marinov, A.; Masod, R.; Majumdar, N.; Merlin, J. A.; Mitselmakher, G.; Mohanty, A. K.; Mohamed, S.; Mohapatra, A.; Molnar, J.; Muhammad, S.; Mukhopadhyay, S.; Naimuddin, M.; Nuzzo, S.; Oliveri, E.; Pant, L. M.; Paolucci, P.; Park, I.; Passeggio, G.; Passamonti, L.; Pavlov, B.; Philipps, B.; Piccolo, D.; Pierluigi, D.; Postema, H.; Puig Baranac, A.; Radi, A.; Radogna, R.; Raffone, G.; Ranieri, A.; Rashevski, G.; Riccardi, C.; Rodozov, M.; Rodrigues, A.; Ropelewski, L.; RoyChowdhury, S.; Russo, A.; Ryu, G.; Ryu, M. S.; Safonov, A.; Salva, S.; Saviano, G.; Sharma, A.; Sharma, A.; Sharma, R.; Shah, A. H.; Shopova, M.; Sturdy, J.; Sultanov, G.; Swain, S. K.; Szillasi, Z.; Talvitie, J.; Tatarinov, A.; Tuuva, T.; Tytgat, M.; Vai, I.; Van Stenis, M.; Venditti, R.; Verhagen, E.; Verwilligen, P.; Vitulo, P.; Volkov, S.; Vorobyev, A.; Wang, D.; Wang, M.; Yang, U.; Yang, Y.; Yonamine, R.; Zaganidis, N.; Zenoni, F.; Zhang, A.

    2016-07-01

    A novel approach which uses Fiber Bragg Grating (FBG) sensors has been utilized to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

  16. Extending Bragg peak of heavy ion beam and melanoma cell inactivation measurement

    Institute of Scientific and Technical Information of China (English)

    LiQiang; WeiZeng-Quan; 等

    1998-01-01

    A rotating range modulator was designed and manufactured.which is applied to extend Bragg peak of heavy ion beam.Bragg curves of 75MeV/u 16O and 75MeV/u 12C ion beams through this range modulator were measured respectively and two evident spread-out Bragg peaks corresponding to the modulated beams above are shown.In addition,inactivation effect of the modulated 75MeV/u 16O ion beam at nine different penetration depths on melanoma cells(B16) was measured.Results indicate that lethal effects at the spread-out Bragg peak region are larger than at the plateau of the particle beam entrance.

  17. Trends and future of fiber Bragg grating sensing technologies: tailored draw tower gratings (DTGs)

    Science.gov (United States)

    Lindner, E.; Hartung, A.; Hoh, D.; Chojetzki, C.; Schuster, K.; Bierlich, J.; Rothhardt, M.

    2014-05-01

    Today fiber Bragg gratings are commonly used in sensing technology as well as in telecommunications. Numerous requirements must be satisfied for their application as a sensor such as the number of sensors per system, the measurement resolution and repeatability, the sensor reusability as well as the sensor costs. In addition current challenges need to be met in the near future for sensing fibers to keep and extend their marketability such as the suitability for sterilization, hydrogen darkening or the separation of strain and temperature (or pressure and temperature). In this contribution we will give an outlook about trends and future of the fiber Bragg gratings in sensing technologies. Specifically, we will discuss how the use of draw tower grating technology enables the production of tailored Bragg grating sensing fibers, and we will present a method of separating strain and temperature by the use of a single Bragg grating only, avoiding the need for additional sensors to realize the commonly applied temperature compensation.

  18. Fiber Bragg Grating (FBG) sensors as flatness and mechanical stretching sensors

    CERN Document Server

    Abbaneo, D; Abbrescia, M.; Abdelalim, A.A.; Abi Akl, M.; Aboamer, O.; Acosta, D.; Ahmad, A.; Ahmed, W.; Ahmed, W.; Aleksandrov, A.; Aly, R.; Altieri, P.; Asawatangtrakuldee, C.; Aspell, P.; Assran, Y.; Awan, I.; Bally, S.; Ban, Y.; Banerjee, S.; Barashko, V.; Barria, P.; Bencze, G.; Beni, N.; Benussi, L.; Bhopatkar, V.; Bianco, S.; Bos, J.; Bouhali, O.; Braghieri, A.; Braibant, S.; Buontempo, S.; Calabria, C.; Caponero, M.; Caputo, C.; Cassese, F.; Castaneda, A.; Cauwenbergh, S.; Cavallo, F.R.; Celik, A.; Choi, M.; Choi, S.; Christiansen, J.; Cimmino, A.; Colafranceschi, S.; Colaleo, A.; Conde Garcia, A.; Czellar, S.; Dabrowski, M.M.; De Lentdecker, G.; De Oliveira, R.; De Robertis, G.; Dildick, S.; Dorney, B.; Elmetenawee, W.; Endroczi, G.; Errico, F.; Fenyvesi, A.; Ferry, S.; Furic, I.; Giacomelli, P.; Gilmore, J.; Golovtsov, V.; Guiducci, L.; Guilloux, F.; Gutierrez, A.; Hadjiiska, R.M.; Hassan, A.; Hauser, J.; Hoepfner, K.; Hohlmann, M.; Hoorani, H.; Iaydjiev, P.; Jeng, Y.G.; Kamon, T.; Karchin, P.; Korytov, A.; Krutelyov, S.; Kumar, A.; Kim, H.; Lee, J.; Lenzi, T.; Litov, L.; Loddo, F.; Madorsky, A.; Maerschalk, T.; Maggi, M.; Magnani, A.; Mal, P.K.; Mandal, K.; Marchioro, A.; Marinov, A.; Masod, R.; Majumdar, N.; Merlin, J.A.; Mitselmakher, G.; Mohanty, A.K.; Mohamed, S.; Mohapatra, A.; Molnar, J.; Muhammad, S.; Mukhopadhyay, S.; Naimuddin, M.; Nuzzo, S.; Oliveri, E.; Pant, L.M.; Paolucci, P.; Park, I.; Passeggio, G.; Passamonti, L.; Pavlov, B.; Philipps, B.; Piccolo, D.; Pierluigi, D.; Postema, H.; Puig Baranac, A.; Radi, A.; Radogna, R.; Raffone, G.; Ranieri, A.; Rashevski, G.; Riccardi, C.; Rodozov, M.; Rodrigues, A.; Ropelewski, L.; RoyChowdhury, S.; Russo, A.; Ryu, G.; Ryu, M.S.; Safonov, A.; Salva, S.; Saviano, G.; Sharma, A.; Sharma, A.; Sharma, R.; Shah, A.H.; Shopova, M.; Sturdy, J.; Sultanov, G.; Swain, S.K.; Szillasi, Z.; Talvitie, J.; Tatarinov, A.; Tuuva, T.; Tytgat, M.; Vai, I.; Van Stenis, M.; Venditti, R.; Verhagen, E.; Verwilligen, P.; Vitulo, P.; Volkov, S.; Vorobyev, A.; Wang, D.; Wang, M.; Yang, U.; Yang, Y.; Yonamine, R.; Zaganidis, N.; Zenoni, F.; Zhang, A.

    2016-01-01

    A novel approach which uses Fibre Bragg Grating (FBG) sensors has been utilised to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

  19. Impact of Saturable Gain/Loss on Bistability of Nonlinear Parity-Time Bragg Gratings

    CERN Document Server

    Phang, Sendy; Susanto, Hadi; Benson, Trevor M; Sewell, Phillip

    2014-01-01

    We report on the impact of realistic gain and loss models on the bistable operation of nonlinear parity-time Bragg gratings. In our model we include both dispersive and saturable gain and show that levels of gain/loss saturation can have significant impact on the bistable operation of a nonlinear PT Bragg grating based on GaAs material. The hysteresis of the nonlinear PT Bragg grating is analyzed for different levels of gain and loss and different saturation levels. We show that high saturation levels can improve the nonlinear operation by reducing the intensity at which the bistability occurs. However when the saturation intensity is low, saturation inhibits PT phenomena in a nonlinear PT Bragg grating.

  20. Fiber sensing system based on a bragg grating and optical time domain reflectometry

    OpenAIRE

    Chin, Sanghoon; Thévenaz, Luc

    2013-01-01

    Optic fiber sensor characterized in that the sensing fiber is provided with a continuous Bragg grating covering the entire fiber length which is dedicated to sensing and along which spatially resolved measurements are performed.

  1. High-speed two-dimensional laser scanner based on Bragg gratings stored in photothermorefractive glass.

    Science.gov (United States)

    Yaqoob, Zahid; Arain, Muzammil A; Riza, Nabeel A

    2003-09-10

    A high-speed free-space wavelength-multiplexed optical scanner with high-speed wavelength selection coupled with narrowband volume Bragg gratings stored in photothermorefractive (PTR) glass is reported. The proposed scanner with no moving parts has a modular design with a wide angular scan range, accurate beam pointing, low scanner insertion loss, and two-dimensional beam scan capabilities. We present a complete analysis and design procedure for storing multiple tilted Bragg-grating structures in a single PTR glass volume (for normal incidence) in an optimal fashion. Because the scanner design is modular, many PTR glass volumes (each having multiple tilted Bragg-grating structures) can be stacked together, providing an efficient throughput with operations in both the visible and the infrared (IR) regions. A proof-of-concept experimental study is conducted with four Bragg gratings in independent PTR glass plates, and both visible and IR region scanner operations are demonstrated.

  2. A fiber Bragg based semi distributed pressure sensor system for in-vivo vascular applications

    NARCIS (Netherlands)

    Nieuwland, R.A.; Cheng, L.K.; Lemmen, M.H.J.; Oostenbrink, R.H.; Harmsma, P.J.; Schreuder, J.J.

    2014-01-01

    An overview of a fiber Bragg based sensor system, developed for in-vivo vascular pressure and temperature sensing, is presented. The focus is on sensor miniaturization and interrogator optimization to reach a viable sensor system.

  3. High-speed two-dimensional laser scanner based on Bragg gratings stored in photothermorefractive glass.

    Science.gov (United States)

    Yaqoob, Zahid; Arain, Muzammil A; Riza, Nabeel A

    2003-09-10

    A high-speed free-space wavelength-multiplexed optical scanner with high-speed wavelength selection coupled with narrowband volume Bragg gratings stored in photothermorefractive (PTR) glass is reported. The proposed scanner with no moving parts has a modular design with a wide angular scan range, accurate beam pointing, low scanner insertion loss, and two-dimensional beam scan capabilities. We present a complete analysis and design procedure for storing multiple tilted Bragg-grating structures in a single PTR glass volume (for normal incidence) in an optimal fashion. Because the scanner design is modular, many PTR glass volumes (each having multiple tilted Bragg-grating structures) can be stacked together, providing an efficient throughput with operations in both the visible and the infrared (IR) regions. A proof-of-concept experimental study is conducted with four Bragg gratings in independent PTR glass plates, and both visible and IR region scanner operations are demonstrated. PMID:14503693

  4. Effects of the Facet Reflectivity of a Laser Diode on Fiber Bragg Grating Semiconductor Lasers

    Institute of Scientific and Technical Information of China (English)

    Honggang; Yu; Chang-Qing; Xu; Na; Li; Zhilin; Peng; Jacek; Wojcik; Peter; Mascher

    2003-01-01

    Effects of facet reflectivity of a laser diode on the performance of fiber Bragg grating semiconductor lasers are studied experimentally. Facet reflectivity of less than 10-4 is necessary to obtain stable oscillation wavelength.

  5. An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures

    OpenAIRE

    C. Y. Wei; Ye, Chen-Chun; James, Stephen W.; Tatam, Ralph P.; Irving, Phil E.

    2001-01-01

    This paper developed a method to evaluate the strain transfer efficiency of fibre Bragg grating sensors to host structures. Various coatings were applied to fibre Bragg grating sensors after being fabricated. They were epoxy, silane agent and polypropylene, representing different surface properties. A neat epoxy resin plate was used as the host in which the coated fibre sensors were embedded in the central layer. The tensile strain output from the FBGs was compared with that...

  6. Computer-Generated Holograms for Recording Multiple-Phase-Shifte Fiber Bragg Grating Corrugations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new method of fabricating multiple-phase-shifte fiber Bragg grating by CGHs is proposed. The authors present an example of such CGH by which a section multiple-phase-shifte fiber Bragg grating with two π/2 phase shifts and grating length L=21.2 μm was produced. The authors describe the production process and finally give an example of a reconstructed fiber grating with two phase-shifts.

  7. Uniform Fiber Bragg Grating modeling and simulation used matrix transfer method

    Directory of Open Access Journals (Sweden)

    Abdallah Ikhlef

    2012-01-01

    Full Text Available This paper presents the modeling and simulation of an optical fiber Bragg grating for maximum reflectivity, minimum side lobe. Gating length represents as one of the critical parameters in contributing to a high performance fiber Bragg grating. The reflection spectra and side lobes strength were analyzed with different lengths .The side lobes have been suppressed using raised cosine apodization while maintaining the peak reflectivity. Such simulations are based on solving coupled mode equations by transfer matrix method.

  8. Ionoacoustic tomography of the proton Bragg peak in combination with ultrasound and optoacoustic imaging

    OpenAIRE

    Stephan Kellnberger; Walter Assmann; Sebastian Lehrack; Sabine Reinhardt; Peter Thirolf; Daniel Queirós; George Sergiadis; Günther Dollinger; Katia Parodi; Vasilis Ntziachristos

    2016-01-01

    Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg peak positioning inside tissue. We introduce ionoacoustic tomography based ...

  9. Strain and temperature sensors using multimode optical fiber Bragg gratings and correlation signal processing

    OpenAIRE

    Lim, J; Yang, QP; Jones, BE; Jackson, PR

    2002-01-01

    Multimode fiber optic Bragg grating sensors for strain and temperature measurements using correlation signal processing methods have been developed. Two multimode Bragg grating sensors were fabricated in 62/125 m graded-index silica multimode fiber; the first sensor was produced by the holographic method and the second sensor by the phase mask technique. The sensors have signal reflectivity of approximately 35% at peak wavelengths of 835 nm and 859 nm, respectively. Strain testing...

  10. A temperature insensitive Bragg grating sensor - using orthogonal polar polarisation modes for in situ temperature compensation

    OpenAIRE

    Parker, R M; J.C.Gates; Grossel, M. C.; P.G.R.Smith

    2010-01-01

    An exposed Bragg grating incorporated into a planar waveguide forms an optical device that acts as a refractive index sensor. The exposed evanescent field causes the Bragg peak to be sensitive to the refractive index of its surroundings and can be used to detect changes in this environment. The method reported is able to provide accurate temperature compensation by applying a scaling factor derived from measurement of the birefringence of the transverse electric (TE) and transverse magnetic (...

  11. Karakterisasi Fiber Bragg Grating (FBG) Untuk Pengembangan Sistem Sensor Strain Tanah

    OpenAIRE

    Sinuhaji, Depi Santi

    2010-01-01

    Fiber Bragg Grating (FBG) is a periodic change of refractive index which is the length of optical fiber. Has been developed Fiber Bragg Grating (FBG)-based laser diodes for monitoring landslide-prone areas. This sensor has been developed because high sensitivity and is not affected by electromagnetic induction that can be placed at a distance from the location where the power supply and monitor. FBG transmission peak will shift when the grating is change resulting from a change in temperature...

  12. Practical biological spread-out Bragg peak design of carbon beam

    OpenAIRE

    Kim, Chang Hyeuk; Lee, Hwa-Ryun; Chang, Seduk; Jang, Hong Suk; Kim, Jeong Hwan; Park, Dong Wook; Hwang, Won Taek; Yang, Tea-Keun

    2015-01-01

    The carbon beams show more advantages on the biological properties compared with proton beams in radiation therapy. The carbon beam shows high linear energy transfer (LET) to medium and it increases the relative biological effectiveness (RBE). To design spread-out Bragg peak (SOBP) of biological dose using carbon beam, a practical method was purposed by using the linear-quadratic (LQ) model and Geant4 based Monte Carlo simulation code. The various Bragg peak profiles and LET was calculated fo...

  13. 100 GHz electrically tunable planar Bragg gratings via liquid crystal overlay

    OpenAIRE

    Adikan, F.R.Mahamd; J.C.Gates; Snow, B.D.; Dyadyusha, A.; Major, H.E.; Gawith, C.B.E.; Kaczmarek, M.; P.G.R.Smith

    2007-01-01

    We demonstrate 114GHz electrically tunable liquid crystal Bragg gratings using 170Vpp voltage. The devices were made using direct UV grating writing and use evanescent coupling into an electrically tuned nematic liquid crystal. Reconfigurable integrated optical devices are essential in today's dense and complex telecommunication meshes. A commonly employed component on the silica platform fulfilling the above role is a planar Bragg grating. The ability to tune the reflection peak of these gra...

  14. Uniform Fiber Bragg Grating modeling and simulation used matrix transfer method

    OpenAIRE

    Abdallah Ikhlef; Rachida Hedara; Mohamed Chikh-Bled

    2012-01-01

    This paper presents the modeling and simulation of an optical fiber Bragg grating for maximum reflectivity, minimum side lobe. Gating length represents as one of the critical parameters in contributing to a high performance fiber Bragg grating. The reflection spectra and side lobes strength were analyzed with different lengths .The side lobes have been suppressed using raised cosine apodization while maintaining the peak reflectivity. Such simulations are based on ...

  15. Numerical Analysis of Thermal Dependence of the Spectral Response of Polymer Optical Fiber Bragg Gratings

    OpenAIRE

    Hisham K. Hisham

    2016-01-01

    The thermal dependence of the spectral response (i.e. transmission, reflection and time delay (r) responses) of uniform polymer optical fiber (POF) Bragg gratings has been investigated. In addition to the temperature dependence, the effects of grating strength (kLg) and fiber index modulation (n) have been investigated. Besides high capability of tunable wavelength due to the unique large and negative thermo-optic coefficient of POF, the spectral response for POF Bragg gratings sh...

  16. Anomalous longitudinal mode hops in GaAs/AlGaAs distributed Bragg reflector lasers

    OpenAIRE

    Hofstetter, Daniel; Zappe, H. P.

    2008-01-01

    We investigate normal and anomalous longitudinal mode hops in GaAs/AlGaAs-based distributed Bragg reflector (DBR) lasers; anomalous mode hops are defined as those which move toward shorter wavelengths with increasing temperature, which is unexpected. The two-section DBR lasers discussed in this letter, consisting of a gain section and an unpumped Bragg reflector, typically exhibit one mode hop in a 10 K temperature range. Although the longer wavelength modes are expected to start lasing when ...

  17. Fiber Bragg Gratings in Small-Core Ge-Doped Photonic Crystal Fibers

    Institute of Scientific and Technical Information of China (English)

    Yiping Wang; Hartmut Bartelt; Wolfgang Ecke; Reinhardt Willsch; Jens Kobelke; Michael Kautz; Sven Brueckner; Manfred Rothhardt

    2008-01-01

    This paper reports fiber Bragg gratings (FBGs) inscribed in a small-core Ge-doped photonic crystal fibers with a UV laser and a Talbot inter-ferometer. The responses of such FBGs to temper-ature, strain, bending, and transverse-loading were systematically investigated. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and trans-verse-loading. The bending and transverse- loading properties of the FBGs are sensitive to the fiber orientations.

  18. Asymmetrically pumped Bragg scattering with the effects of nonlinear phase modulation

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Friis, Søren Michael Mørk; Reddy, Dileep V.;

    2014-01-01

    We derive exact solutions to asymmetrically pumped Bragg scattering with nonlinear phase-modulation (NPM) and show that this setup allows for the frequency conversion of many temporal modes, while reducing the effects due to NPM.......We derive exact solutions to asymmetrically pumped Bragg scattering with nonlinear phase-modulation (NPM) and show that this setup allows for the frequency conversion of many temporal modes, while reducing the effects due to NPM....

  19. Structural Health Monitoring of a Tall Building during Construction with Fiber Bragg Grating Sensors

    OpenAIRE

    Li, D. S.; Ren, L.; Li, H. N.; Song, G. B.

    2012-01-01

    Fiber Bragg grating sensors demonstrate a great potential as a structural health monitoring tool for civil structures to ensure structural integrity, durability, and reliability. The advantages of applying fiber optic sensors to a tall building include their immunity to electromagnetic interference and their multiplexing ability to transfer optical signals over a long distance. In the work, fiber Bragg grating sensors, consisting of strain and temperature sensors, are applied to structural mo...

  20. Low-Dispersion Fibre Bragg Gratings Written Using the Polarization Control Method

    DEFF Research Database (Denmark)

    Deyerl, Hans Jürgen; Plougmann, Nikolai; Jensen, Jesper Bo Damm;

    2002-01-01

    We present two fibre Bragg gratings with reduced in-band dispersion for DWDM applications. The gratings were designed by the inverse scattering method and fabricated using the novel polarization control method for UV-writing of advanced gratings.......We present two fibre Bragg gratings with reduced in-band dispersion for DWDM applications. The gratings were designed by the inverse scattering method and fabricated using the novel polarization control method for UV-writing of advanced gratings....

  1. Fiber-optical accelerometers based on polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Stefani, Alessio; Bang, Ole;

    2010-01-01

    Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer.......Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

  2. Efectos rotacionales en redes de Bragg en fibras ópticas

    OpenAIRE

    Arce Diego, José Luis; Muriel Fernández, Miguel Ángel; López Ruisánchez, Roberto; López Higuera, José Miguel

    1997-01-01

    The periodic mode coupling between the right and left circular polarization modes that is induced by a photoinduced fiber grating, with or without lineal birefringence, and with a magnetic field or a twist rate applied to it, is studied and analyzed through the use of the generalized coupled-mode theory. Several novel application of such devices as a fiber Bragg grating twist rate probe, a tuneable optical fiber based on twisted fiber Bragg grating, and an optical filter tuned by magnetic fie...

  3. Numerical Analysis of Thermal Dependence of the Spectral Response of Polymer Optical Fiber Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Hisham K. Hisham

    2016-06-01

    Full Text Available The thermal dependence of the spectral response (i.e. transmission, reflection and time delay (r responses of uniform polymer optical fiber (POF Bragg gratings has been investigated. In addition to the temperature dependence, the effects of grating strength (kLg and fiber index modulation (n have been investigated. Besides high capability of tunable wavelength due to the unique large and negative thermo-optic coefficient of POF, the spectral response for POF Bragg gratings show high stability and larger spectrum bandwidth with temperature variation compare with the silica optical fiber (SOF Bragg gratings, especially with the increase of the kLg value. It was found that by increasing kLg, the peak reflectance value increases and the bandwidth of the Bragg reflector become narrower. Also it’s shown by increasing the kLg value, r deceasing significantly and reach its minimum value at the designed wavelength (B. Furthermore, the r for POF Bragg gratings is less than that for SOF Bragg gratings at the same value of kLg. Also it’s found that the peak reflectivity value increases to around 60% when the n value increases from 110-4 to 510-4.

  4. The Functionality of Fiber Bragg Grating Sensor Compared to that of Foil Gauge

    Directory of Open Access Journals (Sweden)

    Bashir A. Tahir

    2005-01-01

    Full Text Available Technology such as Fiber Bragg Grating (FBG sensors are widely accepted in almost all industries. FBG are being investigated for their applicability in other markets such as smart structures. Fiber optic sensors can also be used in many different applications. Fiber optic sensors are available in several types; among them, the Bragg grating sensor is being studied in this research. For this research work, the main focus was the use of fiber Bragg grating sensors for measuring strain. The key objective of this research; to determine the functionality of fiber Bragg grating sensors compared to that of conventional foil gauges. Fiber Bragg grating sensors were chosen for this research because they have a high potential for various uses in the monitoring of smart structures. The major incentives for this type of research are the current deterioration of civil structures in west Malaysia. The laboratory tests are being reported in this research work including tests of steel straps and an aluminum test specimen. In all the tests, strain was measured using the fiber Bragg grating sensors and compared to values from a conventional foil gauge. The results are being discussed in details. It was inferred that the use of fiber optic technology for the monitoring of civil structures is very promising and the future is sure to bring further advancements and improvements.

  5. Bragg diffraction of fermions at optical potentials; Braggbeugung von Fermionen an optischen Potentialen

    Energy Technology Data Exchange (ETDEWEB)

    Deh, Benjamin

    2008-10-27

    This thesis describes the Bragg diffraction of ultracold fermions at an optical potential. A moving optical lattice was created, by overlaying two slightly detuned lasers. Atoms can be diffracted at this lattice if the detuning fulfills the Bragg condition for resting atoms. This Bragg diffraction is analyzed systematically in this thesis. To this end Rabi oscillations between the diffraction states were driven, as well in the weakly interacting Bragg regime, as in the strongly interacting Kapitza-Dirac regime. Simulations, based on a driven two-, respectively multilevel-system describe the observed effects rather well. Furthermore, the temporal evolution of the diffracted states in the magnetic trapping potential was studied. The anharmonicity of the trap in use and the scattering cross section for p-wave collisions in a {sup 6}Li system was determined from the movement of these states. Moreover the momentum distribution of the fermions was measured with Bragg spectroscopy and first signs of Fermi degeneracy were found. Finally an interferometer with fermions was build, exhibiting a coherence time of more than 100 {mu}s. With this, the possibility for measurement and manipulation of ultracold fermions with Bragg diffraction could bee shown. (orig.)

  6. Development of Bragg Gratings as Shear Stress Monitors in Aerodynamic >Facilities

    Science.gov (United States)

    Parmar, Devandra S.

    1998-04-01

    Two Bragg gratings centered at 1289.565 nm and 1299.432 nm were co-written in the core of a 9/125 telecommunications fiber doped with 10 weight percent germanium. The fiber was mounted in a 126 deep groove, with a 127 diameter semicircular bottom, etched in a flat metal plate used as the test model. A 1 thick epoxy layer bonded the fiber to the metal plate. A thermocouple was also attached to the metal plate in the vicinity of the Bragg fiber. The metal plate was next mounted in the test section of a subsonic wind tunnel. A skin friction balance was also mounted on the wall of the test section. As the wind speed in the tunnel was increased from 0 to 90 m/sec, reflected Bragg wavelengths and the fiber temperatures were recorded continuously. At a windspeed of 38.89 m/sec, the tunnel flow experienced a fan-induced turbulence registered by the skin friction balance as well as the Bragg signals. This commonality of the turbulence signal registration provided a unique calibration datum for the modulus of rigidity of the Bragg fiber assembly. This value of h has been used to calculate the values of shear stress at various tunnel speeds on the basis of Bragg wavelength changes at those speeds.

  7. PROTECTIVE COATINGS OF FIBER BRAGG GRATING FOR MINIMIZING OF MECHANICAL IMPACT ON ITS WAVELENGTH CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    A. S. Munko

    2015-03-01

    Full Text Available The paper deals with the scheme for the study of the Bragg wavelength shift dependence on the applied tensile force. Samples of fiber Bragg gratings with different coatings have been studied: the restored acrylate coating, the heatshrinkable fusion splice protection sleeve without metal rod, the heat-shrinkable fusion splice protection sleeve with a metal rod, the metal capillary, polyvinylchloride tube. For different coatings of diffractive structure, dependences of wavelength shift for the Bragg grating resonance have been obtained on the tensile strength applied to the ends of an optical fiber. It was determined that the studied FBG coatings give the possibility to reduce the mechanical impact on the Bragg wavelength shift for 1.1-15 times as compared to an uncoated waveguide. The most effective version of coated fiber Bragg grating is the heatshrinkable fusion splice protection sleeve with a metal rod. When the force (equal to 6 N is applied to the 100 mm optical fiber area with the inscribed diffractive structure, the Bragg wavelength shift is 7.5 nm for the unprotected sample and 0.5 nm for the one coated with the heat-shrinkable fusion splice protection sleeve.

  8. THz Radiation from Intracavity Saturable Bragg Reflector in Magnetic Field with Self-Started Mode-Locking by Strained Saturable Bragg Reflector

    Science.gov (United States)

    Liu, Tze-An; Huang, Kai-Fung; Pan, Ci-Ling; Liu, Zhenlin; Ono, Shingo; Ohtake, Hideyuki; Sarukura, Nobuhiko

    1999-11-01

    We demonstrate a new configuration for intracavity generation of THz radiation. A magnetic-field-biased saturable Bragg reflector (SBR) located inside the femtosecond laser cavity is the emitter, while a strained saturable Bragg reflector (SSBR) achieves self-started mode-locking without focusing. The calibrated power of the emitted THz radiation is estimated to be approximately 45 nW with a peak frequency at 0.72 THz and width of approximately 0.7 THz under a 0.88 T magnetic field. The quadratic dependence of THz-radiation power by the SBR on the magnetic field is also observed for the first time.

  9. Analysis of volume holographic storage allowing large-angle illumination

    Science.gov (United States)

    Shamir, Joseph

    2005-05-01

    Advanced technological developments have stimulated renewed interest in volume holography for applications such as information storage and wavelength multiplexing for communications and laser beam shaping. In these and many other applications, the information-carrying wave fronts usually possess narrow spatial-frequency bands, although they may propagate at large angles with respect to each other or a preferred optical axis. Conventional analytic methods are not capable of properly analyzing the optical architectures involved. For mitigation of the analytic difficulties, a novel approximation is introduced to treat narrow spatial-frequency band wave fronts propagating at large angles. This approximation is incorporated into the analysis of volume holography based on a plane-wave decomposition and Fourier analysis. As a result of the analysis, the recently introduced generalized Bragg selectivity is rederived for this more general case and is shown to provide enhanced performance for the above indicated applications. The power of the new theoretical description is demonstrated with the help of specific examples and computer simulations. The simulations reveal some interesting effects, such as coherent motion blur, that were predicted in an earlier publication.

  10. Characterization of porous materials by small-angle scattering

    Indian Academy of Sciences (India)

    S Mazumder; D Sen; A K Patra

    2004-07-01

    Characterization of porous materials by small-angle scattering has been extensively pursued for several years now as the pores are often of mesoscopic size and compatible with the length scale accessible by the technique using both neutrons and X-rays as probing radiation. With the availability of ultra small-angle scattering instruments, one can investigate porous materials in the sub-micron length scale. Because of the increased accessible length scale vis-a-vis the multiple scattering effect, conventional data analysis procedures based on single scattering approximation quite often fail. The limitation of conventional data analysis procedures is also pronounced in the case of thick samples and long wavelength of the probing radiation. Effect of multiple scattering is manifested by broadening the scattering profile. Sample thickness for some technologically important materials is often significantly high, as the experimental samples have to replicate all its essential properties in the bulk material. Larger wavelength of the probing radiation is used in some cases to access large length scale and also to minimize the effect of double Bragg reflections.

  11. Palladium coated fibre Bragg grating based hydrogen sensor

    International Nuclear Information System (INIS)

    Detection of steam generator leaks in fast nuclear reactors is carried out by monitoring hydrogen in argon cover-gas. Hydrogen released during sodium cleaning of fast reactor components is required to be monitored. Hydrogen sensors with good sensitivity, stability and response time are required for all the above applications. We report a new type of hydrogen sensor with a Fibre Bragg Grating (FBG) coated with palladium thin film which is used to detect the leak of hydrogen gas in the Steam Generator (SG) module of the Fast Breeder Reactor (FBR). If water leaks into sodium, it results in sodium-water reaction. In this reaction hydrogen and sodium hydroxide are formed. Due to the explosive risk of hydrogen system, hydrogen sensors are of great interest in this case. It is known that hydrogen forms an explosive mixture with air once its concentration exceeds beyond the explosion limit of four percent. The advantages of FBG based hydrogen sensor over the other hydrogen sensors are its inherent property of safety from sparking, immunity to ambient electromagnetic interference. The sensing mechanism in this device is based on mechanical strain that is induced in the palladium coating when it absorbs hydrogen. This process physically stretches the grating and causes the grating period and grating's refractive index, to change. The Bragg wavelength shift is directly proportional to the strain induced and can be directly related to the percentage of hydrogen exposure. The online monitoring of palladium thin film coating on FBG is carried out and recorded the wavelength change and strain induced on the FBG. A hydrogen sensor set up have been fabricated which consists of SS vessel of capacity 10 litres, provided with pressure gauge, Argon filling line with a valve, Hydrogen injection line with flange, a vent line with valve and Hydrogen sensor fixing point. The Palladium coated FBG based Hydrogen sensor is tested in this experimental facility in the exposure of hydrogen in

  12. Small angle neutron scattering

    Directory of Open Access Journals (Sweden)

    Cousin Fabrice

    2015-01-01

    Full Text Available Small Angle Neutron Scattering (SANS is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area… through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer, form factor analysis (I(q→0, Guinier regime, intermediate regime, Porod regime, polydisperse system, structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates, and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast. It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of

  13. Fiber Optic Fabry-Perot Current Sensor Integrated with Magnetic Fluid Using a Fiber Bragg Grating Demodulation

    OpenAIRE

    Ji Xia; Qi Wang; Xu Liu; Hong Luo

    2015-01-01

    An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power o...

  14. Occurrence of Features of Fiber Bragg Grating Spectra Having a Wavelength Corresponding to the Phase Mask Periodicity

    Institute of Scientific and Technical Information of China (English)

    Sui P. Yam; Zourab Brodzeli; Scott A. Wade; Greg W. Baxter; Stephen F. Collins

    2008-01-01

    The use of a phase mask with 536 nm uniform pitch allowed the fabrication of a fiber Bragg grating for use at a Bragg wavelength of 785 nm. Reflection and transmission features at 1552 nm, twice the Bragg wavelength, associated with the phase mask periodicity were observed. However, when phase mask orders other than ±1 were absent during fabrication the features at 1552 nm were not evident.

  15. Accuracy of needle position measurements using fiber Bragg gratings.

    Science.gov (United States)

    Henken, Kirsten; Van Gerwen, Dennis; Dankelman, Jenny; Van Den Dobbelsteen, John

    2012-11-01

    Accurate placement of the needle tip is essential in percutaneous therapies such as radiofrequency ablation (RFA) of liver tumors. Use of a robotic system for navigating the needle could improve the targeting accuracy. Real-time information on the needle tip position is needed, since a needle deflects during insertion in tissue. Needle shape can be reconstructed based on strain measurements within the needle. In the current experiment we determined the accuracy with which the needle tip position can be derived from strain measurements using Fiber Bragg Gratings (FBGs). Three glass fibers equipped with two FBGs each were incorporated in a needle. The needle was clamped at one end and deformed by applying static radial displacements at one or two locations. The FBG output was used for offline estimation of the needle shape and tip position. During deflections of the needle tip up to 12.5 mm, the tip position was estimated with a mean accuracy of 0.89 mm (std 0.42 mm). Adding a second deflection resulted in an error of 1.32 mm (std 0.48 mm). This accuracy is appropriate for applications such as RFA of liver tumors. The results further show that the accuracy can be improved by optimizing the placement of FBGs. PMID:22455615

  16. Nuclear Bragg diffraction of synchrotron x-rays

    International Nuclear Information System (INIS)

    In the last few years several groups have successfully carried out experiments involving the excitation of nuclear resonances using synchrotron radiation. All the experiments so far have used 57Fe as the resonant nucleus. The extremely narrow width of the 14.4 keV resonance in 57Fe makes these experiments very difficult at even the highest-brightness synchrotron beam lines currently available, so much effort is being devoted toward improvements in equipment and techniques. The general aim of this work is to use resonant scattering to produce high-flux beams of extremely monochromatic radiation, which can then be used as source beams for a variety of experiments. This talk, however, will stress the kinds of physics questions that can be answered using broad-band synchrotron radiation to induce resonant nuclear diffraction in perfect crystal samples. Experiments of this type are being carried out today, albeit with difficulty, using present synchrotron sources. They will become technically easy when advanced sources such as the APS become available, and it is expected that nuclear Bragg diffraction will become a standard technique

  17. Perimeter security alarm system based on fiber Bragg grating

    Science.gov (United States)

    Zhang, Cui; Wang, Lixin

    2010-11-01

    With the development of the society and economy and the improvement of living standards, people need more and more pressing security. Perimeter security alarm system is widely regarded as the first line of defense. A highly sensitive Fiber Bragg grating (FBG) vibration sensor based on the theory of the string vibration, combined with neural network adaptive dynamic programming algorithm for the perimeter security alarm system make the detection intelligently. Intelligent information processing unit identify the true cause of the vibration of the invasion or the natural environment by analyzing the frequency of vibration signals, energy, amplitude and duration. Compared with traditional perimeter security alarm systems, such as infrared perimeter security system and electric fence system, FBG perimeter security alarm system takes outdoor passive structures, free of electromagnetic interference, transmission distance through optical fiber can be as long as 20 km It is able to detect the location of event within short period of time (high-speed response, less than 3 second).This system can locate the fiber cable's breaking sites and alarm automatically if the cable were be cut. And the system can prevent effectively the false alarm from small animals, birds, strong wind, scattering things, snowfalls and vibration of sensor line itself. It can also be integrated into other security systems. This system can be widely used in variety fields such as military bases, nuclear sites, airports, warehouses, prisons, residence community etc. It will be a new force of perimeter security technology.

  18. Composite scarf repair monitoring using fiber Bragg grating sensors

    Science.gov (United States)

    Li, Henry C. H.; Herszberg, Israel; Davis, Claire E.; Stoddart, Paul R.

    2007-04-01

    Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair efficacy. This paper describes an SHM technique for the detection of debonding in composite scarf repairs using fibre optic Bragg grating strain sensors. A typical composite sandwich structure with a scarf repair on one surface is examined in this paper. A finite element study was conducted which showed that the strain in the debonded region changed significantly compared to the undamaged state. A differential strain approach was used to facilitate the detection of debonds, where two sensors were strategically positioned so that their strain differential increased as the damage propagated. With the use of matching gratings, this technique greatly reduced the support equipment requirement by converting the spectral information into an intensity-modulated signal, thus allowing a compact photodetector to be used for sensor interrogation. An experimental investigation was conducted to validate the theoretically predicted results. The experimental measurements agreed well with the numerical findings qualitatively, indicating that the proposed scheme has great potential as a simple and effective monitoring technique for composite scarf repairs.

  19. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    Science.gov (United States)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  20. Adaptive Integrated Optical Bragg Grating in Semiconductor Waveguide Suitable for Optical Signal Processing

    Science.gov (United States)

    Moniem, T. A.

    2016-05-01

    This article presents a methodology for an integrated Bragg grating using an alloy of GaAs, AlGaAs, and InGaAs with a controllable refractive index to obtain an adaptive Bragg grating suitable for many applications on optical processing and adaptive control systems, such as limitation and filtering. The refractive index of a Bragg grating is controlled by using an external electric field for controlling periodic modulation of the refractive index of the active waveguide region. The designed Bragg grating has refractive indices programmed by using that external electric field. This article presents two approaches for designing the controllable refractive indices active region of a Bragg grating. The first approach is based on the modification of a planar micro-strip structure of the iGaAs traveling wave as the active region, and the second is based on the modification of self-assembled InAs/GaAs quantum dots of an alloy from GaAs and InGaAs with a GaP traveling wave. The overall design and results are discussed through numerical simulation by using the finite-difference time-domain, plane wave expansion, and opto-wave simulation methods to confirm its operation and feasibility.

  1. Effects of Coating and Diametric Load on Fiber Bragg Gratings as Cryogenic Temperature Sensors

    Science.gov (United States)

    Wu, meng-Chou; Pater, Ruth H.; DeHaven, Stanton L.

    2008-01-01

    Cryogenic temperature sensing was demonstrated using pressurized fiber Bragg gratings (PFBGs) with polymer coating of various thicknesses. The PFBG was obtained by applying a small diametric load to a regular fiber Bragg grating (FBG). The Bragg wavelengths of FBGs and PFBG were measured at temperatures from 295 K to 4.2 K. The temperature sensitivities of the FBGs were increased by the polymer coating. A physical model was developed to relate the Bragg wavelength shifts to the thermal expansion coefficients, Young's moduli, and thicknesses of the coating polymers. When a diametric load of no more than 15 N was applied to a FBG, a pressure-induced transition occurred at 200 K during the cooling cycle. The pressure induced transition yielded PFBG temperature sensitivities three times greater than conventional FBGs for temperatures ranging from 80 to 200 K, and ten times greater than conventional fibers for temperatures below 80 K. PFBGs were found to produce an increased Bragg wavelength shift of 2.2 nm compared to conventional FBGs over the temperature range of 4.2 to 300 K. This effect was independent of coating thickness and attributed to the change of the fiber thermo-optic coefficient.

  2. The influence of adhesive on fiber Bragg grating strain sensor

    Science.gov (United States)

    Chen, Jixuan; Gong, Huaping; Jin, Shangzhong; Li, Shuhua

    2009-08-01

    A fiber Bragg grating (FBG) sensor was fixed on the uniform strength beam with three adhesives, which were modified acrylate, glass glue and epoxy resin. The influence of adhesive on FBG strain sensor was investigated. The strain of FBG sensor was varied by loading weight to the uniform strength beam. The wavelength shift of the FBG sensor fixed by the three kinds of adhesive were measured with different weight at the temperatures 0°C, 10°C, 20°C, 30°C, 40°C. The linearity, sensitivity and their stability at different temperature of FBG sensor which fixed by every kind of adhesives were analyzed. The results show that, the FBG sensor fixed by the modified acrylate has a high linearity, and the linear correlation coefficient is 0.9996. It also has a high sensitivity which is 0.251nm/kg. The linearity and the sensitivity of the FBG sensor have a high stability at different temperatures. The FBG sensor fixed by the glass glue also has a high linearity, and the linear correlation coefficient is 0.9986, but it has a low sensitivity which is only 0.041nm/kg. The linearity and the sensitivity of the FBG sensor fixed by the glass glue have a high stability at different temperatures. When the FBG sensor is fixed by epoxy resin, the sensitivity and linearity is affected significantly by the temperature. When the temperature changes from 0°C to 40°C, the sensitivity decreases from 0.302nm/kg to 0.058nm/kg, and the linear correlation coefficient decreases from 0.9999 to 0.9961.

  3. Efficiency-enhanced AlGaInP Light-Emitting Diodes with Thin Window Layers and Coupled Distributed Bragg Reflectors

    Institute of Scientific and Technical Information of China (English)

    CHEN Yi-Xin; SHEN Guang-Di; ZHU Yan-Xu; GUO Wei-Ling; LI Jian-Jun

    2011-01-01

    @@ A new structure of high-brightness light-emitting diodes (LED) is experimentally demonstrated.The thin window layer is composed of a 300-nm-thick indium-tin-oxide layer and a 500-nm-thick GaP layer for both current spreading and light anti-reflection.The two coupled distributed Bragg reflectors (DBRs) with one for reflecting normal incidence light and the other for reflecting inclined incidence light which is emitted to the GaAs substrate are employed in the LED fabrication.The coupled DBRs in the LED can provide high reflectivity with wide- angle reflection.The effficiency-enhanced AlGaInP LED has the luminance intensity increase of more than 50% compared with conventional LEDs and high reliability with the saturation current 130mA.

  4. A double-Bragg detector with digital signal processing for the event-by-event study of fission in actinide nuclei

    Science.gov (United States)

    Frost, R. J. W.; Smith, A. G.

    2016-09-01

    In the current paper, a windowless double-Bragg chamber incorporating full signal digitisation has been developed for the purpose of studying the energy (E), mass (A), charge (Z) and angular distributions (θ, Φ) of nuclei generated by fission. This device measures E for each fission fragment by collection of the charge produced during ionisation of the fill gas. Subsequent digitisation of the signals from each of two anodes yields information on dE/dx, as well as electron collection time, which can be further used for polar angle (θ) determination. Frisch-grid and cathode signals are also digitised and are used both for anode signal correction and to produce further information on θ. To verify the operation of this detector, three angular determination techniques from the literature were implemented, and the results were found to be consistent with the referenced paper. Current results from the spontaneous fission of 252Cf are presented.

  5. Investigations on birefringence effects in polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Hu, Xiaolian; Saez-Rodriguez, D.; Bang, Ole;

    2014-01-01

    birefringence effects in (m)POFBGs. To achieve this, highly reflective gratings were inscribed with the phase mask technique. They were then monitored in transmission with polarized light. For this, (m)POF sections a few cm in length containing the gratings were glued to angled silica fibers. Polarization...

  6. Characteristics of AlN/GaN nanowire Bragg mirror grown on (001) silicon by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Junseok; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States); Zhou, Zifan [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Guo, Wei [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ooi, Boon S. [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2013-10-28

    GaN nanowires containing AlN/GaN distributed Bragg reflector (DBR) heterostructures have been grown on (001) silicon substrate by molecular beam epitaxy. A peak reflectance of 70% with normal incidence at 560 nm is derived from angle resolved reflectance measurements on the as-grown nanowire DBR array. The measured peak reflectance wavelength is significantly blue-shifted from the ideal calculated value. The discrepancy is explained by investigating the reflectance of the nanoscale DBRs with a finite difference time domain technique. Ensemble nanowire microcavities with In{sub 0.3}Ga{sub 0.7}N nanowires clad by AlN/GaN DBRs have also been characterized. Room temperature emission from the microcavity exhibits considerable linewidth narrowing compared to that measured for unclad In{sub 0.3}Ga{sub 0.7}N nanowires. The resonant emission is characterized by a peak wavelength and linewidth of 575 nm and 39 nm, respectively.

  7. Field analysis of TE and TM modes in photonic crystal Bragg fibers by transmission matrix method

    Directory of Open Access Journals (Sweden)

    M Hosseini Farzad

    2010-03-01

    Full Text Available In this article, we considered the field analysis in photonic crystal Bragg fibers. We apply the method of transmission matrix to calculater the dispersion curves, the longitudinal wave number over wave number versus incident wavelength, and the field distributions of TE and TM modes in the Bragg fiber. Our analysis shows that the field of guided modes is confined in the core and can exist only in particular wavelength bands corresponding to the band-gap of the periodic structure of the clad. From another point of view, light confinement is due to Bragg reflection from high-and low-refractive index layers of the clad. Also, the diagram of average angular frequency with respect to average longitudinal wave number is plotted so that the band gap regions of the clad are clearly observed.

  8. A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

    Institute of Scientific and Technical Information of China (English)

    姜莉; 张东生; 董兴法; 开桂云; 董孝义

    2004-01-01

    A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.

  9. Characteristics of Bragg Gratings in All-Solid Photonic Bandgap Fiber

    Institute of Scientific and Technical Information of China (English)

    Bai-Ou Guan; Zhi Wang; Yang Zhang; Da Chen

    2008-01-01

    We report on fiber Bragg gratings in all-solid photonie bandgap fiber that was composed of a triangular array of high-index Ge-doped rods in pure silica background with fluorine-doped index-depressed layer surrounding the Ge-doped rod. Fiber Bragg gratings were photowritten with 193 nm ArF excimer laser and characterized for their response to strain, temperature, bending, and torsion. These gratings couple light from the forward core mode to not only backward core mode but also backward rod modes. This results in multiple resonance peaks in the reflection spectrum. All resonance wavelengths exhibited the same temperature and strain response with coefficient similar to that of Bragg gratings in standard single-mode fiber. The strength of the resonance peaks corresponding to the backward rod modes showed high sensitivity to bending and torsion.

  10. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    Science.gov (United States)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

  11. Design of a Label-Free, Distributed Bragg Grating Resonator Based Dielectric Waveguide Biosensor

    Directory of Open Access Journals (Sweden)

    Florian Kehl

    2015-01-01

    Full Text Available In this work, we present a resonant, dielectric waveguide device based on distributed Bragg gratings for label-free biosensing applications. The refractive index sensitive optical transducer aims at improving the performance of planar waveguide grating sensor systems with limited Q-factor and dynamic range by combing the advantages of resonant cavities, such as a multitude of resonance peaks with high finesse, with the manageable complexity of waveguide grating couplers. The general sensor concept is introduced and supported by theoretical considerations as well as numerical simulations based on Coupled Mode Theory. In contrast to a single Bragg grating reflector, the presented Fabry-Pérot type distributed Bragg resonator exhibits an extended measurement range as well as relaxed fabrication tolerances. The resulting, relatively simple sensor structure can be fabricated with standard lithographic means and is independent of expensive light-sources and/or detectors, making an affordable but sensitive device, potentially suitable for point-of-care applications.

  12. Fiber Optic Vibration Sensor Based on the Tilted Fiber Bragg Grating

    Directory of Open Access Journals (Sweden)

    Jiali An

    2013-01-01

    Full Text Available A temperature-insensitive fiber optic vibration sensor based on the tilted fiber Bragg grating (TFBG is presented. The sensing head is formed by insertion of a small section of MMF between a single-mode fiber and the TFBG. The reflection light from this tilted fiber Bragg grating includes two parts: the reflected Bragg mode and the cladding modes. The cladding modes were coupled back into the core mode as a function of the multimode fiber. The power of the cladding modes is sensitive to vibration, so the external vibration measurement can be obtained through the cladding mode average output power. Experiment results show that the root mean square (RMS of the detection error of the average power was 0.01 μW within the temperature range from 20 to 70°C, so it is proved to be temperature independent; its frequency response has been tested to 1 KHz.

  13. Bragg Grating Based Sensors in Microstructured Polymer Optical Fibers: Accelerometers and Microphones

    DEFF Research Database (Denmark)

    Stefani, Alessio

    With the growing interest towards fiber Bragg grating sensors and the growing ability in manufacturing polymer optical fibers, the development of polymer fiber Bragg sensors has catched the attention of industries with the goal of developing high performance sensors. This thesis presents...... the development of fiber sensors based on polymer optical fiber Bragg gratings. The whole process from the preform to the device is discussed and reported. A presentation on the fiber drawing technique used is given. Issues encountered when working with polymer fibers and solutions concerning fiber cleaving...... gratings is shown and temperature compensation of strain sensors, by using two adjacent gratings, is demonstrated. Humidity insensitivity in a strain sensor based on a TOPAS fiber is also shown. In order to investigate the possibility of using viscoelastic materials, such as polymers, in dynamic sensors...

  14. Liquid-core low-refractive-index-contrast Bragg fiber sensor

    CERN Document Server

    Qu, Hang

    2011-01-01

    We propose and experimentally demonstrate a low-refractive-index-contrast hollow-core Bragg fiber sensor for liquid analyte refractive index detection. The sensor operates using a resonant sensing principle- when the refractive index of a liquid analyte in the fiber core changes, the resonant confinement of the fiber guided mode will also change, leading to both the spectral shifts and intensity changes in fiber transmission. As a demonstration, we characterize the Bragg fiber sensor using a set of NaCl solutions with different concentrations. Strong spectral shifts are obtained with the sensor experimental sensitivity found to be ~1400nm/RIU (refractive index unit). Besides, using theoretical modeling we show that low-refractive-index-contrast Bragg fibers are more suitable for liquid-analyte sensing applications than their high-refractive-index-contrast counterparts.

  15. Numerical investigation of slow solitons in Bragg gratings with a hyperbolic tangent apodization

    International Nuclear Information System (INIS)

    This paper numerically and analytically investigates the formation and propagation motion of optical soliton in the Bragg grating. We choose the fibre Bragg grating with hyperbolic tangent apodization in the middle section in order to obtain slower solitons. Optical fibre soliton but not Bragg grating soliton is used as input pulse in the discussion, which is much more approximate to the light source for the practical purpose. We discuss in detail the effects of the soliton's velocity with some parameters in the process of transmission. The results show that by choosing special parameters, one can make the soliton slow-down with a little distortion and energy decay and obtain tunable time-delay on a small scale. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  16. Non-Bragg Resonance of Standing Acoustic Wave in a Cylindrical Waveguide with Sinusoidally Perturbed Walls

    Institute of Scientific and Technical Information of China (English)

    TAO Zhi-Yong; XIAO Yu-Meng; WANG Xin-Long

    2005-01-01

    @@ A novel type of acoustic resonance different from the well-known Bragg resonance is predicted theoretically in an acoustic cylindrical waveguide with sinusoidally perturbed hard walls. The resonance is caused by the interaction between the standing acoustic waves, i.e. transverse modes in the waveguide. It results in the frequency spectrum splitting and the appearance of forbidden bands. For small-perturbed wall corrugation, it is found that the shifts of resonant frequencies and the width of the forbidden gap can be as small as the wall amplitude. The appearance of the non-Bragg resonance depends highly on the wall period. When the period is greater than 2.319 times the average cylinder radius, all the non-Bragg resonances cut off. The smaller the wall period, the greater the transverse mode involvement.

  17. Bragg band gaps tunability in an homogeneous piezoelectric rod with periodic electrical boundary conditions

    Science.gov (United States)

    Degraeve, S.; Granger, C.; Dubus, B.; Vasseur, J. O.; Pham Thi, M.; Hladky-Hennion, A.-C.

    2014-05-01

    An homogeneous piezoelectric rod is shown to exhibit Bragg band gaps when an electrical boundary condition is applied periodically with the help of metallic electrodes. An analytical model is developed which formulation depends on the applied electric boundary condition and reveals that Bragg band gaps occurring in this very peculiar phononic crystal are related to the electric charge located on the electrodes. Moreover, via an accurate boundary condition (electrodes connected in short circuit, in open circuit, or through an external capacitance), full tunability of the Bragg band gaps can be achieved. Measurements of ultrasonic transmission present an overall excellent agreement with the theoretical results. This phononic crystal can be easily manufactured and presents many potential applications as frequency filters especially for radio frequency telecommunications.

  18. Numerical investigation of slow solitons in Bragg gratings with a hyperbolic tangent apodization

    Institute of Scientific and Technical Information of China (English)

    Wang Kui-Ru; Cheng Jie-Lin; Sang Xin-Zhu; Chen Gong

    2011-01-01

    This paper numerically and analytically investigates the formation and propagation motion of optical soliton in the Bragg grating. We choose the fibre Bragg grating with hyperbolic tangent apodization in the middle section in order to obtain slower solitons. Optical fibre soliton but not Bragg grating soliton is used as input pulse in the discussion, which is much more approximate to the light source for the practical purpose. We discuss in detail the effects of the soliton's velocity with some parameters in the process of transmission. The results show that by choosing special parameters, one can make the soliton slow-down with a little distortion and energy decay and obtain tunable time-delay on a small scale.

  19. All-Silica Hollow-Core Microstructured Bragg Fibers for Biosensor Application

    DEFF Research Database (Denmark)

    Passaro, Davide; Foroni, Matteo; Poli, Federica;

    2008-01-01

    The possibility to exploit all-silica hollow-core-microstructured Bragg fibers to realize a biosensor useful to detect the DNA hybridization process has been investigated. A Bragg fiber recently fabricated has been considered for the analysis performed by means of a full-vector modal solver based...... on the finite-element method. Since the DNA molecules necessary for the biosensor realization are in aqueous solution, it has been taken into account a microstructured fiber with water-filled holes. The dispersion curve and the confinement loss spectrum have been calculated in order to understand how...... a biofilm layer on the inner surface of the fiber holes can modify the fundamental mode properties. The numerical analysis results have successfully demonstrated the DNA bio-sensor feasibility in hollow-core Bragg fibers....

  20. Acoustical “transparency” induced by local resonance in Bragg bandgaps

    International Nuclear Information System (INIS)

    We show that sound waves can resonantly transmit through Bragg bandgaps in an acoustical duct periodically attached with an array of Helmholtz resonators, forming within the normally forbidden band a transparency window with group velocity smaller than the normal speed of sound. The transparency occurs for the locally resonant frequency so much close to the Bragg one that both the local-resonance-induced bandgap and the Bragg one heavily overlap with each other. The phenomenon seems an acoustical analog of the well-known electromagnetically induced transparency by quantum interference. Different from the Fano-like interference explanation, we also provide a mechanism for the transparency window phenomenon which makes it possible to extend the phenomenon in general

  1. Acoustical “transparency” induced by local resonance in Bragg bandgaps

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Gaokun; Wang, Xinlong, E-mail: xlwang@nju.edu.cn [Key Laboratory of Modern Acoustics and Institute of Acoustics, Nanjing University, Nanjing 210093 (China)

    2014-01-28

    We show that sound waves can resonantly transmit through Bragg bandgaps in an acoustical duct periodically attached with an array of Helmholtz resonators, forming within the normally forbidden band a transparency window with group velocity smaller than the normal speed of sound. The transparency occurs for the locally resonant frequency so much close to the Bragg one that both the local-resonance-induced bandgap and the Bragg one heavily overlap with each other. The phenomenon seems an acoustical analog of the well-known electromagnetically induced transparency by quantum interference. Different from the Fano-like interference explanation, we also provide a mechanism for the transparency window phenomenon which makes it possible to extend the phenomenon in general.

  2. Response of some pi-phase-shifted Bragg gratings to elevated pressure

    Science.gov (United States)

    Bal, Harpreet K.; Dragomir, Nicoleta M.; Sidiroglou, Fotios; Wade, Scott A.; Baxter, Greg W.; Collins, Stephen F.

    2011-05-01

    The effect of pressures up to 200 kPa on pi-phase-shifted Bragg gratings was investigated in several types of fibers placed in a pressure chamber. Standard and alternative types of pi-phase shifted gratings were studied, and changes in reflection spectra caused by pressure changes were monitored. The alternative pi-phase shifted grating was fabricated using a phase mask with 536-nm pitch exhibiting features at twice the Bragg wavelength near 1552 nm due to the interleaved refractive index modulations along the fiber core with the periodicity of the phase mask. The three gratings studied exhibited quite different variation in Bragg wavelength with increased pressure for the different fiber types, and the alternative pi-phase-shifted grating in Corning HI 1060 FLEX fiber also suffered a significant change in the shape of the peaks.

  3. Clear as Crystal: The Story of the Braggs--How X-Ray Crystallography Has Contributed to Science

    Science.gov (United States)

    George, Robert; Patterson, John

    2014-01-01

    Here is a brief history of the work of two of Australia's most famous scientists, Sir William Bragg and his son Sir Lawrence Bragg. Jointly awarded the Nobel Prize in 1915 for their groundbreaking research into the use of X-rays to study the chemical structure and function of molecules, they have contributed to our heritage and to science at…

  4. Double hexagonal close-packed structure revealed in a single colloidal crystal grain by Bragg rod analysis

    NARCIS (Netherlands)

    Meijer, J. M.; Shabalin, A.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobstov, O.; Dzhigaev, D.; Gulden, J.; Byelov, D. V.; Zozulya, A. V.; Sprung, M.; Vartanyants, I. A.; Petukhov, Andrei V.

    2014-01-01

    A coherent X-ray diffraction study of a single colloidal crystal grain composed of silica spheres is reported. The diffraction data contain Bragg peaks and additional features in the form of Bragg rods, which are related to the stacking of the hexagonally close-packed layers. The profile of the Brag

  5. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen

    Science.gov (United States)

    Butov, Oleg V.; Golant, Konstantin M.; Shevtsov, Igor'A.; Fedorov, Artem N.

    2015-08-01

    The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded "in-situ" in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmission spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.

  6. Fiber Bragg gratings in the radiation environment: Change under the influence of radiolytic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Butov, Oleg V., E-mail: obutov@mail.ru; Golant, Konstantin M. [Kotel' nikov Institute of Radio-Engineering and Electronics of RAS, 11-7 Mokhovaya Str., Moscow 125009 (Russian Federation); Shevtsov, Igor' A.; Fedorov, Artem N. [Prolog LLC, PO Box 3007, Obninsk, the Kaluga Region 249033 (Russian Federation)

    2015-08-21

    The change of the transmission spectra of fiber Bragg gratings written in the optical fibers, whose silica cores are doped with either germanium or nitrogen, is studied experimentally under the influence of gamma-radiation. The transmission spectra in the neighborhood of the resonance (Bragg) wavelengths were regularly recorded “in-situ” in the course of irradiation during 24 days. For this purpose, uncoated gratings were placed in a pool near the spent fuel rods of a nuclear reactor. The fibers with the gratings written in them were in immediate contact with water. The estimated total absorbed radiation dose of the fibers is approximately 5 MGy. Molecular hydrogen, which is produced by radiolysis of water and penetrates into the core of silica fiber, is found to interact with the defects of Ge-doped silica induced by gamma-radiation, thereby causing a strong impact on the parameters of the spectrum of the Bragg gratings. On the contrary, in the case of gratings inscribed in N-doped silica fibers, the hydrogen molecules interact with defects induced in the course of laser UV exposure during the grating writing only. The possible subsequent formation of additional defects in N-doped silica under the influence of gamma-radiation has no substantial impact on the transmission spectra of Bragg gratings, which remained stable. The obtained results suggest that a small amount of molecular hydrogen resided in the fiber core is the main source of radiation instability of Ge-doped fiber Bragg grating sensors in radiation environments. These hydrogen molecules can remain in the Bragg gratings, in particular, after the inscription process in the hydrogen-loaded fibers.

  7. Two Comments on Bond Angles

    Science.gov (United States)

    Glaister, P.

    1997-09-01

    Tetrahedral Bond Angle from Elementary Trigonometry The alternative approach of using the scalar (or dot) product of vectors enables the determination of the bond angle in a tetrahedral molecule in a simple way. There is, of course, an even more straightforward derivation suitable for students who are unfamiliar with vectors, or products thereof, but who do know some elementary trigonometry. The starting point is the figure showing triangle OAB. The point O is the center of a cube, and A and B are at opposite corners of a face of that cube in which fits a regular tetrahedron. The required bond angle alpha = AÔB; and using Pythagoras' theorem, AB = 2(square root 2) is the diagonal of a face of the cube. Hence from right-angled triangle OEB, tan(alpha/2) = (square root 2) and therefore alpha = 2tan-1(square root 2) is approx. 109° 28' (see Fig. 1).

  8. Interrogating a Fiber Bragg Grating Vibration Sensor by Narrow Line Width Light

    Institute of Scientific and Technical Information of China (English)

    Jun Chang; Dian-Heng Huo; Liang-Zhu Ma; Xiao-Hui Liu; Tong-Yu Liu; Chang Wang

    2008-01-01

    A method to interrogate fiber Bragg grating vibration sensor by narrow line width light is demonstrated. The interrogation scheme takes advantage of the intensity modulation of narrow spectral bandwidth light, such as distributed feedback laser, when a reflection or transmission spectrum curve of an fiber Bragg grating (FBG) moves due to the strain which is applied on the sensor. The sensor's response to accelerating frequency and amplitude is measured by experiment. The factors which have impacts on the sensitivity of the interrogation system are also discussed.

  9. Magnetic field sensor based on fiber Bragg grating with a spiral microgroove ablated by femtosecond laser.

    Science.gov (United States)

    Dai, Yutang; Yang, Minghong; Xu, Gang; Yuan, Yinquan

    2013-07-15

    A novel magnetic field sensor based on Terfenol-D coated fiber Bragg grating with spiral microstructure was proposed and demonstrated. Through a specially-designed holder, the spiral microstructure was ablated into the fiber Bragg grating (FBG) cladding by femtosecond laser. Due to the spiral microstructure, the sensitivity of FBG coated with magnetostrictive film was enhanced greatly. When the spiral pitch is 50 μm and microgroove depth is 13.5 μm, the sensitivity of the magnetic field sensor is roughly 5 times higher than that of non-microstructured standard FBG. The response to magnetic field is reversible, and could be applicable for magnetic field detection.

  10. Dose ratio proton radiography using the proximal side of the Bragg peak

    OpenAIRE

    Doolan, P. J.; Royle, G; Gibson, A.; Lu, H-M; Prieels, D.; Bentefour, E. H.

    2015-01-01

    Purpose: In recent years there has been a movement towards single-detector proton radiography, due to its potential ease of implementation within the clinical environment. One such single-detector technique is the dose ratio method, in which the dose maps from two pristine Bragg peaks are recorded beyond the patient. To date, this has only been investigated on the distal side of the lower energy Bragg peak, due to the sharp fall-off. We investigate the limits and applicability of the dose rat...

  11. Detecting antiferromagnetism of atoms in an optical lattice via optical Bragg scattering

    OpenAIRE

    Corcovilos, T. A.; Baur, S. K.; Hitchcock, J. M.; Mueller, E. J.; Hulet, R. G.

    2009-01-01

    Antiferromagnetism of ultracold fermions in an optical lattice can be detected by Bragg diffraction of light, in analogy to the diffraction of neutrons from solid state materials. A finite sublattice magnetization will lead to a Bragg peak from the (1/2 1/2 1/2) crystal plane with an intensity depending on details of the atomic states, the frequency and polarization of the probe beam, the direction and magnitude of the sublattice magnetization, and the finite optical density of the sample. Ac...

  12. Novel Distributed Fiber Bragg Grating Sensing System Based on M-Z Interferometer

    Institute of Scientific and Technical Information of China (English)

    WU Guo-qing; BI Wei-hong; LI Hong

    2005-01-01

    One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.

  13. Monitoring of ultraviolet pulse rate dependent photomechanical actuation in carbon nanotubes using fiber Bragg gratings

    Energy Technology Data Exchange (ETDEWEB)

    Shivananju, B. N.; Suri, Ashish [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore (India); Asokan, S. [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore (India); Applied Photonics Initiative, Indian Institute of Science, Bangalore (India); Robert Bosch Centre for Cyber Physical Systems, Indian Institute of Science, Bangalore (India); Misra, Abha, E-mail: abha@iap.iisc.ernet.in [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore (India); Applied Photonics Initiative, Indian Institute of Science, Bangalore (India)

    2014-01-06

    In this Letter, we present a non-contact method of controlling and monitoring photomechanical actuation in carbon nanotubes (CNT) by exposing it to ultra-violet radiation at different pulse rates (10 to 200 Hz). This is accomplished by imparting a reversible photo induced strain (5–330 με) on CNT coated fibre Bragg gratings; CNT undergoes an internal reversible structural change due to cyclic photon absorption that leads to the development of mechanical strain, which in turn allows reversible switching of the Bragg wavelength. The results also reveal an interesting pulse rate dependent rise and fall times of photomechanical actuation in CNT.

  14. A flat microwave photonic filter based on M-Z modulatorand fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    QI Chun-hui; PEI Li; NING Ti-gang; GUO Lan; WU Shu-qiang; ZHAO Rui-feng; RUAN Yi

    2009-01-01

    A new multiple-taps and flat microwave photonic filter, which is composed of fiber Bragg grating, M-Z modulator and erbium-doped fiber, is put forward. The flat band-pass or flat band-stop response can be realized by adjusting the coupler's factor and the reflectivity of the fiber Bragg grating or the gain of the erbium-doped fiber. The free spectral range of the filter can be tuned by controlling the length of the erbium-doped fiber. The potential and feasibility of the proposed filtering structures have been demonstrated by simulation.

  15. Time-dependent Bragg diffraction and short-pulse reflection by one-dimensional photonic crystals

    CERN Document Server

    André, Jean-michel

    2015-01-01

    The time-dependence of the Bragg diffraction by one-dimensional photonic crystals and its influence on the short pulse reflection are studied in the framework of the coupled- wave theory. The indicial response of the photonic crystal is calculated and it appears that it presents a time-delay effect with a transient time conditioned by the extinction length. A numerical simulation is presented for a Bragg mirror in the x-ray domain and a pulse envelope modelled by a sine-squared shape. The potential consequences of the time-delay effect in time-dependent optics of short-pulses are emphasized.

  16. Multiband processing of multimode light: combining 3D photonic lanterns with waveguide Bragg gratings

    OpenAIRE

    Spaleniak, Izabela; Gross, Simon; Jovanovic, Nemanja; Williams, Robert J.; Lawrence, Jon S.; Ireland, Michael J.; Withford, Michael J.

    2013-01-01

    The first demonstration of narrowband spectral filtering of multimode light on a 3D integrated photonic chip using photonic lanterns and waveguide Bragg gratings is reported. The photonic lanterns with multi-notch waveguide Bragg gratings were fabricated using the femtosecond direct-write technique in boro-aluminosilicate glass (Corning, Eagle 2000). Transmission dips of up to 5 dB were measured in both photonic lanterns and reference single-mode waveguides with 10.4-mm-long gratings. The res...

  17. Direct UV written planar Bragg gratings that feature zero fluence induced birefringence

    Science.gov (United States)

    Holmes, Christopher; Cooper, Peter A.; Fernando, Harendra N. J.; Stroll, Andreas; Gates, James C.; Krishnan, Chirenjeevi; Haynes, Roger; Mennea, Paolo L.; Carpenter, Lewis G.; Gawith, Corin B. E.; Roth, Martin M.; Charlton, Martin D.; Smith, Peter G. R.

    2015-12-01

    Direct UV writing is a planar fabrication process capable of simultaneously defining waveguides and Bragg gratings. The technique is fully computer controlled and uniquely uses a small focused spot ~7 μm in diameter for direct writing exposure. This work investigates its use to achieve phase trimming and Bragg grating definition in silica-on-silicon lithographic waveguides. It is observed that birefringence control using direct UV writing can be made independent of exposure fluence with this technique through tailoring substrate stress. The result is demonstrated experimentally and supported theoretically using finite element analysis.

  18. A high sensitive fiber Bragg grating strain sensor with automatic temperature compensation

    Institute of Scientific and Technical Information of China (English)

    Kuo Li; Zhen'an Zhou

    2009-01-01

    A high sensitive fiber Bragg grating (FBG) strain sensor with automatic temperature compensation is demonstrated. FBG is axially linked with a stick and their free ends are fixed to the measured object. When the measured strain changes, the stick does not change in length, but the FBG does. When the temperature changes, the stick changes in length to pull the FBG to realize temperature compensation. In experiments, 1.45 times strain sensitivity of bare FBG with temperature compensation of less than 0.1 nm Bragg wavelength drift over 100℃ shift is achieved.

  19. High sensitivity, low-systematics atom interferometers using Bragg diffraction and Bloch oscillations

    CERN Document Server

    Estey, Brian; Müller, Holger; Kuan, Pei-Chen; Lan, Shau-Yu

    2014-01-01

    We describe a new scheme for atom interferometry based on both large-momentum transfer Bragg beam splitters and Bloch oscillations. Combining the advantages of previous approaches to recoil-sensitive interferometers, we increase the signal and suppress a systematic phase shift caused by Bragg diffraction at least 60-fold, matching experiment to theory; the systematic shift can be eliminated from Mach-Zehnder interferometers. We demonstrate high contrast, interference with up to 4.4 million radians of phase difference between freely evolving matter waves, and a resolution of $\\delta \\alpha/\\alpha=0.33\\,$ppb$\\sqrt{\\rm 6h}$ available to measurements of the fine structure constant.

  20. Finite-difference modeling of Bragg fibers with ultrathin cladding layers via adaptive coordinate transformation

    DEFF Research Database (Denmark)

    Shyroki, Dzmitry; Lægsgaard, Jesper; Bang, Ole;

    As an alternative to the finite-element analysis or subgridding, coordinate transformation is used to “stretch” the fine-structured cladding of a Bragg fiber, and then the fullvector, equidistant-grid finite-difference computations of the modal structure are performed.......As an alternative to the finite-element analysis or subgridding, coordinate transformation is used to “stretch” the fine-structured cladding of a Bragg fiber, and then the fullvector, equidistant-grid finite-difference computations of the modal structure are performed....

  1. Dual Measurements of Pressure and Temperature With Fiber Bragg Grating Sensor

    OpenAIRE

    Tahreer S. Mansour; Fahad M. Abdulhussein

    2015-01-01

    The fiber Bragg grating (FBG) technology has been rapidly applied in the sensing technology field. In this work, uniform FBG was used as pressure sensor based on measuring related Bragg wavelength shift. The pressure was applied directly by air compressor to the sensor and the pressure was ranged from 1 to 6 bar. This sensor also was affected by the external temperature so as a result it could be used as a temperature sensor. This sensor could be used to monitor the pressure of dams. It has b...

  2. High resolution Bragg-Fresnel optics for nanometer scale methods with soft X-rays

    OpenAIRE

    Erko, A.

    1994-01-01

    The main principles and some applications of Bragg-Fresnel multilayer optics are described. An elliptical Bragg-Fresnel multilayer lens (BFML), designed and fabricated in the IMT RAS has been used for 2-dimensional focusing of the white X-ray synchrotron beam. For the beam energy of about 12 KeV the spot size checked with the knife edge method was about 1µm. As an example of a successful application of this optical element in x-ray imaging, the fluorescence X-Ray scanning LURE-IMT microprobe ...

  3. A Directly-Written Monolithic Waveguide-Laser Incorporating a DFB Waveguide-Bragg Grating

    CERN Document Server

    Marshall, Graham D; Ams, Martin; Piper, James A; Withford, Michael J

    2008-01-01

    We report the fabrication and performance of the first C-band directly-written monolithic waveguide-laser. The waveguide-laser device was created in an Erbium and Ytterbium doped phosphate glass host and consisted of an optical waveguide that included a distributed feedback Bragg grating structure. The femtosecond laser direct-write technique was used to create both the waveguide and the waveguide-Bragg grating simultaneously and in a single processing step. The waveguide-laser was optically pumped at approximately 980 nm and lased at 1537nm with a bandwidth of less than 4 pm.

  4. Dynamic Landslide Deformation Monitoring with Fiber Bragg Grating Sensors

    Science.gov (United States)

    Moore, J. R.; Gischig, V.; Button, E.; Loew, S.

    2009-12-01

    Fiber optic (FO) strain sensors are a promising new technology for in-situ landslide monitoring. General performance advantages include high resolution, fast sampling rate, and insensitivity to electrical disturbances. Here we describe a new FO monitoring system based on long-gage fiber Bragg grating sensors installed at the Randa Rockslide Laboratory in southern Switzerland. We highlight the advantages and disadvantages of the system, describe relevant first results, and compare FO data to that from traditional instruments already installed on site. The Randa rock slope has been the subject of intensive research since its failure in 1991. Around 5 million cubic meters of rock remains unstable today, moving at rates up to 20 mm / year. Traditional in-situ monitoring techniques have been employed to understand the mechanics and driving forces of the currently unstable rock mass, however these investigations are limited by the resolution and low sampling rate of the sensors. The new FO monitoring system has micro-strain resolution and offers the capability to detect sub-micrometer scale deformations in both triggered-dynamic and continuous measurements. Two types of sensors have been installed: fully-embedded borehole sensors encased in grout at depths of 38, 40, and 68 m, and surface extensometers spanning active tension cracks. Dynamic measurements are triggered by sensor deformation and recorded at 100 Hz, while continuous measurements are logged every 5 minutes. Since installation in August 2008, the FO monitoring system has been operational 90% of the time. Time series deformation data show movement rates consistent with previous borehole extensometer surveys. Accelerated displacements following installation are likely related to long-term curing and dewatering of the grout. A number of interesting transients have been recorded, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new

  5. The Semiotic and Conceptual Genesis of Angle

    Science.gov (United States)

    Tanguay, Denis; Venant, Fabienne

    2016-01-01

    In the present study, we try to understand how students at the end of primary school conceive of angle: Is an angle a magnitude for them or a geometric figure, and how do they manage to coordinate the two aspects in their understanding of the concepts of angle and of angle measurement? With the aim of better grasping the way "angle" is…

  6. Miniature and low cost fiber bragg grating interrogator for structural monitoring in nano-satellites

    NARCIS (Netherlands)

    Toet, P.M.; Hagen, R.A.J.; Hakkesteegt, H.C.; Lugtenburg, J.; Maniscalco, M.P.

    2014-01-01

    In this paper we present a newly developed Fiber Optic measurement system, consisting of Fiber Bragg Grating (FBG) sensors and an FBG interrogator. The development of the measuring system is part of the PiezoElectric Assisted Smart Satellite Structure (PEASSS) project, which was initiated at the beg

  7. Plasmid DNA damage by heavy ions at spread-out Bragg peak energies

    NARCIS (Netherlands)

    Dang, H. M.; van Goethem, M. J.; van der Graaf, E. R.; Brandenburg, S.; Hoekstra, R.; Schlatholter, T.

    2010-01-01

    Interaction of ionizing radiation with plasmid DNA can lead to formation of single strand breaks, double strand breaks and clustered lesions. We have investigated the response of the synthetic plasmid pBR322 in aqueous solution upon irradiation with (12)C ions under spread-out Bragg peak conditions

  8. Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis

    NARCIS (Netherlands)

    Sulyanova, Elena A.; Shabalin, Anatoly; Zozulya, Alexey V.; Meijer, Janne-Mieke; Dzhigaev, Dmitry; Gorobtsov, Oleg; Kurta, Ruslan P.; Lazarev, Sergey; Lorenz, Ulf; Singer, Andrej; Yefanov, Oleksandr; Zaluzhnyy, Ivan; Besedin, Ilya; Sprung, Michael; Petukhov, A. V.; Vartanyants, Ivan A.

    2015-01-01

    In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of

  9. Silica Bridge Impact on Hollow-core Bragg Fiber Transmission Properties

    DEFF Research Database (Denmark)

    Poli, F.; Foroni, M.; Giovanelli, D.;

    2007-01-01

    The silica bridges impact on the hollow-core Bragg fiber guiding properties is investigated. Results demonstrate that silica nanosupports are responsible for the surface mode presence, which causes the peaks experimentally measured in the transmission spectrum. © 2006 Optical Society of America....

  10. Intensity Modulation of Hybrid Soliton Pulsed Source with Fibre Bragg Grating External Cavity

    Institute of Scientific and Technical Information of China (English)

    Nuran Dogru; M.Sadettin Ozyazici

    2004-01-01

    Resonance peak spectral splitting (RPSS) in the intensity modulation of a hybrid soliton pulsed source, where fibre Bragg gratings are used as an external cavity, can be suppressed by introducing a suitable linear chirp rate in a Gaussian apodized grating. Antireflection-coated reflectivity and gain suppression factor does not strongly affect the RPSS.

  11. Monolithic Distributed Bragg Reflector Cavities in Al2O3 with Quality Factors Exceeding 106

    NARCIS (Netherlands)

    Bernhardi, E.H.; Lu, Q.; Wolferen, van H.A.G.M.; Wörhoff, K.; Ridder, de R.M.; Pollnau, M.

    2011-01-01

    >The design, fabrication, and characterization of surface relief Bragg gratings integrated with aluminum oxide ridge waveguides are reported. After patterning a photoresist layer by laser interference lithography, uniform gratings with a depth of 120 nm and a period of 507 nm were etched into the Si

  12. Preparation and Characterization of Bragg Fibers for Delivery of Laser Radiation at 1064 nm

    Directory of Open Access Journals (Sweden)

    V. Matejec

    2013-04-01

    Full Text Available Bragg fibers offer new performance for transmission of high laser energies over long distances. In this paper theoretical modeling, preparation and characterization of Bragg fibers for delivery laser radiation at 1064 nm are presented. Investigated Bragg fibers consist of the fiber core with a refractive index equal to that of silica which is surrounded by three pairs of circular layers. Each pair is composed of one layer with a high and one layer with a low refractive index and characterized by a refractive-index difference around 0.03. Propagation constants and radiation losses of the fundamental mode in such a structure were calculated on the basis of waveguide optics. Preforms of the Bragg fibers were prepared by the MCVD method using germanium dioxide, phosphorous pentoxide and fluorine as silica dopants. The fibers with a diameter of 170 m were drawn from the preforms. Refractive-index profiles, angular distributions of the output power and optical losses of the prepared fibers were measured. Results of testing the fibers for delivery radiation of a pulse Nd:YAG laser at 1064 nm are also shown.

  13. Novel Tunable PMD Compensation Technology Using Linear Chirped Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-min; YU Zhong-yuan; YANG Hong-bo; ZHANG Xiao-guang; YANG Bo-jun

    2004-01-01

    Based on uniform fiber Bragg grating bonded with a magnetostrictive rod in the non-uniform magnetic field, a novel PMD compensation technique is proposed. This all- fiber PMD compensation technology is cost-effective and flexible in designing the differential group delay profile.

  14. Bragg concentrators for hard (> 10keV) x-ray astronomy: Status report

    DEFF Research Database (Denmark)

    Pareschi, G.; Frontera, F.; Pasqualini, G.

    1997-01-01

    The use of focusing telescopes in hard X-ray (E > 10 keV) astronomy will provide better flux sensitivity and imaging performances with respect to the direct-viewing detectors, utilized until now. We present recent results obtained from our group regarding the possible use of Bragg-diffraction tec...

  15. Perturbative modeling of Bragg-grating-based biosensors in photonic-crystal fibers

    DEFF Research Database (Denmark)

    Burani, Nicola; Lægsgaard, Jesper

    2005-01-01

    We present a modeling study carried out to support the design of a novel, to our knowledge, kind of photonic-crystal fiber (PCF)-based sensor. This device, based on a PCF Bragg grating, detects the presence of selected single-stranded DNA molecules, hybridized to a biofilm in the air holes of the...

  16. Time-dependent variation of fiber Bragg grating reflectivity in PMMA-based polymer optical fibers

    DEFF Research Database (Denmark)

    Saez-Rodriguez, D.; Nielsen, Kristian; Bang, Ole;

    2015-01-01

    In this Letter, we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fiber Bragg gratings (FBGs) inscribed in microstructured polymer optical fiber (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase...

  17. Humidity insensitive step-index polymer optical fibre Bragg grating sensors

    DEFF Research Database (Denmark)

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio;

    2015-01-01

    We have fabricated and characterised a humidity insensitive step index(SI) polymer optical fibre(POF) Bragg grating sensors. The fibre was made based on the injection molding technique, which is an efficient method for fast, flexible and cost effective preparation of the fibre preform...

  18. Effects of nonlinear phase modulation on low-conversion four-wave mixing Bragg scattering

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; McKinstrie, C. J.; Rottwitt, Karsten

    We consider the effects of nonlinear phase modulation (NPM) on frequency converseon by Bragg scattering. Previously we found that arbitrary mode reshaping without temporal entanglement (separability) was possible. When NPM is included, the modes are chirped and the separability is no longer...

  19. Fiber Bragg Grating Sensor for Fault Detection in Radial and Network Transmission Lines

    Science.gov (United States)

    Moghadas, Amin A.; Shadaram, Mehdi

    2010-01-01

    In this paper, a fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by Fiber Bragg Grating (FBG). The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signal. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN) algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system. PMID:22163416

  20. Fiber Bragg Grating Sensor for Fault Detection in Radial and Network Transmission Lines

    Directory of Open Access Journals (Sweden)

    Mehdi Shadaram

    2010-10-01

    Full Text Available In this paper, a fiber optic based sensor capable of fault detection in both radial and network overhead transmission power line systems is investigated. Bragg wavelength shift is used to measure the fault current and detect fault in power systems. Magnetic fields generated by currents in the overhead transmission lines cause a strain in magnetostrictive material which is then detected by Fiber Bragg Grating (FBG. The Fiber Bragg interrogator senses the reflected FBG signals, and the Bragg wavelength shift is calculated and the signals are processed. A broadband light source in the control room scans the shift in the reflected signal. Any surge in the magnetic field relates to an increased fault current at a certain location. Also, fault location can be precisely defined with an artificial neural network (ANN algorithm. This algorithm can be easily coordinated with other protective devices. It is shown that the faults in the overhead transmission line cause a detectable wavelength shift on the reflected signal of FBG and can be used to detect and classify different kind of faults. The proposed method has been extensively tested by simulation and results confirm that the proposed scheme is able to detect different kinds of fault in both radial and network system.

  1. Bragg waveguide grating as a 1d photonic band gap structure: COST 268 modelling task

    NARCIS (Netherlands)

    Ctyroky, J.; Helfert, S.; Pregla, R.; Bienstman, P.; Baets, R.; Ridder, de R.; Stoffer, R.; Klaasse, G.; Petracek, J.; Lalanne, P.; Hugonin, J.P.; Rue, de la R.M.

    2002-01-01

    Modal reflection, transmission and loss of deeply etched Bragg waveguide gratings were modelled by six European laboratories using independently developed two-dimensional (2D) numerical codes based on four different methods, with very good mutual agreement. It was found that (rather weak) material d

  2. Focused ion beam nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides

    NARCIS (Netherlands)

    Ay, Feridun; Uranga, Amaia; Bradley, Jonathan D.B.; Wörhoff, Kerstin; Ridder, de René M.; Pollnau, Markus; Ridder, de R.M.; Ay, F.; Kauppinen, L.J.

    2008-01-01

    We report our recent results on an optimization study of focused ion beam (FIB) nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides. By optimizing FIB milling parameters such as ion current, dwell time, loop repetitions, scanning strategy, and applying a top metal layer for reducing c

  3. Two-Dimensional Cavity Resonant Modes of Si Based Bragg Reflection Ridge Waveguide

    Institute of Scientific and Technical Information of China (English)

    CHEN San; Lu Hong-Yan; CHEN Kun-Ji; XU Jun; MA Zhong-Yuan; LI Wei; HUANG Xin-Fan

    2011-01-01

    @@ Si-based ridge-waveguides with Bragg reflectors are fabricated based on our method.Three resonant peaks could be obviously identified from the photoluminescence spectra, and field patterns of these resonant peaks, simulated by the finite difference time domain (FDTD) method, confirm that these peaks originate from cavity resonances.The resonant wavelengths and spatial angular distribution are given by the resonant models, which agree well with the experimental data.Experimentally, a simple method is proposed to testify the experimental and theoretical results.Such devices based on Bragg reflectors may have potential applications in light-emitting diodes, lasers and integrated photonic circuits.%Si-based ridge-waveguides with Bragg reflectors are fabricated based on our method. Three resonant peaks could be obviously identified from the photoluminescence spectra, and field patterns of these resonant peaks, simulated by the finite difference time domain (FDTD) method, confirm that these peaks originate from cavity resonances. The resonant wavelengths and spatial angular distribution are given by the resonant models, which agree well with the experimental data. Experimentally, a simple method is proposed to testify the experimental and theoretical results. Such devices based on Bragg reflectors may have potential applications in light-emitting diodes, lasers and integrated photonic circuits.

  4. Bragg Gratings in Crystalline Waveguides Fabricated by Focused Ion Beam Milling

    NARCIS (Netherlands)

    Inurrategi, I.; Ay, F.; Geskus, D.; Aravazhi, S.; Gadgil, V.J.; Wörhoff, K.; Pollnau, M.

    2010-01-01

    Results of an optimization study of deeply-etched Bragg gratings in KY(WO4)2:Yb3+ to obtain photonic cavity structures are reported. By optimizing parameters such as dose per area, dwell time and pixel resolution the redeposition effects are minimized and 4.3um-deep gratings are achieved.

  5. Coherent propagation of a short polarised radiation pulse in a one-dimensional resonance Bragg grating

    NARCIS (Netherlands)

    Maimistov, A. I.; Polikarpov, V. V.

    2006-01-01

    The propagation of an optical ultrashort pulse in a resonance Bragg grating is considered taking into account the polarisation of electromagnetic radiation. It is assumed that the grating is formed by thin films containing two-level atoms with the triply degenerate upper energy level. The system of

  6. Dynamic interrogator for elastic wave sensing using Fabry Perot filters based on fiber Bragg gratings.

    Science.gov (United States)

    Harish, Achar V; Varghese, Bibin; Rao, Babu; Balasubramaniam, Krishnan; Srinivasan, Balaji

    2015-07-01

    Use of in-fiber Fabry-Perot (FP) filters based on fiber Bragg gratings as both sensor as well as an interrogator for enhancing the detection limit of elastic wave sensing is investigated in this paper. The sensitivity of such a demodulation scheme depends on the spectral discrimination of the sensor and interrogator gratings. Simulations have shown that the use of in-fiber FP filters with high finesse provide better performance in terms of sensitivity compared to the demodulation using fiber Bragg gratings. Based on these results, a dynamic interrogator capable of sensing acoustic waves with amplitude of less than 1 micro-strain over frequencies of 10 kHz to several 100 kHz has been implemented. Frequency response of the fiber Bragg gratings in the given experimental setup has been compared to that of the conventional piezo sensors demonstrating that fiber Bragg gratings can be used over a relatively broad frequency range. Dynamic interrogator has been packaged in a compact box without any degradation in its performance.

  7. Doubly curved imaging Bragg crystal spectrometer for X-ray astronomy

    DEFF Research Database (Denmark)

    Byrnak, B. P.; Christensen, Finn Erland; Westergaard, Niels Jørgen Stenfeldt;

    1985-01-01

    An X-ray spectrometer which is sensitive in the 0.5-7-keV energy range and is intended for use onboard astronomical satellites has been studied. The Bragg reflected rays from a doubly bent crystal positioned downstream of the focal plane of a grazing-incidence concentrator are focused along the a...

  8. Long all-active monolithic mode-locked lasers with surface-etched bragg gratings

    DEFF Research Database (Denmark)

    Larsson, David; Yvind, Kresten; Hvam, Jørn Märcher

    2007-01-01

    We have fabricated 4.4-mm-long monolithic InAlGaAsP–InP mode-locked lasers with integrated deeply surface etched distributed Bragg reflector (DBR) mirrors. The lasers produce 3.7-ps transform-limited Gaussian pulses with 10-mW average output power and 250-fs absolute timing jitter. The performance...

  9. Calibration and modelling of the SODART-OXS Bragg spectrometer onboard the SRG satellite

    DEFF Research Database (Denmark)

    Halm, Ingolf; Wiebicke, Hans-Joachim; Christensen, Finn Erland;

    1998-01-01

    The SODART X-ray telescope includes an Objective Crystal Spectrometer (OXS) providing a high energy resolving power by Bragg reflection upon crystals. To cover a wide energy range, 3 types of natural crystals (LiF, Si, RAP) and a Co/C multilayer structure upon Si are used in the ranges 5-11 keV, ...

  10. Bragg Resonator Cyclotron Resonance Maser Experiments Driven by a Microsecond, Intense Electron Beam Accelerator

    Science.gov (United States)

    Choi, Jin Joo

    The cyclotron resonance maser (CRM) has proven to be attractive for many high power microwave applications such as fusion plasma heating, radar/communications, and high gradient RF accelerators. Most of the previous CRM experiments with MV electron beams have been conducted with short (gyrotron modes. Considerably less power from the TE_{11} gyro -BWO was observed for the Bragg resonator with ripples fully -outward. The microwave emission from the TE_ {21} absolute instability in the Bragg resonator with ripples fully-outward was successfully suppressed by lowering the cavity magnetic field. These three undesired oscillations, (TE _{21} absolute instability, TE _{11} gyro-BWO, TE _{51} second and third harmonic), were the most serious competing modes in the present Bragg resonator CRM experiments, apparently suppressing the TE _{31} CARM oscillation. For the Bragg resonator with ripples half-inward, we have performed gyrotron experiments with a high current electron beam. In these experiments, we have observed mode competition between the TE_{21 } absolute instability and the TE_ {11} gyro-BWO interaction by the use of frequency measurements and gas breakdown diagnostics.

  11. A novel tunable polarization mode dispersion compensator with strain chirped fiber Bragg gratings

    Institute of Scientific and Technical Information of China (English)

    Yumin Liu(刘玉敏); Zhongyuan Yu(俞重远); Yuan Zheng(郑远); Xiaoguang Zhang(张晓光); Bojun Yang(杨伯君)

    2004-01-01

    A tunable polarization mode dispersion (PMD) compensator based on strain-chirped fiber Bragg gratings (FBGs) is proposed. It natures in flexible designing, large tuning range, without using linear or nonlinear chirped phase mask, fast tuning response time, continuously adjustable, all-fiber based, compact, and cheap.

  12. Polymer PCF Bragg grating sensors based on poly(methyl methacrylate) and TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, Ian P; Webb, David J; Kalli, Kyriacos;

    2011-01-01

    Fibre Bragg grating (FBG) sensors have been fabricated in polymer photonic crystal fibre (PCF). Results are presented using two different types of polymer optical fibre (POF); first multimode PCF with a core diameter of 50μm based on poly(methyl methacrylate) (PMMA) and second, endlessly single m...

  13. 870nm Bragg grating in single mode TOPAS microstructured polymer optical fibre

    DEFF Research Database (Denmark)

    Yuan, Wu; Webb, David J.; Kalli, Kyriacos;

    2011-01-01

    We report the fabrication and characterization of a fiber Bragg grating (FBG) with 870 nm resonance wavelength in a single-mode TOPAS microstructured polymer optical fiber (mPOF). The grating has been UV-written with the phase-mask technique using a 325 nm HeCd laser. The static tensile strain se...

  14. A Novel Fiber Bragg Grating with Triangular Spectrum and Its Application in Strain Sensor

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A novel fiber Bragg grating with triangular spectrum is presented. A strain sensor based on this fiber grating is proposed. Experiments showed that the sensor has advantages of high sensitivity, wider measuring range and immunity to fluctuation of the light source power.

  15. Effects of nonlinear phase modulation on Bragg scattering in the low-conversion regime

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Cargill, D. S.; McKinstrie, C. J.;

    2012-01-01

    In this paper, we consider the effects of nonlinear phase modulation on frequency conversion by four-wave mixing (Bragg scattering) in the low-conversion regime. We derive the Green functions for this process using the time-domain collision method, for partial collisions, in which the four fields...

  16. Wavelength Tuning in the Two-Section Distributed Bragg Reflector Laser Fabricatedby Quantum-Well Intermixing

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The two-section tunable ridge waveguide distributed Bragg reflector (DBR) lasers fabricated by strained In xGa1-xAsyP1-y The threshold current of the laser is 51mA. The tunable range of the laser is 3.2nm and the side mode suppression ratio (SMSR) is more than 38dB.

  17. Direct Writing of Fiber Bragg Grating in Microstructured Polymer Optical Fiber

    DEFF Research Database (Denmark)

    Stefani, Alessio; Stecher, Matthias; Town, G. E.;

    2012-01-01

    We report point-by-point laser direct writing of a 1520-nm fiber Bragg grating in a microstructured polymer optical fiber (mPOF). The mPOF is specially designed such that the microstructure does not obstruct the writing beam when properly aligned. A fourth-order grating is inscribed in the m...

  18. Floquet-Bloch vs. Nicolson-Ross-Weir Extraction for Magneto-Dielectric Bragg Stacks

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    2014-01-01

    We extract and compare the permittivity and permeability from a dielectric and a magnetodielectric Bragg stack with the Floquet-Bloch (FB) method for the infinite stack and the Nicolson-Ross- Weir (NRW) method for the finite stack. While the extracted propagation constants are identical, the wave...

  19. High-sensitivity Cryogenic Temperature Sensors using Pressurized Fiber Bragg Gratings

    Science.gov (United States)

    Wu, Meng-Chou; DeHaven, Stanton L.

    2006-01-01

    Cryogenic temperature sensing was studied using a pressurized fiber Bragg grating (PFBG). The PFBG was obtained by simply applying a small diametric load to a regular fiber Bragg grating (FBG), which was coated with polyimide of a thickness of 11 micrometers. The Bragg wavelength of the PFBG was measured at temperatures from 295 to 4.2 K. A pressure-induced transition occurred at 200 K during the cooling cycle. As a result the temperature sensitivity of the PFBG was found to be nonlinear but reach 24 pm/K below 200 K, more than three times the regular FBG. For the temperature change from 80 K to 10 K, the PFBG has a total Bragg wavelength shift of about 470 pm, 10 times more than the regular FBG. From room temperature to liquid helium temperature the PFBG gives a total wavelength shift of 3.78 nm, compared to the FBG of 1.51 nm. The effect of the coating thickness on the temperature sensitivity of the gratings is also discussed.

  20. 3D flexible needle steering in soft-tissue phantoms using fiber bragg grating sensors

    NARCIS (Netherlands)

    Abayazid, Momen; Kemp, Marco; Misra, Sarthak

    2013-01-01

    Needle insertion procedures are commonly used for surgical interventions. In this paper, we develop a three-dimensional (3D) closed-loop control algorithm to robotically steer flexible needles with an asymmetric tip towards a target in a soft-tissue phantom. Twelve Fiber Bragg Grating (FBG) sensors

  1. Modelling and Simulation of Temperature Sensitivity of Bragg Grating Sensor for Structural Health Monitoring Application

    Directory of Open Access Journals (Sweden)

    Bilkish Mondal

    2014-03-01

    Full Text Available Here in this paper we presented the modelling of Fiber Bragg Grating (FBG as temperature sensor for structural health monitoring application is geometrically designed in the wavelength window of 1.568-1.580μm. Simulation has been done by using optical software R-Soft (GratingMOD.

  2. William and Lawrence Bragg father and son the most extraordinary collaboration in science

    CERN Document Server

    Jenkin, John

    2008-01-01

    This joint biography is of William and Lawrence Bragg, who changed all of science in the 20th-century with the development of X-ray crystallography, and by mentoring the mid-century discovery of the structure of DNA. Their stories are vivid examples of science teaching and research in a colonial setting (Australia).

  3. Tunable mode-locked semiconductor laser with Bragg mirror external cavity

    DEFF Research Database (Denmark)

    Yvind, Kresten; Jørgensen, T.; Birkedal, Dan;

    2002-01-01

    We present a simplified design for a wavelength tunable external cavity mode-locked laser by employing a wedged GaAs/AlGaAs Bragg mirror. The device emits 4-6 ps pulses at 10 GHz and is tunable over 15 nm. Although, in the present configuration, tunability is limited to 15 nm, however, we have sh...

  4. Frequency scaling for angle gathers

    KAUST Repository

    Zuberi, M. A H

    2014-01-01

    Angle gathers provide an extra dimension to analyze the velocity after migration. Space-shift and time shift-imaging conditions are two methods used to obtain angle gathers, but both are reasonably expensive. By scaling the time-lag axis of the time-shifted images, the computational cost of the time shift imaging condition can be considerably reduced. In imaging and more so Full waveform inversion, frequencydomain Helmholtz solvers are used more often to solve for the wavefields than conventional time domain extrapolators. In such cases, we do not need to extend the image, instead we scale the frequency axis of the frequency domain image to obtain the angle gathers more efficiently. Application on synthetic data demonstrate such features.

  5. Angle independent velocity spectrum determination

    DEFF Research Database (Denmark)

    2014-01-01

    An ultrasound imaging system (100) includes a transducer array (102) that emits an ultrasound beam and produces at least one transverse pulse-echo field that oscillates in a direction transverse to the emitted ultrasound beam and that receive echoes produced in response thereto and a spectral vel...... velocity estimator (110) that determines a velocity spectrum for flowing structure, which flows at an angle of 90 degrees and flows at angles less than 90 degrees with respect to the emitted ultrasound beam, based on the received echoes....

  6. Systematic variations in divergence angle

    CERN Document Server

    Okabe, Takuya

    2012-01-01

    Practical methods for quantitative analysis of radial and angular coordinates of leafy organs of vascular plants are presented and applied to published phyllotactic patterns of various real systems from young leaves on a shoot tip to florets on a flower head. The constancy of divergence angle is borne out with accuracy of less than a degree. It is shown that apparent fluctuations in divergence angle are in large part systematic variations caused by the invalid assumption of a fixed center and/or by secondary deformations, while random fluctuations are of minor importance.

  7. Dosimetric response of radiochromic films to protons of low energies in the Bragg peak region

    Science.gov (United States)

    Battaglia, M. C.; Schardt, D.; Espino, J. M.; Gallardo, M. I.; Cortés-Giraldo, M. A.; Quesada, J. M.; Lallena, A. M.; Miras, H.; Guirado, D.

    2016-06-01

    One of the major advantages of proton or ion beams, applied in cancer treatment, is their excellent depth-dose profile exhibiting a low dose in the entrance channel and a distinct dose maximum (Bragg peak) near the end of range in tissue. In the region of the Bragg peak, where the protons or ions are almost stopped, experimental studies with low-energy particle beams and thin biological samples may contribute valuable information on the biological effectiveness in the stopping region. Such experiments, however, require beam optimization and special dosimetry techniques for determining the absolute dose and dose homogeneity for very thin biological samples. At the National Centre of Accelerators in Seville, one of the beam lines at the 3 MV Tandem Accelerator was equipped with a scattering device, a special parallel-plate ionization chamber with very thin electrode foils and target holders for cell cultures. In this work, we present the calibration in absolute dose of EBT3 films [Gafchromic radiotherapy films, http://www.ashland.com/products/gafchromic-radiotherapy-films] for proton energies in the region of the Bragg peak, where the linear energy transfer increases and becomes more significant for radiobiology studies, as well as the response of the EBT3 films for different proton energy values. To irradiate the films in the Bragg peak region, the energy of the beam was degraded passively, by interposing Mylar foils of variable thickness to place the Bragg peak inside the active layer of the film. The results obtained for the beam degraded in Mylar foils are compared with the dose calculated by means of the measurement of the beam fluence with an ionization chamber and the energy loss predicted by srim2008 code.

  8. Multi-Stress Monitoring System with Fiber-Optic Mandrels and Fiber Bragg Grating Sensors in a Sagnac Loop

    OpenAIRE

    Hyunjin Kim; Umesh Sampath; Minho Song

    2015-01-01

    Fiber Bragg grating sensors are placed in a fiber-optic Sagnac loop to combine the grating temperature sensors and the fiber-optic mandrel acoustic emission sensors in single optical circuit. A wavelength-scanning fiber-optic laser is used as a common light source for both sensors. A fiber-optic attenuator is placed at a specific position in the Sagnac loop in order to separate buried Bragg wavelengths from the Sagnac interferometer output. The Bragg wavelength shifts are measured with scanni...

  9. Femtosecond laser inscription of Bragg and complex gratings in coated and encapsulated silica and low-loss polymer optical fibers

    Science.gov (United States)

    Kalli, Kyriacos; Lacraz, Amedee; Polis, Michael; Othonos, Andreas

    2015-09-01

    The development of wavelength filters, such as Bragg and superstructure gratings in glass and polymer optical fibers, using a femtosecond laser is reported. By using a femtosecond laser operating in the green, which offers greater inscription efficiency, we demonstrate the reliable inscription of Bragg and superstructure gratings in coated silica and low-loss CYTOP polymer optical fibers. We employ line by line and point by point inscription methods, allowing for multiple and overlapping gratings in the fiber core. Moreover, we demonstrate a novel fibre Bragg grating inscription technique to modify and add versatility to an existing, encapsulated optical fiber pressure sensor.

  10. Experimental and numerical investigations of oscillations in extracted material parameters for finite Bragg stacks using the NRW method

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    2012-01-01

    for three specific configurations of its constituent unit cell. Particular attention is devoted to the absence/presence of certain oscillations in the extracted material parameters, depending on the unit cell configuration. The results for the finite Bragg stack are further verified to agree with those...... of an infinite Bragg stack, for which the dispersion equation is used in conjunction with the Floquet-Bloch harmonics expansion to extract the material parameters. It is shown that the extracted material parameters for the finite and infinite Bragg stacks agree for the symmetric unit cell configuration....

  11. Large angle measurement by interferometry

    Science.gov (United States)

    Apostol, Dan; Blanaru, Constantin; Damian, Victor S.; Logofatu, Petre-Catalin; Tumbar, R.; Dobroiu, Adrian

    1995-03-01

    An interferometric set-up able to measure angles as large as +180 degree(s) is presented. The principle of the method is to measure a linear displacement (translation) produced by a crank-gear mechanism which converts the angular movement of a rotating table. The optical scheme and consideration on the accuracy of the method are presented.

  12. Discovering the Inscribed Angle Theorem

    Science.gov (United States)

    Roscoe, Matt B.

    2012-01-01

    Learning to play tennis is difficult. It takes practice, but it also helps to have a coach--someone who gives tips and pointers but allows the freedom to play the game on one's own. Learning to act like a mathematician is a similar process. Students report that the process of proving the inscribed angle theorem is challenging and, at times,…

  13. Contactless angle detection using permalloy

    NARCIS (Netherlands)

    Eijkel, Kees J.; Rijk, Rolf

    1988-01-01

    An overview is given of measurements on angle detectors. The detectors consist of a pair of planar-Hall elements opposite to a rotatable magnet. The measurements are performed on a number of planar-Hall elements of different shape and size, and show good agreement with a previously described theoret

  14. Double differential cross sections for proton induced electron emission from molecular analogues of DNA constituents for energies in the Bragg peak region

    Science.gov (United States)

    Rudek, Benedikt; Bennett, Daniel; Bug, Marion U.; Wang, Mingjie; Baek, Woon Yong; Buhr, Ticia; Hilgers, Gerhard; Champion, Christophe; Rabus, Hans

    2016-09-01

    For track structure simulations in the Bragg peak region, measured electron emission cross sections of DNA constituents are required as input for developing parameterized model functions representing the scattering probabilities. In the present work, double differential cross sections were measured for the electron emission from vapor-phase pyrimidine, tetrahydrofuran, and trimethyl phosphate that are structural analogues to the base, the sugar, and the phosphate residue of the DNA, respectively. The range of proton energies was from 75 keV to 135 keV, the angles ranged from 15° to 135°, and the electron energies were measured from 10 eV to 200 eV. Single differential and total electron emission cross sections are derived by integration over angle and electron energy and compared to the semi-empirical Hansen-Kocbach-Stolterfoht (HKS) model and a quantum mechanical calculation employing the first Born approximation with corrected boundary conditions (CB1). The CB1 provides the best prediction of double and single differential cross section, while total cross sections can be fitted with semi-empirical models. The cross sections of the three samples are proportional to their total number of valence electrons.

  15. An Angle Criterion for Riesz Bases

    DEFF Research Database (Denmark)

    Lindner, Alexander M; Bittner, B.

    1999-01-01

    We present a characterization of Riesz bases in terms ofthe angles between certain finite dimensional subspaces. Correlationsbetween the bounds of the Riesz basis and the size of the angles arederived.......We present a characterization of Riesz bases in terms ofthe angles between certain finite dimensional subspaces. Correlationsbetween the bounds of the Riesz basis and the size of the angles arederived....

  16. Carbide precipitates in solution-quenched PH13-8 Mo stainless steel: A small-angle neutron scattering investigation

    Indian Academy of Sciences (India)

    D Sen; A K Patra; S Mazumder; J Mittra; G K Dey; P K De

    2004-08-01

    This paper deals with the small-angle neutron scattering (SANS) investigation on solution-quenched PH13-8 Mo stainless steel. From the nature of the variation of the functionality of the profiles for varying specimen thickness and also from the transmission electron microscopy (TEM), it has been established that the small-angle scattering signal predominantly originates from the block-like metallic carbide precipitates in the specimen. The contribution due to double Bragg reflection is not significant in the present case. The single scattering profile has been extracted from the experimental profiles corresponding to different values of specimen thickness. In order to avoid complexity and non-uniqueness of the multi-parameter minimization for randomly oriented polydisperse block-like precipitate model, the data have been analyzed assuming randomly oriented polydisperse cylindrical particle model with a locked aspect ratio.

  17. Metal-coated second-order fibre Bragg gratings produced by infrared femtosecond radiation for dual temperature and strain sensing

    Science.gov (United States)

    Chah, K.; Kinet, D.; Caucheteur, C.

    2016-05-01

    We report highly localized second-order fibre Bragg gratings at 1585 nm inscribed by point-by-point focused infrared femtosecond pulses. A thin gold coating deposited on the fibre outer surface at the grating location allows shielding the cladding mode resonances from the outer medium, so that they remain present in the transmitted amplitude spectrum. The Bragg resonance of the second-order grating is surrounded by high-order cladding mode resonances of the first-order grating. These cladding modes exhibit the same temperature sensitivity as the Bragg resonance (10.6 pm/°C) but high differential strain sensitivity (-0.55 pm/μepsilon versus 1.20 pm/μepsilon for the Bragg mode). Therefore, the conditioning of the matrix inversion as demodulation method is fully satisfied, yielding a new design of fibre sensor able to discriminate between temperature and strain, with an unprecedented sensitivity.

  18. Fabrication of the Long Bragg Grating by Excimer Laser Micro Machining with High-Precision Positioning XXY Platform

    Directory of Open Access Journals (Sweden)

    Jian-Zhong Wu

    2014-03-01

    Full Text Available With the advancement of technology, the application of fiber Bragg grating is widely used as a Bragg grating sensor. Fiber Bragg grating is fabrication using excimer laser machining with the phase masker. The grating length is decided by the width of laser beam. In this paper, we proposed fabrication of the long Bragg grating by excimer Laser micro machining with a high-precision positioning XXY platform. The high-precision positioning XXY platform plays an important role for long FBG. It needs seriously to combine three short FBGs. Therefore, we can obtain a long FBG with 15mm length. This method can provide a solution to fabricate long FBG by using cheap laser with high-precision positioning XXY platform.

  19. Wide-angle electron detector

    International Nuclear Information System (INIS)

    The design, functioning, and main calibration, characteristics of a wide-angle detector, capable of recording electrons with energies >= 8 keV and insensitive to u.v. solar radiation are described. A description of the sensor (electron trap) and its electronics in the analog (DEGAFOC) and counting (DEGAFOI) modes is given. Examples of telemetry recordings, illustrating the operation of the detector are included. (Auth.)

  20. Gaia basic angle monitoring system

    Science.gov (United States)

    Gielesen, W.; de Bruijn, D.; van den Dool, T.; Kamphues, F.; Mekking, J.; Calvel, B.; Laborie, A.; Coatantiec, C.; Touzeau, S.; Erdmann, M.; Gare, P.; Monteiro, D.

    2013-09-01

    The Gaia mission1 will create an extraordinarily precise three-dimensional map of more than one billion stars in our Galaxy. The Gaia spacecraft2, built by EADS Astrium, is part of ESA's Cosmic Vision programme and scheduled for launch in 2013. Gaia measures the position, distance and motion of stars with an accuracy of 24 micro-arcsec using two telescopes at a fixed mutual angle of 106.5°, named the `Basic Angle', at an operational temperature of 100 K. This accuracy requires ultra-high stability at cryogenic conditions, which can only be achieved by using Silicon Carbide for both the optical bench and the telescopes. TNO has developed, built and space qualified the Silicon carbide Basic Angle Monitoring (BAM) on-board metrology system3 for this mission, measuring the relative motion of Gaia's telescopes with accuracies in the range of 0.5 micro-arcsec. This is achieved by a system of two laser interferometers able to detect Optical Path Differences (OPD) as small as 1.5 picometer rms. Following a general introduction on Gaia and the use of Silicon Carbide as base material this paper addresses the specific challenges towards the cryogenic application of the Gaia BAM including design, integration and verification/qualification by testing.

  1. LHC Report: playing with angles

    CERN Multimedia

    Mike Lamont for the LHC team

    2016-01-01

    Ready (after a machine development period), steady (running), go (for a special run)!   The crossing angles are an essential feature of the machine set-up. They have to be big enough to reduce the long-range beam-beam effect. The LHC has recently enjoyed a period of steady running and managed to set a new record for “Maximum Stable Luminosity Delivered in 7 days” of 3.29 fb-1 between 29 August and 4 September. The number of bunches per beam remains pegged at 2220 because of the limitations imposed by the SPS beam dump. The bunch population is also somewhat reduced due to outgassing near one of the injection kickers at point 8. Both limitations will be addressed during the year-end technical stop, opening the way for increased performance in 2017. On 10 and 11 September, a two day machine development (MD) period took place. The MD programme included a look at the possibility of reducing the crossing angle at the high-luminosity interaction points. The crossing angles are an ess...

  2. Momentum distribution dynamics of a Tonks-Girardeau gas: Bragg reflections of a quantum many-body wavepacket

    OpenAIRE

    Pezer, R.; Buljan, H.

    2006-01-01

    The dynamics of the momentum distribution and the reduced single-particle density matrix (RSPDM) of a Tonks-Girardeau (TG) gas is studied in the context of Bragg-reflections of a many-body wavepacket. We find strong suppression of a Bragg-reflection peak for a dense TG wavepacket; our observation illustrates dependence of the momentum distribution on the interactions/wavefunction symmetry. The momentum distribution is calculated with a fast algorithm based on a formula expressing the RSPDM vi...

  3. Highly tunable Terahertz filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides

    OpenAIRE

    Kangwen Li; Xunpeng Ma; Zuyin Zhang; Lina Wang; Haifeng Hu; Yun Xu; Guofeng Song

    2013-01-01

    A highly tunable terahertz (THz) filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides is proposed and demonstrated numerically by means of the Finite Element Method. The results reveal that a sharp peak with high Q-value presents in the band gap of Bragg grating waveguide with a defect, and the position of the sharp peak can be modified greatly by changing the intensity of the transverse magnetic field applied to the device. Compared to the situ...

  4. Dual wavelength erbium-doped fiber laser with a lateral pressure-tuned Hi-Bi fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    Lingyun Xiong(熊凌云); Guiyun Kai(开桂云); Lei Sun(孙磊); Xinhuan Feng(冯新焕); Chunxian Xiao(肖纯贤); Yange Liu(刘艳格); Shuzhong Yuan(袁树忠); Xiaoyi Dong(董孝义)

    2004-01-01

    Tunable dual wavelength erbium-doped fiber laser (EDFL) with stable oscillation at room temperature is proposed and demonstrated. This laser utilizes a Bragg grating fabricated in a high birefringence fiber as the wavelength-selective component, and then achieves the stable dual wavelength oscillation by introducing the polarization hole burning effect. Furthermore, by applying lateral strain upon the fiber Bragg grating (FBG), the space of the laser dual wavelengths can be tuned continuously.

  5. Investigation of code reconfigurable fibre Bragg gratings for Optical Code Division Multiple Access (OCDMA) and Optical Packet Switching (OPS) Networks

    OpenAIRE

    Tian, Chun

    2009-01-01

    This thesis documents my work in the telecommunication system laboratory at the Optoelectronics Research Centre, towards the implementation of code reconfigurable OCDMA and all-optical packet switching nodes based on fibre Bragg grating (FBG) technology. My research work involves characterizing the performance of various gratings, specifically high reflectivity, short chip duration, long code sequences, multiple phase level and tunable superstructured fiber Bragg gratings (SSFBGs), by using t...

  6. Dynamic analysis and temperature measurements of concrete cantilever beam using fibre Bragg gratings

    Science.gov (United States)

    da Silva, Jean Carlos Cardozo; Martelli, Cicero; Kalinowski, Hypolito José; Penner, Elisabeth; Canning, John; Groothoff, Nathaniel

    2007-01-01

    We analyzed the action of fire, causing degradation in a concrete cantilever beam using dynamic testing. The structure was fitted with two fibre Bragg gratings (FBG) sensors. One of them measured vibration and the other measured the temperature inside of the cantilever beam, while the beam was exposed to fire. A high-temperature probe based on a simple packaging system, which isolates the sensing FBG from any mechanical action, was developed. A low-cost fibre Bragg grating interrogation system, including easy assembly and maintenance, was used for the measurements. The temperature in the cantilever beam increased until 150 °C and a reduction in the strength of concrete was observed through modal analysis. Results reveal a considerable reduction in strength occurs even with exposures to moderate temperatures (less than 90 °C).

  7. A Laue–Bragg monolithic beam splitter for efficient X-ray 2-beam imaging

    Energy Technology Data Exchange (ETDEWEB)

    Oberta, P., E-mail: peter.oberta@rigaku.com [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Na Slovance 2, CZ-18221 Praha 8 (Czech Republic); Mokso, R. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

    2013-03-01

    Newly emerging techniques for probing matter simultaneously by two spatially and angularly separated X-ray beams require efficient and versatile beam splitting. We present a Laue–Bragg monolithic crystal beam splitter in the form of an L-shaped monolithic Si crystal. By simultaneous Laue and Bragg diffractions the X-ray beam is split into a transmitted polychromatic and a diffracted monochromatic branch with a spatial separation of tens of millimeters. The energy spectrum of the transmitted branch can be tuned via diffraction on a second crystal re-creating a beam intersection on the sample. We propose three multi-modal imaging setups exploiting the large angular separation of the two intersecting beams provided by the proposed optics. Photon efficiency and dual-energy operation are the main assets of our scheme as compared to other existing setups. The theoretical description for an energy range between 10 keV and 30 keV was developed.

  8. EIT-like transmission by interaction between multiple Bragg scattering and local plasmonic resonances

    Science.gov (United States)

    Liu, Z. Z.; Zhang, Q.; Xiao, J. J.

    2016-01-01

    We study the optical properties associated with both the polariton gap and the Bragg gap in periodic resonator-waveguide coupled systems, based on the temporal coupled mode theory and the transfer matrix method. Using the complex band and the transmission spectrum, it is feasible to tune the interaction between multiple Bragg scattering and local resonance, which may give rise to analogous phenomena of electromagnetically induced transparency (EIT). We further design a plasmonic slot waveguide side-coupled with local plasmonic resonators to demonstrate the EIT-like effects in the near-infrared band. Numerical calculations show that realistic amounts of metal Joule loss may destroy the interference and the total absorption is enhanced in the transparency window due to the near zero group velocity of the guiding wave.

  9. A strain-induced birefringent double-clad fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    Lijun Li; Lei Sun; Wande Fan; Zhi Wang; Jianhua Luo; Shenggui Fu; Shuzhong Yuan; Xiaoyi Dong

    2005-01-01

    @@ A strain-induced birefringence double-clad (DC) fiber Bragg grating (FBG) is proposed and demonstrated.The grating is fabricated in the core of rectangular inner cladding double clad fiber by using phase mask method. By applying lateral strain on the grating, the birefringence is induced. In order to detect the birefringent effect of the grating, we use it as the output mirror of a laser. When lateral strain is applied,the grating becomes birefringent. Therefore, one reflection peak of double-clad fiber Bragg grating becomes two peaks and the laser also lases in two wavelengths. The wavelength spacing of the laser can be tuned from 0 to 0.8 nm. The absolute wavelengths for the two polarizations can be tuned 1.2 and 2.0 nm,respectively.

  10. Measurements of Ion Stopping Around the Bragg Peak in High-Energy-Density Plasmas.

    Science.gov (United States)

    Frenje, J A; Grabowski, P E; Li, C K; Séguin, F H; Zylstra, A B; Gatu Johnson, M; Petrasso, R D; Glebov, V Yu; Sangster, T C

    2015-11-13

    For the first time, quantitative measurements of ion stopping at energies around the Bragg peak (or peak ion stopping, which occurs at an ion velocity comparable to the average thermal electron velocity), and its dependence on electron temperature (T(e)) and electron number density (n(e)) in the range of 0.5-4.0 keV and 3×10(22) to 3×10(23) cm(-3) have been conducted, respectively. It is experimentally demonstrated that the position and amplitude of the Bragg peak varies strongly with T(e) with n(e). The importance of including quantum diffraction is also demonstrated in the stopping-power modeling of high-energy-density plasmas. PMID:26613448

  11. Multiband processing of multimode light: combining 3D photonic lanterns with waveguide Bragg gratings

    CERN Document Server

    Spaleniak, Izabela; Jovanovic, Nemanja; Williams, Robert J; Lawrence, Jon S; Ireland, Michael J; Withford, Michael J

    2013-01-01

    The first demonstration of narrowband spectral filtering of multimode light on a 3D integrated photonic chip using photonic lanterns and waveguide Bragg gratings is reported. The photonic lanterns with multi-notch waveguide Bragg gratings were fabricated using the femtosecond direct-write technique in boro-aluminosilicate glass (Corning, Eagle 2000). Transmission dips of up to 5 dB were measured in both photonic lanterns and reference single-mode waveguides with 10.4-mm-long gratings. The result demonstrates efficient and symmetrical performance of each of the gratings in the photonic lantern. Such devices will be beneficial to space-division multiplexed communication systems as well as for units for astronomical instrumentation for suppression of the atmospheric telluric emission from OH lines.

  12. Large Bragg Reflection from One-Dimensional Chains of Trapped Atoms Near a Nanoscale Waveguide

    Science.gov (United States)

    Corzo, Neil V.; Gouraud, Baptiste; Chandra, Aveek; Goban, Akihisa; Sheremet, Alexandra S.; Kupriyanov, Dmitriy V.; Laurat, Julien

    2016-09-01

    We report experimental observations of a large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period nearly commensurate with the resonant wavelength, we observe a reflectance of up to 75% for the guided mode. Each atom behaves as a partially reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum network capabilities and the study of many-body effects emerging from long-range interactions.

  13. Dose ratio proton radiography using the proximal side of the Bragg peak

    Energy Technology Data Exchange (ETDEWEB)

    Doolan, P. J., E-mail: paul.doolan.09@ucl.ac.uk; Royle, G.; Gibson, A. [Department of Medical Physics and Bioengineering, University College London, London WC1E 6BT (United Kingdom); Lu, H.-M. [Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Prieels, D.; Bentefour, E. H. [Ion Beam Applications (IBA), 3 Chemin du Cyclotron, Louvain la Neuve B-1348 (Belgium)

    2015-04-15

    Purpose: In recent years, there has been a movement toward single-detector proton radiography, due to its potential ease of implementation within the clinical environment. One such single-detector technique is the dose ratio method in which the dose maps from two pristine Bragg peaks are recorded beyond the patient. To date, this has only been investigated on the distal side of the lower energy Bragg peak, due to the sharp falloff. The authors investigate the limits and applicability of the dose ratio method on the proximal side of the lower energy Bragg peak, which has the potential to allow a much wider range of water-equivalent thicknesses (WET) to be imaged. Comparisons are made with the use of the distal side of the Bragg peak. Methods: Using the analytical approximation for the Bragg peak, the authors generated theoretical dose ratio curves for a range of energy pairs, and then determined how an uncertainty in the dose ratio would translate to a spread in the WET estimate. By defining this spread as the accuracy one could achieve in the WET estimate, the authors were able to generate lookup graphs of the range on the proximal side of the Bragg peak that one could reliably use. These were dependent on the energy pair, noise level in the dose ratio image and the required accuracy in the WET. Using these lookup graphs, the authors investigated the applicability of the technique for a range of patient treatment sites. The authors validated the theoretical approach with experimental measurements using a complementary metal oxide semiconductor active pixel sensor (CMOS APS), by imaging a small sapphire sphere in a high energy proton beam. Results: Provided the noise level in the dose ratio image was 1% or less, a larger spread of WETs could be imaged using the proximal side of the Bragg peak (max 5.31 cm) compared to the distal side (max 2.42 cm). In simulation, it was found that, for a pediatric brain, it is possible to use the technique to image a region with a

  14. Probing 2D Quantum Turbulence in Atomic Superfluid Gas using Bragg Scattering

    CERN Document Server

    Seo, Sang Won; Kim, Joon Hyun; Shin, Yong-il

    2016-01-01

    We demonstrate the use of spatially resolved Bragg spectroscopy for detection of the quantum vortex circulation signs in an atomic Bose-Einstein condensate (BEC). High-velocity atoms near the vortex cores are resonantly scattered from the BEC, and the vortex signs are determined from the scattered atom positions relative to the corresponding vortex cores. Using this method, we investigate decaying 2D quantum turbulence in a highly oblate BEC at temperatures of $\\sim 0.5 T_c$, where $T_c$ is the critical temperature of the trapped sample. Clustering of like-sign vortices is not observed; rather, the measured vortex configurations reveal weak pair correlations between the vortices and antivortices in the turbulent BEC. Our Bragg scattering method enables a direct experimental study of 2D quantum turbulence in BECs.

  15. Liquid Resin Infusion process monitoring with embedded superimposed long period and short period Bragg grating sensor.

    Directory of Open Access Journals (Sweden)

    Robert L.

    2010-06-01

    Full Text Available We propose here the monitoring of the Liquid Resin Infusion (LRI process for using a superimposed long period (LPG and short period (FBG Bragg grating sensor. Monitoring of such a process is usually made measuring simultaneously temperature and strain by the use of an electro-optical device (FBG-Thermocouple. It has been shown that an applied solicitation is measured by a wavelength shift with a different sensitivity for LPG and FBG; thus strain and temperature influences can be determined separately by measuring corresponding wavelength shifts. The reported configuration is based on the use of these two Bragg gratings types written in the same fibre section, which allows us to discriminate the contributions of the temperature and strain. The sensor is embedded in a composite specimen manufactured by LRI process for monitoring in real time and simultaneously the applied temperature and strain.

  16. Covalent Attachment of Carbohydrate Derivatives to an Evanescent Wave Fiber Bragg Grating Biosensor

    Directory of Open Access Journals (Sweden)

    Christopher J. Stanford

    2009-01-01

    Full Text Available A carbohydrate-based biosensor was prepared by functionalization of the surface of an etched fiber Bragg grating with a glucopyranosyl-siloxane conjugate. Functionalization of the surface with the conjugate resulted in a Bragg grating shift of 24 pm. This shift in the refractive index is consistent with a theoretical shift calculated assuming monolayer coverage of the glucose conjugate on the sensor. The resulting functionalized fiber was shown to interact selectively with concanavalin A (Con A, a glucose binding protein (lectin. Exposure of the glucose-functionalized fiber to peanut agglutinin, a galactosebinding lectin, did not result in a change of the refractive index corresponding to a binding event.

  17. William Henry Bragg in Adelaide: beginning research at a colonial locality.

    Science.gov (United States)

    Jenkin, John

    2004-03-01

    This essay presents an account of W. H. Bragg's earliest research program in Australia during the years 1904-1907: a study of the behavior of alpha particles from radioactive decay. It is suggested that problems associated with distance and isolation played a pivotal role in Bragg's thinking and acting during this period and that his use of two "advocates," Ernest Rutherford and Frederick Soddy, was essential to the success of the program. It is further argued that this account supports a substantial amendment of the center-periphery model of colonial science to embrace a much closer attention to place and locality; that is, it supports a polycentric model (in which the center might still be prominent). PMID:15301067

  18. Proof of Concept of Impact Detection in Composites Using Fiber Bragg Grating Arrays

    Directory of Open Access Journals (Sweden)

    Ander Montero

    2013-09-01

    Full Text Available Impact detection in aeronautical structures allows predicting their future reliability and performance. An impact can produce microscopic fissures that could evolve into fractures or even the total collapse of the structure, so it is important to know the location and severity of each impact. For this purpose, optical fibers with Bragg gratings are used to analyze each impact and the vibrations generated by them. In this paper it is proven that optical fibers with Bragg gratings can be used to detect impacts, and also that a high-frequency interrogator is necessary to collect valuable information about the impacts. The use of two interrogators constitutes the main novelty of this paper.

  19. Dual Measurements of Pressure and Temperature With Fiber Bragg Grating Sensor

    Directory of Open Access Journals (Sweden)

    Tahreer S. Mansour

    2015-06-01

    Full Text Available The fiber Bragg grating (FBG technology has been rapidly applied in the sensing technology field. In this work, uniform FBG was used as pressure sensor based on measuring related Bragg wavelength shift. The pressure was applied directly by air compressor to the sensor and the pressure was ranged from 1 to 6 bar. This sensor also was affected by the external temperature so as a result it could be used as a temperature sensor. This sensor could be used to monitor the pressure of dams. It has been shown from the result that the sensor is very sensitive to the pressure and the sensitivity was (67 pmar and is very sensitive to temperature and the sensitivity was (10pm oC.

  20. Fiber optic relative humidity sensor based on the tilted fiber Bragg grating coated with graphene oxide

    Science.gov (United States)

    Wang, Youqing; Shen, Changyu; Lou, Weimin; Shentu, Fengying; Zhong, Chuan; Dong, Xinyong; Tong, Limin

    2016-07-01

    A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10-80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.

  1. A Noncontact Force Sensor Based on a Fiber Bragg Grating and Its Application for Corrosion Measurement

    Directory of Open Access Journals (Sweden)

    Antonio C. Bruno

    2013-08-01

    Full Text Available A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining the sensor at a constant standoff distance, material loss due to corrosion increases the distance between the magnet and the corroded surface, which decreases the magnetic force. This will decrease the strain in the optical fiber shifting the reflected Bragg wavelength. The measured shift for the optical fiber used was 1.36 nm per Newton. Models were developed to optimize the magnet geometry for a specific sensor standoff distance and for particular corrosion pit depths. The sensor was able to detect corrosion pits on a fuel storage tank bottom with depths in the sub-millimeter range.

  2. Detecting stripe phase in spin-orbit coupled condensates via optical Bragg scattering

    Science.gov (United States)

    Putra, Andika; Carcoba, Francisco Salces; Yue, Yuchen; Sugawa, Seiji; Spielman, Ian

    2016-05-01

    The stripe phase in spin-orbit coupled condensates has been predicted theoretically but not yet been observed. This peculiar feature, analogue to supersolidity, originates from the interaction effects and spin-momentum locking between different spin states. Motivated by recent observation of antiferromagnetic correlations in cold atoms, we explore the feasibility of Bragg diffraction to observe the stripe phase. Here, we create spin-orbit coupled condensates in f = 1 ground state manifold of Rb87 using a pair of cross-polarized 790.02 nm counter-propagating laser beams. Using similar setup, we make a spin-dependent one dimensional lattice and demonstrate Bragg scattering of light to calibrate the atomic density distribution. This enables us to do a direct measure of the stripe phase.

  3. Sensitivity of Bragg gratings in birefringent optical fiber to transverse compression between conforming materials.

    Science.gov (United States)

    Dennison, Christopher R; Wild, Peter M

    2010-04-20

    A theoretical and experimental investigation of the transverse load sensitivity of Bragg gratings in birefringent fibers to conforming contact is presented. A plane elasticity model is used to predict the contact dimensions between a conforming material and optical fiber and the principal stresses, indicating birefringence, created as a result of this contact. The transverse load sensitivity of commercially available birefringent fiber is experimentally measured for two cases of conforming contact. Theoretical and experimental results show that birefringent optical fiber can be used to make modulus-independent measurements of contact load. Therefore, Bragg gratings could be applied to conforming contact load measurements while avoiding some of the complications associated with existing contact sensors: specifically, the necessity to precalibrate by using materials with mechanical properties identical to those found in situ.

  4. Novel simulation method for fiber Bragg grating under inhomogeneous strain fields

    Institute of Scientific and Technical Information of China (English)

    YUN Bin-feng; LU Chang-gui; WANG Zhu-yuan; WANG Yi-ping; CUI Yi-ping

    2005-01-01

    The spectra of fiber Bragg grating (FBG) in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method can be employed for exact simulation of the spectrum of Bragg grating in such field, but the convergence speed is slow. On the other hand, although the transfer matrix method could be used with higher convergence speed, the precision is poor because of the neglect of the grads of strain change. By improving the FBG equivalent period, a novel simulation method based on a modified transfer matrix method is proposed, which has the advantage of quick-convergence as well as good accuracy.

  5. Feasibility studies of Bragg probe for noninvasive carotid pulse waveform assessment

    Science.gov (United States)

    Leitão, Cátia; Bilro, Lúcia; Alberto, Nélia; Antunes, Paulo; Lima, Hugo; André, Paulo S.; Nogueira, Rogério; Pinto, João L.

    2013-01-01

    The arterial stiffness evaluation is largely reported as an independent predictor of cardiovascular diseases. The central pulse waveform can provide important data about arterial health and has been studied in patients with several pathologies, such as diabetes mellitus, coronary artery disease and hypertension. The implementation and feasibility studies of a fiber Bragg grating probe for noninvasive monitoring of the carotid pulse are described based on fiber Bragg grating technology. Assessment tests were carried out in carotids of different volunteers and it was possible to detect the carotid pulse waveform in all subjects. In one of the subjects, the sensor was also tested in terms of repeatability. Although further tests will be required for clinical investigation, the first studies suggest that the developed sensor can be a valid alternative to electromechanical tonometers.

  6. Photonic crystal fibre Brillouin laser based on Bragg grating Fabry-Perot cavity

    Institute of Scientific and Technical Information of China (English)

    Geng Dan; Yang Dong-Xiao; Shen Guo-Feng; Zhang Xian-Min

    2008-01-01

    A photonic crystal fibre Brillouin laser based on fibre Bragg grating Fabry-Perot cavity is presented. A highly nonlinear photonic crystal fibre 25 m in length is used as Brillouin gain medium and fibre Bragg grating Fabry-Perot cavity is chosen in order to enhance the laser conversion efficiency and suppress the higher-order Stokes waves. The laser reaches the threshold at input power of 35 mW, and the experimental laser conversion efficiency achieves 18% of the input power of 140 mW and does not show higher-order Stokes waves. A photonic crystal fibre BriUouin laser withshorter fibre length and lower threshold is experimentally realized.

  7. Spectral interference fringes in chirped large-mode-area fiber Bragg gratings

    Science.gov (United States)

    Poozesh, Reza; Madanipour, Khosro; Vatani, Vahid

    2016-09-01

    Spectral interference fringes were experimentally observed in chirped large mode area fiber Bragg grating (CFBG) in the overlapping region of the reflected spectrum of fiber modes by a high resolution spectrometer. It was demonstrated that the interference is due to optical path difference of the reflected modes in slight chirped FBGs. By assuming chirped fiber Bragg gratings as a Fabry-Perot (FP) cavity, free spectral range (FSR) of FP was calculated 0.08 nm which is matched with measurement very well. Furthermore, the experiments show that axial tension and temperature changes of the CFBG do not have observable effects on the magnitude of FSR, however coiling of the fiber deceases spectral interference fringe amplitude without sensible effect on FSR magnitude. The results of this work can be utilized in bending sensors.

  8. Ionoacoustic tomography of the proton Bragg peak in combination with ultrasound and optoacoustic imaging

    Science.gov (United States)

    Kellnberger, Stephan; Assmann, Walter; Lehrack, Sebastian; Reinhardt, Sabine; Thirolf, Peter; Queirós, Daniel; Sergiadis, George; Dollinger, Günther; Parodi, Katia; Ntziachristos, Vasilis

    2016-07-01

    Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg peak positioning inside tissue. We introduce ionoacoustic tomography based on detection of ion induced ultrasound waves as a technique to provide feedback on the ion beam profile. We demonstrate for 20 MeV protons that ion range imaging is possible with submillimeter accuracy and can be combined with clinical ultrasound and optoacoustic tomography of similar precision. Our results indicate a simple and direct possibility to correlate, in-vivo and in real-time, the conventional ultrasound echo of the tumor region with ionoacoustic tomography. Combined with optoacoustic tomography it offers a well suited pre-clinical imaging system.

  9. Anderson localization in a partially random Bragg grating and a conserved area theorem

    CERN Document Server

    Mafi, Arash

    2015-01-01

    We investigate the gradual emergence of the disorder-related phenomena in intermediate regimes between a deterministic periodic Bragg grating and a fully random grating and highlight two critical properties of partially disordered Bragg gratings. First, the integral of the logarithm of the transmittance over the reciprocal wavevector space is a conserved quantity. Therefore, adding disorder merely redistributes the transmittance over the reciprocal space. Second, for any amount of disorder, the average transmittance decays exponentially with the number of grating layers in the simple form of $\\exp(-\\eta N)$ for sufficiently large $N$, where $\\eta$ is a constant and $N$ is the number of layers. Conversely, the simple exponential decay form does not hold for small $N$ except for a highly disordered system. Implications of these findings are demonstrated.

  10. Dental composite resins: measuring the polymerization shrinkage using optical fiber Bragg grating sensors

    Science.gov (United States)

    Ottevaere, H.; Tabak, M.; Chah, K.; Mégret, P.; Thienpont, H.

    2012-04-01

    Polymerization shrinkage of dental composite materials is recognized as one of the main reasons for the development of marginal leakage between a tooth and filling material. As an alternative to conventional measurement methods, we propose optical fiber Bragg grating (FBG) based sensors to perform real-time strain and shrinkage measurements during the curing process of dental resin cements. We introduce a fully automated set-up to measure the Bragg wavelength shift of the FBG strain sensors and to accurately monitor the linear strain and shrinkage of dental resins during curing. Three different dental resin materials were studied in this work: matrix-filled BisGMA-based resins, glass ionomers and organic modified ceramics.

  11. Inversion Domain Boundaries in GaN Wires Revealed by Coherent Bragg Imaging.

    Science.gov (United States)

    Labat, Stéphane; Richard, Marie-Ingrid; Dupraz, Maxime; Gailhanou, Marc; Beutier, Guillaume; Verdier, Marc; Mastropietro, Francesca; Cornelius, Thomas W; Schülli, Tobias U; Eymery, Joël; Thomas, Olivier

    2015-09-22

    Interfaces between polarity domains in nitride semiconductors, the so-called Inversion Domain Boundaries (IDB), have been widely described, both theoretically and experimentally, as perfect interfaces (without dislocations and vacancies). Although ideal planar IDBs are well documented, the understanding of their configurations and interactions inside crystals relies on perfect-interface assumptions. Here, we report on the microscopic configuration of IDBs inside n-doped gallium nitride wires revealed by coherent X-ray Bragg imaging. Complex IDB configurations are evidenced with 6 nm resolution and the absolute polarity of each domain is unambiguously identified. Picoscale displacements along and across the wire are directly extracted from several Bragg reflections using phase retrieval algorithms, revealing rigid relative displacements of the domains and the absence of microscopic strain away from the IDBs. More generally, this method offers an accurate inner view of the displacements and strain of interacting defects inside small crystals that may alter optoelectronic properties of semiconductor devices. PMID:26322655

  12. Tunable Light Filtering in a Bragg Mirror/Heavily-Doped Semiconducting Nanocrystal Composite

    CERN Document Server

    Kriegel, Ilka

    2014-01-01

    Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors, band-pass filters with high reflectivity represent good candidates. However, their optical characteristics are determined at the stage of fabrication. Heavily doped semiconductor nanocrystals (NCs) on the other hand deliver a high degree of optical tunability through the active modulation of their carrier density ultimately influencing their plasmonic absorption properties. Here, we propose the design of a tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis-NIR) spectral region when employing varying carrier densities. As tunable component we implemented a d...

  13. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    Science.gov (United States)

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-01-01

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data. PMID:27669251

  14. 976 nm single-frequency distributed Bragg reflector fiber laser.

    Science.gov (United States)

    Zhu, Xiushan; Shi, Wei; Zong, Jie; Nguyen, Dan; Norwood, Robert A; Chavez-Pirson, Arturo; Peyghambarian, N

    2012-10-15

    A single-frequency distributed Bragg reflector (DBR) fiber laser at 976 nm was developed with a 2 cm long highly ytterbium-doped phosphate fiber and a pair of silica fiber Bragg gratings. More than 100 mW of linearly polarized output was achieved from the all-fiber DBR laser with a linewidth less than 3 kHz. The outstanding features of this single-frequency laser also include ultralow relative intensity noise and high wavelength stability. This fiber laser is an excellent seeder for high-power 976 nm narrow-linewidth laser amplifiers that can be used for efficient coherent blue-light generation through frequency doubling. PMID:23073399

  15. Non-Bragg-gap solitons in one-dimensional Kerr-metamaterial Fibonacci heterostructures

    Science.gov (United States)

    Reyes-Gómez, E.; Cavalcanti, S. B.; Oliveira, L. E.

    2015-06-01

    A detailed study of non-Bragg-gap solitons in one-dimensional Kerr-metamaterial quasiperiodic Fibonacci heterostructures is performed. The transmission coefficient is numerically obtained by combining the transfer-matrix formalism in the metamaterial layers with a numerical solution of the nonlinear differential equation in the Kerr slabs, and by considering the loss effects in the metamaterial slabs. A switching from states of no transparency in the linear regime to high-transparency states in the nonlinear regime is observed for both zero-order and plasmon-polariton gaps. The spatial localization of the non-Bragg-gap solitons is also examined, and the symmetry properties of the soliton waves are briefly discussed.

  16. EIT-like transmission by interaction between multiple Bragg scattering and local plasmonic resonances

    CERN Document Server

    Liu, Z Z; Xiao, J J

    2015-01-01

    We study the optical properties associated to both the polariton gap and the Bragg gap in periodic resonator-waveguide coupled system, based on the temporal coupled mode theory and the transfer matrix method. By the complex band and the transmission spectrum, it is feasible to tune the interaction between multiple Bragg scattering and the local resonance, which may give rise to analogous phenomena of electromagnetically induced transparency (EIT). We further design a plasmonic slot waveguide side-coupled with local plasmonic resonator to demonstrate the EIT-like effects in the near-infared band. Numerical calculations show that realistic amount of metal Joule loss may destroy the interference and the total absorption is enhanced in the transparency windwo due to the near zero group velocity of the guiding wave.

  17. Measuring the fine structure constant with Bragg diffraction and Bloch oscillations

    Science.gov (United States)

    Yu, Chenghui; Estey, Brian; Parker, Richard; Dudley, Jordan; Müller, Holger

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We have suppressed many systematic effects known in most atom interferometers with Raman beam splitters such as light shift, Zeeman effect shift as well as vibration. We have also simulated multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implemented spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  18. Measuring h /mCs and the Fine Structure Constant with Bragg Diffraction and Bloch Oscillations

    Science.gov (United States)

    Parker, Richard

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We suppress many systematic effects, e.g., Zeeman shifts and effects from Earth's gravity and vibrations, use Bloch oscillations to increase the signal and reduce the diffraction phase, simulate multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implement spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  19. Coupled-modetheory for magneto-optical fiber Bragg grating under non-uniform magnetic field

    Institute of Scientific and Technical Information of China (English)

    LIU Fen; WU Bao-jian; LU Xin

    2011-01-01

    According to the perturbation theory,the coupled-mode equations for guided optical waves in the magneto-optical fiber Bragg gratings(MFBGs) under non-uniform magnetic field are derived.The equivalent relation between the magneticallyinduced non-uniform fiber Bragg grating(MnFBG) and the corresponding non-magnetic chirped grating is expressed and verified by the piecewise-uniform MFBG model under linear magnetic field.On the basis of the equivalent relation,the MnFBGs can be effectively investigated by means of simulations.The characteristics of the MnFBGs under three typical magnetic field distributions with application to optical pulse compression are simulated,and the minimal pulse width can be achieved for the same magneto-optical coupling parameter of 2.2 × 103 m-1.

  20. Practical biological spread-out Bragg peak design of carbon beam

    CERN Document Server

    Kim, Chang Hyeuk; Chang, Seduk; Jang, Hong Suk; Kim, Jeong Hwan; Park, Dong Wook; Hwang, Won Taek; Yang, Tea-Keun

    2015-01-01

    The carbon beams show more advantages on the biological properties compared with proton beams in radiation therapy. The carbon beam shows high linear energy transfer (LET) to medium and it increases the relative biological effectiveness (RBE). To design spread-out Bragg peak (SOBP) of biological dose using carbon beam, a practical method was purposed by using the linear-quadratic (LQ) model and Geant4 based Monte Carlo simulation code. The various Bragg peak profiles and LET was calculated for each slice at the target region. To generate appropriate biological SOBP, a set of weighting factor, which is a power function in terms of energy step, was applied to the obtained each physical dose. The designed biological SOBP showed 1.34 % of uniformity.

  1. Large Bragg Reflection from One-Dimensional Chains of Trapped Atoms Near a Nanoscale Waveguide

    CERN Document Server

    Corzo, N V; Chandra, A; Goban, A; Sheremet, A S; Kupriyanov, D V; Laurat, J

    2016-01-01

    We report experimental observations of large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period close to commensurate with the resonant wavelength, we observe a reflectance up to 75% for the guided mode. Each atom behaves as a partially-reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would allow for novel quantum network capabilities and many-body effects emerging from long-range interactions.

  2. Strain Sharing Assessment in Woven Fiber Reinforced Concrete Beams Using Fiber Bragg Grating Sensors.

    Science.gov (United States)

    Montanini, Roberto; Recupero, Antonino; De Domenico, Fabrizio; Freni, Fabrizio

    2016-09-22

    Embedded fiber Bragg grating sensors have been extensively used worldwide for health monitoring of smart structures. In civil engineering, they provide a powerful method for monitoring the performance of composite reinforcements used for concrete structure rehabilitation and retrofitting. This paper discusses the problem of investigating the strain transfer mechanism in composite strengthened concrete beams subjected to three-point bending tests. Fiber Bragg grating sensors were embedded both in the concrete tensioned surface and in the woven fiber reinforcement. It has been shown that, if interface decoupling occurs, strain in the concrete can be up to 3.8 times higher than that developed in the reinforcement. A zero friction slipping model was developed which fitted very well the experimental data.

  3. Characterizing Fiber Bragg Grating Index Profiles to Improve the Writing Process

    DEFF Research Database (Denmark)

    Espejo, M.J.; Svalgaard, Mikael; Dyer, S.D.

    2006-01-01

    We demonstrate an accurate method for identifying both systematic and random errors in a fiber Bragg grating (FBG) writing system and show its application to calibration of the writing process. We first measure the FBG impulse response using low-coherence interferometry, and then we calculate......-beam dithered phase mask FBG writing system. We demonstrate the ability to identify errors in the writing process that would not likely be found from a measurement of the FBG reflection spectrum alone....

  4. Experimental research on spatial filtering of deformed laser beam by transmitting volume Bragg grating

    Institute of Scientific and Technical Information of China (English)

    Guangwei Zheng; Benjian Shen; Jichun Tan; Yanlan He; Xiao Wang

    2011-01-01

    Using transmitting volume Bragg gratings (TVBG) as a basis, an experiment on one-dimensional spatial filtering of a deformed laser beam is designed. The deformed laser beam results from a He-Ne laser beam modulated by an amplitude modulation plate with a spatial frequency of 7.2 mm-1. Results show that when the central wave vector of the deformed beam satisfies the Bragg law of TVBG, the spatial profile of the -1st forward-diffracted order is similar to that of the undeformed He-Ne laser beam due to the TVBG with a spatial frequency selective bandwidth of less than 5.0 mm-1. The higher frequency components of the deformed beam are filtered out in the optical near field. Thus, the TVBG cleanup of the spatiallydeformed laser beam is realized experimentally.%@@ Using transmitting volume Bragg gratings (TVBG) as a basis, an experiment on one-dimensional spatial filtering of a deformed laser beam is designed.The deformed laser beam results from a He-Ne laser beam modulated by an amplitude modulation plate with a spatial frequency of 7.2 mm-1.Results show that when the central wave vector of the deformed beam satisfies the Bragg law of TVBG, the spatial profile of the -1st forward-diffracted order is similar to that of the undeformed He-Ne laser beam due to the TVBG with a spatial frequency selective bandwidth of less than 5.0 mm-1.The higher frequency components of the deformed beam are filtered out in the optical near field.Thus, the TVBG cleanup of the spatially-deformed laser beam is realized experimentally.

  5. Measurement Model for the Maximum Strain in Beam Structures Using Multiplexed Fiber Bragg Grating Sensors

    OpenAIRE

    Se Woon Choi; Jihoon Lee; Bo Hwan Oh; Hyo Seon Park

    2013-01-01

    This study develops a strain measurement model for beam structures subjected to multiloading conditions by defining the strain-shape function and participation factors to overcome the limitations of strain measurements using fiber Bragg grating (FBG) strain sensors. Using the proposed model, the maximum strain in a beam is obtained by the sum of the strains caused by the different loadings acting separately. In this paper, the strain-shape functions for various loading and support conditions ...

  6. Inverse-Gaussian-Apodized Fiber Bragg Grating for Dual Wavelength Lasing

    CERN Document Server

    Lin, Bo; Tjin, Swee Chuan; Tang, Dingyuan; Hao, Jianzhong; Tay, Chia Meng; Liang, Sheng

    2010-01-01

    A fiber Bragg grating (FBG) with an inverse-Gaussian apodization function is proposed and fabricated. It is shown that such a FBG possesses easily controllable dual-wavelength narrow transmission peaks. Incorporating such a FBG filter in a fiber laser with a linear cavity, stable dual-wavelength emission with 0.146 nm wavelength spacing is obtained. It provides a simple and low cost approach of achieving the dual-wavelength fiber laser operation.

  7. 100 GHz electrically tunable planar Bragg grating via nematic liquid crystal overlay towards reconfigurable WDM networks

    OpenAIRE

    Adikan, Faisal Rafiq Mahamd; Gates, James C.; Major, Huw E.; Gawith, Corin B.E.; Smith, Peter G. R.; Dyadyusha, Andriy; Kaczmarek, Malgosia; Sparrow, Ian J.G.

    2007-01-01

    Novel liquid crystal-based integrated optical devices with >140GHz electrical tuning are presented for application towards reconfigurable wavelength division multiplexing (WDM) networks. Initial results with Bragg wavelength tuning covering five 25GHz WDM channel spacing have been achieved with 170V (peak-to-peak) sinusoidal voltages applied across electro-patterned ITO-covered glass electrodes placed 60?m apart. These prototype devices were fabricated using direct UV grating writing, with an...

  8. Performance analysis of peak tracking techniques for fiber Bragg grating interrogation systems

    OpenAIRE

    Olivero, Massimo; Tosi, Daniele; Perrone, Guido

    2012-01-01

    In this paper, we propose a spectral correlation-based technique for tracking the wavelength shift of a fiber Bragg grating. We compared this approach, by means of a Monte Carlo numerical simulation, to the typical peak tracking techniques applied in classic interrogation systems. As result, we obtained a considerable gain in terms of noise tolerance (about 20 dB), which can be further incremented by selecting large-bandwidth gratings. This permits to increase the power budget of a fiber Brag...

  9. Anomalous thermal dynamics of Bragg gratings inscribed in germanosilicate optical fiber

    OpenAIRE

    Rahman, A.; Madhav, Venu K; B. Srinivasan; S. Asokan

    2009-01-01

    An interesting, periodic appearance of a new peak has been observed in the reflected spectrum of a Fiber Bragg Grating (FBG) inscribed in a germanosilicate fiber during thermal treatment. The new peak occurs on the longer wavelength side of the spectrum during heating and on the shorter wavelength side during cooling, following an identical reverse dynamics. Comparison with a commercial grating with 99.9% reflectivity shows a similar decay dynamics. It is proposed that the distortion due to s...

  10. Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis

    OpenAIRE

    Sulyanova, Elena; Shabalin, Anatoly; Yefanov, Oleksandr; Zaluzhnyy, Ivan; Besedin, Ilya; Sprung, Michael; Petukhov, Andrei; Vartaniants, Ivan; Zozulya, Alexey; Meijer, Janne-Mieke; Dzhigaev, Dmitry; Gorobtsov, Oleg; Kurta, Ruslan; Lazarev, Sergey; Lorenz, Ulf

    2015-01-01

    In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson–Hall plots based on mosaic block model. T...

  11. Time division multiplexing of 106 weak fiber Bragg gratings using a ring cavity configuration

    Science.gov (United States)

    Wang, Zhi; Wen, Hongqiao; Luo, Zhihui; Dai, Yutang

    2016-06-01

    A time division multiplexing of 106 weak fibers Bragg gratings (FBGs) based on a ring resonant-cavity is demonstrated. A semiconductor optical amplifier is connected in the cavity to function as an amplifier as well as a switch. The 106 weak FBGs are written along a SMF-28 fiber in serial with peak reflectivity of about -30 dB and equal separations of 5 m. The crosstalk and spectral distortion are investigated through both theoretical analysis and experiments.

  12. Post-Impact Fatigue Damage Monitoring Using Fiber Bragg Grating Sensors

    OpenAIRE

    Chow-Shing Shin; Shien-Kuei Liaw; Shi-Wei Yang

    2014-01-01

    It has been shown that impact damage to composite materials can be revealed by embedded Fiber Bragg Gratings (FBG) as a broadening and splitting of the latter’s characteristic narrow peak reflected spectrum. The current work further subjected the impact damaged composite to cyclic loading and found that the FBG spectrum gradually submerged into a rise of background intensity as internal damages progressed. By skipping the impact, directing the impact to positions away from the FBG and examin...

  13. Measurements of Ion Stopping around the Bragg Peak in High-Energy-Density Plasmas

    Science.gov (United States)

    Frenje, Johan

    2015-11-01

    Over the last few decades, ion stopping in weakly- to strongly-coupled High-Energy-Density (HED) plasmas has been subject to extensive analytical and numerical studies, but only a limited set of experimental data exists to check the validity of these theories. Most of these experiments also did not probe the detailed characteristics of the Bragg peak (peak ion stopping) where the ion velocity is similar to the average thermal electron velocity. To the best of our knowledge, only one exploratory attempt to do this was conducted by Hicks et al., who were able to describe qualitatively the behavior of the Bragg peak for one plasma condition. The work described in this presentation makes significant advances over previous experimental efforts by quantitatively assessing the characteristics of the ion stopping, ranging from low-velocity stopping, through the Bragg peak, to high-velocity stopping for different HED plasma conditions. This was achieved by measuring the energy loss of DD-tritons, D3He-alphas, DD-protons and D3He-protons, with distinctly different velocities, and the results indicate that the stopping power varies strongly with Te and ne. This effort represents the first experimental test of state-of-art plasma-stopping-power theories around the Bragg peak, which is an important first step in our efforts of getting a fundamental understanding of DT-alpha stopping in HED plasmas, a prerequisite for understanding ignition margins in various implosion designs with varying hot spot areal density at the National Ignition Facility. The work described here was performed in part at the LLE National Laser User's Facility (NLUF), and was supported in part by US DOE (Grant No. DE-FG03- 03SF22691), LLNL (subcontract Grant No. B504974) and LLE (subcontract Grant No. 412160-001G).

  14. Special Apodized Fiber Bragg Grating for Flat-top Band-pass Reflectivity Filter

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-min; YU Zhong-yuan; YANG Hong-bo; YANG Bo-jun; YU Li; ZHANG Xiao-guang

    2004-01-01

    The characteristics of special apodized fiber Bragg grating (FBG) in flat-top pass-band as reflectivity filter are presented. This special apodized FBG was designed by the particle swarm optimization algorithm. Compared with conventional apodized FBG, the special apodized FBG presented was more robust in the flat-top pass-band characteristic even if the strength of grating is very week. This technology is very interesting in designing the filter for wavelength division multiplexing system.

  15. Channel Spectral Separation Narrowing for Spectral Beam Combining by Apodisation of the Reflecting Volume Bragg Grating

    OpenAIRE

    Shen Benjian; Tan Jichun; Guangwei Zheng; Yanlan He

    2011-01-01

    The sidelobe in diffraction efficiency of reflecting volume Bragg grating (RVBG) limits the wavelength channel spectral separation, which determines the combining power output in spectral beam combining (SBC) systems. A novel SBC system based on the apodised RVBG has been proposed to suppress the sidelobe. Several apodised RVBGs have been compared and the optimal apodised RVBG is obtained by using the chain-matrix approach. Numerical results show that the sidelobe could be suppressed excellen...

  16. Three-hole microstructured optical fiber for efficient Fiber Bragg Grating refractometer

    OpenAIRE

    Phan Huy, Minh Châu; Laffont, Guillaume; Dewynter, Véronique; Ferdinand, Pierre; Roy, Philippe; Auguste, Jean-Louis; Pagnoux, Dominique; Blanc, Wilfried; Dussardier, Bernard

    2007-01-01

    International audience We present a photosensitive three-hole microstructured optical fiber specifically designed to improve the refractive index sensitivity of a standard Fiber Bragg Grating (FBG) sensor photowritten in the suspended Ge-doped silica core. We describe the specific photowriting procedure used to realize gratings in such a fiber. We then determine their spectral sensitivity to the refractive index changes of material filling the holes surrounding the core. The sensitivity is...

  17. Analysis of sampled fiber Bragg gratings in polarization-maintaining fiber

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A novel type of sampled fiber Bragg gratings (FBGs) written in polarization-maintaining fiber (PMF) is proposed.The reflection spectrum,time delay,and group velocity dispersion (GVD) of the gratings are analyzed.In addition,the reflection spectrum is optimized by apodization.The scheme of multi-wavelength output based on the gratings is proposed,which could be used as a multi-wavelength polarization filter in the density wavelength division multiplexed (DWDM) system.

  18. Railway track component condition monitoring using optical fibre Bragg grating sensors

    International Nuclear Information System (INIS)

    The use of optical fibre Bragg grating (FBG) strain sensors to monitor the condition of safety critical rail components is investigated. Fishplates, switchblades and stretcher bars on the Stagecoach Supertram tramway in Sheffield in the UK have been instrumented with arrays of FBG sensors. The dynamic strain signatures induced by the passage of a tram over the instrumented components have been analysed to identify features indicative of changes in the condition of the components. (paper)

  19. Railway track component condition monitoring using optical fibre Bragg grating sensors

    Science.gov (United States)

    Buggy, S. J.; James, S. W.; Staines, S.; Carroll, R.; Kitson, P.; Farrington, D.; Drewett, L.; Jaiswal, J.; Tatam, R. P.

    2016-05-01

    The use of optical fibre Bragg grating (FBG) strain sensors to monitor the condition of safety critical rail components is investigated. Fishplates, switchblades and stretcher bars on the Stagecoach Supertram tramway in Sheffield in the UK have been instrumented with arrays of FBG sensors. The dynamic strain signatures induced by the passage of a tram over the instrumented components have been analysed to identify features indicative of changes in the condition of the components.

  20. 3D printed sensing patches with embedded polymer optical fibre Bragg gratings

    Science.gov (United States)

    Zubel, Michal G.; Sugden, Kate; Saez-Rodriguez, D.; Nielsen, K.; Bang, O.

    2016-05-01

    The first demonstration of a polymer optical fibre Bragg grating (POFBG) embedded in a 3-D printed structure is reported. Its cyclic strain performance and temperature characteristics are examined and discussed. The sensing patch has a repeatable strain sensitivity of 0.38 pm/μepsilon. Its temperature behaviour is unstable, with temperature sensitivity values varying between 30-40 pm/°C.

  1. Plasmonic V-groove waveguides with Bragg grating filters via nanoimprint lithography

    DEFF Research Database (Denmark)

    Smith, Cameron L. C.; Desiatov, Boris; Goykmann, Ilya;

    2012-01-01

    We demonstrate spectral filtering with state-of-the-art Bragg gratings in plasmonic V-groove waveguides fabricated by wafer scale processing based on nanoimprint lithography. Transmission spectra of the devices having 16 grating periods exhibit spectral rejection of the channel plasmon polaritons...... with effective refractive index values calculated by finite element simulations in COMSOL. The results represent advancement towards the implementation of plasmonic V-grooves with greater functional complexity and mass-production compatibility....

  2. Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

    OpenAIRE

    Ander Montero; Idurre Saez de Ocariz; Ion Lopez; Pablo Venegas; Javier Gomez; Joseba Zubia

    2011-01-01

    This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT tecniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural...

  3. Field Deployable Fiber Bragg Grating Strain Patch for Long-Term Stable Health Monitoring Applications

    OpenAIRE

    Gerhard Kalinka; Wolfgang Habel; Nadine Kusche; Vivien Schukar

    2013-01-01

    A fiber Bragg grating (FBG) strain patch specially adapted for long-term and high-strain applications has been developed and characterized. The design concept for the patch is based on a glass-fiber reinforced plastic (gfrp) carrier material. The developed concept for the FBG integration into the carrier material was derived from reliable integration procedure of FBG sensors into composite structures. The patches’ temperature sensitivity, strain gauge factor, fiber–matrix ...

  4. Structural monitoring system with fiber Bragg grating sensors: Implementation and software solution

    CERN Document Server

    Fedorov, Aleksey; Makhrov, Ilya; Pozhar, Nikolay; Anufriev, Maxim; Pnev, Alexey; Karasik, Valeriy

    2014-01-01

    We present a structural health monitoring system for nondestructive testing of composite materials based on the fiber Bragg grating sensors and specialized software solution. Developed structural monitoring system has potential applications for preliminary tests of novel composite materials as well as real-time structural health monitoring of industrial objects. The software solution realizes control for the system, data processing and alert of an operator.

  5. Tunable Mesoporous Bragg Reflectors Based on Block-Copolymer Self-Assembly

    OpenAIRE

    Guldin, S.; Kolle, M.; Stefik, M.; Langford, R; Eder, D.; Wiesner, U.; Steiner, U.

    2011-01-01

    Mesoporous Bragg reflectors are a promising materials platform for photovoltaics, light emission, and sensing. A fast and versatile fabrication route that relies on the self-assembly of the block copolymer poly(isoprene-b-ethylene oxide) in combination with simple sol-gel chemistry is reported. The method allows extended control over porosity and pore size in the resulting inorganic material and results in high-quality optical elements.

  6. A versatile, highly-efficient, high-resolution von Hamos Bragg crystal x-ray spectrometer

    International Nuclear Information System (INIS)

    An efficient, high-resolution, vertical-focusing, Bragg crystal x-ray spectrometer has been specifically designed and constructed for use in measurements of x rays produced in collisions of energetic heavy ions. In this report the design and resulting operational characteristics of the final instrument are fully described. A wide variety of sample data is also included to illustrate the utility of this device in several areas of research. 14 refs., 38 figs

  7. Focused radiation hepatitis after Bragg-peak proton therapy for hepatocellular carcinoma: CT findings

    International Nuclear Information System (INIS)

    Radiation hepatitis is clearly demonstrated by noncontrast and contrast enhanced CT following radiotherapy for liver diseases. Radiation hepatitis is dependent on dose distribution and is usually demonstrated as nonsegmental bandlike lesion after photon therapy. We report a case of focused, oval-shaped radiation hepatitis that was induced by photon therapy. The attenuation difference was localized in a high-dose area caused by Bragg-peak proton therapy. 17 refs., 2 figs

  8. Reconstruction of strain distribution in fiber Bragg grat-ings with differential evolution algorithm

    Institute of Scientific and Technical Information of China (English)

    WEN Xiao-yan; YU Qoan

    2008-01-01

    Differential evolution algorithm is used to solve the inverse problem of strain distribution in tibet Bragg grating (FBG).Linear and nonlinear strain profiles are reconstructed based on the reflection spectra. An approximate solution could beobtained within only 50 rounds of evolutions. Numerical examples show good agreements between target strain profilesand reconstructed ones. Online performance analysis illuminates the efficiency and practicality of differential evolutionalgorithm in solving the inverse problem of FBG.

  9. A Fiber-Optical Intrusion Alarm System Based on Quasi-Distributed Fiber Bragg Grating Sensors

    Institute of Scientific and Technical Information of China (English)

    Qi Jiang; Yun-Jiang Rao; De-Hong Zeng

    2008-01-01

    A fiber-optical intrusion alarm system based on quasi-distributed fiber Bragg grating (FBG) sensors is demonstrated in this paper. The algorithms of empirical mode decomposition (EMD) and wavelet packet characteristic entropy are adopted to determine the intrusion location. The intrusion alarm software based on the Labview is developed, and it is also proved by the experiments. The results show that such a fiber-optical intrusion alarm system can offer the automatic intrusion alarm in real-time.

  10. Study on Bragg Curve Spectrometry for Identifying Heavy Ions for AMS Measurement

    Institute of Scientific and Technical Information of China (English)

    LIGuo-qiang; HEMing; GUANYong-jing; DONGKe-jun; WANGHui-juan; LUOLi-xiong; JIANGShan

    2003-01-01

    Isobaric interference is the main problem that should be overcome in AMS. High resolution detectors should be used in AMS measurement, so that a Bragg curve detector was set up in Chinese Institute of Atomic Energy. The detector has a better energy and charge resolution over quite a wide range, and the total energy of particles entered into the detector is lost in the gas chamber.

  11. Bragg Gratings Induced in Birefringent Optical Fiber with an Elliptical Stress Cladding

    Directory of Open Access Journals (Sweden)

    I. K. Meshkovskiy

    2013-01-01

    Full Text Available The paper presents the results of writing of type I and high-performance type II fiber Bragg gratings in birefringent optical fiber with an elliptical stress cladding by a single 20 ns pulse of KrF excimer laser (248 nm. The gratings’ efficiency produced by a single pulse was up to 100%. Experimental results on visualization of these gratings are presented.

  12. Sensitivity of contact-free fiber Bragg grating sensor to ultrasonic Lamb wave

    Science.gov (United States)

    Wee, Junghyun; Hackney, Drew; Peters, Kara; Wells, Brian; Bradford, Philip

    2016-04-01

    Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring (SHM) systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves requires a high signal-to-noise ratio because Lamb waves have a low amplitude. This paper investigates the signal transfer between Lamb waves propagating in an aluminum plate collected by an optical fiber containing a FBG. The fiber is bonded to the plate at locations away from the FBG. The Lamb waves are converted into longitudinal and flexural traveling waves propagating along the optical fiber, which are then transmitted to the Bragg grating. The signal wave amplitude is measured for different distances between the bond location and the Bragg grating. Bonding the optical fiber away from the FBG location and closer to the signal source produces a significant increase in signal amplitude, here measured to be 5.1 times that of bonding the Bragg grating itself. The arrival time of the different measured wave coupling paths are also calculated theoretically, verifying the source of the measured signals. The effect of the bond length to Lamb wavelength ratio is investigated, showing a peak response as the bond length is reduced compared to the wavelength. This study demonstrates that coupling Lamb waves into guided traveling waves in an optical fiber away from the FBG increases the signal-to-noise ratio of Lamb wave detection, as compared to direct transfer of the Lamb wave to the optical fiber at the location of the FBG.

  13. High-strain fiber bragg gratings for structural fatigue testing of military aircraft

    Science.gov (United States)

    Davis, Claire; Tejedor, Silvia; Grabovac, Ivan; Kopczyk, James; Nuyens, Travis

    2012-09-01

    This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings (FBGs) for application as distributed strain sensors during structural fatigue testing of military platforms. The influence of the FBG fabrication process on sensor reliability is investigated. In addition, methodologies for broad-area packaging and surface-mounting of FBG sensing arrays to defense platforms are developed and tested.

  14. Photonic Bloch oscillations and Wannier-Stark ladders in exponentially chirped Bragg gratings.

    Science.gov (United States)

    Wilkinson, P B

    2002-05-01

    The formation of photonic Bloch oscillations and Wannier-Stark ladders is demonstrated in an exponentially chirped one-dimensional Bragg grating. The photonic Bloch oscillations are investigated using Hamiltonian optics, and direct analogies are made with electron dynamics in periodic potentials. The results of transfer matrix calculations are presented, which show the existence of a photonic Wannier-Stark ladder that should be detectable in experiments.

  15. A Fiber Bragg Grating—Bimetal Temperature Sensor for Solar Panel Inverters

    OpenAIRE

    Mohd Afiq Ismail; Nizam Tamchek; Muhammad Rosdi Abu Hassan; Dambul, Katrina D.; Jeyraj Selvaraj; Nasrudin Abd Rahim; Seyed Reza Sandoghchi; Faisal Rafiq Mahamd Adikan

    2011-01-01

    This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorize...

  16. Fiber optic Bragg grating sensor network installed in a concrete road bridge

    Science.gov (United States)

    Maaskant, Robert; Alavie, A. Tino; Measures, Raymond M.; Ohn, Myo M.; Karr, Shawn E.; Glennie, Derek J.; Wade, C.; Tadros, Gamil; Rizkalla, Sami

    1994-05-01

    The installation of a fiber optic Bragg grating strain sensor network in a new road bridge is described. These sensors are attached to prestressing tendons embedded in prefabricated concrete girders. Three types of prestressing tendons are being monitored: conventional steel strand and two types of carbon fibers reinforced plastic tendons. Sensor durability issues are reviewed and the installation is described. Initial measurements indicate that the sensors are operational and provide some early comparison of tendon performance.

  17. Bragg-Scattering conversion at telecom wavelengths towards the photon counting regime

    CERN Document Server

    Krupa, Katarzyna; Kozlov, Victor V; Couderc, Vincent; Di Bin, Philippe; Wabnitz, Stefan; Barthélémy, Alain; Labonté, Laurent; Tanzilli, Sébastien

    2012-01-01

    We experimentally study Bragg-scattering four-wave mixing in a highly nonlinear fiber at telecom wavelengths using photon counters. We explore the polarization dependence of this process with a continuous wave signal in the macroscopic and attenuated regime, with a wavelength shift of 23 nm. Our measurements of mean photon numbers per second under various pump polarization configurations agree well with the theoretical and numerical predictions based on classical models. We discuss the impact of noise under these different polarization configurations.

  18. Compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits

    Science.gov (United States)

    Hey Tow, Kenny; Llera, Miguel; Le Floch, Sébastien; Salvadé, Yves; Thévenaz, Luc

    2016-05-01

    In this communication, a novel compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits is reported. Our proposed technique can potentially be used to optimize any drilling process, requiring the use of small drill bits, through direct temperature measurement at the drill bit instead of relying on indirect parameters (speed of rotation, applied force) in order to avoid an overheating as it is currently done nowadays.

  19. Silicon waveguide polarization rotation Bragg grating with phase shift section and sampled grating scheme

    Science.gov (United States)

    Okayama, Hideaki; Onawa, Yosuke; Shimura, Daisuke; Yaegashi, Hiroki; Sasaki, Hironori

    2016-08-01

    We describe a Bragg grating with a phase shift section and a sampled grating scheme that converts input polarization to orthogonal polarization. A very narrow polarization-independent wavelength peak can be generated by phase shift structures and polarization-independent multiple diffraction peaks by sampled gratings. The characteristics of the device were examined by transfer matrix and finite-difference time-domain methods.

  20. Magneto-Optic Fiber Bragg Gratings with Application to High-Resolution Magnetic Field Sensors

    Institute of Scientific and Technical Information of China (English)

    Bao-Jian Wu; Ying Yang; Kun Qiu

    2008-01-01

    Magneto-optic fiber Bragg gratings (MFBG) based on magneto-optic materials have a lot of potential applications for sensing and optical signal processing. The transmission and reflection spectra of guided optical waves in the MFBG are investigated. According to the sensitivity of MFBG spectral lines to the magneto-optic coupling intensity varying with applied magnetic field, a novel magnetic field sensor of high-resolution up to 0.01 nm/(kA/m) is predicted.

  1. A Noncontact Force Sensor Based on a Fiber Bragg Grating and Its Application for Corrosion Measurement

    OpenAIRE

    Antonio C. Bruno; Clara J. Pacheco

    2013-01-01

    A simple noncontact force sensor based on an optical fiber Bragg grating attached to a small magnet has been proposed and built. The sensor measures the force between the magnet and any ferromagnetic material placed within a few millimeters of the sensor. Maintaining the sensor at a constant standoff distance, material loss due to corrosion increases the distance between the magnet and the corroded surface, which decreases the magnetic force. This will decrease the strain in the optical fiber...

  2. Experimental Study on Friction in Ferrules during Compression Tuning of Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    Ling Zhao; Jianxin Geng; Lin Li; Zujie Fang

    2003-01-01

    The effect of friction in ferules on compression tuning characteristics of fiber Bragg gratings (FBG) was observed and analyzed in this paper. It was demonstrated that the friction would make a non-uniform strain in the FBG and degradations of its reflection spectrum. To avoid the effect, some measures have been applied. Near 9 nm tuning range can be obtained with good spectral performance.

  3. Monitoring damage development in composite repairs using chirped fibre Bragg grating sensors.

    OpenAIRE

    Rito, Rodolfo N.L.

    2015-01-01

    Composite repairs are often used for damaged structures in order to recover the mechanical properties of the original structure. During service, there is the possibility that damage will occur in the repaired region and hence it would be useful to be able to monitor such repairs. This research investigates the use of chirped fibre Bragg grating (CFBG) sensors to monitor the development of fatigue damage initiation and growth in the repaired region of three different repair systems, i.e. glass...

  4. Applicability of a vibration sensor based on the optical fiber Bragg grating in radiation environment

    CERN Document Server

    Fujita, K; Nakazawa, M; Takahashi, H

    2003-01-01

    Fiber Bragg grating (FBG) is a kind of an optical device developing rapidly in these years and it has various excellent characteristics as a sensor. To investigate applicability of FBG as vibration sensor to nuclear plants, measurement systems were developed and tested. As a result, the FBGs could detect vibration even in gamma-ray environment. Moreover, vibration of a component around a cooling system at the YAYOI reactor could be detected successfully with FBG based sensors.

  5. Theoretical methods for the calculation of Bragg curves and 3D distributions of proton beams

    OpenAIRE

    Ulmer, Waldemar; Matsinos, Evangelos

    2010-01-01

    The well-known Bragg-Kleeman rule RCSDA = A dot E0p has become a pioneer work in radiation physics of charged particles and is still a useful tool to estimate the range RCSDA of approximately monoenergetic protons with initial energy E0 in a homogeneous medium. The rule is based on the continuous-slowing-down-approximation (CSDA). It results from a generalized (nonrelativistic) Langevin equation and a modification of the phenomenological friction term. The complete integration of this equatio...

  6. Coal conversion at Picatinny Arsenal and Forts Campbell, Bragg, and Gordon: A feasibility study. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lin, M.C.; Thurber, L.; Durbin, T.; Tarvin, R.

    1993-12-01

    Public Law 99-190 requires the Department of Defense to increase the use of coal at its facilities in the United States. This study investigated the feasibility of converting oil- and gas-fired heating plants to coal firing at four Army installations: Fort Bragg, NC; Fort Campbell, KY; Fort Gordon, GA; and Picatinny Arsenal, NJ. Information on the energy systems at the selected sites was gathered by site visit and survey, and project life cycle cost (LCC) was computationally estimated. The study concluded that, for the four installations, there would be a lower life-cycle cost (LCC) in maintaining the status quo than in building new plants. However, where new plant construction is planned, the larger the plants, the better its potential for cost-effectively using coal as a plant fuel. The use of coal at a new plant at Fort Bragg was found to be more cost effective than gas or oil, and may result in significant cost savings. For the other three installations studied, significant price increases in alternate fuels would be required before coal would become economically feasible (31 to 73 percent for gas, and 50 to 84 percent for 6 fuel oil). Ft. Bragg, NC, Army coal conversion program, Ft. Campbell, KY, Coal-fixed technologies, Ft. Gordon, GA, Cost-effectiveness.

  7. Efficient interpretation algorithm for embedded Bragg gratings for damage detection in composites

    Science.gov (United States)

    Prabhugoud, Mohanraj; Peters, Kara J.

    2003-07-01

    The goal of a structural health monitoring system is to detect, locate, and identify damages in a structure during its lifetime. The concept of structural health monitoring is particularly important for fiber reinforced composites due to the complexity of the possible failure mechanisms. The goal of this work is to simulate the response of optical fiber Bragg grating sensors to multi-component loading for their implementation in structural health monitoring algorithms for composites. A simulation method is presented to determine the effects of axial, bending and shear loading on an embedded optical fiber Bragg grating sensor. The effect of fiber bending on the Bragg grating sensor is experimentally verified by embedding the sensor in a solid cone, clamped at the base and subjected to a point load at the apex. Next, a numerically efficient method to calculate the response of sensors embedded in a unidirectional composite is developed using both finite element analysis and optimal shear-lag theory and taking into account the above effects. The limitations of the optimal shear-lag theory are derived through comparison with the finite element results. The application of this method is demonstrated through a numerical example, simulating the response of sensors embedded in one fiber layer to a transverse crack.

  8. Narrow band SWIR hyperspectral imaging: a new approach based on volume Bragg grating

    Science.gov (United States)

    Verhaegen, M.; Lessard, S.; Blais-Ouellette, S.

    2012-06-01

    Volume Bragg grating technology has enabled the development of a new type of staring hyperspectral camera. Based on Bragg Tunable filters, these hyperspectral cameras have both high spectral and spatial resolution, and significantly higher sensitivity than competing technologies like push broom spectrometer, liquid crystal tunable filters, or acousto-optic tunable filters. They are minimally sensitive to polarization and their spectral isolation can reach 106. Here we thus present an innovative tool to collect SWIR hyperspectral data with high spectral and spatial resolution. This new instrument is based on a 3nm bandwidth Bragg Tunable Filter, continuously tunable from 1.0um and 2.5um. Because high spectral resolution also means less light per channel, a low noise custom HgCdTe (MCT) camera was also developed to meet the requirement of the filter. The high speed capability of more than 300 fps and the low operating temperature of 200K (deep cooled option to 77K) allow full frame 500 spectral channel datacube acquisitions in minimal time. Basic principle of this imaging filter will be reviewed as well as the custom MCT camera performances. High resolution hyperspectral measurements will be demonstrated between 1.0um and 2.5um on different objects.

  9. Strain measurements on concrete beam and carbon fiber cable with distributed optical fiber Bragg grating sensors

    Science.gov (United States)

    Nellen, Philipp M.; Bronnimann, Rolf; Sennhauser, Urs J.; Askins, Charles G.; Putnam, Martin A.

    1996-09-01

    We report on civil engineering applications of wavelength multiplexed optical fiber Bragg grating arrays directly produced on the draw tower for testing and surveying advanced structures and materials such as carbon fiber reinforced concrete elements and prestressing cables. We equipped a 6 by 0.9 by 0.5 m concrete beam, which was reinforced with carbon fiber reinforced epoxy laminates, and a 7-m long prestressing carbon fiber cable made of seven twisted strands, with optical fiber Bragg grating sensors. Static strains up to 8000 micrometers/m and dynamic strains up to 1200 micrometers/m were measured with a Michelson interferometer used as Fourier spectrometer with a resolution of about 10 micrometers/m for all sensors. Comparative measurements with electrical resistance strain gauges were in good agreement with the fiber optical results. We installed the fiber sensors in two different arrangements: some Bragg grating array elements measured local strain while others were applied in an extensometric configuration to measure moderate strain over a base length of 0.1 to 1 m.

  10. Sensitivity Enhancement of Strain Sensing Utilizing a Differential Pair of Fiber Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Ping Wang

    2012-03-01

    Full Text Available In strain measurement applications, the matched fiber Bragg gratings (FBG method is generally used to reduce temperature dependence effects. The FBG parameters have to be designed to meet the requirements by the particular application. The bandwidth and slope of the FBG has to be balanced well, according to the measurement range, accuracy and sensitivity. A sensitivity enhanced strain demodulation method without sacrificing the measurement range for FBG sensing systems is proposed and demonstrated utilizing a pair of reference FBGs. One of the reference FBGs and the sensing FBG have almost the same Bragg wavelength, while the other reference FBGs has a Bragg wavelength offset relative to the sensing FBG. Reflected optical signals from the sensing FBG pass through two reference FBGs, and subtract from each other after the detection. Doubled strain measurement sensitivity is obtained by static rail load experiments compared to the general matched grating approach, and further verified in dynamic load experiments. Experimental results indicate that such a method could be used for real-time rail strain monitoring applications.

  11. Plasmonic Fano interference produced by gold nano-disks on a dielectric Bragg stack

    Science.gov (United States)

    Hajebifard, Akram; Berini, Pierre

    2015-09-01

    Fano interference is predicted in a structure consisting of a periodic array of uncoupled gold nano-disks (AuNDs) supported by a Bragg stack. The phenomenon occurs due to resonant interference between the reflection spectrum of the Bragg stack and localized surface plasmon resonances (LSPRs) on the AuNDs. Fitting the computational results to the Fano lineshape formula yields the Fano parameters of the resonances including their linewidth. One of the most important advantages of the structure is that the linewidth of the Fano resonances (˜9 nm) is much narrower than the bandwidth of the LSPR nano-disks (˜80 nm) and the reflection bandwidth of the Bragg stack on which the disks are supported (˜100 nm). The narrow Fano linewidth and the ease with which they can be interrogated using perpendicularly incident light makes the structure attractive for biosensing applications. The bulk sensitivities and figure of merit of Fano resonances in a proposed design are 44 nm/RIU (redshift) and -52 nm/RIU (blueshift), and ˜4 RIU-1, respectively.

  12. Blood pressure manometer using a twin Bragg grating Fabry-Perot interferometer

    Science.gov (United States)

    van Brakel, Adriaan; Swart, Pieter L.; Chtcherbakov, Anatoli A.; Shlyagin, Mikhail G.

    2005-02-01

    We propose the use of optical fiber Bragg gratings in a non-invasive blood pressure waveform monitor. Bragg gratings can be written in a Fabry-Perot interferometric configuration to yield a method of strain measurement that has both a high resolution and a wide unambiguous range. This fiber Bragg grating Fabry-Perot interferometer (FBGI) can be used as a sensor to detect strain resulting from blood pressure applied to the walls of an artery situated near the patient"s skin. Strain measurements taken on the skin surface, typically over the radial artery at the wrist, are encoded as phase shifts of the FBGI signal. These phase shifts may be obtained by the analytic representation of the interferometer signal in the wavelength domain or by Fourier analysis in the frequency domain. For the proof of concept a realistic physical model was constructed to simulate pressure conditions at the actual sensor location. The operation of the device is demonstrated by measurements of pressure-pulse waveforms obtained in real-time. This sensor was also successfully tested on human patients, and these results are also presented. Since it yields continuous readings of blood pressure non-invasively, further application of the optical manometer may yield an alternative to conventional sphygmomanometry.

  13. Single-pulse coherent anti-Stokes Raman spectroscopy via fiber Bragg grating

    Science.gov (United States)

    Oh, Seung Ryeol; Park, Joo Hyun; Kwon, Won Sik; Kim, Jin Hwan; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

    2016-03-01

    Fiber Bragg grating is used in a variety of applications. In this study, we suggest compact, cost-effective coherent anti- Stokes Raman spectroscopy which is based on the pulse shaping methods via commercialized fiber Bragg grating. The experiment is performed incorporating a commercialized femtosecond pulse laser system (MICRA, Coherent) with a 100 mm length of 780-HP fiber which is inscribed 50 mm of Bragg grating. The pump laser for coherent anti-Stokes Raman spectroscopy has a bandwidth of 90 nm and central wavelength of 815 nm with a notch shaped at 785 nm. The positive chirped pulse is compensated by chirped mirror set. We compensate almost 14000 fs2 of positive group delay dispersion for the transform-limited pulse at the sample position. The pulse duration was 15 fs with average power of 50 mW, and showed an adequate notch shape. Finally, coherent anti-Stokes Raman signals are observed using a spectrometer (Jobin Yvon Triax320 and TE-cooled Andor Newton EMCCD). We obtained coherent anti-Stokes Raman signal of acetone sample which have Raman peak at the spectral finger-print region. In conclusion, the proposed method is more simple and cost-effective than the methods of previous research which use grating pairs and resonant photonic crystal slab. Furthermore, the proposed method can be used as endoscope application.

  14. Optical fiber laser sensor with a cavity of 8.6 Km formed by two fiber Bragg gratings used as mirrors

    CERN Document Server

    May, M; Vázquez, R A; Basurto, M A; Shlyagin, M G; Márquez, I

    2002-01-01

    We report the operation of a fiber laser sensor made by an Erbium Doped Fiber pumped at 980 nm, an 8.67 km passive fiber and two fiber Bragg gratings placed at the ends of the laser cavity. Under normal conditions, the Bragg gratings have different reflection wavelengths and laser emission is not generated. The two Bragg gratings can be placed at the same reflection wavelength when the Bragg grating with the lowest reflective wavelength is strained which can be used as a sensor element. The laser generation thus shows that the Bragg grating is under strain. Furthermore, our configuration give us the possibility for knowing the distance between two Bragg gratings when the laser beating frequency is measured. A measurement precision better than 25 m in 8.67 Km is shown to be feasible. (Author)

  15. Ocular Biometry in Angle Closure

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Razeghinejad

    2013-01-01

    Full Text Available Purpose: To compare ocular biometric parameters in primary angle closure suspects (PACS, primary angle closure glaucoma (PACG and acute primary angle closure (APAC. Methods: This cross-sectional study was performed on 113 patients including 33 cases of PACS, 45 patients with PACG and 35 subjects with APAC. Central corneal thickness (CCT, axial length (AL, anterior chamber depth (ACD and lens thickness (LT were measured with an ultrasonic biometer. Lens-axial length factor (LAF, relative lens position, corrected ACD (CACD and corrected lens position were calculated. The parameters were measured bilaterally but only data from the right eyes were compared. In the APAC group, biometric parameters were also compared between affected and unaffected fellow eyes. Logistic regression analysis was performed to identify risk factors. Results: No statistically significant difference was observed in biometric parameters between PACS and PACG eyes, or between affected and fellow eyes in the APAC group (P>0.05 for all comparisons. However, eyes with APAC had thicker cornea (P=0.001, thicker lens (P<0.0001, shallower ACD (P=0.009, shallower CACD (P=0.003 and larger LAF (P<0.0001. Based on ROC curve analysis, lower ACD, and larger LT, LAF and CCT values were associated with APAC. In the APAC group, LAF (P<0.0001 and CCT (P=0.001 were significant risk factors. Conclusion: This study revealed no significant difference in biometric characteristics in eyes with PACS and PACG. However, larger LAF and CCT were predictive of APAC.

  16. Opening Angles of Collapsar Jets

    OpenAIRE

    Mizuta, Akira; Ioka, Kunihito

    2013-01-01

    We investigate the jet propagation and breakout from the stellar progenitor for gamma-ray burst (GRB) collapsars by performing two-dimensional relativistic hydrodynamic simulations and analytical modeling. We find that the jet opening angle is given by $\\theta_j \\sim 1/5 \\Gamma_{0}$, and infer the initial Lorentz factor of the jet at the central engine, $\\Gamma_0$, is a few for existing observations of $\\theta_j$. The jet keeps the Lorentz factor low inside the star by converging cylindricall...

  17. Small angle scattering and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, J.P. [Laboratoire Leon Brillouin (LLB) - Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1996-12-31

    The determination of polymer structure is a problem of interest for both statistical physics and industrial applications. The average polymer structure is defined. Then, it is shown why small angle scattering, associated with isotopic substitution, is very well suited to the measurement of the chain conformation. The corresponding example is the old, but pedagogic, measurement of the chain form factor in the polymer melt. The powerful contrast variation method is illustrated by a recent determination of the concentration profile of a polymer interface. (author) 12 figs., 48 refs.

  18. Structural characterization of the phospholipid stabilizer layer at the solid-liquid interface of dispersed triglyceride nanocrystals with small-angle x-ray and neutron scattering

    Science.gov (United States)

    Schmiele, Martin; Schindler, Torben; Unruh, Tobias; Busch, Sebastian; Morhenn, Humphrey; Westermann, Martin; Steiniger, Frank; Radulescu, Aurel; Lindner, Peter; Schweins, Ralf; Boesecke, Peter

    2013-06-01

    Dispersions of crystalline nanoparticles with at least one sufficiently large unit cell dimension can give rise to Bragg reflections in the small-angle scattering range. If the nanocrystals possess only a small number of unit cells along these particular crystallographic directions, the corresponding Bragg reflections will be broadened. In a previous study of phospholipid stabilized dispersions of β-tripalmitin platelets [Unruh, J. Appl. Crystallogr.JACGAR0021-889810.1107/S0021889807044378 40, 1008 (2007)], the x-ray powder pattern simulation analysis (XPPSA) was developed. The XPPSA method facilitates the interpretation of the rather complicated small-angle x-ray scattering (SAXS) curves of such dispersions of nanocrystals. The XPPSA method yields the distribution function of the platelet thicknesses and facilitates a structural characterization of the phospholipid stabilizer layer at the solid-liquid interface between the nanocrystals and the dispersion medium from the shape of the broadened 001 Bragg reflection. In this contribution an improved and extended version of the XPPSA method is presented. The SAXS and small-angle neutron scattering patterns of dilute phospholipid stabilized tripalmitin dispersions can be reproduced on the basis of a consistent simulation model for the particles and their phospholipid stabilizer layer on an absolute scale. The results indicate a surprisingly flat arrangement of the phospholipid molecules in the stabilizer layer with a total thickness of only 12 Å. The stabilizer layer can be modeled by an inner shell for the fatty acid chains and an outer shell including the head groups and additional water. The experiments support a dense packing of the phospholipid molecules on the nanocrystal surfaces rather than isolated phospholipid domains.

  19. Comparison of recoated fiber Bragg grating sensors under tension on a steel coupon

    Science.gov (United States)

    Rivera, E.; Thomson, D. J.; Mufti, A. A.

    2005-05-01

    One of the key elements in a structural health monitoring system is the sensing element and data acquisition system. One type of fiber optic sensor used to measure strain is the fiber Bragg grating. Bragg gratings are fabricated using different methods. One method involves placing a mask pattern over the optical fiber and projecting UV light through it to change the refractive index of the core. However, before the grating is written into the core of the fibre, the outer fibre coatings must be stripped away either mechanically or chemically. Fibre Bragg gratings are then recoated after the grating has been written to maintain the strength and flexibility of the fibre by protecting the exposed glass from damage. Acrylate and polyimide are two types of recoat material typically used on fibre Bragg grating sensors. This work is a controlled comparison of polyimide and acrylate recoated fibres for Bragg grating strain sensors. The comparison was carried out using a tension test coupon with recoated FBG and electrical strain gauges bonded to its surface. The tension test specimen was made of cold rolled steel and was designed according to ASTM A30-97a standard. The dimensions were chosen such that three fibre optic sensors and a strain gauge can be attached on each side. The load was applied in 40 μɛ steps until the strain reached approximately 200 ´ɛ. The load was then incrementally decreased back to zero. FBG sensors from 2 manufacturers were compared. For the first manufacturer the Acrylate coated sensors required a gauge factor is 0.75 in order for electrical and FBG strain readings to agree. For Polyimide coated sensors, the appropriate gauge factor was very close to the theoretically predicted value of 0.8. Using these gauge factors, the error between the first manufacturers sensor readings and the strain gauges was well within +/-5´ɛ. On the other hand, the second manufacturers sensors did not perform nearly as well. Their readings were substantially lower

  20. The Q-angle and sport

    DEFF Research Database (Denmark)

    Hahn, Thomas; Foldspang, Anders

    1997-01-01

    Quadriceps muscle contraction tends to straighten the Q angle. We expected that sports comprising a high amount of quadriceps training could be associated with low Q angles. The aim of the present study was to estimate the Q angle in athletes and to investigate its potential associations...... with participation in sport. Three hundred and thirty-nine athletes had their Q angle measured. The mean of right-side Q angles was higher than left side, and the mean Q angle was higher in women than in men. The Q angle was positively associated with years of jogging, and negatively with years of soccer, swimming...... and sports participation at all. It is concluded that the use of Q angle measurements is questionable....

  1. Device for Measuring Landslide Critical Angle

    Institute of Scientific and Technical Information of China (English)

    Li Xueling; Xia Weisheng; Huang Daoyou; Yu Yun

    2016-01-01

    The mountain landslide has high destructive effects, discussion of its landslide critical angle has always been one of the major concerns, and we designed a system that can automatically measure the landslide critical angle. This equipment consists of the

  2. The qualitative criterion of transient angle stability

    OpenAIRE

    Lyu, R; Xue, Y.; Xue, F; Wu, Qiuwei; Yang, Guangya; Zhou, H; Ju, P.

    2015-01-01

    In almost all the literatures, the qualitative assessment of transient angle stability extracts the angle information of generators based on the swing curve. As the angle (or angle difference) of concern and the threshold value rely strongly on the engineering experience, the validity and robust of these criterions are weak. Based on the stability mechanism from the extended equal area criterion (EEAC) theory and combining with abundant simulations of real system, this paper analyzes the crit...

  3. 30 CFR 56.19037 - Fleet angles.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Fleet angles. 56.19037 Section 56.19037 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Sheaves § 56.19037 Fleet angles. Fleet angles on hoists installed after November 15, 1979, shall not...

  4. 30 CFR 57.19037 - Fleet angles.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Fleet angles. 57.19037 Section 57.19037 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... Sheaves § 57.19037 Fleet angles. Fleet angles on hoists installed after November 15, 1979, shall not...

  5. Effect of interstitial air holes on Bragg gratings in photonic crystal fibre with a Ge-doped core

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui-Jia; Li Shu-Guang; Hou Lan-Tian

    2009-01-01

    The effect of interstitial air holes on Bragg gratings in photonic crystal fibre (PCF) with a Ge-doped core is numerically investigated by using thc beam propagation method (BPM). It is shown that the interstitial air holes (IAHs) can make Bragg resonance wavelength λ3 shift a little towards short wavelengths and incrcase λB - λ1 (the wavelength spacing between the main peak with Bragg resonance wavelength λB and the first side peak with wavelength λ1) and the coupling coefficient κ of Bragg resonance. Moreover, when the ratio of air hole diameter (d) to pitch (A),d/A, is small, IAHs can suppress the cladding mode resonance. When d/A is large, IAHs increase the number of mode that could strongly interact with the fundamental mode. By comparing the transmission spectral characteristics of PCF-based fibrc Bragg grating (FBG) with IAHs with those without IAtIs at the same air-filling fraction, it is clarified that the change of transmission spectral characteristics of PCF-based FBG with IAHs is not due to a simple change in air-filling fraction. It is also closely related to the distribution of interstitial air holes.

  6. Numerical analysis of the harmonic components of the Bragg wavelength content in spectral responses of apodized fiber Bragg gratings written by means of a phase mask with a variable phase step height.

    Science.gov (United States)

    Osuch, Tomasz

    2016-02-01

    The influence of the complex interference patterns created by a phase mask with variable diffraction efficiency in apodized fiber Bragg grating (FBGs) formation on their reflectance spectra is studied. The effect of the significant contributions of the zeroth and higher (m>±1) diffraction orders on the Bragg wavelength peak and its harmonic components is analyzed numerically. The results obtained for Gaussian and tanh apodization profiles are compared with similar data calculated for a uniform grating. It is demonstrated that when an apodized FBG is written using a phase mask with variable diffraction efficiency, significant enhancement of the harmonic components and a reduction of the Bragg wavelength peak in the grating spectral response are observed. This is particularly noticeable for the Gaussian apodization profile due to the substantial contributions of phase mask sections with relatively small phase steps in the FBG formation. PMID:26831768

  7. Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite

    Directory of Open Access Journals (Sweden)

    Ilka Kriegel

    2015-01-01

    Full Text Available Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs, on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis–NIR spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2−xSe NCs and a film of indium tin oxide (ITO NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2−x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device.

  8. The use of fiber Bragg grating sensors in biomechanics and rehabilitation applications: the state-of-the-art and ongoing research topics.

    Science.gov (United States)

    Al-Fakih, Ebrahim; Abu Osman, Noor Azuan; Mahamd Adikan, Faisal Rafiq

    2012-01-01

    In recent years, fiber Bragg gratings (FBGs) are becoming increasingly attractive for sensing applications in biomechanics and rehabilitation engineering due to their advantageous properties like small size, light weight, biocompatibility, chemical inertness, multiplexing capability and immunity to electromagnetic interference (EMI). They also offer a high-performance alternative to conventional technologies, either for measuring a variety of physical parameters or for performing high-sensitivity biochemical analysis. FBG-based sensors demonstrated their feasibility for specific sensing applications in aeronautic, automotive, civil engineering structure monitoring and undersea oil exploration; however, their use in the field of biomechanics and rehabilitation applications is very recent and its practicality for full-scale implementation has not yet been fully established. They could be used for detecting strain in bones, pressure mapping in orthopaedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs), forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics. This article aims to provide a comprehensive overview of all the possible applications of FBG sensing technology in biomechanics and rehabilitation and the status of ongoing researches up-to-date all over the world, demonstrating the FBG advances over other existing technologies. PMID:23201977

  9. The Use of Fiber Bragg Grating Sensors in Biomechanics and Rehabilitation Applications: The State-of-the-Art and Ongoing Research Topics

    Directory of Open Access Journals (Sweden)

    Faisal Rafiq Mahamd Adikan

    2012-09-01

    Full Text Available In recent years, fiber Bragg gratings (FBGs are becoming increasingly attractive for sensing applications in biomechanics and rehabilitation engineering due to their advantageous properties like small size, light weight, biocompatibility, chemical inertness, multiplexing capability and immunity to electromagnetic interference (EMI. They also offer a high-performance alternative to conventional technologies, either for measuring a variety of physical parameters or for performing high-sensitivity biochemical analysis. FBG-based sensors demonstrated their feasibility for specific sensing applications in aeronautic, automotive, civil engineering structure monitoring and undersea oil exploration; however, their use in the field of biomechanics and rehabilitation applications is very recent and its practicality for full-scale implementation has not yet been fully established. They could be used for detecting strain in bones, pressure mapping in orthopaedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs, forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics. This article aims to provide a comprehensive overview of all the possible applications of FBG sensing technology in biomechanics and rehabilitation and the status of ongoing researches up-to-date all over the world, demonstrating the FBG advances over other existing technologies.

  10. Estimating needle-tissue interaction forces for hollow needles using fiber Bragg grating sensors

    Science.gov (United States)

    Kumar, Saurabh; Shrikanth, V.; Bharadwaj, Amrutur; Asokan, Sundarrajan; Bobji, M. S.

    2016-03-01

    Brachytherapy and neurological procedures can benefit from real-time estimation of needle-tissue interaction forces, specifically for robotic or robot-assisted procedures. Fiber Bragg Grating Sensors provide advantages of very small size and electromagnetic immunity for use in measurement of the forces directly at the needle tip. This has advantages compared to measurements at the needle shaft which require extensive models of the friction between needle and tissues with varying depth. This paper presents the measurement of tip forces for a hollow needle and compensation for bending when encountering regions of varying stiffness in phantoms with multiple layers prepared using Polydimethylsiloxane.

  11. Stability of gap solitons in dual-core Bragg gratings with cubic-quintic nonlinearity

    International Nuclear Information System (INIS)

    We investigate the existence and stability of quiescent gap solitons in a system of two linearly coupled Bragg gratings with cubic-quintic nonlinearity. It is found that the model supports two disjoint families of solitons that fill the entire bandgap. There exist symmetric and asymmetric solitons in each family. Exact analytical solutions of symmetric solitons for both families are found. The stability of solitons is investigated by means of systematic numerical stability analysis. The effect of quintic nonlinearity and coupling coefficient on the stability of solitons and the stability regions are analyzed. (letter)

  12. All-fiber amplifier similariton laser based on a fiber Bragg grating filter.

    Science.gov (United States)

    Olivier, Michel; Gagnon, Mathieu; Duval, Simon; Bernier, Martin; Piché, Michel

    2015-12-01

    This article presents, for the first time to our knowledge, an all-fiber amplifier similariton laser based on a fiber Bragg grating filter. The laser emits 2.9 nJ pulses at a wavelength of 1554 nm with a repetition rate of 31 MHz. The dechirped pulses have a duration of 89 fs. The characteristic features of the pulse profile and spectrum along with the dynamics of the laser are highlighted in representative simulations. These simulations also address the effect of the filter shape and detuning with respect to the gain spectral peak. PMID:26625073

  13. Conical Correlations, Bragg Peaks, and Transverse Flow Deflections in Jet Tomography

    OpenAIRE

    Betz, Barbara; Noronha, Jorge; Torrieri, Giorgio; Gyulassy, Miklos; Rischke, Dirk H.

    2009-01-01

    We use (3+1)-dimensional ideal hydrodynamics to describe a variety of different jet energy loss scenarios for a jet propagating through an opaque medium. The conical correlations obtained for fully stopped jets, revealing a Bragg peak, are discussed as well as results from pQCD and AdS/CFT. Moreover, we investigate transverse flow deflection. It is demonstrated that a double-peaked away-side structure can be formed due to the different contributions of several possible jet trajectories throug...

  14. Conical Correlations, Bragg Peaks, and Transverse Flow Deflections in Jet Tomography

    CERN Document Server

    Betz, Barbara; Torrieri, Giorgio; Gyulassy, Miklos; Rischke, Dirk H

    2009-01-01

    We use (3+1)-dimensional ideal hydrodynamics to describe a variety of different jet energy loss scenarios for a jet propagating through an opaque medium. The conical correlations obtained for fully stopped jets, revealing a Bragg peak, are discussed as well as results from pQCD and AdS/CFT. Moreover, we investigate transverse flow deflection. It is demonstrated that a double-peaked away-side structure can be formed due to the different contributions of several possible jet trajectories through an expanding medium.

  15. Gamma radiation-induced blue shift of resonance peaks of Bragg gratings in pure silica fibres

    Science.gov (United States)

    Faustov, A. V.; Gusarov, A. I.; Mégret, P.; Wuilpart, M.; Kinet, D.; Zhukov, A. V.; Novikov, S. G.; Svetukhin, V. V.; Fotiadi, A. A.

    2016-02-01

    We report the first observation of a significant gamma radiation-induced blue shift of the reflection/transmission peak of fibre Bragg gratings inscribed into pure-silica core fibres via multiphoton absorption of femtosecond pulses. At a total dose of ~100 kGy, the shift is ~20 pm. The observed effect is attributable to the ionising radiation-induced decrease in the density of the silica glass when the rate of colour centre formation is slow. We present results of experimental measurements that provide the key parameters of the dynamics of the gratings for remote dosimetry and temperature sensing.

  16. Experimental and theoretical analysis of fiber Bragg gratings under Transverse Force to a Small Grating Section

    Institute of Scientific and Technical Information of China (English)

    WU Fei; LI Li-xin; LI Ya-pin; LI Zhi-quan

    2005-01-01

    Fiber Bragg grating under transverse force on a small grating section is studied by numerical simulation and experimentation. A numerical simulation based on the transfer matrix method is used to calculate the consequent changes in reflected spectrum. The reflected spectra of the FBG subjected to the transverse force split into two main peaks, and the split point shifted linearly and periodically versus the applied force. The split point is shifted in the bandwidth with the period of 11N, and the sensitivity of the split point wavelength shift versus the applied force is 0.05 nm/N in one period. The experimental results show good agreement with the simulation analysis.

  17. Orientation-Dependent Displacement Sensor Using an Inner Cladding Fiber Bragg Grating.

    Science.gov (United States)

    Yang, Tingting; Qiao, Xueguang; Rong, Qiangzhou; Bao, Weijia

    2016-01-01

    An orientation-dependent displacement sensor based on grating inscription over a fiber core and inner cladding has been demonstrated. The device comprises a short piece of multi-cladding fiber sandwiched between two standard single-mode fibers (SMFs). The grating structure is fabricated by a femtosecond laser side-illumination technique. Two well-defined resonances are achieved by the downstream both core and cladding fiber Bragg gratings (FBGs). The cladding resonance presents fiber bending dependence, together with a strong orientation dependence because of asymmetrical distribution of the "cladding" FBG along the fiber cross-section. PMID:27626427

  18. Grating solitons near the photonic bandgap of a fiber Bragg grating

    Energy Technology Data Exchange (ETDEWEB)

    Senthilnathan, K. [Photonics Research Center and Department of Electronic and Information Engineering, Hong Kong Polytechnic University, Hong Kong (China); Ramesh Babu, P. [Department of Physics, Vellore Institute of Technology, Deemed University, Vellore 632014 (India); Porsezian, K. [Department of Physics, Pondicherry University, Pondicherry 605014 (India)]. E-mail: porsz@hotmail.com; Santhanam, V. [Department of Physics, Presidency College, University of Madras, Chennai 600005 (India); Gnanasekaran, S. [Department of Physics, Anna University, Chennai 600025 (India)

    2007-07-15

    In this paper, we consider the nonlinear pulse propagation through a fiber Bragg grating (FBG) structure wherein the nonlinearity includes both cubic and quintic effects. We study theoretically the formation of bright grating solitons in such a FBG when the carrier frequency of a nonlinear laser pulse is detuned out of the proper edge of the photonic bandgap (PBG). By using multiple scale analysis, we investigate the generation of the bright soliton near the PBG with the higher order linear and nonlinear effects. We also study the impact of quintic nonlinearity on the dispersion curves by deriving the nonlinear dispersion relation from the governing equations.

  19. Compact wavelength add-drop multiplexers using Bragg gratings in coupled dielectric-loaded plasmonic waveguides

    CERN Document Server

    Biagi, Giulio; Radko, Ilya P; Rubahn, Horst-Günter; Pedersen, Kjeld; Bozhevolnyi, Sergey I

    2016-01-01

    We report a novel design of a compact wavelength add-drop multiplexer utilizing dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs). The DLSPPW-based configuration exploits routing properties of directional couplers and filtering abilities of Bragg gratings. We present practical realization of a 20-$\\mu$m-long device operating at telecom wavelengths that can reroute optical signals separated by approximately 70 nm in the wavelength band. We characterize the performance of the fabricated structures using scanning near-field optical microscopy as well as leakage-radiation microscopy and support our findings with numerical simulations.

  20. Stainless steel component with compressed fiber Bragg grating for high temperature sensing applications

    Science.gov (United States)

    Jinesh, Mathew; MacPherson, William N.; Hand, Duncan P.; Maier, Robert R. J.

    2016-05-01

    A smart metal component having the potential for high temperature strain sensing capability is reported. The stainless steel (SS316) structure is made by selective laser melting (SLM). A fiber Bragg grating (FBG) is embedded in to a 3D printed U-groove by high temperature brazing using a silver based alloy, achieving an axial FBG compression of 13 millistrain at room temperature. Initial results shows that the test component can be used for up to 700°C for sensing applications.