Block Copolymer Nanocomposites with High Refractive Index Contrast for One-Step Photonics.

PubMed

Song, Dong-Po; Li, Cheng; Li, Wenhao; Watkins, James J

2016-01-26

Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn > 0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems.

Parameter analysis of a photonic crystal fiber with raised-core index profile based on effective index method

NASA Astrophysics Data System (ADS)

Seraji, Faramarz E.; Rashidi, Mahnaz; Khasheie, Vajieh

2006-08-01

Photonic crystal fibers (PCFs) with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.

Highly birefringent suspended-core photonic microcells for refractive-index sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057; Jin, Wa

2014-08-11

An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10{sup −2}. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

Positive phase evolution of waves propagating along a photonic crystal with negative index of refraction.

PubMed

Martínez, Alejandro; Martí, Javier

2006-10-16

We analyze propagation of electromagnetic waves in a photonic crystal at frequencies at which it behaves as an effective medium with a negative index in terms of refraction at its interface with free space. We show that the phase evolution along the propagation direction is positive, despite the fact that the photonic crystal displays negative refraction following Snell's law, and explain it in terms of the Fourier components of the Bloch wave. Two distinct behaviors are found at frequencies far and close to the band edge of the negative-index photonic band. These findings contrast with the negative phase evolution that occurs in left-handed materials, so care has to be taken when applying the term left-handed to photonic crystals.

Nanoimprinted High-Refractive Index Active Photonic Nanostructures Based on Quantum Dots for Visible Light

DOE PAGES

Pina-Hernandez, Carlos; Koshelev, Alexander; Dhuey, Scott; ...

2017-12-15

A novel method to realizing printed active photonic devices was developed using nanoimprint lithography (NIL), combining a printable high-refractive index material and colloidal CdSe/CdS quantum dots (QDs) for applications in the visible region. Active media QDs were applied in two different ways: embedded inside a printable high-refractive index matrix to form an active printable hybrid nanocomposite, and used as a uniform coating on top of printed photonic devices. As a proof-of-demonstration for printed active photonic devices, two-dimensional (2-D) photonic crystals as well as 1D and 2D photonic nanocavities were successfully fabricated following a simple reverse-nanoimprint process. We observed enhanced photoluminescencemore » from the 2D photonic crystal and the 1D nanocavities. Outstandingly, the process presented in this study is fully compatible with large-scale manufacturing where the patterning areas are only limited by the size of the corresponding mold. This work shows that the integration of active media and functional materials is a promising approach to the realization of integrated photonics for visible light using high throughput technologies. We believe that this work represents a powerful and cost-effective route for the development of numerous nanophotonic structures and devices that will lead to the emergence of new applications.« less

Omnidirectional and multi-channel filtering by photonic quantum wells with negative-index materials.

PubMed

Lin, Mi; Ouyang, Zhengbiao; Xu, Jun; Qiu, Gaoxin

2009-03-30

We propose a type of photonic quantum well made of two different photonic crystals with negative- and positive-index materials. It is demonstrated by transfer matrix method that, omnidirectional and multichannel filtering can be achieved. Resonance tunneling modes, or the multi-channel filtering modes, are found to exist when a passband of the well photonic crystal is located inside the gap of the barrier photonic crystals. And for each passband of the well photonic crystal in the photonic bandgap of the barrier photonic crystal, the number of modes is the same as the number of periods in the well photonic crystals. Moreover, the modes are insensitive to the incident angle from 0 to 85 degrees and the scaling of the barrier photonic crystals at a certain range. Such structures are useful for all-direction receiving, sending, or linking-up of multi-channel signals in wireless-communication networks. And they can be applied in signal-detection systems to enhance signal-detection sensitivity.

Mid-infrared refractive index sensing using optimized slotted photonic crystal waveguides

NASA Astrophysics Data System (ADS)

Kassa-Baghdouche, Lazhar; Cassan, Eric

2018-02-01

Slotted photonic crystal waveguides (SPCWs) were designed to act as refractive index sensing devices at mid-infrared (IR) wavelengths around λ = 3.6 μm. In particular, effort was made to engineer the input and output slot waveguide interfaces in order to increase the effective sensitivity through resonant tapering. A slotted PhC waveguide immersed in air and liquid cladding layers was considered. To determine the performance of the sensor, the sensitivity of the device was estimated by calculating the shift in the upper band edge of the output transmission spectrum. The results showed that the sensitivity of a conventionally designed SPCW followed by modifications in the structure parameter yielded a 510 nm shift in the wavelength position of the upper band edge, indicating a sensitivity of more than 1150 nm per refractive index unit (RIU) with an insertion loss level of -0.3 dB. This work demonstrates the viability of photonic crystal waveguide high sensitivity devices in the Mid-IR, following a transposition of the concepts inherited from the telecom band and an optimization of the design, in particular a minimization of photonic device insertion losses.

A bi-prism interferometer for hard x-ray photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isakovic, A.F.; Siddons, D.; Stein, A.

2010-04-06

Micro-fabricated bi-prisms have been used to create an interference pattern from an incident hard X-ray beam, and the intensity of the pattern probed with fluorescence from a 30 nm-thick metal film. Maximum fringe visibility exceeded 0.9 owing to the nano-sized probe and the choice of single-crystal prism material. A full near-field analysis is necessary to describe the fringe field intensities, and the transverse coherence lengths were extracted at APS beamline 8-ID-I. It is also shown that the maximum number of fringes is dependent only on the complex refractive index of the prism material.

Amorphous silicon as high index photonic material

NASA Astrophysics Data System (ADS)

Lipka, T.; Harke, A.; Horn, O.; Amthor, J.; Müller, J.

2009-05-01

Silicon-on-Insulator (SOI) photonics has become an attractive research topic within the area of integrated optics. This paper aims to fabricate SOI-structures for optical communication applications with lower costs compared to standard fabrication processes as well as to provide a higher flexibility with respect to waveguide and substrate material choice. Amorphous silicon is deposited on thermal oxidized silicon wafers with plasma-enhanced chemical vapor deposition (PECVD). The material is optimized in terms of optical light transmission and refractive index. Different a-Si:H waveguides with low propagation losses are presented. The waveguides were processed with CMOS-compatible fabrication technologies and standard DUV-lithography enabling high volume production. To overcome the large mode-field diameter mismatch between incoupling fiber and sub-μm waveguides three dimensional, amorphous silicon tapers were fabricated with a KOH etched shadow mask for patterning. Using ellipsometric and Raman spectroscopic measurements the material properties as refractive index, layer thickness, crystallinity and material composition were analyzed. Rapid thermal annealing (RTA) experiments of amorphous thin films and rib waveguides were performed aiming to tune the refractive index of the deposited a-Si:H waveguide core layer after deposition.

Multiband super-resolution imaging of graded-index photonic crystal flat lens

NASA Astrophysics Data System (ADS)

Xie, Jianlan; Wang, Junzhong; Ge, Rui; Yan, Bei; Liu, Exian; Tan, Wei; Liu, Jianjun

2018-05-01

Multiband super-resolution imaging of point source is achieved by a graded-index photonic crystal flat lens. With the calculations of six bands in common photonic crystal (CPC) constructed with scatterers of different refractive indices, it can be found that the super-resolution imaging of point source can be realized by different physical mechanisms in three different bands. In the first band, the imaging of point source is based on far-field condition of spherical wave while in the second band, it is based on the negative effective refractive index and exhibiting higher imaging quality than that of the CPC. However, in the fifth band, the imaging of point source is mainly based on negative refraction of anisotropic equi-frequency surfaces. The novel method of employing different physical mechanisms to achieve multiband super-resolution imaging of point source is highly meaningful for the field of imaging.

Hard two-photon contribution to elastic lepton-proton scattering determined by the OLYMPUS experiment

NASA Astrophysics Data System (ADS)

Hasell, D. K.; OLYMPUS Collaboration

2018-02-01

The OLYMPUS collaboration has recently made a precise measurement of the positron-proton to electron-proton elastic scattering cross section ratio, R 2γ, over a wide range of the virtual photon polarization, 0.456 < ɛ < 0.978. This provides a direct measure of hard two-photon exchange in elastic lepton-proton scattering widely thought to explain the discrepancy observed between unpolarized and polarized measurements of the proton form factor ratio, {μ }p{G}Ep/{G}Mp. The OLYMPUS results are small, within 1% on unity, over the range of momentum transfers measured and significantly lower than theoretical calculations that can explain part of the observed discrepancy in terms of two-photon exchange at higher momentum transfers. However, the results are in reasonable agreement with predictions based on phenomenological fits to the available form factor data. The motivation for measuring R 2γ will be presented followed by a description of the OLYMPUS experiment. The importance of radiative corrections in the analysis will be shown also. Then we will present the OLYMPUS results and compare with results from two similar experiments and theoretical calculations.

Engineering photonic nanojet by a graded-index micro-cuboid

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Yen, Tzu-Ping; Minin, Oleg V.; Minin, Igor V.

2018-04-01

In the present paper the basic characteristics (length, peak intensity, and full-width half-maximum) of nanojets formed in the vicinity of dielectric core-shell cuboids with different types of index grading are investigated by finite-difference time domain method. The latitudinal and longitudinal sizes of a nanojet and its peak intensity depending on the optical contrast variation of cuboids core-shells are numerically investigated. It has been shown that it is possible to control and elongate the nanojet abnormally. It also was shown that graded cuboid with dimensions of 4 × 4 × 4 wavelength may has FWHM of a jet less than uniform cuboid with dimensions of 1 × 1 × 1 wavelength. At wavelength of 600 nm graded index cuboid with dimensions of 4 × 4 × 4 wavelength and index grading = 2 allow to form photonic jet with FWHM about 232 nm or 0.39 wavelength.

Effective group index of refraction in non-thermal plasma photonic crystals

NASA Astrophysics Data System (ADS)

Mousavi, A.; Sadegzadeh, S.

2015-11-01

Plasma photonic crystals (PPCs) are periodic arrays that consist of alternate layers of micro-plasma and dielectric. These structures are used to control the propagation of electromagnetic waves. This paper presents a survey of research on the effect of non-thermal plasma with bi-Maxwellian distribution function on one dimensional PPC. A plasma with temperature anisotropy is not in thermodynamic equilibrium and can be described by the bi-Maxwellian distribution function. By using Kronig-Penny's model, the dispersion relation of electromagnetic modes in one dimensional non-thermal PPC (NPPC) is derived. The band structure, group velocity vg, and effective group index of refraction neff(g) of such NPPC structure with TeO2 as the material of dielectric layers have been studied. The concept of negative group velocity and negative neff(g), which indicates an anomalous behaviour of the PPCs, are also observed in the NPPC structures. Our numerical results provide confirmatory evidence that unlike PPCs there are finite group velocity and non-zero effective group indexes of refraction in photonic band gaps (PBGs) that lie in certain ranges of normalized frequency. In other words, inside the PBGs of NPPCs, neff(g) becomes non-zero and photons travel with a finite group velocity. In this special case, this velocity varies alternately between 20c and negative values of the order 103c (c is the speed of light in vacuum).

Second-harmonic generation at angular incidence in a negative-positive index photonic band-gap structure.

PubMed

D'Aguanno, Giuseppe; Mattiucci, Nadia; Scalora, Michael; Bloemer, Mark J

2006-08-01

In the spectral region where the refractive index of the negative index material is approximately zero, at oblique incidence, the linear transmission of a finite structure composed of alternating layers of negative and positive index materials manifests the formation of a new type of band gap with exceptionally narrow band-edge resonances. In particular, for TM-polarized (transverse magnetic) incident waves, field values that can be achieved at the band edge may be much higher compared to field values achievable in standard photonic band-gap structures. We exploit the unique properties of these band-edge resonances for applications to nonlinear frequency conversion, second-harmonic generation, in particular. The simultaneous availability of high field localization and phase matching conditions may be exploited to achieve second-harmonic conversion efficiencies far better than those achievable in conventional photonic band-gap structures. Moreover, we study the role played by absorption within the negative index material, and find that the process remains efficient even for relatively high values of the absorption coefficient.

Effective group index of refraction in non-thermal plasma photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mousavi, A.; Sadegzadeh, S., E-mail: sadegzadeh@azaruniv.edu

Plasma photonic crystals (PPCs) are periodic arrays that consist of alternate layers of micro-plasma and dielectric. These structures are used to control the propagation of electromagnetic waves. This paper presents a survey of research on the effect of non-thermal plasma with bi-Maxwellian distribution function on one dimensional PPC. A plasma with temperature anisotropy is not in thermodynamic equilibrium and can be described by the bi-Maxwellian distribution function. By using Kronig-Penny's model, the dispersion relation of electromagnetic modes in one dimensional non-thermal PPC (NPPC) is derived. The band structure, group velocity v{sub g}, and effective group index of refraction n{sub eff}(g)more » of such NPPC structure with TeO{sub 2} as the material of dielectric layers have been studied. The concept of negative group velocity and negative n{sub eff}(g), which indicates an anomalous behaviour of the PPCs, are also observed in the NPPC structures. Our numerical results provide confirmatory evidence that unlike PPCs there are finite group velocity and non-zero effective group indexes of refraction in photonic band gaps (PBGs) that lie in certain ranges of normalized frequency. In other words, inside the PBGs of NPPCs, n{sub eff}(g) becomes non-zero and photons travel with a finite group velocity. In this special case, this velocity varies alternately between 20c and negative values of the order 10{sup 3}c (c is the speed of light in vacuum)« less

Interplay of short-range correlations and nuclear symmetry energy in hard-photon production from heavy-ion reactions at Fermi energies

NASA Astrophysics Data System (ADS)

Yong, Gao-Chan; Li, Bao-An

2017-12-01

Within an isospin- and momentum-dependent transport model for nuclear reactions at intermediate energies, we investigate the interplay of the nucleon-nucleon short-range correlations (SRCs) and nuclear symmetry energy Esym(ρ ) on hard-photon spectra in collisions of several Ca isotopes on 112Sn and 124Sn targets at a beam energy of 45 MeV/nucleon. It is found that over the whole spectra of hard photons studied, effects of the SRCs overwhelm those owing to the Esym(ρ ) . The energetic photons come mostly from the high-momentum tails (HMTs) of single-nucleon momentum distributions in the target and projectile. Within the neutron-proton dominance model of SRCs based on the consideration that the tensor force acts mostly in the isosinglet and spin-triplet nucleon-nucleon interaction channel, there are equal numbers of neutrons and protons, thus a zero isospin asymmetry in the HMTs. Therefore, experimental measurements of the energetic photons from heavy-ion collisions at Fermi energies have the great potential to help us better understand the nature of SRCs without any appreciable influence by the uncertain Esym(ρ ) . These measurements will be complementary to but also have some advantages over the ongoing and planned experiments using hadronic messengers from reactions induced by high-energy electrons or protons. Because the underlying physics of SRCs and Esym(ρ ) are closely correlated, a better understanding of the SRCs will, in turn, help constrain the nuclear symmetry energy more precisely in a broad density range.

Dirac cones induced by accidental degeneracy in photonic crystals and zero-refractive-index materials.

PubMed

Huang, Xueqin; Lai, Yun; Hang, Zhi Hong; Zheng, Huihuo; Chan, C T

2011-05-29

A zero-refractive-index metamaterial is one in which waves do not experience any spatial phase change, and such a peculiar material has many interesting wave-manipulating properties. These materials can in principle be realized using man-made composites comprising metallic resonators or chiral inclusions, but metallic components have losses that compromise functionality at high frequencies. It would be highly desirable if we could achieve a zero refractive index using dielectrics alone. Here, we show that by employing accidental degeneracy, dielectric photonic crystals can be designed and fabricated that exhibit Dirac cone dispersion at the centre of the Brillouin zone at a finite frequency. In addition to many interesting properties intrinsic to a Dirac cone dispersion, we can use effective medium theory to relate the photonic crystal to a material with effectively zero permittivity and permeability. We then numerically and experimentally demonstrate in the microwave regime that such dielectric photonic crystals with reasonable dielectric constants manipulate waves as if they had near-zero refractive indices at and near the Dirac point frequency.

Resolution enhancement of 2-photon microscopy using high-refractive index microspheres

NASA Astrophysics Data System (ADS)

Tehrani, Kayvan Forouhesh; Darafsheh, Arash; Phang, Sendy; Mortensen, Luke J.

2018-02-01

Intravital microscopy using multiphoton processes is the standard tool for deep tissue imaging inside of biological specimens. Usually, near-infrared and infrared light is used to excite the sample, which enables imaging several mean free path inside a scattering tissues. Using longer wavelengths, however, increases the width of the effective multiphoton Point Spread Function (PSF). Many features inside of cells and tissues are smaller than the diffraction limit, and therefore not possible to distinguish using a large PSF. Microscopy using high refractive index microspheres has shown promise to increase the numerical aperture of an imaging system and enhance the resolution. It has been shown that microspheres can image features λ/7 using single photon process fluorescence. In this work, we investigate resolution enhancement for Second Harmonic Generation (SHG) and 2-photon fluorescence microscopy. We used Barium Titanate glass microspheres with diameters ˜20-30 μm and refractive index ˜1.9-2.1. We show microsphere-assisted SHG imaging in bone collagen fibers. Since bone is a very dense tissue constructed of bundles of collagen fibers, it is nontrivial to image individual fibers. We placed microspheres on a dense area of the mouse cranial bone, and achieved imaging of individual fibers. We found that microsphere assisted SHG imaging resolves features of the bone fibers that are not readily visible in conventional SHG imaging. We extended this work to 2-photon microscopy of mitochondria in mouse soleus muscle, and with the help of microsphere resolving power, we were able to trace individual mitochondrion from their ensemble.

Liquid core photonic crystal fiber with low-refractive-index liquids for optofluidic applications.

PubMed

Park, Jiyoung; Kang, Doo-Eui; Paulson, Bjorn; Nazari, Tavakol; Oh, Kyunghwan

2014-07-14

A defectless hexagonal air-silica photonic crystal fiber (PCF) structure with its central hole selectively filled by a low-refractive-index liquid is numerically analyzed. Despite the fact that the refractive index of the liquid is significantly lower than that of silica, we found an optimal range of waveguide parameters to ensure light guidance through the liquid core in the fundamental mode, maximizing the light-liquid interaction over a desired wavelength range. Using the vectorial finite element method (FEM), we report detailed parametric studies in terms of the effective index, chromatic dispersion, optical loss, and modal intensity distribution of the liquid core PCFs.

Refractive index engineering of high performance coupler for compact photonic integrated circuits

NASA Astrophysics Data System (ADS)

Liu, Lu; Zhou, Zhiping

2017-04-01

High performance couplers are highly desired in many applications, but the design is limited by nearly unchangeable material refractive index. To tackle this issue, refractive index engineering method is investigated, which can be realized by subwavelength grating. Subwavelength gratings are periodical structures with pitches small enough to locally synthesize the refractive index of photonic waveguides, which allows direct control of optical profile as well as easier fabrication process. This review provides an introduction to the basics of subwavelength structures and pay special attention to the design strategies of some representative examples of subwavelength grating devices, including: edge couplers, fiber-chip grating couplers, directional couplers and multimode interference couplers. Benefited from the subwavelength grating which can engineer the refractive index as well as birefringence and dispersion, these devices show better performance when compared to their conventional counterparts.

Giant refractive-index modulation by two-photon reduction of fluorescent graphene oxides for multimode optical recording.

PubMed

Li, Xiangping; Zhang, Qiming; Chen, Xi; Gu, Min

2013-10-02

Graphene oxides (GOs) have emerged as precursors offering the potential of a cost-effective and large-scale production of graphene-based materials. Despite that their intrinsic fluorescence property has already brought interest of researchers for optical applications, to date, refractive-index modulation as one of the fundamental aspects of optical properties of GOs has received less attention. Here we reported on a giant refractive-index modulation on the order of 10(-2) to 10(-1), accompanied by a fluorescence intensity change, through the two-photon reduction of GOs. These features enabled a mechanism for multimode optical recording with the fluorescence contrast and the hologram-encoded refractive-index modulation in GO-dispersed polymers for security-enhanced high-capacity information technologies. Our results show that GO-polymer composites may provide a new material platform enabling flexible micro-/nano-photonic information devices.

On-chip integrated optofluidic complex refractive index sensing using silicon photonic crystal nanobeam cavities.

PubMed

Zhang, Xingwang; Zhou, Guangya; Shi, Peng; Du, Han; Lin, Tong; Teng, Jinghua; Chau, Fook Siong

2016-03-15

Complex refractive index sensing is proposed and experimentally demonstrated in optofluidic sensors based on silicon photonic crystal nanobeam cavities. The sensitivities are 58 and 139 nm/RIU, respectively, for the real part (n) and the imaginary part (κ) of the complex refractive index, and the corresponding detection limits are 1.8×10(-5) RIU for n and 4.1×10(-6) RIU for κ. Moreover, the capability of the complex refractive index sensing method to detect the concentration composition of the ternary mixture is demonstrated without the surface immobilization of functional groups, which is impossible to realize with the conventional refractive index sensing scheme.

Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering Determined by the OLYMPUS Experiment.

PubMed

Henderson, B S; Ice, L D; Khaneft, D; O'Connor, C; Russell, R; Schmidt, A; Bernauer, J C; Kohl, M; Akopov, N; Alarcon, R; Ates, O; Avetisyan, A; Beck, R; Belostotski, S; Bessuille, J; Brinker, F; Calarco, J R; Carassiti, V; Cisbani, E; Ciullo, G; Contalbrigo, M; De Leo, R; Diefenbach, J; Donnelly, T W; Dow, K; Elbakian, G; Eversheim, P D; Frullani, S; Funke, Ch; Gavrilov, G; Gläser, B; Görrissen, N; Hasell, D K; Hauschildt, J; Hoffmeister, Ph; Holler, Y; Ihloff, E; Izotov, A; Kaiser, R; Karyan, G; Kelsey, J; Kiselev, A; Klassen, P; Krivshich, A; Lehmann, I; Lenisa, P; Lenz, D; Lumsden, S; Ma, Y; Maas, F; Marukyan, H; Miklukho, O; Milner, R G; Movsisyan, A; Murray, M; Naryshkin, Y; Perez Benito, R; Perrino, R; Redwine, R P; Rodríguez Piñeiro, D; Rosner, G; Schneekloth, U; Seitz, B; Statera, M; Thiel, A; Vardanyan, H; Veretennikov, D; Vidal, C; Winnebeck, A; Yeganov, V

2017-03-03

The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5  fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.

Suzaku Detection of Diffuse Hard X-Ray Emission Outside Vela X

NASA Technical Reports Server (NTRS)

Katsuda, Satoru; Mori, Koji; Petre, Robert; Yamaguchi, Hiroya; Tsunemi, Hiroshi; Bocchino, Fabrizio; Bamba, Aya; Miceli, Marco; Hewitt, John W.; Temim, Tea;

Broadband photon-photon interactions mediated by cold atoms in a photonic crystal fiber

PubMed Central

Litinskaya, Marina; Tignone, Edoardo; Pupillo, Guido

2016-01-01

We demonstrate theoretically that photon-photon attraction can be engineered in the continuum of scattering states for pairs of photons propagating in a hollow-core photonic crystal fiber filled with cold atoms. The atoms are regularly spaced in an optical lattice configuration and the photons are resonantly tuned to an internal atomic transition. We show that the hard-core repulsion resulting from saturation of the atomic transitions induces bunching in the photonic component of the collective atom-photon modes (polaritons). Bunching is obtained in a frequency range as large as tens of GHz, and can be controlled by the inter-atomic separation. We provide a fully analytical explanation for this phenomenon by proving that correlations result from a mismatch of the quantization volumes for atomic excitations and photons in the continuum. Even stronger correlations can be observed for in-gap two-polariton bound states. Our theoretical results use parameters relevant for current experiments and suggest a simple and feasible way to induce interactions between photons. PMID:27170160

Optical properties and indentation hardness of thin-film acrylated epoxidized oil

NASA Astrophysics Data System (ADS)

Rahman, Mohammad Syuhaimi Ab.; Shaktur, Khaled Mohamed; Mohammad, Rahmah; Zalikha, Wan Aimi; Nawi, Norwimie; Mohd, Ahmad Faiza

2012-02-01

Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

Image transfer properties by photonic crystal slab with negative refractive index

NASA Astrophysics Data System (ADS)

Chen, Hongbo; Chen, Xiaoshuang; Zhou, Renlong; Lu, Wei

2008-04-01

We have studied the properties of image transferred by photonic crystal (PhC) slab with negative refractive index n=-1 and confirmed the negative refractive phonomenon, but not found the saturated image properties as expected. It is found that real images will not be formed when the source distance larger than the thickness of PhC, and the transferred images are virtual images. Furthermore, comparing the quality of images transferred by a PhC slab and a cascaded stack of photonic crystal slab (CSPS), we found that the transferred images are distorted in both situations. The image resolution is good along the direction parallel to the slab interface, but bad along the direction normal to the slab interface. Simulation results show that the image formed by a CSPS is no better than a PhC slab.

Hardness as a modification index for malting red and white sorghum (kaffir) grains.

PubMed

Uvere, Peter O; Ngoddy, Patrick O; Nwankwo, Chibuzo S

2014-03-30

This study investigated changes in the resistance to fracture of malting red and white sorghum grains using a hardness tester as another method for monitoring grain modification. Grain hardness decreased progressively from 134.35 N and 137.29 N in malting red and white sorghums and levelled off after 120 h at 76.98 N and 69.14 N. In the red grain malts traditionally used for burukutu production, moisture content (r = -0.983), dhurrinase activity (r = -0.981), malting loss (r = -0.981), free amino nitrogen (r = -0.909) and cold water extract (r = -0.908) were better indicators of grain hardness than root length (r = -0.89). In the white sorghum malts, malting loss (r = -0.988), dhurrinase activity (r = -0.954) and diastatic activity (r = -0.936) were better indicators of grain modification than root length (r = -0.916). The soluble nitrogen ratio at the end of malting was lower in the red (0.049) compared with the white (0.0548). Grain hardness using a hand-held tester is a simple, fast and good index of modification of malting red and white sorghum grains. Oven-dried red and white sorghum malts could be considered to be well modified at hardness values/indices below 77 N/0.5730 and 72 N/0.5036, respectively. © 2013 Society of Chemical Industry.

Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.

2015-08-10

Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only amore » minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.« less

Radiation hardness assessment of the charge-integrating hybrid pixel detector JUNGFRAU 1.0 for photon science

NASA Astrophysics Data System (ADS)

Jungmann-Smith, J. H.; Bergamaschi, A.; Brückner, M.; Cartier, S.; Dinapoli, R.; Greiffenberg, D.; Jaggi, A.; Maliakal, D.; Mayilyan, D.; Medjoubi, K.; Mezza, D.; Mozzanica, A.; Ramilli, M.; Ruder, Ch.; Schädler, L.; Schmitt, B.; Shi, X.; Tinti, G.

2015-12-01

JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications in free electron lasers, particularly SwissFEL, and synchrotron light sources. JUNGFRAU is an automatic gain switching, charge-integrating detector which covers a dynamic range of more than 104 photons of an energy of 12 keV with a good linearity, uniformity of response, and spatial resolving power. The JUNGFRAU 1.0 application-specific integrated circuit (ASIC) features a 256 × 256 pixel matrix of 75 × 75 μm2 pixels and is bump-bonded to a 320 μm thick Si sensor. Modules of 2 × 4 chips cover an area of about 4 × 8 cm2. Readout rates in excess of 2 kHz enable linear count rate capabilities of 20 MHz (at 12 keV) and 50 MHz (at 5 keV). The tolerance of JUNGFRAU to radiation is a key issue to guarantee several years of operation at free electron lasers and synchrotrons. The radiation hardness of JUNGFRAU 1.0 is tested with synchrotron radiation up to 10 MGy of delivered dose. The effect of radiation-induced changes on the noise, baseline, gain, and gain switching is evaluated post-irradiation for both the ASIC and the hybridized assembly. The bare JUNGFRAU 1.0 chip can withstand doses as high as 10 MGy with minor changes to its noise and a reduction in the preamplifier gain. The hybridized assembly, in particular the sensor, is affected by the photon irradiation which mainly shows as an increase in the leakage current. Self-healing of the system is investigated during a period of 11 weeks after the delivery of the radiation dose. Annealing radiation-induced changes by bake-out at 100 °C is investigated. It is concluded that the JUNGFRAU 1.0 pixel is sufficiently radiation-hard for its envisioned applications at SwissFEL and synchrotron beam lines.

The role of group index engineering in series-connected photonic crystal microcavities for high density sensor microarrays

PubMed Central

Zou, Yi; Chakravarty, Swapnajit; Zhu, Liang; Chen, Ray T.

2014-01-01

We experimentally demonstrate an efficient and robust method for series connection of photonic crystal microcavities that are coupled to photonic crystal waveguides in the slow light transmission regime. We demonstrate that group index taper engineering provides excellent optical impedance matching between the input and output strip waveguides and the photonic crystal waveguide, a nearly flat transmission over the entire guided mode spectrum and clear multi-resonance peaks corresponding to individual microcavities that are connected in series. Series connected photonic crystal microcavities are further multiplexed in parallel using cascaded multimode interference power splitters to generate a high density silicon nanophotonic microarray comprising 64 photonic crystal microcavity sensors, all of which are interrogated simultaneously at the same instant of time. PMID:25316921

Photodiode radiation hardness, lyman-alpha emitting galaxies and photon detection in liquid argon neutrino detectors

NASA Astrophysics Data System (ADS)

Baptista, Brian

2013-12-01

My dissertation is comprised of three projects: 1) studies of Lyman-alpha Emitting galaxies (LAEs), 2) radiation hardness studies of InGaAs photodiodes (PDs), and 3) scintillation photon detection in liquid argon (LAr) neutrino detectors. I began work on the project that has now become WFIRST, developing a science case that would use WFIRST after launch for the observation of LAEs. The radiation hardness of PDs was as an effort to support the WFIRST calibration team. When WFIRST was significantly delayed, I joined an R&D effort that applied my skills to work on photon detection in LAr neutrino detectors. I report results on a broadband selection method developed to detect high equivalent width (EW) LAEs. Using photometry from the CFHT-Legacy Survey Deep 2 and 3 fields, I have spectroscopically confirmed 63 z=2.5-3.5 LAEs using the WIYN/Hydra spectrograph. Using UV continuum-fitting techniques I computed properties such as EWs, internal reddening and star formation rates. 62 of my LAEs show evidence to be normal dust-free LAEs. Second, I present an investigation into the effects of ionizing proton radiation on commercial off-the-shelf InGaAs PDs. I developed a monochromator-based test apparatus that utilized NIST-calibrated reference PDs. I tested the PDs for changes to their dark current, relative responsivity as a function of wavelength, and absolute responsivity. I irradiated the test PDs using 30, 52, and 98 MeV protons at the IU Cyclotron Facility. I found the InGaAs PDs showed increased dark current as the fluence increased with no evidence of broadband response degradation at the fluences expected at an L2 orbit and a 10-year mission lifetime. Finally, I detail my efforts on technology development of both optical detector technologies and waveshifting light guide construction for LAr vacuum UV scintillation light. Cryogenic neutrino detectors use photon detection for both accelerator based science and for SNe neutrino detection and proton decay. I have

Ge-rich graded-index Si1-xGex devices for MID-IR integrated photonics

NASA Astrophysics Data System (ADS)

Ramirez, J. M.; Vakarin, V.; Liu, Q.; Frigerio, J.; Ballabio, A.; Le Roux, X.; Benedikovic, D.; Alonso-Ramos, C.; Isella, G.; Vivien, L.; Marris-Morini, D.

2018-02-01

Mid-infrared (mid-IR) silicon photonics is becoming a prominent research with remarkable potential in several applications such as in early medical diagnosis, safe communications, imaging, food safety and many more. In the quest for the best material platform to develop new photonic systems, Si and Ge depart with a notable advantage over other materials due to the high processing maturity accomplished during the last part of the 20th century through the deployment of the CMOS technology. From an optical viewpoint, combining Si with Ge to obtain SiGe alloys with controlled stoichiometry is also of interest for the photonic community since permits to increase the effective refractive index and the nonlinear parameter, providing a fascinating playground to exploit nonlinear effects. Furthermore, using Ge-rich SiGe gives access to a range of deep mid-IR wavelengths otherwise inaccessible (λ 2-20 μm). In this paper, we explore for the first time the limits of this approach by measuring the spectral loss characteristic over a broadband wavelength range spanning from λ = 5.5 μm to 8.5 μm. Three different SiGe waveguide platforms are compared, each one showing higher compactness than the preceding through the engineering of the vertical Ge profile, giving rise to different confinement characteristics to the propagating modes. A flat propagation loss characteristic of 2-3 dB/cm over the entire wavelength span is demonstrated in Ge-rich graded-index SiGe waveguides of only 6 μm thick. Also, the role of the overlap fraction of the confined optical mode with the Si-rich area at the bottom side of the epitaxial SiGe waveguide is put in perspective, revealing a lossy characteristic compared to the other designs were the optical mode is located in the Ge-rich area at the top of the waveguide uniquely. These Ge-rich graded-index SiGe waveguides may pave the way towards a new generation of photonic integrated circuits operating at deep mid-IR wavelengths.

Tunability of temperature dependent THz photonic band gaps in 1-D photonic crystals composed of graded index materials and semiconductor InSb

NASA Astrophysics Data System (ADS)

Singh, Bipin K.; Pandey, Praveen C.; Rastogi, Vipul

2018-05-01

Tunable temperature dependent terahertz photonic band gaps (PBGs) in one-dimensional (1-D) photonic crystal composed of alternating layers of graded index and semiconductor materials are demonstrated. Results show the influence of temperature, geometrical parameters, grading profile and material damping factor on the PBGs. Number of PBG increases with increasing the layer thickness and their bandwidth can be tuned with external temperature and grading parameters. Lower order band gap is more sensitive to the temperature which shows increasing trend with temperature, and higher order PBGs can also be tuned by controlling the external temperature. Band edges of PBGs are shifted toward higher frequency side with increasing the temperature. Results show that the operational frequencies of PBGs are unaffected when loss involved. This work enables to design tunable Temperature dependent terahertz photonic devices such as reflectors, sensors and filters etc.

Photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing.

PubMed

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10(-4)-8.88 × 10(-4) RIU or 1.02 × 10(-4)-9.04 × 10(-4) RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications.

How to Distinguish Neutron Star and Black Hole X-ray Binaries? Spectral Index and Quasi-Periodic Oscillation Frequency Correlation

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Shaposhnikov, Nickolai

2005-01-01

Recent studies have revealed strong correlations between 1-10 Hz frequencies of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources when seen in the low/hard state, the steep power-law (soft) state, and in transition between these states. In the soft state these index-QPO frequency correlations show a saturation of the photon index GAMMA approximately equal to 2.7 at high values of the low frequency nu(sub L). This saturation effect was previously identified as a black hole signature. In this paper we argue that this saturation does not occur, at least for one neutron star (NS) source 4U 1728-34, for which the index GAMMA monotonically increases with nu(sub L) to the values of 6 and higher. We base this conclusion on our analysis of approximately 1.5 Msec of RXTE archival data for 4U 1728-34. We reveal the spectral evolution of the Comptonized blackbody spectra when the source transitions from the hard to soft states. The hard state spectrum is a typical thermal Comptonization spectrum of the soft photons which originate in the disk and the NS outer photospheric layers. The hard state photon index is GAMMA approximately 2. The soft state spectrum consists of two blackbody components which are only slightly Comptonized. Thus we can claim (as expected from theory) that in NS sources thermal equilibrium is established for the soft state. To the contrary in BH sources, the equilibrium is never established due to the presence of the BH horizon. The emergent BH spectrum, even in the high/soft state, has a power law component. We also identify the low QPO frequency nu(sub L) as a fundamental frequency of the quasi-spherical component of the transition layer (presumably related to the corona and the NS and disk magnetic closed field lines). The lower frequency nu(sub SL) is identified as the frequency of oscillations of a quasi-cylindrical configuration of the TL (presumably related to the NS and disk magnetic

High Sensitivity Refractive Index Sensor Based on Dual-Core Photonic Crystal Fiber with Hexagonal Lattice.

PubMed

Wang, Haiyang; Yan, Xin; Li, Shuguang; An, Guowen; Zhang, Xuenan

2016-10-08

A refractive index sensor based on dual-core photonic crystal fiber (PCF) with hexagonal lattice is proposed. The effects of geometrical parameters of the PCF on performances of the sensor are investigated by using the finite element method (FEM). Two fiber cores are separated by two air holes filled with the analyte whose refractive index is in the range of 1.33-1.41. Numerical simulation results show that the highest sensitivity can be up to 22,983 nm/RIU(refractive index unit) when the analyte refractive index is 1.41. The lowest sensitivity can reach to 21,679 nm/RIU when the analyte refractive index is 1.33. The sensor we proposed has significant advantages in the field of biomolecule detection as it provides a wide-range of detection with high sensitivity.

Photons, photon jets, and dark photons at 750 GeV and beyond.

PubMed

Dasgupta, Basudeb; Kopp, Joachim; Schwaller, Pedro

2016-01-01

In new physics searches involving photons at the LHC, one challenge is to distinguish scenarios with isolated photons from models leading to "photon jets". For instance, in the context of the 750 GeV diphoton excess, it was pointed out that a true diphoton resonance [Formula: see text] can be mimicked by a process of the form [Formula: see text], where S is a new scalar with a mass of 750 GeV and a is a light pseudoscalar decaying to two collinear photons. Photon jets can be distinguished from isolated photons by exploiting the fact that a large fraction of photons convert to an [Formula: see text] pair inside the inner detector. In this note, we quantify this discrimination power, and we study how the sensitivity of future searches differs for photon jets compared to isolated photons. We also investigate how our results depend on the lifetime of the particle(s) decaying to the photon jet. Finally, we discuss the extension to [Formula: see text], where there are no photons at all but the dark photon [Formula: see text] decays to [Formula: see text] pairs. Our results will be useful in future studies of the putative 750 GeV signal, but also more generally in any new physics search involving hard photons.

A cylindrical optical black hole using graded index photonic crystals

NASA Astrophysics Data System (ADS)

Wang, Hung-Wen; Chen, Lien-Wen

2011-05-01

The electromagnetic wave propagation of a two-dimensional optical black hole with graded index photonic crystals for transverse magnetic modes is studied. The implementation of the proposed system is validated in the metamaterial regime. The finite element method is employed in order to confirm the optical properties of the designed device. Numerical simulations show that the light incident on the device is bent toward the central area and absorbed by the inner core. As a result, the artificial optical black hole can effectively absorb the incident waves from all directions. The structure is composed of two kinds of real isotropic materials, which eases the experimental fabrication.

Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing

PubMed Central

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10−4–8.88 × 10−4 RIU or 1.02 × 10−4–9.04 × 10−4 RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications. PMID:22736988

High Sensitivity Refractive Index Sensor Based on Dual-Core Photonic Crystal Fiber with Hexagonal Lattice

PubMed Central

Wang, Haiyang; Yan, Xin; Li, Shuguang; An, Guowen; Zhang, Xuenan

2016-01-01

A refractive index sensor based on dual-core photonic crystal fiber (PCF) with hexagonal lattice is proposed. The effects of geometrical parameters of the PCF on performances of the sensor are investigated by using the finite element method (FEM). Two fiber cores are separated by two air holes filled with the analyte whose refractive index is in the range of 1.33–1.41. Numerical simulation results show that the highest sensitivity can be up to 22,983 nm/RIU(refractive index unit) when the analyte refractive index is 1.41. The lowest sensitivity can reach to 21,679 nm/RIU when the analyte refractive index is 1.33. The sensor we proposed has significant advantages in the field of biomolecule detection as it provides a wide-range of detection with high sensitivity. PMID:27740607

Radiation hardness studies of CdTe thin films for clinical high-energy photon beam detectors

NASA Astrophysics Data System (ADS)

Shvydka, Diana; Parsai, E. I.; Kang, J.

2008-02-01

In radiation oncology applications, the need for higher-quality images has been driven by recent advances in radiation delivery systems that require online imaging. The existing electronic imaging devices commonly used to acquire portal images implement amorphous silicon (a-Si) detector, which exhibits poor image quality. Efforts for improvement have mostly been in the areas of noise and scatter reduction through software. This has not been successful due to inherent shortcomings of a-Si material. Cadmium telluride (CdTe) semiconductor has long been recognized as highly suitable for use in X-ray detectors in both spectroscopic and imaging applications. Development of such systems has mostly concentrated on single crystal CdTe. Recent advances in thin-film deposition technology suggest replacement of crystalline material with its polycrystalline counterpart, offering ease of large-area device fabrication and achievement of higher resolution as well as a favorable cost difference. While bulk CdTe material was found to have superior radiation hardness, thin films have not been evaluated from that prospective, in particular under high-energy photon beam typical of radiation treatment applications. We assess the performance of thin-film CdTe devices utilizing 6 MeV photon beam and find no consistent trend for material degradation under doses far exceeding the typical radiation therapy detector lifetime dose.

Hard scattering in γp interactions

NASA Astrophysics Data System (ADS)

Ahmed, T.; Andreev, V.; Andrieu, B.; Arpagaus, M.; Babayev, A.; Bärwolff, H.; Ban, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Beck, G. A.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Berthon, U.; Bertrand-Coremans, G.; Besancon, M.; Biddulph, P.; Binder, E.; Bizot, J. C.; Blobel, V.; Borras, K.; Bosetti, P. C.; Boudry, V.; Bourdarios, C.; Brasse, F.; Braun, U.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Colombo, M.; Coughlan, J. A.; Courau, A.; Coutures, C.; Cozzika, G.; Criegee, L.; Cvach, J.; Dainton, J. B.; Danilov, M.; Dann, A. W. E.; Dau, W. D.; David, M.; Deffur, E.; Delcourt, B.; DelBuono, L.; Devel, M.; DeRoeck, A.; Dingus, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Drescher, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Eberle, M.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellis, N. N.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Feng, Y.; Fensome, I. F.; Ference, J.; Ferrarotto, F.; Flauger, W.; Fleischer, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formanek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Fuhrmann, P.; Gabathuler, E.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gellrich, A.; Gennis, M.; Gensch, U.; Genzel, H.; Gerhards, R.; Gillespie, D.; Godfrey, L.; Goerlach, U.; Goerlich, L.; Goldberg, M.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Greif, H.; Grindhammer, G.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Handschuh, D.; Hanlon, E. M.; Hapke, M.; Harjes, J.; Hartz, P.; Haydar, R.; Haynes, W. J.; Heatherington, J.; Hedberg, V.; Hedgecock, R.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hildesheim, W.; Hill, P.; Hilton, C. D.; Hladky, J.; Hoeger, K. C.; Huet, Ph.; Hufnagel, H.; Huot, N.; Ibbotson, M.; Jabiol, M. A.; Jacholkowska, A.; Jacobson, C.; Jaffre, M.; Jönsson, L.; Johannsen, K.; Johnson, D.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kasarian, S.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kenyon, I. R.; Kermiche, S.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurca, T.; Kurzhöfer, J.; Kuznik, B.; Lander, R.; Landon, M. P. J.; Langkau, R.; Lanius, P.; Laporte, J. F.; Lebedev, A.; Lenhardt, U.; Leuschner, A.; Leverenz, C.; Levin, D.; Levonian, S.; Ley, Ch.; Lindström, G.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lüers, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, A.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milone, V.; Monnier, E.; Moreau, F.; Moreels, J.; Morris, J. V.; Morton, J. M.; Müller, K.; Murin, P.; Murray, S. A.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Newton, D.; Nguyen, H. K.; Niebergall, F.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Orenstein, S.; Ould-Saada, F.; Pascaud, C.; Patel, G. D.; Peppel, E.; Peters, S.; Phillips, H. T.; Phillips, J. P.; Pichler, Ch.; Pilgram, W.; Pitzl, D.; Prosi, R.; Raupach, F.; Rauschnabel, K.; Reimer, P.; Ribarics, P.; Riech, V.; Riedlberger, J.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rudowicz, M.; Ruffer, M.; Rusakov, S.; Rybicki, K.; Ryseck, E.; Sacton, J.; Sahlmann, N.; Sanchez, E.; Sankey, D. P.; Savitsky, M.; Schacht, P.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmitz, W.; Schröder, V.; Schulz, M.; Schwind, A.; Scobel, W.; Seehausen, U.; Sell, R.; Seman, M.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Smolik, L.; Soloviev, Y.; Spitzer, H.; Staroba, P.; Steenbock, M.; Steffen, P.; Steinberg, R.; Steiner, H.; Stella, B.; Stephens, K.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Taylor, R. E.; Thompson, G.; Thompson, R. J.; Tichomirov, I.; Trenkel, C.; Truöl, P.; Tchernyshov, V.; Turnau, J.; Tutas, J.; Urban, L.; Usik, A.; Valkar, S.; Valkarova, A.; Vallee, C.; VanEsch, P.; Vartapetian, A.; Vasdik, J.; Vecko, M.; Verrecchia, P.; Vick, R.; Villet, G.; Vogel, E.; Wacker, K.; Walker, I. W.; Walther, A.; Weber, G.; Wegener, D.; Wegner, A.; Wellisch, H. P.; Willard, S.; Winde, M.; Winter, G.-G.; Wolff, M. Th.; Womersley, L. A.; Wright, A. E.; Wulff, N.; Yiou, T. P.; Zacek, J.; Zavada, P.; Zeitnitz, C.; Ziaeepour, H.; Zimmer, M.; Zimmermann, W.; Zomer, F.; H1 Collaboration

1992-12-01

We report on the investigation of the final state in interactions of quasi-real photons with protons. The data were taken with the H1 detector at the HERA ep collider. Evidence for hard interactions is seen in both single particle spectra and jet formation. The data can best be described by inclusion of resolved photon processess as predicted by QCD.

Fermi Observations of GRB 090510: A Short Hard Gamma-Ray Burst with an Additional, Hard Power-Law Component from 10 keV to GeV Energies

DOE PAGES

Ackermann, M.; Asano, K.; Atwood, W. B.; ...

2010-05-27

We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi observatory. GRB 090510 is the first burst detected by the LAT that shows strong evidence for a deviation from a Band spectral fitting function during the prompt emission phase. The time-integrated spectrum is fit by the sum of a Band function with E peak = 3.9 ± 0.3 MeV, which is the highest yet measured, and a hard power-law component with photon index –1.62 ± 0.03 that dominates the emission below ≈20more » keV and above ≈100 MeV. The onset of the high-energy spectral component appears to be delayed by ~0.1 s with respect to the onset of a component well fit with a single Band function. A faint GBM pulse and a LAT photon are detected 0.5 s before the main pulse. During the prompt phase, the LAT detected a photon with energy 30.5 +5.8 –2.6 GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, Γ≳ 1200, using simple γγ opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the ≈100 keV-few MeV flux. Stricter high confidence estimates imply Γ ≳ 1000 and still require that the outflows powering short GRBs are at least as highly relativistic as those of long-duration GRBs. Finally, implications of the temporal behavior and power-law shape of the additional component on synchrotron/synchrotron self-Compton, external-shock synchrotron, and hadronic models are considered.« less

On the Nature of the Compact Object in SS 433: Observational Evidence of X-ray Photon Index Saturation

NASA Astrophysics Data System (ADS)

Seifina, Elena; Titarchuk, Lev

2010-10-01

We present an analysis of the X-ray spectral properties observed from the black hole candidate (BHC) binary SS 433. We have analyzed Rossi X-ray Timing Explorer data from this source, coordinated with Green Bank Interferometer/RATAN-600. We show that SS 433 undergoes an X-ray spectral transition from the low hard state to the intermediate state (IS). We show that the X-ray broadband energy spectra during all spectral states are well fitted by a sum of the so-called bulk motion Comptonization (BMC) component and by two (broad and narrow) Gaussians for the continuum and line emissions, respectively. In addition to these spectral model components, we also find a strong feature that we identify as a "blackbody-like (BB)" component in which the color temperature is in the range of 4-5 keV in 24 IS spectra during the radio outburst decay in SS 433. Our observational results on the "high-temperature BB" bump lead us to suggest the presence of gravitationally redshifted annihilation line emission in this source. In fact, this spectral feature has been recently reproduced in Monte Carlo simulations by Laurent & Titarchuk. We have also established the photon index saturation at about 2.3 in index versus mass accretion correlation. This index-mass accretion correlation allows us to evaluate the low limit of the black hole (BH) mass of the compact object in SS 433, M_{{bh}}≳ 2 solar masses, using the scaling method using BHC GX 339 - 4 as a reference source. Our estimate of the BH mass in SS 433 is consistent with the recent BH mass measurement using the radial velocity measurements of the binary system by Hillwig & Gies, who find that Mx = (4.3 ± 0.8) solar masses. This is the smallest BH mass found up to now among all BH sources. Moreover, the index saturation effect versus mass accretion rate revealed in SS 433, as in a number of other BH candidates, is strong observational evidence for the presence of a BH in SS 433.

On the Nature of the Compact Object in SS 433. Observational Evidence of X-Ray Photon Index Saturation

NASA Technical Reports Server (NTRS)

Seifina, Elena; Titarchuk, Lev

2010-01-01

We present an analysis of the X-ray spectral properties observed from black hole , candidate (BHC) binary SS 433. We have analyzed Rossi X-ray Time Explorer (RXTE) data from this source, coordinated with Green Bank Interferometer/RATAN-600. We show that SS 433 undergoes a X-ray spectral transition from the low hard state (LHS) to the intermediate state (IS). We show that the X-ray broad-band energy spectra during all spectral states are well fit by a sum of so called "Bulk Motion Comptonization (BMC) component" and by two (broad and narrow) Gaussians for the continuum and line emissions respectively. In addition to these spectral model components we also find a strong feature that we identify as a" blackbody-like (BB)" component which color temperature is in the range of 4-5 keV in 24 IS spectra during the radio outburst decay in SS 433. Our observational results on the "high temperature BB" bump leads us to suggest the presence of gravitationally redshifted annihilation line emission in this source. In fact this spectral feature has been recently reproduced in Monte Carlo simulations by Laurent and Titarchuk. We have also established the photon index saturation at about 2.3 in index vs mass accretion correlation. This index-mass accretion correlation allows us to evaluate the low limit of black hole (BH) mass of compact object in SS 433, M(sub bh) approximately > 2 solar masses, using the scaling method using BHC GX 339-4 as a reference source. Our estimate of the BH mass in SS 433 is consistent with recent BH mass measurement using the radial-velocity measurements of the binary system by Hillwig & Gies who find that M(sub x)( = (4.3 +/- 0.8) solar masses. This is the smallest BH mass found up to now among all BH sources. Moreover, the index saturation effect versus mass accretion rate revealed in SS 433, like in a number of other BH candidates, is the strong observational evidence for the presence of a BH in SS 433.

Observation of hard processes in rapidity gap events in γp interactions at HERA

NASA Astrophysics Data System (ADS)

Ahmed, T.; Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; Babaev, A.; Baehr, J.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Brasse, F.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Colombo, M.; Contreras, J. G.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Danilov, M.; Dau, W. D.; Daum, K.; David, M.; Deffur, E.; Delcourt, B.; Del Buono, L.; De Roeck, A.; De Wolf, E. A.; Di Nezza, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Droutskoi, V.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Ehrlichmann, H.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Erdmann, W.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gebauer, M.; Gellrich, A.; Genzel, H.; Gerhards, R.; Goerlach, U.; Goerlach, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Gonzalez-Pineiro, B.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Grindhammer, G.; Gruber, A.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Hampel, M.; Hanlon, E. M.; Hapke, M.; Haynes, W. J.; Heatherington, J.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hess, M. F.; Hildesheim, W.; Hill, P.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Höppner, M.; Horisberger, R.; Huet, Ph.; Hufnagel, H.; Ibbotson, M.; Itterbeck, H.; Jabiol, M.-A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, T.; Jönsson, L.; Johannsen, K.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kant, D.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Ko, W.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Krüner-Marquis, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Kuznik, B.; Lacour, D.; Lamarche, F.; Lander, R.; Landon, M. P. J.; Lange, W.; Lanius, P.; Laporte, J.-F.; Lebedev, A.; Leverenz, C.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Linsel, F.; Lipinski, J.; List, B.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Mercer, D.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milstead, D.; Moreau, F.; Morris, J. V.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Newman, P. R.; Newton, D.; Neyret, D.; Nguyen, H. K.; Niebergall, F.; Niebuhr, C.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg-Werther, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Peppel, E.; Perez, E.; Phillips, J. P.; Pichler, Ch.; Pitzl, D.; Pope, G.; Prell, S.; Prosi, R.; Rädel, G.; Raupach, F.; Reimer, P.; Reinshagen, S.; Ribarics, P.; Rick, H.; Riech, V.; Riedlberger, J.; Riess, S.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Rylko, R.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Savitsky, M.; Schacht, P.; Schiek, S.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Schwind, A.; Seehausen, U.; Sefkow, F.; Seidel, M.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorni, I. O.; Smirnov, P.; Smith, J. R.; Soloviev, Y.; Spitzer, H.; Starosta, R.; Steenbock, M.; Steffen, P.; Steinberg, R.; Stella, B.; Stephens, K.; Stier, J.; Stiewe, J.; Stösslein, U.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Taylor, R. E.; Tchernyshov, V.; Thiebaux, C.; Thompson, G.; Truöl, P.; Turnau, J.; Tutas, J.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Van Esch, P.; Van Mechelen, P.; Vartapetian, A.; Vazdik, Y.; Vecko, M.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Walker, I. W.; Walther, A.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wellisch, H. P.; West, L. R.; Willard, S.; Winde, M.; Winter, G.-G.; Wright, A. E.; Wünsch, E.; Wulff, N.; Yiou, T. P.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zimmer, M.; Zimmermann, W.; Zomer, F.; Zuber, K.

1995-02-01

Events with no hadronic energy flow in a large interval of pseudo-rapidity in the proton direction are observed in photon-proton interactions at an average centre of mass energy <√s γp> of 200 GeV These events are interpreted as photon diffractive dissociation. Evidence for hard scattering in photon diffractive dissociation is demonstrated using inclusive single particle spectra, thrust as a function of transverse energy, and the observation of jet production. The data can be described by a Monte Carlo calculation including hard photon-pomeron scattering.

Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction

NASA Astrophysics Data System (ADS)

Sargsian, Misak

2008-10-01

We discus recent developments in theory of high energy two-body break-up of few-nucleon systems. The characteristics of these reactions are such that the hard two-body quasielastic subprocess can be clearly separated from the accompanying soft subprocesses. We discuss in details the hard rescattering model (HRM) in which hard photodisintegration develops in two stages. At first, photon knocks-out an energetic quark which rescatters subsequently with a quark of the other nucleon. The latter provides a mechanism of sharing the initial high momentum of the photon between two outgoing nucleons. This final state hard rescattering can be expressed through the hard NN scattering amplitude. Within HRM we discuss hard break-up reactions involving D and 3He targets and demonstrate how these reactions are sensitive to the dynamics of hard pn and pp interaction. Another development of HRM is the prediction of new helicity selection mechanism for hard two-body reactions, which was apparently confirmed in the recent JLab experiment.

Gamma-ray luminosity and photon index evolution of FSRQ blazars and contribution to the gamma-ray background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singal, J.; Ko, A.; Petrosian, V., E-mail: jsingal@richmond.edu

We present the redshift evolutions and distributions of the gamma-ray luminosity and photon spectral index of flat spectrum radio quasar (FSRQ) type blazars, using non-parametric methods to obtain the evolutions and distributions directly from the data. The sample we use for analysis consists of almost all FSRQs observed with a greater than approximately 7σ detection threshold in the first-year catalog of the Fermi Gamma-ray Space Telescope's Large Area Telescope, with redshifts as determined from optical spectroscopy by Shaw et al. We find that FSQRs undergo rapid gamma-ray luminosity evolution, but negligible photon index evolution, with redshift. With these evolutions accountedmore » for we determine the density evolution and luminosity function of FSRQs and calculate their total contribution to the extragalactic gamma-ray background radiation, resolved and unresolved, which is found to be 16(+10/–4)%, in agreement with previous studies.« less

CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation.

PubMed

Hahn, C; Weber, G; Märtin, R; Höfer, S; Kämpfer, T; Stöhlker, Th

2016-04-01

Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays - such as laser-generated plasmas - is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.

CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation

NASA Astrophysics Data System (ADS)

Hahn, C.; Weber, G.; Märtin, R.; Höfer, S.; Kämpfer, T.; Stöhlker, Th.

2016-04-01

Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays — such as laser-generated plasmas — is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.

CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahn, C., E-mail: christoph.hahn@uni-jena.de; Höfer, S.; Kämpfer, T.

Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays — such as laser-generated plasmas — is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy.more » Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.« less

Photonic jet reconstruction for particle refractive index measurement by digital in-line holography.

PubMed

Sentis, Matthias P L; Onofri, Fabrice R A; Lamadie, Fabrice

2017-01-23

A new and computationally efficient approach is proposed for determining the refractive index of spherical and transparent particles, in addition to their size and 3D position, using digital in-line holography. The method is based on the localization of the maximum intensity position of the photonic jet with respect to the particle center retrieved from the back propagation of recorded holograms. Rigorous electromagnetic calculations and experimental results demonstrate that for liquid-liquid systems and droplets with a radius > 30µm, a refractive index measurement with a resolution inferior to 4 × 10^-3 is achievable, revealing a significant potential for the use of this method to investigate multiphase flows. The resolution for solid or liquid particles in gas is expected to be lower but sufficient for the recognition of particle material.

Discovery of Diffuse Hard X-Ray Emission from the Vicinity of PSR J1648-4611 with Suzaku

NASA Astrophysics Data System (ADS)

Sakai, Michito; Matsumoto, Hironori; Haba, Yoshito; Kanou, Yasufumi; Miyamoto, Youhei

2013-06-01

We observed the pulsar PSR J1648-4611 with Suzaku. Two X-ray sources, Suzaku J1648-4610 (Src A) and Suzaku J1648-4615 (Src B), were found in the field of view. Src A is coincident with the pulsar PSR J1648-4611, which was also detected by the Fermi Gamma-ray Space Telescope. A hard-band image indicates that Src A is spatially extended. We found point sources in the vicinity of Src A by using a Chandra image of the same region, but the point sources have soft X-ray emission, and cannot explain the hard X-ray emission of Src A. The hard-band spectrum of Src A can be reproduced by a power-law model with a photon index of 2.0+0.9-0.7. The X-ray flux in the 2-10 keV band is 1.4 × 10-13 erg cm-2 s-1. The diffuse emission suggests a pulsar wind nebula around PSR J1648&"8211;4611, but the luminosity of Src A is much larger than that expected from the spin-down luminosity of the pulsar. Parts of the very-high-energy γ-ray emission of HESS J1646-458 may be powered by this pulsar wind nebula driven by PSR J1648-4611. Src B has soft emission, and its X-ray spectrum can be described by a power-law model with a photon index of 3.0+1.4-0.8. The X-ray flux in the 0.4-10 keV band is 6.4 × 10-14 erg s-1 cm-2. No counterpart for Src B has been found in the literature.

AstroSat /LAXPC Observation of Cygnus X-1 in the Hard State

DOE Office of Scientific and Technical Information (OSTI.GOV)

Misra, Ranjeev; Pahari, Mayukh; Yadav, J S

2017-02-01

We report the first analysis of data from AstroSat /LAXPC observations of Cygnus X-1 in 2016 January. LAXPC spectra reveals that the source was in the canonical hard state, represented by a prominent thermal Comptonization component having a photon index of ∼1.8 and high temperature of kT{sub e} > 60 keV along with weak reflection and possible disk emission. The power spectrum can be characterized by two broad lorentzian functions centered at ∼0.4 and ∼3 Hz. The rms of the low-frequency component decreases from ∼15% at around 4 keV to ∼10% at around 50 keV, while that of the high-frequencymore » one varies less rapidly from ∼13.5% to ∼11.5% in the same energy range. The time lag between the hard (20–40 keV) and soft (5–10 keV) bands varies in a step-like manner being nearly constant at ∼50 milliseconds from 0.3 to 0.9 Hz, decreasing to ∼8 milliseconds from 2 to 5 Hz and finally dropping to ∼2 milliseconds for higher frequencies. The time lags increase with energy for both the low and high-frequency components. The event mode LAXPC data allows for flux resolved spectral analysis on a timescale of 1 s, which clearly shows that the photon index increased from ∼1.72 to ∼1.80 as the flux increased by nearly a factor of two. We discuss the results in the framework of the fluctuation propagation model.« less

Realization of a complementary medium using dielectric photonic crystals.

PubMed

Xu, Tao; Fang, Anan; Jia, Ziyuan; Ji, Liyu; Hang, Zhi Hong

2017-12-01

By exploiting the scaling invariance of photonic band diagrams, a complementary photonic crystal slab structure is realized by stacking two uniformly scaled double-zero-index dielectric photonic crystal slabs together. The space cancellation effect in complementary photonic crystals is demonstrated in both numerical simulations and microwave experiments. The refractive index dispersion of double-zero-index dielectric photonic crystal is experimentally measured. Using pure dielectrics, our photonic crystal structure will be an ideal platform to explore various intriguing properties related to a complementary medium.

Control of Fano resonances in photonic crystal nanobeams side-coupled with nanobeam cavities and their applications to refractive index sensing

NASA Astrophysics Data System (ADS)

Meng, Zi-Ming; Li, Zhi-Yuan

2018-03-01

We study the control of Fano resonances in a 2D photonic crystal nanobeam (PCN) side-coupled with a photonic crystal nanobeam cavity (PCNC) by choosing different cavity modes, the position of the photonic bandgap of PCNs and the displacement between PCNs and PCNCs. By increasing the refractive index of the holes and the surrounding medium, it is found that the air mode cavity with even mirror-reflection symmetry holds the highest sensitivity (538 nm/RIU RIU, refractive index unit) and maximal figure of merit (FOM  =  516). Our results can be extended to a practical 3D configuration, where an air-suspended silicon PCN is side-coupled with a PCNC. Although the sensitivity is only 192 nm/RIU for our 3D structures, the maximal FOM is as large as 2095 due to the deep transmission valley. The sensitivity of our PCN-PCNC structures can be further improved by designing PCNCs with electric field concentrated in the air region as much as possible. Our PCN-PCNC structures do not require ultrahigh Q and can be fabricated on the silicon-on-insulator platform, which is compatible with CMOS processing. Therefore, our proposed PCN-PCNC structures provide feasible solutions for realizing label-free sensitive integrated refractive index sensors.

Spatial dispersion of index components required for building invisibility cloak medium from photonic crystals

NASA Astrophysics Data System (ADS)

Jamilan, Saeid; Semouchkin, George; Gandji, Navid P.; Semouchkina, Elena

2018-04-01

The opportunities to use dielectric photonic crystals (PhCs) as the media of cylindrical invisibility cloaks, designed using transformation optics (TO) concepts, are investigated. It is shown that TO-based prescriptions for radial index dispersion, responsible for turning waves around hidden objects, can be dropped if the PhC media support self-collimation of waves in bent crystals. Otherwise, to provide prescribed anisotropy of index dispersion, it is possible to employ PhCs with rectangular lattices. It is found, however, that at acceptable cloak thicknesses, modifications of crystal parameters do not allow for achieving the prescribed level of index anisotropy. This problem is solved by finding the reduced spatial dispersion law for the radial index component, which is characterized by decreased against TO-prescriptions values near the target and increased values in outer layers of the cloak. The cloak utilizing reduced prescriptions for indices is shown to perform almost as efficiently as a TO-based cloak, in terms of both wave front restoration behind the target and reducing the total scattering cross-width of the target.

Multimodal hard x-ray nanoprobe facility by nested Montel mirrors aimed for 40nm resolution at Taiwan Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Gung-Chian, E-mail: gcyin@nsrrc.org.tw; Chang, Shi-Hung; Chen, Bo-Yi

2016-01-28

The hard X-ray nanoprobe facility at Taiwan Photon Source (TPS) provides multimodal X-ray detections, including XRF, XAS, XEOL, projection microscope, CDI, etc. Resulting from the large numerical aperture obtained by utilizing nested Montel mirrors, the beamline with a moderate length 75 meters can conduct similar performance with those beamlines longer than 100 meters. The mirrors are symmetrically placed with a 45 degrees cut. The beamline optics is thus designed to take the advantage of the symmetry of mirrors such that a round focal spot is accomplished. The size and the divergence of the focus spot are simulated around 40 nm andmore » 6.29 mrad, respectively. The whole facility including the beamline and the stations will be operated under vacuum to preserve the photon coherence as well as to prevent the system from unnecessary environmental interference. A SEM in close cooperation with laser interferometers is equipped to precisely locate the position of the sample. This endstation is scheduled to be commissioned in the fall of 2016.« less

Radiation and Temperature Hard Multi-Pixel Avalanche Photodiodes

NASA Technical Reports Server (NTRS)

Bensaoula, Abdelhak (Inventor); Starikov, David (Inventor); Pillai, Rajeev (Inventor)

2017-01-01

The structure and method of fabricating a radiation and temperature hard avalanche photodiode with integrated radiation and temperature hard readout circuit, comprising a substrate, an avalanche region, an absorption region, and a plurality of Ohmic contacts are presented. The present disclosure provides for tuning of spectral sensitivity and high device efficiency, resulting in photon counting capability with decreased crosstalk and reduced dark current.

Anneal-induced enhancement of refractive index and hardness of silicophosphate glasses containing six-fold coordinated silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Huidan, E-mail: hdzeng@ecust.edu.cn; Jiang, Qi; Li, Xiang

2015-01-12

A considerable number of optical devices have significantly benefited from the development of phosphate glasses as substrate materials. Introducing silica into sodium phosphate is an effective method to enhance its mechanical and optical properties. Through annealing treatment, the tetrahedral silicon oxide network structure (Si{sup (4)}) can be transformed into an octahedral structure (Si{sup (6)}) with more constraints. Here, we use high-temperature Raman and Nuclear Magnetic Resonance to reveal the mechanism of transformation between the Si{sup (4)} and Si{sup (6)} silicon oxide structures. The increase of the Si{sup (6)} content results in the phosphate glasses having higher refractive index and hardness.more » Based on this, the refractive index contribution of SiO{sub 6} is obtained.« less

Evaluating the Relationships Between NTNU/SINTEF Drillability Indices with Index Properties and Petrographic Data of Hard Igneous Rocks

NASA Astrophysics Data System (ADS)

Aligholi, Saeed; Lashkaripour, Gholam Reza; Ghafoori, Mohammad; Azali, Sadegh Tarigh

2017-11-01

Thorough and realistic performance predictions are among the main requisites for estimating excavation costs and time of the tunneling projects. Also, NTNU/SINTEF rock drillability indices, including the Drilling Rate Index™ (DRI), Bit Wear Index™ (BWI), and Cutter Life Index™ (CLI), are among the most effective indices for determining rock drillability. In this study, brittleness value (S20), Sievers' J-Value (SJ), abrasion value (AV), and Abrasion Value Cutter Steel (AVS) tests are conducted to determine these indices for a wide range of Iranian hard igneous rocks. In addition, relationships between such drillability parameters with petrographic features and index properties of the tested rocks are investigated. The results from multiple regression analysis revealed that the multiple regression models prepared using petrographic features provide a better estimation of drillability compared to those prepared using index properties. Also, it was found that the semiautomatic petrography and multiple regression analyses provide a suitable complement to determine drillability properties of igneous rocks. Based on the results of this study, AV has higher correlations with studied mineralogical indices than AVS. The results imply that, in general, rock surface hardness of hard igneous rocks is very high, and the acidic igneous rocks have a lower strength and density and higher S20 than those of basic rocks. Moreover, DRI is higher, while BWI is lower in acidic igneous rocks, suggesting that drill and blast tunneling is more convenient in these rocks than basic rocks.

Widened photonic functionality of asymmetric high-index contrast/photonic crystal gratings

NASA Astrophysics Data System (ADS)

Nguyen, Hai Son; Dubois, Florian; Letartre, Xavier; Leclercq, Jean-Louis; Seassal, Christian; Viktorovitch, Pierre

2016-03-01

In this presentation we emphasize that, within the variety of parameters usable for the design of HCGs, the transverse (vertical) symmetry properties of HCGs provide a power-full joystick for the dispersion engineering of guided mode resonances. We concentrate on asymmetric HCGs designed to accommodate guided mode resonances with ultra-flat zero-curvature dispersion characteristics (or photons with ultra-heavy effective mass), as well as with Dirac cone shaped linear dispersion characteristics. Examples of the great potential of this family of asymmetric HCGs will include the development of a platform for polaritonic devices and the production of micro-lasers particularly suited for hybrid III-V / silicon heterogeneous photonic integration, along CMOS compatible technological schemes.

Silicon Oxycarbide Waveguides for Photonic Applications

NASA Astrophysics Data System (ADS)

Memon, Faisal Ahmed; Morichetti, Francesco; Melloni, Andrea

2018-01-01

Silicon oxycarbide thin films deposited with rf reactive magnetron sputtering a SiC target are exploited to demonstrate photonic waveguides with a high refractive index of 1.82 yielding an index contrast of 18% with silica glass. The propagation losses of the photonic waveguides are measured at the telecom wavelength of 1.55 μm by cut-back technique. The results demonstrate the potential of silicon oxycarbide for photonic applications.

Scaling of the photon index vs. mass accretion rate correlation and estimate of black hole mass in M101 ULX-1

NASA Astrophysics Data System (ADS)

Titarchuk, Lev; Seifina, Elena

2016-01-01

We report the results of Swift and Chandra observations of an ultraluminous X-ray source, ULX-1 in M101. We show strong observational evidence that M101 ULX-1 undergoes spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of M101 ULX-1 are well fitted by the so-called bulk motion Comptonization (BMC) model for all spectral states. We have established the photon index (Γ) saturation level, Γsat = 2.8 ± 0.1, in the Γ versus mass accretion rate (Ṁ) correlation. This Γ-Ṁ correlation allows us to evaluate black hole (BH) mass in M101 ULX-1 to be MBH ~ (3.2-4.3) × 104 M⊙, assuming the spread in distance to M101 (from 6.4 ± 0.5 Mpc to 7.4 ± 0.6 Mpc). For this BH mass estimate we apply the scaling method, using Galactic BHs XTE J1550-564, H 1743-322 and 4U 1630-472 as reference sources. The Γ vs. Ṁ correlation revealed in M101 ULX-1 is similar to that in a number of Galactic BHs and clearly exhibits the correlation along with the strong Γ saturation at ≈ 2.8. This is robust observational evidence for the presence of a BH in M101 ULX-1. We also find that the seed (disk) photon temperatures are low, on the order of 40-100 eV, which is consistent with high BH mass in M101 ULX-1. Thus, we suggest that the central object in M101 ULX-1 has intermediate BH mass on the order of 104 solar masses.

The Hadronic Origin of the Hard Gamma-Ray Spectrum from Blazar 1ES 1101-232

NASA Astrophysics Data System (ADS)

Cao, Gang; Wang, Jiancheng

2014-03-01

The very hard γ-ray spectrum from distant blazars challenges the traditional synchrotron self-Compton (SSC) model, which may indicate that there is a contribution from an additional high-energy component beyond the SSC emission. In this paper, we study the possible origin of the hard γ-ray spectrum from distant blazars. We develop a model to explain the hard γ-ray spectrum from blazar 1ES 1101-232. In the model, the optical and X-ray radiation would come from the synchrotron radiation of primary electrons and secondary pairs and the GeV emission would be produced by the SSC process, however, the hard γ-ray spectrum would originate from the decay of neutral pion produced through proton-photon interactions with the synchrotron radiation photons within the jet. Our model can explain the observed spectral energy distribution of 1ES 1101-232 well, especially the very hard γ-ray spectrum. However, our model requires a very large proton power to efficiently produce the γ-ray through proton-photon interactions.

Manufacturing method of photonic crystal

DOEpatents

Park, In Sung; Lee, Tae Ho; Ahn, Jin Ho; Biswas, Rana; Constant, Kristen P.; Ho, Kai-Ming; Lee, Jae-Hwang

2013-01-29

A manufacturing method of a photonic crystal is provided. In the method, a high-refractive-index material is conformally deposited on an exposed portion of a periodic template composed of a low-refractive-index material by an atomic layer deposition process so that a difference in refractive indices or dielectric constants between the template and adjacent air becomes greater, which makes it possible to form a three-dimensional photonic crystal having a superior photonic bandgap. Herein, the three-dimensional structure may be prepared by a layer-by-layer method.

An index for evaluating difficulty of Chewing Index for chewable tablets.

PubMed

Gupta, Abhay; Chidambaram, Nallaperumal; Khan, Mansoor A

2015-02-01

Chewing difficulty index, a potential measure of difficulty in chewing the chewable tablets, has been described herein as the product of tablet thickness and tablet hardness measured under the diametral loading. The proposed index was evaluated by measuring the dimensions and mechanical strength of commercial and in-house prepared chewable tablets. Data collected on tablets with different thickness but same hardness or tensile strength suggests that the proposed index provides a good assessment of the force needed to chew the chewable tablets. Influence of brief exposure to salivary fluid during chewing on the mechanical strength of the chewable tablets was also evaluated. Thirty seconds exposure to the simulated salivary fluid was also found to significantly reduce (p < 0.05) the hardness and the chewing difficulty index of a number of evaluated chewable tablet drug products.

STATISTICAL STUDY of HARD X-RAY SPECTRAL CHARACTERISTICS OF SOLAR FLARES

NASA Astrophysics Data System (ADS)

Alaoui, M.; Krucker, S.; Saint-Hilaire, P.; Lin, R. P.

2009-12-01

We investigate the spectral characteristics of 75 solar flares at the hard X-ray peak time observed by RHESSI (Ramaty High Energy Solar Spectroscopic Imager) in the energy range 12-150keV. At energies above 40keV, the Hard X-ray emission is mostly produced by bremsstrahlung of suprathermal electrons as they interact with the ambient plasma in the chromosphere. The observed photon spectra therefore provide diagnostics of electron acceleration processes in Solar flares. We will present statistical results of spectral fitting using two models: a broken power law plus a thermal component which is a direct fit of the photon spectrum and a thick target model plus a thermal component which is a fit of the photon spectra with assumptions on the electrons emitting bremsstrahlung in the thick target approximation.

Flexible photonic crystal membranes with nanoparticle high refractive index layers.

PubMed

Karrock, Torben; Paulsen, Moritz; Gerken, Martina

2017-01-01

Flexible photonic crystal slabs with an area of 2 cm 2 are fabricated by nanoimprint replication of a 400 nm period linear grating nanostructure into a ≈60 µm thick polydimethylsiloxane membrane and subsequent spin coating of a high refractive index titanium dioxide nanoparticle layer. Samples are prepared with different nanoparticle concentrations. Guided-mode resonances with a quality factor of Q ≈ 40 are observed. The highly flexible nature of the membranes allows for stretching of up to 20% elongation. Resonance peak positions for unstretched samples vary from 555 to 630 nm depending on the particle concentration. Stretching results in a resonance shift for these peaks of up to ≈80 nm, i.e., 3.9 nm per % strain. The color impression of the samples observed with crossed-polarization filters changes from the green to the red regime. The high tunability renders these membranes promising for both tunable optical devices as well as visualization devices.

Nanoporous hard data: optical encoding of information within nanoporous anodic alumina photonic crystals

NASA Astrophysics Data System (ADS)

Santos, Abel; Law, Cheryl Suwen; Pereira, Taj; Losic, Dusan

2016-04-01

Herein, we present a method for storing binary data within the spectral signature of nanoporous anodic alumina photonic crystals. A rationally designed multi-sinusoidal anodisation approach makes it possible to engineer the photonic stop band of nanoporous anodic alumina with precision. As a result, the transmission spectrum of these photonic nanostructures can be engineered to feature well-resolved and selectively positioned characteristic peaks across the UV-visible spectrum. Using this property, we implement an 8-bit binary code and assess the versatility and capability of this system by a series of experiments aiming to encode different information within the nanoporous anodic alumina photonic crystals. The obtained results reveal that the proposed nanosized platform is robust, chemically stable, versatile and has a set of unique properties for data storage, opening new opportunities for developing advanced nanophotonic tools for a wide range of applications, including sensing, photonic tagging, self-reporting drug releasing systems and secure encoding of information.Herein, we present a method for storing binary data within the spectral signature of nanoporous anodic alumina photonic crystals. A rationally designed multi-sinusoidal anodisation approach makes it possible to engineer the photonic stop band of nanoporous anodic alumina with precision. As a result, the transmission spectrum of these photonic nanostructures can be engineered to feature well-resolved and selectively positioned characteristic peaks across the UV-visible spectrum. Using this property, we implement an 8-bit binary code and assess the versatility and capability of this system by a series of experiments aiming to encode different information within the nanoporous anodic alumina photonic crystals. The obtained results reveal that the proposed nanosized platform is robust, chemically stable, versatile and has a set of unique properties for data storage, opening new opportunities for

Generation of highly confined photonic nanojet using crescent-shape refractive index profile in microsphere

NASA Astrophysics Data System (ADS)

Patel, H. S.; Kushwaha, P. K.; Swami, M. K.

2018-05-01

Photonic nanojets (PNJs) owing to their sub-wavelength near-field features have found many interesting applications like nanoscopy, nano photolithography, high density optical storage, enhancement of Raman signal and single molecule spectroscopy etc. More recently, the focus of research has been on tailoring of PNJs either for better confinement and thus higher peak intensity or for elongation of nanojet for high resolution far field applications. In this paper, we show that crescent-shape refractive index profile (CSRP) of microspheres can be used to generate highly confined PNJ. By optimizing the refractive index of different layers in CSRP microsphere, we show a free space confinement down to ∼ λ / 4 . 5 (FWHM ∼ 110 nm for excitation with 500 nm wavelength). Further, it was observed that the optical properties of substrates also modulate the PNJ characteristics and lead to a further improvement in the transverse confinement to ∼ λ / 6 . 7.

Spatial Resolution and Refractive Index Contrast of Resonant Photonic Crystal Surfaces for Biosensing

PubMed Central

Triggs, G. J.; Fischer, M.; Stellinga, D.; Scullion, M. G.; Evans, G. J. O.; Krauss, T. F.

2015-01-01

By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast Δn. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10−2. We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At Δn = 0.077, we observe resolutions of 2 and 6 μm parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45° results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for Δn < 0.01, where we observe a resolution exceeding 10 μm for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution. PMID:26356353

Photonic band gap and defects modes in inorganic/organic photonic crystal based on Si and HMDSO layers deposited by sputtering and PECVD

NASA Astrophysics Data System (ADS)

Amri, R.; Sahel, S.; Gamra, D.; Lejeune, M.; Clin, M.; Zellama, K.; Bouchriha, H.

2018-02-01

Hybrid inorganic/organic one dimensional photonic crystal based on alternating layers of Si/HMDSO is elaborated. The inorganic silicon is deposited by radiofrequency magnetron sputtering and the organic HMDSO is deposited by PECVD technique. As the Si refractive index is n = 3.4, and the refractive index of HMDSO layer depend on the deposition conditions, to get a photonic crystal with high and low refractive index presenting a good contrast, we have varied the radiofrequency power of PECVD process to obtain HMDSO layer with low refractive index (n = 1.45). Photonic band gap of this hybrid structure is obtained from the transmission and reflection spectra and appears after 9 alternative layers of Si/HMDSO. The introduction of defects in our photonic crystal leads to the emergence of localized modes within the photonic band gap. Our results are interpreted by using a theoretical model based on transfer matrix.

A hard X-ray nanoprobe beamline for nanoscale microscopy

PubMed Central

Winarski, Robert P.; Holt, Martin V.; Rose, Volker; Fuesz, Peter; Carbaugh, Dean; Benson, Christa; Shu, Deming; Kline, David; Stephenson, G. Brian; McNulty, Ian; Maser, Jörg

2012-01-01

The Hard X-ray Nanoprobe Beamline (or Nanoprobe Beamline) is an X-ray microscopy facility incorporating diffraction, fluorescence and full-field imaging capabilities designed and operated by the Center for Nanoscale Materials and the Advanced Photon Source at Sector 26 of the Advanced Photon Source at Argonne National Laboratory. This facility was constructed to probe the nanoscale structure of biological, environmental and material sciences samples. The beamline provides intense focused X-rays to the Hard X-ray Nanoprobe (or Nanoprobe) which incorporates Fresnel zone plate optics and a precision laser sensing and control system. The beamline operates over X-ray energies from 3 to 30 keV, enabling studies of most elements in the periodic table, with a particular emphasis on imaging transition metals. PMID:23093770

A hard X-ray nanoprobe beamline for nanoscale microscopy.

PubMed

Winarski, Robert P; Holt, Martin V; Rose, Volker; Fuesz, Peter; Carbaugh, Dean; Benson, Christa; Shu, Deming; Kline, David; Stephenson, G Brian; McNulty, Ian; Maser, Jörg

2012-11-01

The Hard X-ray Nanoprobe Beamline (or Nanoprobe Beamline) is an X-ray microscopy facility incorporating diffraction, fluorescence and full-field imaging capabilities designed and operated by the Center for Nanoscale Materials and the Advanced Photon Source at Sector 26 of the Advanced Photon Source at Argonne National Laboratory. This facility was constructed to probe the nanoscale structure of biological, environmental and material sciences samples. The beamline provides intense focused X-rays to the Hard X-ray Nanoprobe (or Nanoprobe) which incorporates Fresnel zone plate optics and a precision laser sensing and control system. The beamline operates over X-ray energies from 3 to 30 keV, enabling studies of most elements in the periodic table, with a particular emphasis on imaging transition metals.

Hard breakup of two nucleons from the He3 nucleus

NASA Astrophysics Data System (ADS)

Sargsian, Misak M.; Granados, Carlos

2009-07-01

We investigate a large angle photodisintegration of two nucleons from the He3 nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon breakup reaction through the convolution of photon-quark scattering, NN hard scattering amplitude, and nuclear spectral function, which can be calculated using a nonrelativistic He3 wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for NN scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as s-11. Second, the s11 weighted cross section will have the shape of energy dependence similar to that of s10 weighted NN elastic scattering cross section. Also one predicts an enhancement of the pp breakup relative to the pn breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn breakup cross sections. This is due to the fact that the same-helicity pp-component is strongly suppressed in the ground state wave function of He3. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer NN breakup reactions for circularly polarized photons. For the pp breakup this asymmetry is predicted to be zero while for the pn it is close to (2)/(3).

High index glass thin film processing for photonics and photovoltaic (PV) applications

NASA Astrophysics Data System (ADS)

Ogbuu, Okechukwu Anthony

To favorably compete with fossil-fuel technology, the greatest challenge for thin film solar-cells is to improve efficiency and reduce material cost. Thickness scaling to thin film reduces material cost but affects the light absorption in the cells; therefore a concept that traps incident photons and increases its optical path length is needed to boost absorption in thin film solar cells. One approach is the integration of low symmetric gratings (LSG), using high index material, on either the front-side or backside of 30 um thin c-Si cells. In this study, Multicomponent TeO2--Bi2O 3--ZnO (TBZ) glass thin films were prepared using RF magnetron sputtering under different oxygen flow rates. The influences of oxygen flow rate on the structural and optical properties of the resulting thin films were investigated. The structural origin of the optical property variation was studied using X-ray diffraction, X-ray photoelectron spectroscopy, Raman Spectroscopy, and transmission electron microscopy. The results indicate that TBZ glass thin film is a suitable material for front side LSG material photovoltaic and photonics applications due to their amorphous nature, high refractive index (n > 2), broad band optical transparency window, low processing temperature. We developed a simple maskless method to pattern sputtered tellurite based glass thin films using unconventional agarose hydrogel mediated wet etching. Conventional wet etching process, while claiming low cost and high throughput, suffers from reproducibility and pattern fidelity issues due to the isotropic nature of wet chemical etching when applied to glasses and polymers. This method overcomes these challenges by using an agarose hydrogel stamp to mediate a conformal etching process. In our maskless method, agarose hydrogel stamps are patterned following a standard soft lithography and replica molding process from micropatterned masters and soaked in a chemical etchant. The micro-scale features on the stamp are

Discovery of Diffuse Hard X-ray Emission associated with Jupiter

NASA Astrophysics Data System (ADS)

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

Our discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter is reported. Recent Chandra and XMM-Newton observations revealed several types of X-rays in the vicinity of Jupiter such as auroral and disk emission from Jupiter and faint diffuse X-rays from the Io Plasma Torus (see Bhardwaj et al. 2007 for review). To investigate possible diffuse hard X-ray emission around Jupiter with the highest sensitivity, we conducted data analysis of Suzaku XIS observations of Jupiter on Feb 2006. After removing satellite and planetary orbital motions, we detected a significant diffuse X-ray emission extending to ~6 x 3 arcmin with the 1-5 keV X-ray luminosity of ~3e15 erg/s. The emitting region very well coincided with the Jupiter's radiation belts. The 1-5 keV X-ray spectrum was represented by a simple power law model with a photon index of 1.4. Such a flat continuum strongly suggests non-thermal origin. Although such an emission can be originated from multiple background point sources, its possibility is quite low. We hence examined three mechanisms, assuming that the emission is truly diffuse: bremsstrahlung by keV electrons, synchrotron emission by TeV electrons, and inverse Compton scattering of solar photons by MeV electrons. The former two can be rejected because of the X-ray spectral shape and implausible existence of TeV electrons around Jupiter, respectively. The last possibility was found to be possible because tens MeV electrons, which have been confirmed in inner radiation belts (Bolton et al. 2002), can kick solar photons to the keV energy range and provide a simple power-law continuum. We estimated an average electron density from the X-ray luminosity assuming the oblate spheroid shaped emitting region with 8 x 8 x 4 Jovian radii. The necessary density was 0.02 1/cm3 for 50 MeV electrons. Hence, our results may suggest a new particle acceleration phenomenon around Jupiter.

Efficacy of massage treatment technique in masseter muscle hardness: robotic experimental approach.

PubMed

Hiraiwa, Yuichiro; Ariji, Yoshiko; Kise, Yoshitaka; Sakuma, Shigemitsu; Kurita, Kenichi; Ariji, Eiichiro

2013-10-01

The study aimed to clarify the masseter muscle hardness in patients with myofascial pain, to examine their changes after massage, and to analyze whether the hardness can be an index for massage treatment. Sixteen patients with myofascial pain (12 with unilateral and 4 with bilateral masseter muscle pain) and 24 healthy volunteers were enrolled in this study. The masseter hardness between patients and the healthy volunteers was compared. The changes in the hardness in patients after massage were examined. The relation of the hardness with massage regimens and efficacies was analyzed. There was a significant right-and-left difference of the hardness in patients, although there was no difference in the healthy volunteers. The hardness decreased after massage. The pretreatment asymmetry index of the hardness showed a significant correlation with the massage pressure. It was concluded that there was a significant difference between the right and left masseter hardness in patients with myofascial pain. After massage treatment, the masseter hardness and right-and-left difference decreased. The hardness may be an index for determining the massage pressure.

Integrated Photonics Research Topical Meeting (1993)

DTIC Science & Technology

1994-06-01

81 DMD Time Domain Methods .................................. 107 IME Photonic Circuits and Lightwave Reception...index change near the band edge using a small interference -ellipsometry bridge and presented several results of nt of refractive index change An[51. In... interference -ellipsometry bridge at the photon energies near Eg, especially E>Eg, and compared to previous theories. [11. Manning, R Olshans]y, and C. B. Su

Very hard states in neutron star low-mass X-ray binaries

NASA Astrophysics Data System (ADS)

Parikh, A. S.; Wijnands, R.; Degenaar, N.; Altamirano, D.; Patruno, A.; Gusinskaia, N. V.; Hessels, J. W. T.

2017-07-01

We report on unusually very hard spectral states in three confirmed neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248 and IGR J18245-2452) at a luminosity between ˜1036 and 1037 erg s-1. When fitting the Swift X-ray spectra (0.5-10 keV) in those states with an absorbed power-law model, we found photon indices of Γ ˜ 1, significantly lower than the Γ = 1.5-2.0 typically seen when such systems are in their so called hard state. For individual sources, very hard spectra were already previously identified, but here we show for the first time that likely our sources were in a distinct spectral state (I.e. different from the hard state) when they exhibited such very hard spectra. It is unclear how such very hard spectra can be formed; if the emission mechanism is similar to that operating in their hard states (I.e. up-scattering of soft photons due to hot electrons), then the electrons should have higher temperatures or a higher optical depth in the very hard state compared to those observed in the hard state. By using our obtained Γ as a tracer for the spectral evolution with luminosity, we have compared our results with those obtained by Wijnands et al. Our sample of sources follows the same track as the other neutron star systems in Wijnands et al., confirming their general results. However, we do not find that the accreting millisecond pulsars are systematically harder than the non-pulsating systems.

Hard and flexible optical printed circuit board

NASA Astrophysics Data System (ADS)

Lee, El-Hang; Lee, Hyun Sik; Lee, S. G.; O, B. H.; Park, S. G.; Kim, K. H.

2007-02-01

We report on the design and fabrication of hard and flexible optical printed circuit boards (O-PCBs). The objective is to realize generic and application-specific O-PCBs, either in hard form or flexible form, that are compact, light-weight, low-energy, high-speed, intelligent, and environmentally friendly, for low-cost and high-volume universal applications. The O-PCBs consist of 2-dimensional planar arrays of micro/nano-scale optical wires, circuits and devices that are interconnected and integrated to perform the functions of sensing, storing, transporting, processing, switching, routing and distributing optical signals on flat modular boards. For fabrication, the polymer and organic optical wires and waveguides are first fabricated on a board and are used to interconnect and integrate micro/nano-scale photonic devices. The micro/nano-optical functional devices include lasers, detectors, switches, sensors, directional couplers, multi-mode interference devices, ring-resonators, photonic crystal devices, plasmonic devices, and quantum devices. For flexible boards, the optical waveguide arrays are fabricated on flexible poly-ethylen terephthalate (PET) substrates by UV embossing. Electrical layer carrying VCSEL and PD array is laminated with the optical layer carrying waveguide arrays. Both hard and flexible electrical lines are replaced with high speed optical interconnection between chips over four waveguide channels up to 10Gbps on each. We discuss uses of hard or flexible O-PCBs for telecommunication systems, computer systems, transportation systems, space/avionic systems, and bio-sensor systems.

Reconfigurable topological photonic crystal

NASA Astrophysics Data System (ADS)

Shalaev, Mikhail I.; Desnavi, Sameerah; Walasik, Wiktor; Litchinitser, Natalia M.

2018-02-01

Topological insulators are materials that conduct on the surface and insulate in their interior due to non-trivial topology of the band structure. The edge states on the interface between topological (non-trivial) and conventional (trivial) insulators are topologically protected from scattering due to structural defects and disorders. Recently, it was shown that photonic crystals (PCs) can serve as a platform for realizing a scatter-free propagation of light waves. In conventional PCs, imperfections, structural disorders, and surface roughness lead to significant losses. The breakthrough in overcoming these problems is likely to come from the synergy of the topological PCs and silicon-based photonics technology that enables high integration density, lossless propagation, and immunity to fabrication imperfections. For many applications, reconfigurability and capability to control the propagation of these non-trivial photonic edge states is essential. One way to facilitate such dynamic control is to use liquid crystals (LCs), which allow to modify the refractive index with external electric field. Here, we demonstrate dynamic control of topological edge states by modifying the refractive index of a LC background medium. Background index is changed depending on the orientation of a LC, while preserving the topology of the system. This results in a change of the spectral position of the photonic bandgap and the topological edge states. The proposed concept might be implemented using conventional semiconductor technology, and can be used for robust energy transport in integrated photonic devices, all-optical circuity, and optical communication systems.

Nanoporous hard data: optical encoding of information within nanoporous anodic alumina photonic crystals.

PubMed

Santos, Abel; Law, Cheryl Suwen; Pereira, Taj; Losic, Dusan

2016-04-21

Herein, we present a method for storing binary data within the spectral signature of nanoporous anodic alumina photonic crystals. A rationally designed multi-sinusoidal anodisation approach makes it possible to engineer the photonic stop band of nanoporous anodic alumina with precision. As a result, the transmission spectrum of these photonic nanostructures can be engineered to feature well-resolved and selectively positioned characteristic peaks across the UV-visible spectrum. Using this property, we implement an 8-bit binary code and assess the versatility and capability of this system by a series of experiments aiming to encode different information within the nanoporous anodic alumina photonic crystals. The obtained results reveal that the proposed nanosized platform is robust, chemically stable, versatile and has a set of unique properties for data storage, opening new opportunities for developing advanced nanophotonic tools for a wide range of applications, including sensing, photonic tagging, self-reporting drug releasing systems and secure encoding of information.

Spectral Index and Quasi-Periodic Oscillation Frequency Correlation in Black Hole (BH) Sources: Observational Evidence of Two Phases and Phase Transition in BHs

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Fiorito, Ralph

2004-01-01

Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources, in low hard states, steep power-law (soft) states and in transition between these states. The observations indicate that the X-ray spectrum of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission indicated the probable presence of a jet. Strong QPOs (less than 20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant ( i.e. 60-90% ). This evidence contradicts the dominant long standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model, that identifies and explains the origin of the QPOs and how they are imprinted on the properties of power-law flux component. We argue the existence of a bounded compact coronal region which is a natural consequence of the adjustment of Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) hard state, in which the TL is optically thin and very hot (kT approx. greater than 50 keV) producing photon upscattering via thermal Componization; the photon spectrum index Gamma appprox.1.5 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius; (2) a soft state which is optically thick and relatively cold (approx. less than 5 keV); the index for this state, Gamma approx. 2.8 is determined by soft-photon

Spectral Index and Quasi-Periodic Oscillation Frequency Correlation in Black Hole Sources: Observational Evidence of Two Phases and Phase Transition in Black Holes

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Fiorito, Ralph

2004-01-01

Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasi-periodic oscillations (QPOs) and the spectral power law index of several black hole (BH) candidate sources, in low (hard) states, steep power law (soft) states, and transitions between these states. The observations indicate that the X-ray spectra of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission, indicating the probable presence of a jet. Strong QPOs (>20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant (i.e., 60%90%). This evidence contradicts the dominant, long-standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model that identifies and explains the origin of the QPOs and how they are imprinted on the properties of the power-law flux component. We argue for the existence of a bounded compact coronal region that is a natural consequence of the adjustment of the Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) a hard state, in which the TL is optically thin and very hot (kT approximately greater than 50 keV), producing photon upscattering via thermal Comptonization (the photon spectrum index Gamma approximates 1.7 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius), and (2) a soft state that is optically thick and relatively cold (kT approximately less than 5 keV the index for this state, Gamma

Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction

NASA Astrophysics Data System (ADS)

Sargsian, Misak; Granados, Carlos

2009-05-01

We investigate hard photodisintegration of two nucleons from ^3He nucleus within the framework of hard rescattering model (HRM). In HRM a quark of one nucleon knocked-out by incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with high relative momentum. HRM allows to express the amplitude of two-nucleon break-up reaction through the convolution of photon-quark scattering, NN hard scattering amplitude and nuclear spectral function which can be calculated using nonrelativistic ^3He wave function. HRM predicts several specific features for hard break-up reaction. First, the cross section will approximately scale as s-11. Also one predicts comparable or larger cross section for pp break up as compared to that of pn break-up, which is opposite to what is observed in low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn break-up cross sections. This is due to the fact that same-helicity pp-component is strongly suppressed in the ground state wave function of ^3He. Due to this suppression HRM predicts significantly different asymmetries for the cross section of polarization transfer NN break-up reactions for circularly polarized photons. For the pp break-up this asymmetry is predicted to be zero while for the pn it is close to 23.

Hard Photodisintegration of 3He

NASA Astrophysics Data System (ADS)

Granados, Carlos

2011-02-01

Large angle photodisintegration of two nucleons from the 3He nucleus is studied within the framework of the hard rescattering model (HRM). In the HRM the incoming photon is absorbed by one nucleon's valence quark that then undergoes a hard rescattering reaction with a valence quark from the second nucleon producing two nucleons emerging at large transverse momentum . Parameter free cross sections for pp and pn break up channels are calculated through the input of experimental cross sections on pp and pn elastic scattering. The calculated cross section for pp breakup and its predicted energy dependency are in good agreement with recent experimental data. Predictions on spectator momentum distributions and helicity transfer are also presented.

Spectral and Timing Properties of the Black Hole X-Ray Binary H1743-322 in the Low/Hard State Studied with Suzaku

NASA Astrophysics Data System (ADS)

Shidatsu, M.; Ueda, Y.; Yamada, S.; Done, C.; Hori, T.; Yamaoka, K.; Kubota, A.; Nagayama, T.; Moritani, Y.

2014-07-01

We report on the results from Suzaku observations of the Galactic black hole X-ray binary H1743-322 in the low/hard state during its outburst in 2012 October. We appropriately take into account the effects of dust scattering to accurately analyze the X-ray spectra. The time-averaged spectra in the 1-200 keV band are dominated by a hard power-law component of a photon index of ≈1.6 with a high-energy cutoff at ≈60 keV, which is well described with the Comptonization of the disk emission by the hot corona. We estimate the inner disk radius from the multi-color disk component, and find that it is 1.3-2.3 times larger than the radius in the high/soft state. This suggests that the standard disk was not extended to the innermost stable circular orbit. A reflection component from the disk is detected with R = Ω/2π ≈ 0.6 (Ω is the solid angle). We also successfully estimate the stable disk component independent of the time-averaged spectral modeling by analyzing short-term spectral variability on a ~1 s timescale. A weak low-frequency quasi-periodic oscillation at 0.1-0.2 Hz is detected, whose frequency is found to correlate with the X-ray luminosity and photon index. This result may be explained by the evolution of the disk truncation radius.

Hard X-ray Emission along the Z Track in GX 17 + 2

NASA Astrophysics Data System (ADS)

Ding, G. Q.; Huang, C. P.

2015-09-01

Using the data from the Proportional Counter Array (PCA) and the High-Energy X-ray Timing Experiment (HEXTE) on board Rossi X-Ray Timing Explorer for Z source GX 17 + 2, we investigate the evolution of its PCA spectra and HEXTE spectra along a `Z' track on its hardness-intensity diagram. A hard X-ray tail is detected in the HEXTE spectra. The detected hard X-ray tails are discontinuously scattered throughout the Z track. The found hard X-ray tail hardens from the horizontal branch, through the normal branch, to the flaring branch in principle and it contributes ˜(20-50)% of the total flux in 20-200 keV. Our joint fitting results of the PCA + HEXTE spectra in 3-200 keV show that the portion of Comptonization in the Bulk-Motion Comptonization (BMC) model accounts for the hard X-ray tail, which indicates that the BMC process could be responsible for the detected hard tail. The temperature of the seed photons for BMC is ˜2.7 keV, implying that these seed photons might be emitted from the surface of the neutron star (NS) or the boundary layer between the NS and the disk and, therefore, this process could take place around the NS or in the boundary layer.

Hard X-ray index of refraction tomography of a whole rabbit knee joint: A feasibility study.

PubMed

Gasilov, S; Mittone, A; Horng, A; Geith, T; Bravin, A; Baumbach, T; Coan, P

2016-12-01

We report results of the computed tomography reconstruction of the index of refraction in a whole rabbit knee joint examined at the photon energy of 51keV. Refraction based images make it possible to delineate the bone, cartilage, and soft tissues without adjusting the contrast window width and level. Density variations, which are related to tissue composition and are not visible in absorption X-ray images, are detected in the obtained refraction based images. We discuss why refraction-based images provide better detectability of low contrast features than absorption images. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Polarization observables in hard rescattering mechanism of deuteron photodisintegration

NASA Astrophysics Data System (ADS)

Sargsian, Misak M.

2004-05-01

Polarization properties of high energy photodisintegration of the deuteron are studied within the framework of the hard rescattering mechanism (HRM). In HRM, a quark of one nucleon knocked-out by the incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with high relative momentum. Summation of all relevant quark rescattering amplitudes allows us to express the scattering amplitude of the reaction through the convolution of a hard photon-quark interaction vertex, the large angle p-n scattering amplitude and the low momentum deuteron wave function. Within HRM, it is demonstrated that the polarization observables in hard photodisintegration of the deuteron can be expressed through the five helicity amplitudes of NN scattering at high momentum transfer. At 90° CM scattering HRM predicts the dominance of the isovector channel of hard pn rescattering, and it explains the observed smallness of induced, Py and transfered, Cx polarizations without invoking the argument of helicity conservation. Namely, HRM predicts that Py and Cx are proportional to the φ5 helicity amplitude which vanishes at θcm=90° due to symmetry reasons. HRM predicts also a nonzero value for Cz in the helicity-conserving regime and a positive Σ asymmetry which is related to the dominance of the isovector channel in the hard reinteraction. We extend our calculations to the region where large polarization effects are observed in pp scattering as well as give predictions for angular dependences.

Comprehensive Analysis of RXTE Data from Cyg X-1. Spectral Index-Quasi-Periodic Oscillation Frequency-Luminosity Correlations

NASA Technical Reports Server (NTRS)

Shaposhnikov, Nickolai; Titarchuk, Lev

2006-01-01

We present timing and spectral analysis of approx. 2.2 Ms of Rossi X-ray Time Explorer (RXTE) archival data from Cyg X-1. Using the generic Comptonization model we reveal that the spectrum of Cyg X-1 consists of three components: a thermal seed photon spectrum, a Comptonized part of the seed photon spectrum and the iron line. We find a strong correlation between 0.1-20 Hz frequencies of quasiperiodic oscillations (QPOs) and the spectral power-law index. Presence of two spectral phases (states) are clearly seen in the data when the spectral indices saturate at low and high values of QPO frequencies. This saturation effect was discovered earlier in a number of black hole candidate (BHC) sources and now we strongly confirm this phenomenon in Cyg X-1. In the soft state this index- QPO frequency correlation shows a saturation of the photon index Gamma approx. 2.1 at high values of the low frequency upsilon(sub L). The saturation level of Gamma approx. 2.1 is the lowest value found yet in BHCs. The bolometric luminosity does not show clear correlation with the index. We also show that Fe K(sub alpha) emission line strength (equivalent width, EW) correlates with the QPO frequency. EW increases from 200 eV in the low/hard state to 1.5 keV in the high/soft state. The revealed observational correlations allow us to propose a scenario for the spectral transition and iron line formation which occur in BHC sources. We also present the spectral state (the power-law index) evolution for eight years of Cyg X-1 observations by RXTE.

Brain refractive index measured in vivo with high-NA defocus-corrected full-field OCT and consequences for two-photon microscopy.

PubMed

Binding, Jonas; Ben Arous, Juliette; Léger, Jean-François; Gigan, Sylvain; Boccara, Claude; Bourdieu, Laurent

2011-03-14

Two-photon laser scanning microscopy (2PLSM) is an important tool for in vivo tissue imaging with sub-cellular resolution, but the penetration depth of current systems is potentially limited by sample-induced optical aberrations. To quantify these, we measured the refractive index n' in the somatosensory cortex of 7 rats in vivo using defocus optimization in full-field optical coherence tomography (ff-OCT). We found n' to be independent of imaging depth or rat age. From these measurements, we calculated that two-photon imaging beyond 200 µm into the cortex is limited by spherical aberration, indicating that adaptive optics will improve imaging depth.

High-sensitivity refractive index sensors based on fused tapered photonic crystal fiber

NASA Astrophysics Data System (ADS)

Fu, Xing-hu; Xie, Hai-yang; Yang, Chuan-qing; Qu, Yu-wei; Zhang, Shun-yang; Fu, Guang-wei; Guo, Xuan; Bi, Wei-hong

2016-05-01

In this paper, a novel liquid refractive index (RI) sensor based on fused tapered photonic crystal fiber (PCF) is proposed. It is fabricated by fusing and tapering a section of PCF which is spliced with two single-mode fibers (SMFs). Due to the fused biconical taper method, the sensor becomes longer and thinner, to make the change of the outside RI has more direct effects on the internal optical field of the PCF, which finally enhances the sensitivity of this sensor. Experimental results show that the transmission spectra of the sensor are red-shifted obviously with the increase of RI. The longer the tapered region of the sensor, the higher the sensitivity is. This sensor has the advantages of simple structure, easy fabrication, high performance and so on, so it has potential applications in RI measurement.

Low index contrast heterostructure photonic crystal cavities with high quality factors and vertical radiation coupling

NASA Astrophysics Data System (ADS)

Ge, Xiaochen; Minkov, Momchil; Fan, Shanhui; Li, Xiuling; Zhou, Weidong

2018-04-01

We report here design and experimental demonstration of heterostructure photonic crystal cavities resonating near the Γ point with simultaneous strong lateral confinement and highly directional vertical radiation patterns. The lateral confinement is provided by a mode gap originating from a gradual modulation of the hole radii. High quality factor resonance is realized with a low index contrast between silicon nitride and quartz. The near surface-normal directional emission is preserved when the size of the core region is scaled down. The influence of the cavity size parameters on the resonant modes is also investigated theoretically and experimentally.

Two-Photon Emission of a Hydrogenlike Atom with Photon Polarization and Electron Spin States Taken into Account

NASA Astrophysics Data System (ADS)

Skobelev, V. V.

2017-02-01

The process of two-photon emission ( Ze)* → ( Ze) + 2 γ of a hydrogenlike atom is considered with spin states of the electron and polarization of the photons taken into account, which had not been done before. A general expression for the probability of the process per unit time has been obtained for different polarization states of the photons with a formulation of hard and soft selection rules for the quantum numbers m and l. It is shown that by virtue of the established specifics of the properties of the two-photon emission process (absence of a Zeeman effect and dependence of the probability on the polarization states of the photons), it can in principle be identified against the background of single-photon emission ( Ze)* → ( Ze) + γ, despite the presence of additional small factors: 1) α = e 2/ ћc ≈ 1/137 of the perturbation theory in e, and 2) the square of the atomic expansion parameter ( Zα)2 in the expression for the probability.

Low loss photonic components in high index bismuth borate glass by femtosecond laser direct writing.

PubMed

Yang, Weijia; Corbari, Costantino; Kazansky, Peter G; Sakaguchi, Koichi; Carvalho, Isabel C S

2008-09-29

Single mode, low loss waveguides were fabricated in high index bismuth borate glass by femtosecond laser direct writing. A specific set of writing parameters leading to waveguides perfectly mode matched to standard single-mode fibers at 1.55 microm with an overall insertion loss of approximately 1 dB and with propagation loss below 0.2 dB/cm was identified. Photonic components such as Y-splitters and directional couplers were also demonstrated. A close agreement between their performances and theoretical predictions based upon the characterization of the waveguide properties is shown. Finally, the nonlinear refractive index of the waveguides has been measured to be 6.6 x 10(-15) cm(2)/W by analyzing self-phase modulation of the propagating femtosecond laser pulse at the wavelength of 1.46 microm. Broadening of the transmitted light source as large as 500 nm was demonstrated through a waveguide with the length of 1.8 cm.

Holographic photon production in heavy ion collisions

NASA Astrophysics Data System (ADS)

Iatrakis, Ioannis; Kiritsis, Elias; Shen, Chun; Yang, Di-Lun

2017-04-01

The thermal-photon emission from strongly coupled gauge theories at finite temperature is calculated using holographic models for QCD in the Veneziano limit (V-QCD). The emission rates are then embedded in hydrodynamic simulations combined with prompt photons from hard scattering and the thermal photons from hadron gas to analyze the spectra and anisotropic flow of direct photons at RHIC and LHC. The results from different sources responsible for the thermal photons in QGP including the weakly coupled QGP (wQGP) from perturbative calculations, strongly coupled N = 4 super Yang-Mills (SYM) plasma (as a benchmark for reference), and Gubser's phenomenological holographic model are then compared. It is found that the direct-photon spectra are enhanced in the strongly coupled scenario compared with the ones in the wQGP, especially at high momenta. Moreover, both the elliptic flow and triangular flow of direct photons are amplified at high momenta for V-QCD and the SYM plasma. The results are further compared with experimental observations.

Numerical and experimental investigation of long-period gratings in photonic crystal fiber for refractive index sensing of gas media.

PubMed

Tian, Fei; He, Zonghu; Du, Henry

2012-02-01

We have used the finite-difference frequency-domain (FDFD) method to simulate the core mode to cladding mode couplings in long-period gratings (LPGs) in photonic crystal fiber (PCF). Four sets of LPG-PCF have been fabricated with respective periodicities of 590, 540, 515, and 490 μm, resulting in corresponding resonance wavelengths (RWs) of 1241, 1399, 1494, and 1579 nm. We show both theoretically and experimentally that the longer the RW, the more sensitive the LPG-PCF is to the index change in Ar. We demonstrate a robust sensitivity of 517 nm per refractive index unit using the LPG-PCF at 1579 nm RW.

Dressed Hard States and Black Hole Soft Hair.

PubMed

Mirbabayi, Mehrdad; Porrati, Massimo

2016-11-18

A recent, intriguing Letter by Hawking, Perry, and Strominger suggests that soft photons and gravitons can be regarded as black hole hair and may be relevant to the black hole information paradox. In this Letter we make use of factorization theorems for infrared divergences of the S matrix to argue that by appropriately dressing in and out hard states, the soft-quanta-dependent part of the S matrix becomes essentially trivial. The information paradox can be fully formulated in terms of dressed hard states, which do not depend on soft quanta.

Nonlinear silicon photonics

NASA Astrophysics Data System (ADS)

Borghi, M.; Castellan, C.; Signorini, S.; Trenti, A.; Pavesi, L.

2017-09-01

Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.

Coexistence of positive and negative refractive index sensitivity in the liquid-core photonic crystal fiber based plasmonic sensor.

PubMed

Shuai, Binbin; Xia, Li; Liu, Deming

2012-11-05

We present and numerically characterize a liquid-core photonic crystal fiber based plasmonic sensor. The coupling properties and sensing performance are investigated by the finite element method. It is found that not only the plasmonic mode dispersion relation but also the fundamental mode dispersion relation is rather sensitive to the analyte refractive index (RI). The positive and negative RI sensitivity coexist in the proposed design. It features a positive RI sensitivity when the increment of the SPP mode effective index is larger than that of the fundamental mode, but the sensor shows a negative RI sensitivity once the increment of the fundamental mode gets larger. A maximum negative RI sensitivity of -5500nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.50-1.53. The effects of the structural parameters on the plasmonic excitations are also studied, with a view of tuning and optimizing the resonant spectrum.

In-line optofluidic refractive index sensing in a side-channel photonic crystal fiber.

PubMed

Zhang, Nan; Humbert, Georges; Wu, Zhifang; Li, Kaiwei; Shum, Perry Ping; Zhang, Nancy Meng Ying; Cui, Ying; Auguste, Jean-Louis; Dinh, Xuan Quyen; Wei, Lei

2016-11-28

An in-line optofluidic refractive index (RI) sensing platform is constructed by splicing a side-channel photonic crystal fiber (SC-PCF) with side-polished single mode fibers. A long-period grating (LPG) combined with an intermodal interference between LP₀₁ and LP₁₁ core modes is used for sensing the RI of the liquid in the side channel. The resonant dip shows a nonlinear wavelength shift with increasing RI over the measured range from 1.3330 to 1.3961. The RI response of this sensing platform for a low RI range of 1.3330-1.3780 is approximately linear, and exhibits a sensitivity of 1145 nm/RIU. Besides, the detection limit of our sensing scheme is improved by around one order of magnitude by introducing the intermodal interference.

Photonic crystal sensors: Physics and applications

NASA Astrophysics Data System (ADS)

Dinodiya, Sapna; Suthar, B.; Bhargava, A.

2018-05-01

Photonic sensors have evolved rapidly in last few decades because of the major requirement of sensing applications in optical communication and biomedical diagnostics. Photonic crystals are of tremendous use in designing photonic sensors. Any physical phenomenon, for instance temperature, pressure, strain, and presence of chemicals and bio molecules that can alter periodicity and refractive index of structure of the photonic crystal, can be sensed by measuring optical properties like spectral pattern of reflected and transmitted power. The physics and applications of various photonic crystal sensors are presented in this article.

Experimental Overview of Direct Photon Results in Heavy Ion Collisions

NASA Astrophysics Data System (ADS)

Novitzky, Norbert

2016-07-01

Direct photons are color blind probes and thus they provide unique opportunities to study the colored medium created in heavy ion collisions. There are many different sources of direct photons each probing different physics processes as the system evolves. In basic 2 → 2 processes the prompt photons from primary hard scatterings offer the most precise measurements of the outgoing parton energy in the opposite direction. In heavy ion collisions the created medium emits photons as thermal radiation, whose rate and anisotropies provide a unique prospective on the properties and evolution of the system. Recent results on direct photons from the LHC and RHIC experiments are briefly summarized in this paper.

Enhanced emission of quantum dots embedded within the high-index dielectric regions of photonic crystal slabs

DOE Office of Scientific and Technical Information (OSTI.GOV)

See, Gloria G.; Naughton, Matt S.; Kenis, Paul J. A.

2016-04-25

We demonstrate a method for combining sputtered TiO{sub 2} deposition with liquid phase dip-coating of a quantum dot (QD) layer that enables precise depth placement of QD emitters within a high-index dielectric film, using a photonic crystal (PC) slab resonator to demonstrate enhanced emission from the QDs when they are located at a specific depth within the film. The depth of the QDs within the PC is found to modulate the resonant wavelength of the PC as well as the emission enhancement efficiency, as the semiconducting material embedded within the dielectric changes its spatial overlap with the resonant mode.

In-line photonic microcells based on the elliptical microfibers for refractive index sensors applications

NASA Astrophysics Data System (ADS)

Jin, Wa; Liu, Xuejing; Jin, Wei

2017-10-01

We report the fabrication of in-line photonic microcells (PMCs) by encapsulating tapered elliptical microfibers (MFs) inside glass tubes. The encapsulation does not change the optical property of the MF but protects the elliptical MF from external disturbance and contamination and makes the micro-laboratory robust. Such micro-laboratory can be easily integrated into standard fiber-optic circuits with low loss, making the elliptical MF-based devices more practical for real-world applications. Evanescent field sensing is realized by fabricating micro-channel on the PMC for ingress/egress of sample liquids/gas. Based on the encapsulated elliptical MF PMCs, we demonstrated RI sensitivity of 2024 nm per refractive index unit (nm/RIU) in gaseous environment and 21231 nm/RIU in water.

Analysis of an optically controlled photonic switch.

PubMed

Attard, A E

1999-05-20

The principle that the coupling of light between two fiber waveguides can be controlled by the resonant interference of a third waveguide has been developed [Attard, Appl. Opt. 37, 2296-2302 (1998)]. Here significant details concerning the operation of a photonic switch are obtained, and a more complete analysis is presented. Multiple-resonant conditions are identified for slab and fiber control waveguides at large indices of refraction. Thus a selection of materials with an appropriate refractive index and a Kerr coefficient is rendered more easily. Furthermore it is shown that the light used to control the index of refraction in the control waveguide does not enter the output of the photonic switch but remains confined to the control waveguide, for either a slab or a multimode fiber control waveguide. Spatial fluctuations of the control light beam in the control waveguide do not affect the operation of the photonic switch. Tolerances have been determined for the spacing between the control waveguide and the photonic coupler and also for the index of refraction of the control waveguide.

Square array photonic crystal fiber-based surface plasmon resonance refractive index sensor

NASA Astrophysics Data System (ADS)

Liu, Min; Yang, Xu; Zhao, Bingyue; Hou, Jingyun; Shum, Ping

2017-12-01

Based on surface plasmon resonance (SPR), a novel refractive index (RI) sensor comprising a square photonic crystal fiber (PCF) is proposed to realize the detection of the annular analyte. Instead of hexagon structure, four large air-holes in a square array are introduced to enhance the sensitivity by allowing two polarization directions of the core mode to be more sensitive. The gold is used as the only plasmonic material. The design purpose is to reduce the difficulty in gold deposition and enhance the RI sensitivity. The guiding properties and the effects of the parameters on the performance of the sensor are numerically investigated by the Finite Element Method (FEM). By optimizing the structure, the sensor can exhibit remarkable sensitivity up to 7250 nm/RIU and resolution of 1.0638 × 10-5 RIU with only one plasmonic material, which is very competitive compared with the other reported externally coated and single-layer coated PCF-based SPR (PCF-SPR) sensors, to our best knowledge.

Observation of hard scattering in photoproduction at HERA

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Sugano, K.; Stanek, R.; Talaga, R. L.; Thron, J.; Arzarello, F.; Ayed, R.; Barbagli, G.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; D'Auria, S.; Del Papa, C.; Frasconi, F.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Lin, Q.; Lisowski, B.; Maccarrone, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Barreiro, F.; Crittenden, J.; Dabbous, H.; Desch, K.; Diekmann, B.; Geerts, M.; Geitz, G.; Gutjahr, B.; Hartmann, H.; Hartmann, J.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Kramarczyk, S.; Kückes, M.; Mass, A.; Mengel, S.; Mollen, J.; Müsch, H.; Paul, E.; Schattevoy, R.; Schneider, B.; Schneider, J.-L.; Wedemeyer, R.; Cassidy, A.; Cussans, D. G.; Dyce, N.; Fawcett, H. F.; Foster, B.; Gilmore, R.; Heath, G. P.; Lancaster, M.; Llewellyn, T. J.; Malos, J.; Morgado, C. J. S.; Tapper, R. J.; Wilson, S. S.; Rau, R. R.; Bernstein, A.; Caldwell, A.; Gialas, I.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Barillari, T.; Schioppa, M.; Susinno, G.; Burkot, W.; Chwastowski, J.; Dwuraźny, A.; Eskreys, A.; Nizioł, B.; Jakubowski, Z.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Borzemski, P.; Eskreys, K.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Kulka, J.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kȩdzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Coldewey, C.; Dannemann, A.; Dierks, K.; Dorth, W.; Drews, G.; Erhard, P.; Flasiński, M.; Fleck, I.; Fürtjes, A.; Gläser, R.; Göttlicher, P.; Haas, T.; Hagge, L.; Hain, W.; Hasell, D.; Hultschig, H.; Jahnen, G.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Manczak, O.; Momayezi, M.; Nickel, S.; Notz, D.; Park, I.; Pösnecker, K.-U.; Rohde, M.; Ros, E.; Schneekloth, U.; Schroeder, J.; Schulz, W.; Selonke, F.; Tscheslog, E.; Tsurugai, T.; Turkot, F.; Vogel, W.; Woeniger, T.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, A.; Rethfeldt, C.; Schlenstedt, S.; Casalbuoni, R.; De Curtis, S.; Dominici, D.; Francescato, A.; Nuti, M.; Pelfer, P.; Anzivino, G.; Casaccia, R.; Laakso, I.; De Pasquale, S.; Qian, S.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Forbes, J. R.; Jamieson, V. A.; Raine, C.; Saxon, D. H.; Gloth, G.; Holm, U.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Wick, K.; Hofmann, A.; Kröger, W.; Krüger, J.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Salomon, R.; Seidman, A.; Schott, W.; Wiik, B. H.; Zetsche, F.; Bacon, T. C.; Butterworth, I.; Markou, C.; McQuillan, D.; Miller, D. B.; Mobayyen, M. M.; Prinias, A.; Vorvolakos, A.; Bienz, T.; Kreutzmann, H.; Mallik, U.; McCliment, E.; Roco, M.; Wang, M. Z.; Cloth, P.; Filges, D.; Chen, L.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Cases, G.; Hervás, L.; Labarga, L.; del Peso, J.; Roldán, J.; Terrón, J.; de Trocóniz, J. F.; Ikraiam, F.; Mayer, J. K.; Smith, G. R.; Corriveau, F.; Gilkinson, D. J.; Hanna, D. S.; Hung, L. W.; Mitchell, J. W.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; Ullmann, R.; Bashindzhagyan, G. L.; Ermolov, P. F.; Golubkov, Y. A.; Kuzmin, V. A.; Kuznetsov, E. N.; Savin, A. A.; Voronin, A. G.; Zotov, N. P.; Bentvelsen, S.; Dake, A.; Engelen, J.; de Jong, P.; de Jong, S.; de Kamps, M.; Kooijman, P.; Kruse, A.; van der Lugt, H.; O'Dell, V.; Straver, J.; Tenner, A.; Tiecke, H.; Uijterwaal, H.; Vermeulen, J.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Yoshida, R.; Bylsma, B.; Durkin, L. S.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, S. K.; Romanowski, T. A.; Seidlein, R.; Blair, G. A.; Butterworth, J. M.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Gingrich, D. M.; Hallam-Baker, P. M.; Harnew, N.; Khatri, T.; Long, K. R.; Luffman, P.; McArthur, I.; Morawitz, P.; Nash, J.; Smith, S. J. P.; Roocroft, N. C.; Wilson, F. F.; Abbiendi, G.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Fanin, C.; Gasparini, F.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Lim, J. N.; Oh, B. Y.; Whitmore, J.; Bonori, M.; Contino, U.; D'Agostini, G.; Guida, M.; Iori, M.; Mari, S.; Marini, G.; Mattioli, M.; Monaldi, D.; Nigro, A.; Hart, J. C.; McCubbin, N. A.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Heusch, C.; Hubbard, B.; Leslie, J.; Ng, J. S. T.; O'Shaughnessy, K.; Sadrozinski, H. F.; Seiden, A.; Badura, E.; Biltzinger, J.; Chaves, H.; Rost, M.; Seifert, R. J.; Walenta, A. H.; Weihs, W.; Zech, G.; Dagan, S.; Heifetz, R.; Levy, A.; Zer-Zion, D.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kasai, S.; Kuze, M.; Nagasawa, Y.; Nakao, M.; Okuno, H.; Tokushuku, K.; Watanabe, T.; Yamada, S.; Chiba, M.; Hamatsu, R.; Hirose, T.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Arneodo, M.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Bhadra, S.; Brkic, M.; Burow, B. D.; Chlebana, F. S.; Crombie, M. B.; Hartner, G. F.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Prentice, J. D.; Sampson, C. R.; Stairs, G. G.; Teuscher, R. J.; Yoon, T.-S.; Bullock, F. W.; Catterall, C. D.; Giddings, J. C.; Jones, T. W.; Khan, A. M.; Lane, J. B.; Makkar, P. L.; Shaw, D.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Stojda, K.; Stopczyński, A.; Szwed, R.; Tymieniecka, T.; Walczak, R.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Abramowicz, H.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Montag, A.; Revel, D.; Shapira, A.; Ali, I.; Behrens, B.; Camerini, U.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Lomperski, M.; Loveless, R. J.; Nylander, P.; Ptacek, M.; Reeder, D. D.; Smith, W. H.; Silverstein, S.; Frisken, W. R.; Furutani, K. M.; Iga, Y.; ZEUS Collaboration

1992-12-01

We report a study of electron proton collisions at very low Q2, corresponding to virtual photoproduction at centre of mass energies in the range 100-295 GeV. The distribution in transverse energy of the observed hadrons is much harder than can be explained by soft processes. Some of the events show back-to-back two-jet production at the rate and with the characteristics expected from hard two-body scattering. A subset of the two-jet events have energy in the electron direction consistent with that expected from the photon remnant in resolved photon processes.

Probing buried layers by photoelectron spectromicroscopy with hard x-ray excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiemann, C.; Patt, M.; Cramm, S.

We report about a proof-of-principle experiment which explores the perspectives of performing hard x-ray photoemission spectromicroscopy with high lateral resolution. Our results obtained with an energy-filtered photoemission microscope at the PETRA III storage ring facility using hard x-ray excitation up to 6.5 keV photon energy demonstrate that it is possible to obtain selected-area x-ray photoemission spectra from regions less than 500 nm in diameter.

Harmonic distortion in microwave photonic filters.

PubMed

Rius, Manuel; Mora, José; Bolea, Mario; Capmany, José

2012-04-09

We present a theoretical and experimental analysis of nonlinear microwave photonic filters. Far from the conventional condition of low modulation index commonly used to neglect high-order terms, we have analyzed the harmonic distortion involved in microwave photonic structures with periodic and non-periodic frequency responses. We show that it is possible to design microwave photonic filters with reduced harmonic distortion and high linearity even under large signal operation.

Magneto-photonic crystal optical sensors with sensitive covers

NASA Astrophysics Data System (ADS)

Dissanayake, Neluka; Levy, Miguel; Chakravarty, A.; Heiden, P. A.; Chen, N.; Fratello, V. J.

2011-08-01

We report on a magneto-photonic crystal on-chip optical sensor for specific analyte detection with polypyrrole and gold nano particles as modified photonic crystal waveguide cover layers. The reaction of the active sensor material with various analytes modifies the electronic structure of the sensor layer causing changes in its refractive index and a strong transduction signal. Magneto-photonic crystal enhanced polarization rotation sensitive to the nature of the cover layer detects the index modification upon analyte adsorption. A high degree of selectivity and sensitivity are observed for aqueous ammonia and methanol with polypyrrole and for thiolated-gold- with gold-nanoparticles covers.

Towards shot-noise limited diffraction experiments with table-top femtosecond hard x-ray sources.

PubMed

Holtz, Marcel; Hauf, Christoph; Weisshaupt, Jannick; Salvador, Antonio-Andres Hernandez; Woerner, Michael; Elsaesser, Thomas

2017-09-01

Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu K α wavelength with a photon flux of up to 10 9 photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments. We present a detailed analysis of the photon statistics and temporal fluctuations of the x-ray flux, together with experimental strategies to optimize the sensitivity of optical pump/x-ray probe experiments. We demonstrate measurements close to the shot-noise limit of the x-ray source.

Towards shot-noise limited diffraction experiments with table-top femtosecond hard x-ray sources

PubMed Central

Holtz, Marcel; Hauf, Christoph; Weisshaupt, Jannick; Salvador, Antonio-Andres Hernandez; Woerner, Michael; Elsaesser, Thomas

2017-01-01

Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu Kα wavelength with a photon flux of up to 109 photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments. We present a detailed analysis of the photon statistics and temporal fluctuations of the x-ray flux, together with experimental strategies to optimize the sensitivity of optical pump/x-ray probe experiments. We demonstrate measurements close to the shot-noise limit of the x-ray source. PMID:28795079

Beamlike photon pairs entangled by a 2x2 fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lo, Hsin-Pin; Department of Electrophysics, National Chiao-Tung University, Hsinchu, 300, Taiwan; Yabushita, Atsushi

Polarization-entangled photon pairs have been widely used as a light source of quantum communication. The polarization-entangled photon pairs are generally obtained at the crossing points of the light cones that are generated from a type-II nonlinear crystal. However, it is hard to pick up the photon pairs coming out from the crossing points because of their invisible wavelength and low intensity. In our previous work, we succeeded in generating polarization-entangled photon pairs by overlapping two light paths for the photon-pair generation. The photon pairs could be entangled in all of the generated photon pairs without clipping the crossing points, evenmore » with some difficulty in its alignment to overlap the two light paths. In this paper, we have developed an optical system which generates polarization-entangled photon pairs using a beamlike photon pair, without the difficulty in alignment. The measured results show that the photon pairs generated in the system are entangled in their polarizations.« less

Photonic crystal surface-emitting lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2015-06-23

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-planemore » feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.« less

A stable wavelength-tunable triggered source of single photons and cascaded photon pairs at the telecom C-band

NASA Astrophysics Data System (ADS)

Zeuner, Katharina D.; Paul, Matthias; Lettner, Thomas; Reuterskiöld Hedlund, Carl; Schweickert, Lucas; Steinhauer, Stephan; Yang, Lily; Zichi, Julien; Hammar, Mattias; Jöns, Klaus D.; Zwiller, Val

2018-04-01

The implementation of fiber-based long-range quantum communication requires tunable sources of single photons at the telecom C-band. Stable and easy-to-implement wavelength-tunability of individual sources is crucial to (i) bring remote sources into resonance, (ii) define a wavelength standard, and (iii) ensure scalability to operate a quantum repeater. So far, the most promising sources for true, telecom single photons are semiconductor quantum dots, due to their ability to deterministically and reliably emit single and entangled photons. However, the required wavelength-tunability is hard to attain. Here, we show a stable wavelength-tunable quantum light source by integrating strain-released InAs quantum dots on piezoelectric substrates. We present triggered single-photon emission at 1.55 μm with a multi-photon emission probability as low as 0.097, as well as photon pair emission from the radiative biexciton-exciton cascade. We achieve a tuning range of 0.25 nm which will allow us to spectrally overlap remote quantum dots or tuning distant quantum dots into resonance with quantum memories. This opens up realistic avenues for the implementation of photonic quantum information processing applications at telecom wavelengths.

Imaging of cochlear tissue with a grating interferometer and hard X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, Claus-Peter; Shintani-Smith, Stephanie; Fishman, Andrew

This article addresses an important current development in medical and biological imaging: the possibility of imaging soft tissue at resolutions in the micron range using hard X-rays. Challenging environments, including the cochlea, require the imaging of soft tissue structure surrounded by bone. We demonstrate that cochlear soft tissue structures can be imaged with hard X-ray phase contrast. Furthermore, we show that only a thin slice of the tissue is required to introduce a large phase shift. It is likely that the phase contrast image of the soft tissue structures is sufficient to image the structures even if surrounded by bone.more » For the present set of experiments, structures with low-absorption contrast have been visualized using in-line phase contrast imaging and a grating interferometer. The experiments have been performed at the Advanced Photon Source at Argonne National Laboratories, a third generation source of synchrotron radiation. The source provides highly coherent X-ray radiation with high-photon flux (>10{sup 12} photons/s) at high-photon energies (5-70 keV). Radiographic and light microscopy images of the gerbil cochlear slice samples were compared. It has been determined that a 20-{micro}m thick tissue slice induces a phase shift between 1/3{pi} and 2/3{pi}.« less

Graphene-deposited photonic crystal fibers for continuous refractive index sensing applications.

PubMed

Tan, Y C; Tou, Z Q; Chow, K K; Chan, C C

2015-11-30

We present a pilot demonstration of an optical fiber based refractive index (RI) sensor involving the deposition of graphene onto the surface of a segment of a photonic crystal fiber (PCF) in a fiber-based Mach-Zehnder Interferometer (MZI). The fabrication process is relatively simple and only involves the fusion splicing of a PCF between two single mode fibers. The deposition process relies only on the cold transfer of graphene onto the PCF segment, without the need for further physical or chemical treatment. The graphene overlay modified the sensing scheme of the MZI RI sensor, allowing the sensor to overcome limitations to its detectable RI range due to free spectral range issues. This modification also allows for continuous measurements to be obtained without the need for reference values for the range of RIs studied and brings to light the potential for simultaneous dual parameter sensing. The sensor was able to achieve a RI sensitivity of 9.4 dB/RIU for the RIs of 1.33-1.38 and a sensitivity of 17.5 dB/RIU for the RIs of 1.38-1.43. It also displayed good repeatability and the results obtained were consistent with the modeling.

Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

NASA Astrophysics Data System (ADS)

Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

2016-02-01

We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

A biosensor based on photonic crystal surface waves with an independent registration of the liquid refractive index.

PubMed

Konopsky, Valery N; Alieva, Elena V

2010-01-15

A high-precision optical biosensor technique capable of independently determining the refractive index (RI) of liquids is presented. Photonic crystal surface waves were used to detect surface binding events, while an independent registration of the critical angle was used for accurate determination of the liquid RI. This technique was tested using binding of biotin molecules to a streptavidin monolayer at low and high biotin concentrations. The attained baseline noise is 5x10(-13) m/Hz(1/2) for adlayer thickness changes and 9x10(-8) RIU/Hz(1/2) for RI changes. Copyright 2009 Elsevier B.V. All rights reserved.

Manipulation of photons at the surface of three-dimensional photonic crystals.

PubMed

Ishizaki, Kenji; Noda, Susumu

2009-07-16

In three-dimensional (3D) photonic crystals, refractive-index variations with a periodicity comparable to the wavelength of the light passing through the crystal give rise to so-called photonic bandgaps, which are analogous to electronic bandgaps for electrons moving in the periodic electrostatic potential of a material's crystal structure. Such 3D photonic bandgap crystals are envisioned to become fundamental building blocks for the control and manipulation of photons in optical circuits. So far, such schemes have been pursued by embedding artificial defects and light emitters inside the crystals, making use of 3D bandgap directional effects. Here we show experimentally that photons can be controlled and manipulated even at the 'surface' of 3D photonic crystals, where 3D periodicity is terminated, establishing a new and versatile route for photon manipulation. By making use of an evanescent-mode coupling technique, we demonstrate that 3D photonic crystals possess two-dimensional surface states, and we map their band structure. We show that photons can be confined and propagate through these two-dimensional surface states, and we realize their localization at arbitrary surface points by designing artificial surface-defect structures through the formation of a surface-mode gap. Surprisingly, the quality factors of the surface-defect mode are the largest reported for 3D photonic crystal nanocavities (Q up to approximately 9,000). In addition to providing a new approach for photon manipulation by photonic crystals, our findings are relevant for the generation and control of plasmon-polaritons in metals and the related surface photon physics. The absorption-free nature of the 3D photonic crystal surface may enable new sensing applications and provide routes for the realization of efficient light-matter interactions.

Analysis of wave propagation in a two-dimensional photonic crystal with negative index of refraction: plane wave decomposition of the Bloch modes.

PubMed

Martínez, Alejandro; Míguez, Hernán; Sánchez-Dehesa, José; Martí, Javier

2005-05-30

This work presents a comprehensive analysis of electromagnetic wave propagation inside a two-dimensional photonic crystal in a spectral region in which the crystal behaves as an effective medium to which a negative effective index of refraction can be associated. It is obtained that the main plane wave component of the Bloch mode that propagates inside the photonic crystal has its wave vector k' out of the first Brillouin zone and it is parallel to the Poynting vector ( S' ? k'> 0 ), so light propagation in these composites is different from that reported for left-handed materials despite the fact that negative refraction can take place at the interface between air and both kinds of composites. However, wave coupling at the interfaces is well explained using the reduced wave vector ( k' ) in the first Brillouin zone, which is opposed to the energy flow, and agrees well with previous works dealing with negative refraction in photonic crystals.

Excitation of Bloch surface wave on tapered fiber coated with one-dimensional photonic crystal for refractive index sensing.

PubMed

Tu, Tianyu; Pang, Fufei; Zhu, Shan; Cheng, Jiajing; Liu, Huanhuan; Wen, Jianxiang; Wang, Tingyun

2017-04-17

We have theoretically and experimentally demonstrated a novel approach to excite Bloch surface wave (BSW) on tapered optical fibers, which are coated with one-dimensional photonic crystal (1DPC) consisting of periodic TiO₂ and Al₂O₃ by atomic layer deposition technology. Two resonant dips are found in transmission spectra that are originated from the excitation of BSW for p-polarized light and s-polarized light, respectively. For the first time, we have demonstrated the developed device for refractive index (RI) sensing.

Hard QCD rescattering in few nucleon systems

NASA Astrophysics Data System (ADS)

Maheswari, Dhiraj; Sargsian, Misak

2017-01-01

The theoretical framework of hard QCD rescattering mechanism (HRM) is extended to calculate the high energy γ3 He -> pd reaction at 900 center of mass angle. In HRM model , the incoming high energy photon strikes a quark from one of the nucleons in the target which subsequently undergoes hard rescattering with the quarks from the other nucleons generating hard two-body baryonic system in the final state of the reaction. Based on the HRM, a parameter free expression for the differential cross section for the reaction is derived, expressed through the 3 He -> pd transition spectral function, hard pd -> pd elastic scattering cross section and the effective charge of the quarks being interchanged in the hard rescattering process. The numerical estimates obtained from this expression for the differential cross section are in a good agreement with the data recently obtained at the Jefferson Lab experiment, showing the energy scaling of cross section with an exponent of s-17, also consistent with the quark counting rule. The angular and energy dependences of the cross section are also predicted within HRM which are in good agreement with the preliminary data of these distributions. Research is supported by the US Department of Energy.

Photon interferometry of Au+Au collisions at the BNL Relativistic Heavy-Ion Collider.

PubMed

Bass, Steffen A; Müller, Berndt; Srivastava, Dinesh K

2004-10-15

We calculate the two-body correlation function of direct photons produced in central Au+Au collisions at the Relativistic Heavy-Ion Collider. Our calculation includes contributions from the early preequilibrium phase in which photons are produced via hard parton scatterings as well as radiation of photons from a thermalized quark-gluon plasma and the subsequent expanding hadron gas. We find that high energy photon interferometry provides a faithful probe of the details of the space-time evolution and of the early reaction stages of the system.

Hard breakup of the deuteron into two Δ -isobars

NASA Astrophysics Data System (ADS)

Granados, Carlos; Sargsian, Misak

2011-04-01

Photodisintegration of the deuteron into two Δ-isobars at large center of mass angles is studied within the QCD hard rescattering model (HRM). According to the HRM, the reaction proceeds in three main steps: the photon knocks the quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons emerging at large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of pn --> ΔΔ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. We predict that the cross section of the deuteron breakup to Δ++Δ- is 4-5 times larger than that of the breakup to the Δ+Δ0 channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard Δ-isobars are the result of the disintegration of initial ΔΔ components of the deuteron wave function. In this case, the angular distributions and cross sections of the breakup in both Δ++Δ- and Δ+Δ0 channels are expected to be similar. This work was supported by U.S. Department of Energy Grant under contract DE-FG02-01ER41172, and by the FIU DEA program.

Magnetic photon splitting and gamma ray burst spectra

NASA Technical Reports Server (NTRS)

Baring, Matthew G.

1992-01-01

The splitting of photons into two photons becomes both possible and significant in magnetic fields in excess of 10(exp 12) Gauss. Below the threshold energy, 2m sub e c(exp 2) for single photon pair production, splitting can be an astronomically observable phenomenon evident in gamma ray burst spectra. In such circumstances, it was found that magnetic photon splitting reprocesses the gamma ray burst continuum by degrading the photon energy, with a net effect that is quite similar to pair cascade reprocessing of the spectrum. Results are presented for the spectral modifications due to splitting, taking into account the different probabilities for splitting for different polarization modes. Unpolarized and polarized pair cascade photon spectra form the input spectra for the model, which calculates the resulting splitting reprocessed spectra numerically by solving the photon kinetic equations for each polarization mode. This inclusion of photon polarizations is found to not alter previous predictions that splitting produce a significant flattening of the hard X ray continuum and a bump at MeV energies below a pair production turnover. The spectrum near the bump is always strongly polarized.

Spin polarized photons from an axially charged plasma at weak coupling: Complete leading order

DOE PAGES

Mamo, Kiminad A.; Yee, Ho-Ung

2016-03-24

In the presence of (approximately conserved) axial charge in the QCD plasma at finite temperature, the emitted photons are spin aligned, which is a unique P- and CP-odd signature of axial charge in the photon emission observables. We compute this “P-odd photon emission rate” in a weak coupling regime at a high temperature limit to complete leading order in the QCD coupling constant: the leading log as well as the constant under the log. As in the P-even total emission rate in the literature, the computation of the P-odd emission rate at leading order consists of three parts: (1) Comptonmore » and pair annihilation processes with hard momentum exchange, (2) soft t- and u-channel contributions with hard thermal loop resummation, (3) Landau-Pomeranchuk-Migdal resummation of collinear bremsstrahlung and pair annihilation. In conclusion, we present analytical and numerical evaluations of these contributions to our P-odd photon emission rate observable.« less

Improvement of density resolution in short-pulse hard x-ray radiographic imaging using detector stacks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borm, B.; Gärtner, F.; Khaghani, D.

2016-09-15

We demonstrate that stacking several imaging plates (IPs) constitutes an easy method to increase hard x-ray detection efficiency. Used to record x-ray radiographic images produced by an intense-laser driven hard x-ray backlighter source, the IP stacks resulted in a significant improvement of the radiograph density resolution. We attribute this to the higher quantum efficiency of the combined detectors, leading to a reduced photon noise. Electron-photon transport simulations of the interaction processes in the detector reproduce the observed contrast improvement. Increasing the detection efficiency to enhance radiographic imaging capabilities is equally effective as increasing the x-ray source yield, e.g., by amore » larger drive laser energy.« less

Non-Thermal Hard X-Ray Emission in Galaxy Clusters Observed with the BeppoSAX PDS

NASA Technical Reports Server (NTRS)

Nevalainen, Jukka H.; Oosterbroeck, T.; Bonamente, Max; Six, N. Frank (Technical Monitor)

2002-01-01

We studied the X-ray emission in a sample of clusters using the BeppoSAX PDS instrument in the 20 -- 80 keV energy band. We estimated the non-thermal cluster emission (HXR) by modeling the thermal contribution from the cluster gas and the non-thermal contamination from the AGN in the field, and propagating the corresponding uncertainties. We also evaluated and propagated the systematic uncertainties due to the background fluctuations. The resulting non-thermal component is detected at a sigma level in approx. 50 % of the non-significantly AGN-contaminated clusters, i.e. in clusters A2142, A2256, A3376, Coma, Ophiuchus and Virgo. Furthermore, Virgo is detected at a 4 sigma level. All the clusters detected at a 2 sigma level exhibit some degree of merger signatures, i.e. deviations from the azimuthally symmetric brightness and temperature distributions, while the relaxed clusters are detected at a lower confidence. The data are consistent with a scenario whereby relaxed clusters have no non-thermal hard X-ray component, whereas merger clusters do, with a 20 -- 80 keV luminosity of approx. 10(exp 42-44)((h(sub 50))(exp -2))(erg/s). Consistent with merger boosting of cluster temperatures, the non-thermal luminosity increases by 2-3 orders of magnitude between the average cluster temperatures 2 and 10 keV, as L(sub NTE) is proportional to T(sup j) with j = 2.4+/-0.3. These results corroborate the assumption which is the essential element in most non-thermal hard X-ray emission models. The co-added spectrum of all non-significantly AGN-contaminated clusters indicates a power-law spectrum for the non-thermal component with a photon index of 1.5+/-0.25 at 1 sigma confidence level. Unless there is a high energy cut-off in the electron velocity distribution, the total spectrum implies that Inverse Compton scatter of Cosmic Microwave Background photons from electron population dominates over the non-thermal bremsstrahlung in producing hard X-rays in clusters on the merger

Temperature-insensitive refractive index sensing by use of micro Fabry-Pérot cavity based on simplified hollow-core photonic crystal fiber.

PubMed

Wang, Ying; Wang, D N; Liao, C R; Hu, Tianyi; Guo, Jiangtao; Wei, Huifeng

2013-02-01

A temperature-insensitive micro Fabry-Pérot (FP) cavity based on simplified hollow-core (SHC) photonic crystal fiber (PCF) is demonstrated. Such a device is fabricated by splicing a section of SHC PCF with single mode fibers at both cleaved ends. An extremely low temperature sensitivity of ~0.273 pm/°C is obtained between room temperature and 900°C. By drilling vertical micro-channels using a femtosecond laser, the micro FP cavity can be filled with liquids and functions as a sensitive refractometer and the refractive index sensitivity obtained is ~851.3 nm/RIU (refractive index unit), which indicates an ultra low temperature cross-sensitivity of ~3.2×10(-7) RIU/°C.

Calibration of a time-resolved hard-x-ray detector using radioactive sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoeckl, C., E-mail: csto@lle.rochester.edu; Theobald, W.; Regan, S. P.

A four-channel, time-resolved, hard x-ray detector (HXRD) has been operating at the Laboratory for Laser Energetics for more than a decade. The slope temperature of the hot-electron population in direct-drive inertial confinement fusion experiments is inferred by recording the hard x-ray radiation generated in the interaction of the electrons with the target. Measuring the energy deposited by hot electrons requires an absolute calibration of the hard x-ray detector. A novel method to obtain an absolute calibration of the HXRD using single photons from radioactive sources was developed, which uses a thermoelectrically cooled, low-noise, charge-sensitive amplifier.

Optical properties of periodic, quasi-periodic, and disordered one-dimensional photonic structures

NASA Astrophysics Data System (ADS)

Bellingeri, Michele; Chiasera, Alessandro; Kriegel, Ilka; Scotognella, Francesco

2017-10-01

Photonic structures are building blocks for many optical applications in which light manipulation is required spanning optical filtering, lasing, light emitting diodes, sensing and photovoltaics. The fabrication of one-dimensional photonic structures is achievable with a variety of different techniques, such as spin coating, sputtering, evaporation, pulse laser deposition, or extrusion. Such different techniques enable facile integration of the photonic structure with many types of devices. Photonic crystals are characterized by a spatial modulation of the dielectric constant on the length scale of the wavelength of light giving rise to energy ranges where light cannot propagate through the crystal - the photonic band gap. While mostly photonic crystals are referred to as periodic arrangements, in this review we aim to highlight as well how aperiodicity and disorder affects light modulation. In this review article, we introduce the concepts of periodicity, quasi-periodicity, and disorder in photonic crystals, focussing on the one-dimensional case. We discuss in detail the physical peculiarities, the fabrication techniques, and the applications of periodic, quasi-periodic, and disorder photonic structures, highlighting how the degree of crystallinity matters in the manipulation of light. We report different types of disorder in 1D photonic structures and we discuss their properties in terms of light transmission. We discuss the relationship between the average total transmission, in a range of wavelengths around the photonic band gap of the corresponding photonic crystal, and the homogeneity of the photonic structures, quantified by the Shannon index. Then we discuss the light transmission in structures in which the high refractive index layers are aggregated in clusters following a power law distribution. Finally, in the case of structures in which the high refractive index layers are aggregated in clusters with a truncated uniform distribution, we discuss: i) how

Jet-conversion photons from an anisotropic quark-gluon plasma

NASA Astrophysics Data System (ADS)

Bhattacharya, Lusaka; Roy, Pradip

2010-10-01

We calculate the pT distributions of jet-conversion photons from a quark-gluon plasma with pre-equilibrium momentum-space anisotropy. A phenomenological model has been used for the time evolution of the hard momentum scale phard(τ) and anisotropy parameter ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of the jet-conversion photon pT distribution. For example, with fixed initial condition pre-equilibrium anisotropy, we predict a significant enhancement of the jet-photon pT distribution in the entire region, whereas for pre-equilibrium anisotropy with fixed final multiplicity (FFM), suppression of the jet-conversion photon pT distribution is observed. The results with FFM (as it is the most realistic situation) have been compared with high pT PHENIX photon data. It is found that the data are reproduced well if the isotropization time lies within 1.5 fm/c.

A novel photonic crystal fiber Mach-Zehnder interferometer for enhancing refractive index measurement sensitivity

NASA Astrophysics Data System (ADS)

Zhao, Yong; Xia, Feng; Hu, Hai-feng; Chen, Mao-qing

2017-11-01

A novel refractive index (RI) sensor based on photonic crystal fiber Mach-Zehnder interferometer (PCF-MZI) was proposed. It was realized by cascading a section of PCF with half-taper collapse regions (HTCRs) between two single mode fibers (SMFs). The relationship between RI sensitivity and interference length of the PCF-MZI was firstly investigated. Both simulation and experimental results showed that RI sensitivity increased with the increase of interference length. Afterwards, influence of HTCR parameters on RI sensitivity was experimentally investigated to further improve the sensitivity. With intensification of arc discharge intensity in HTCR fabrication process, HTCR with larger maximum taper diameter and longer collapsed region length was obtained, which enhanced evanescent field of the PCF-MZI and then generated higher RI sensitivity. Consequently, a high RI sensitivity of 181.96 nm/refractive index unit (RIU) was achieved in the RI range of 1.3333-1.3574. Increasing arc discharge intensity in HTCR fabrication process has the capacity to improve RI sensitivity of PCF-MZI and meanwhile provides higher mechanical strength and longer sensor life compared to the traditional method of tapering the fiber, which improves the RI sensitivity at the cost of reducing mechanical strength of the sensor. This PCF-MZI was characterized by high RI sensitivity, ease of fabrication, high mechanical strength, and robustness.

Hard-sphere-like dynamics in highly concentrated alpha-crystallin suspensions

DOE PAGES

Vodnala, Preeti; Karunaratne, Nuwan; Lurio, Laurence; ...

2018-02-02

The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids.

Hard-sphere-like dynamics in highly concentrated alpha-crystallin suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vodnala, Preeti; Karunaratne, Nuwan; Lurio, Laurence

The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids.

Hard-sphere-like dynamics in highly concentrated alpha-crystallin suspensions

NASA Astrophysics Data System (ADS)

Vodnala, Preeti; Karunaratne, Nuwan; Lurio, Laurence; Thurston, George M.; Vega, Michael; Gaillard, Elizabeth; Narayanan, Suresh; Sandy, Alec; Zhang, Qingteng; Dufresne, Eric M.; Foffi, Giuseppe; Grybos, Pawel; Kmon, Piotr; Maj, Piotr; Szczygiel, Robert

2018-02-01

The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f (q ,τ ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids.

Photonic crystals at visible, x-ray, and terahertz frequencies

NASA Astrophysics Data System (ADS)

Prasad, Tushar

Photonic crystals are artificial structures with a periodically varying refractive index. This property allows photonic crystals to control the propagation of photons, making them desirable components for novel photonic devices. Photonic crystals are also termed as "semiconductors of light", since they control the flow of electromagnetic radiation similar to the way electrons are excited in a semiconductor crystal. The scale of periodicity in the refractive index determines the frequency (or wavelength) of the electromagnetic waves that can be manipulated. This thesis presents a detailed analysis of photonic crystals at visible, x-ray, and terahertz frequencies. Self-assembly and spin-coating methods are used to fabricate colloidal photonic crystals at visible frequencies. Their dispersion characteristics are examined through theoretical as well as experimental studies. Based on their peculiar dispersion property called the superprism effect, a sensor that can detect small quantities of chemical substances is designed. A photonic crystal that can manipulate x-rays is fabricated by using crystals of a non-toxic plant virus as templates. Calculations show that these metallized three-dimensional crystals can find utility in x-ray optical systems. Terahertz photonic crystal slabs are fabricated by standard lithographic and etching techniques. In-plane superprism effect and out-of-plane guided resonances are studied by terahertz time-domain spectroscopy, and verified by numerical simulations.

Hard breakup of the deuteron into two Δ isobars

NASA Astrophysics Data System (ADS)

Granados, Carlos G.; Sargsian, Misak M.

2011-05-01

We study high-energy photodisintegration of the deuteron into two Δ isobars at large center of mass angles within the QCD hard rescattering model (HRM). According to the HRM, the process develops in three main steps: the photon knocks a quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons which have large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of pn→ΔΔ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. Calculations show that the angular distribution and the strength of the photodisintegration is mainly determined by the properties of the pn→ΔΔ scattering. We predict that the cross section of the deuteron breakup to Δ++Δ- is 4-5 times larger than that of the breakup to the Δ+Δ0 channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard Δ isobars are the result of the disintegration of the preexisting ΔΔ components of the deuteron wave function. In this case, one expects the angular distributions and cross sections of the breakup in both Δ++Δ- and Δ+Δ0 channels to be similar.

The photon content of the proton

NASA Astrophysics Data System (ADS)

Manohar, Aneesh V.; Nason, Paolo; Salam, Gavin P.; Zanderighi, Giulia

2017-12-01

The photon PDF of the proton is needed for precision comparisons of LHC cross sections with theoretical predictions. In a recent paper, we showed how the photon PDF could be determined in terms of the electromagnetic proton structure functions F 2 and F L measured in electron-proton scattering experiments, and gave an explicit formula for the PDF including all terms up to next-to-leading order. In this paper we give details of the derivation. We obtain the photon PDF using the factorisation theorem and applying it to suitable BSM hard scattering processes. We also obtain the same PDF in a process-independent manner using the usual definition of PDFs in terms of light-cone Fourier transforms of products of operators. We show how our method gives an exact representation for the photon PDF in terms of F 2 and F L , valid to all orders in QED and QCD, and including all non-perturbative corrections. This representation is then used to give an explicit formula for the photon PDF to one order higher than our previous result. We also generalise our results to obtain formulæ for the polarised photon PDF, as well as the photon TMDPDF. Using our formula, we derive the P γ i subset of DGLAP splitting functions to order αα s and α 2, which agree with known results. We give a detailed explanation of the approach that we follow to determine a photon PDF and its uncertainty within the above framework.

Pupil-segmentation-based adaptive optical correction of a high-numerical-aperture gradient refractive index lens for two-photon fluorescence endoscopy.

PubMed

Wang, Chen; Ji, Na

2012-06-01

The intrinsic aberrations of high-NA gradient refractive index (GRIN) lenses limit their image quality as well as field of view. Here we used a pupil-segmentation-based adaptive optical approach to correct the inherent aberrations in a two-photon fluorescence endoscope utilizing a 0.8 NA GRIN lens. By correcting the field-dependent aberrations, we recovered diffraction-limited performance across a large imaging field. The consequent improvements in imaging signal and resolution allowed us to detect fine structures that were otherwise invisible inside mouse brain slices.

Vacuum birefringence in strong magnetic fields: (II) Complex refractive index from the lowest Landau level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hattori, Koichi, E-mail: khattori@yonsei.ac.kr; Itakura, Kazunori, E-mail: kazunori.itakura@kek.jp; Department of Particle and Nuclear Studies, Graduate University for Advanced Studies

2013-07-15

We compute the refractive indices of a photon propagating in strong magnetic fields on the basis of the analytic representation of the vacuum polarization tensor obtained in our previous paper. When the external magnetic field is strong enough for the fermion one-loop diagram of the polarization tensor to be approximated by the lowest Landau level, the propagating mode in parallel to the magnetic field is subject to modification: The refractive index deviates from unity and can be very large, and when the photon energy is large enough, the refractive index acquires an imaginary part indicating decay of a photon intomore » a fermion–antifermion pair. We study dependences of the refractive index on the propagating angle and the magnetic-field strength. It is also emphasized that a self-consistent treatment of the equation which defines the refractive index is indispensable for accurate description of the refractive index. This self-consistent treatment physically corresponds to consistently including the effects of back reactions of the distorted Dirac sea in response to the incident photon. -- Highlights: •Vacuum birefringence and photon decay are described by the complex refractive index. •Resummed photon vacuum polarization tensor in the lowest Landau level is used. •Back reactions from the distorted Dirac sea are self-consistently taken into account. •Self-consistent treatment drastically changes structure in photon energy dependence. •Dependences on photon propagation angle and magnetic-field strength are presented.« less

Grain characterization and milling behaviour of near-isogenic lines differing by hardness.

PubMed

Greffeuille, V; Abecassis, J; Rousset, M; Oury, F-X; Faye, A; L'Helgouac'h, C Bar; Lullien-Pellerin, V

2006-12-01

Wheat grain hardness is a major factor affecting the milling behaviour and end-product quality although its exact structural and biochemical basis is still not understood. This study describes the development of new near-isogenic lines selected on hardness. Hard and soft sister lines were characterised by near infrared reflectance (NIR) and particle size index (PSI) hardness index, grain protein content, thousand kernel weight and vitreousness. The milling behaviour of these wheat lines was evaluated on an instrumented micromill which also measures the grinding energy and flour particle size distribution was investigated by laser diffraction. Endosperm mechanical properties were measured using compression tests. Results pointed out the respective effect of hardness and vitreousness on those characteristics. Hardness was shown to influence both the mode of fracture and the mechanical properties of the whole grain and endosperm. Thus, this parameter also acts on milling behaviour. On the other hand, vitreousness was found to mainly play a role on the energy required to break the grain. This study allows us to distinguish between consequences of hardness and vitreousness. Hardness is suggested to influence the adhesion forces between starch granules and protein matrix whereas vitreousness would rather be related to the endosperm microstructure.

Calculated photonic structures for infrared emittance control

NASA Astrophysics Data System (ADS)

Rung, Andreas; Ribbing, Carl G.

2002-06-01

Using an available program package based on the transfer-matrix method, we calculated the photonic band structure for two different structures: a quasi-three-dimensional crystal of square air rods in a high-index matrix and an opal structure of high-index spheres in a matrix of low index, epsilon = 1.5. The high index used is representative of gallium arsenide in the thermal infrared range. The geometric parameters of the rod dimension, sphere radius, and lattice constants were chosen to give total reflectance for normal incidence, i.e., minimum thermal emittance, in either one of the two infrared atmospheric windows. For these four photonic crystals, the bulk reflectance spectra and the wavelength-averaged thermal emittance as a function of crystal thickness were calculated. The results reveal that potentially useful thermal signature suppression is obtained for crystals as thin as 20-50 mum, i.e., comparable with that of a paint layer.

Reflectance properties of one-dimensional metal-dielectric ternary photonic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, G. N., E-mail: gnpandey2009@gmail.com; Kumar, Narendra; Thapa, Khem B.

2016-05-06

Metallic photonic crystal has a very important application in absorption enhancement in solar cells. It has been found that an ultra-thin metallic layer becomes transparent due to internal scattering of light through the each interface of the dielectric and metal surfaces. The metal has absorption due to their surface plasmon and the plasmon has important parameters for changing optical properties of the metal. We consider ternary metallic-dielectric photonic crystal (MDPC) for having large probabilities to change the optical properties of the MDPC and the photonic crystals may be changed by changing dimensionality, symmetry, lattice parameters, Filling fraction and effective refractivemore » index refractive index contrast. In this present communication, we try to show that the photonic band gap in ternary metal-dielectric photonic crystal can be significantly enlarged when air dielectric constant is considered. All the theoretical analyses are made based on the transfer matrix method together with the Drude model of metal.« less

X-ray two-photon absorption with high fluence XFEL pulses

DOE PAGES

Hoszowska, Joanna; Szlachetko, J.; Dousse, J. -Cl.; ...

2015-09-07

Here, we report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end-station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~10 5 photons/Å 2. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly.

PubMed

Song, Dong-Po; Jacucci, Gianni; Dundar, Feyza; Naik, Aditi; Fei, Hua-Feng; Vignolini, Silvia; Watkins, James J

2018-03-27

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young's modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces.

Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly

PubMed Central

2018-01-01

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young’s modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces. PMID:29681653

Evidence for Secondary Emission as the Origin of Hard Spectra in TeV Blazars

NASA Astrophysics Data System (ADS)

Zheng, Y. G.; Kang, T.

2013-02-01

We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy γ-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE γ-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy γ-rays, especially the shape of the VHE γ-ray tail of the observed spectra, can be explained by secondary γ-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

Photonic crystal fiber refractive-index sensor based on multimode interferometry

NASA Astrophysics Data System (ADS)

Gong, Zhenfeng; Zhang, Xinpu; Liu, Yun; Liu, Zigeng; Peng, Wei

2014-11-01

We report a type of multimode fiber interferometers (MMI) formed in photonic crystal fiber (PCF). To excite the cladding modes from the fundamental core mode of a PCF, a coupling point is formed. To form the coupling point, we used the method that is blowing compressed gas into the air-holes and discharging at one point, and the air-holes in this point will expand due to gas expansion in the discharge process. By placing two coupling points in series, a very simple all-fiber MMI can be implemented. The detailed fabrication process is that the one end of the PCF is tightly sealed by a short section of single mode fiber (SMF) spliced to the PCF. The other end of the PCF is sealed into a gas chamber and the opened air holes are pressurized. The PCF is then heated locally by the fusion splicer and the holes with higher gas pressure will expand locally where two bubbles formed. We tested the RI responses of fabricated sensors at room temperature by immersing the sensor into solutions with different NaCl concentration. Experimental results show that as refractive-index (RI) increases, the resonance wavelength of the MMI moves toward longer wavelengths. The sensitivity coefficients are estimated by the linear fitting line, which is 46nm/RIU, 154mn/RIU with the interferometer lengths (IL) of 3mm and 6mm. The interferometer with larger IL has higher RI sensitivity. The temperature cross-sensitivity of the sensor is also tested. The temperature sensitivity can be as low as -16.0pm/°C.

Hard photodisintegration of 3He into a p d pair

NASA Astrophysics Data System (ADS)

Maheswari, Dhiraj; Sargsian, Misak M.

2017-02-01

The recent measurements of high energy photodisintegration of a 3He nucleus to a p d pair at 90∘ center of mass demonstrated an energy scaling consistent with the quark counting rule with an unprecedentedly large exponent of s-17. To understand the underlying mechanism of this process, we extended the theoretical formalism of the hard rescattering mechanism (HRM) to calculate the γ 3He→p d reaction. In HRM the incoming high energy photon strikes a quark from one of the nucleons in the target which subsequently undergoes hard rescattering with the quarks from the other nucleons, generating a hard two-body system in the final state of the reaction. Within the HRM we derived the parameter-free expression for the differential cross section of the reaction, which is expressed through the 3He→p d transition spectral function, the cross section of hard p d →p d scattering, and the effective charge of the quarks being interchanged during the hard rescattering process. The numerical estimates of all these factors resulted in the magnitude of the cross section, which is surprisingly in good agreement with the data.

A rapid hard-mast index from acorn presence-absence tallies

Treesearch

Cathryn H. Greenberg; Gordon S. Warburton

2007-01-01

We used 21 years of acorn data from visual surveys of oak (Quercus spp.) trees (n ¼ 20,113) conducted in western North Carolina, USA, to develop predictive equations for hard-mast indices (HMIs) based on the proportion of trees bearing acorns (PBA). We calculated PBA using visual estimates of the percentage of oak crown with acorns (PCA), assigning acorn presence if...

Optical sensors based on photonic crystal: a new route

NASA Astrophysics Data System (ADS)

Romano, S.; Torino, S.; Coppola, G.; Cabrini, S.; Mocella, V.

2017-05-01

The realization of miniaturized devices able to accumulate a higher number of information in a smallest volume is a challenge of the technological development. This trend increases the request of high sensitivity and selectivity sensors which can be integrated in microsystems. In this landscape, optical sensors based on photonic crystal technology can be an appealing solution. Here, a new refractive index sensor device, based on the bound states in the continuum (BIC) resonance shift excited in a photonic crystal membrane, is presented. A microfluidic cell was used to control the injection of fluids with different refractive indices over the photonic crystal surface. The shift of very high Q-factor resonances excited into the photonic crystal open cavity was monitored as a function of the refractive index n of the test liquid. The excellent stability we found and the minimal, loss-free optical equipment requirement, provide a new route for achieving high performance in sensing applications.

Anomalous transparency in photonic crystals and its application to point-by-point grating inscription in photonic crystal fibers.

PubMed

Baghdasaryan, Tigran; Geernaert, Thomas; Chah, Karima; Caucheteur, Christophe; Schuster, Kay; Kobelke, Jens; Thienpont, Hugo; Berghmans, Francis

2018-04-03

It is common belief that photonic crystals behave similarly to isotropic and transparent media only when their feature sizes are much smaller than the wavelength of light. Here, we counter that belief and we report on photonic crystals that are transparent for anomalously high normalized frequencies up to 0.9, where the crystal's feature sizes are comparable with the free space wavelength. Using traditional photonic band theory, we demonstrate that the isofrequency curves can be circular in the region above the first stop band for triangular lattice photonic crystals. In addition, by simulating how efficiently a tightly focused Gaussian beam propagates through the photonic crystal slab, we judge on the photonic crystal's transparency rather than on isotropy only. Using this approach, we identified a wide range of photonic crystal parameters that provide anomalous transparency. Our findings indicate the possibility to scale up the features of photonic crystals and to extend their operational wavelength range for applications including optical cloaking and graded index guiding. We applied our result in the domain of femtosecond laser micromachining, by demonstrating what we believe to be the first point-by-point grating inscribed in a multi-ring photonic crystal fiber.

Gamma radiation effects on silicon photonic waveguides.

PubMed

Grillanda, Stefano; Singh, Vivek; Raghunathan, Vivek; Morichetti, Francesco; Melloni, Andrea; Kimerling, Lionel; Agarwal, Anuradha M

2016-07-01

To support the use of integrated photonics in harsh environments, such as outer space, the hardness threshold to high-energy radiation must be established. Here, we investigate the effects of gamma (γ) rays, with energy in the MeV-range, on silicon photonic waveguides. By irradiation of high-quality factor amorphous silicon core resonators, we measure the impact of γ rays on the materials incorporated in our waveguide system, namely amorphous silicon, silicon dioxide, and polymer. While we show the robustness of amorphous silicon and silicon dioxide up to an absorbed dose of 15 Mrad, more than 100× higher than previous reports on crystalline silicon, polymer materials exhibit changes with doses as low as 1 Mrad.

Broadband IR polarizing beam splitter using a subwavelength-structured one-dimensional photonic-crystal layer embedded in a high-index prism.

PubMed

Khanfar, H K; Azzam, R M A

2009-09-20

An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at 45 degrees angle of incidence. A high extinction ratio in reflection (>50 dB) over the 4-12 microm IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view of +/-6.6 degrees and in the presence of grating filling factor errors of up to +/-10%. Comparable results, but with wider field of view, are also obtained with a Ge PCL embedded in a Si prism.

Constraining axion-like-particles with hard X-ray emission from magnetars

NASA Astrophysics Data System (ADS)

Fortin, Jean-François; Sinha, Kuver

2018-06-01

Axion-like particles (ALPs) produced in the core of a magnetar will convert to photons in the magnetosphere, leading to possible signatures in the hard X-ray band. We perform a detailed calculation of the ALP-to-photon conversion probability in the magnetosphere, recasting the coupled differential equations that describe ALP-photon propagation into a form that is efficient for large scale numerical scans. We show the dependence of the conversion probability on the ALP energy, mass, ALP-photon coupling, magnetar radius, surface magnetic field, and the angle between the magnetic field and direction of propagation. Along the way, we develop an analytic formalism to perform similar calculations in more general n-state oscillation systems. Assuming ALP emission rates from the core that are just subdominant to neutrino emission, we calculate the resulting constraints on the ALP mass versus ALP-photon coupling space, taking SGR 1806-20 as an example. In particular, we take benchmark values for the magnetar radius and core temperature, and constrain the ALP parameter space by the requirement that the luminosity from ALP-to-photon conversion should not exceed the total observed luminosity from the magnetar. The resulting constraints are competitive with constraints from helioscope experiments in the relevant part of ALP parameter space.

Design and Tests of the Hard X-Ray Polarimeter X-Calibur

NASA Technical Reports Server (NTRS)

Beilicke, M.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Israel, M. H.; Lee, K.; Krawczynski, H.;

Design and Tests of the Hard X-Ray Polarimeter X-Calibur

NASA Technical Reports Server (NTRS)

Beilicke, M.; Baring, M. G.; Barthelmy, S.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Haba, Y.;

Fast response Fabry-Perot interferometer microfluidic refractive index fiber sensor based on concave-core photonic crystal fiber.

PubMed

Tian, Jiajun; Lu, Zejin; Quan, Mingran; Jiao, Yuzhu; Yao, Yong

2016-09-05

We report a fast response microfluidic Fabry-Perot (FP) interferometer refractive index (RI) fiber sensor based on a concave-core photonic crystal fiber (CPCF), which is formed by directly splicing a section CPCF with a section of single mode fiber. The CPCF is made by cleaving a section of multimode photonic crystal fiber with an axial tension. The shallow concave-core of CPCF naturally forms the FP cavity with a very short cavity length. The inherent large air holes in the cladding of CPCF are used as the open channels to let liquid sample come in and out of FP cavity. In order to shorten the liquid channel length and eliminate the harmful reflection from the outside end face of the CPCF, the CPCF is cleaved with a tilted tensile force. Due to the very small cavity capacity, the short length and the large sectional area of the microfluidic channels, the proposed sensor provides an easy-in and easy-out structure for liquids, leading to great decrement of the measuring time. The proposed sensor exhibits fast measuring speed, the measuring time is less than 359 and 23 ms for distilled water and pure ethanol, respectively. We also experimentally study and demonstrate the superior performances of the sensor in terms of high RI sensitivity, good linear response, low temperature cross-sensitivity and easy fabrication.

Resonant optical tunneling-induced enhancement of the photonic spin Hall effect

NASA Astrophysics Data System (ADS)

Jiang, Xing; Wang, Qingkai; Guo, Jun; Zhang, Jin; Chen, Shuqing; Dai, Xiaoyu; Xiang, Yuanjiang

2018-04-01

Due to the quantum analogy with optics, the resonant optical tunneling effect (ROTE) has been proposed to investigate both the fundamental physics and the practical applications of optical switches and liquid refractive index sensors. In this paper, the ROTE is used to enhance the spin Hall effect (SHE) of transmitted light. It is demonstrated that sandwiching a layer of a high-refractive-index medium (boron nitride crystal) between two low-refractive-index layers (silica) can effectively enhance the photonic SHE due to the increased refractive index gradient and an enhanced evanescent field near the interface between silica and boron nitride. A maximum transverse shift of the horizontal polarization state in the ROTE structure of about 22.25 µm has been obtained, which is at least three orders of magnitude greater than the transverse shift in the frustrated total internal reflection structure. Moreover, the SHE can be manipulated by controlling the component materials and the thickness of the ROTE structure. These findings open the possibility for future applications of photonic SHE in precision metrology and spin-based photonics.

Soft X-ray production by photon scattering in pulsating binary neutron star sources

NASA Technical Reports Server (NTRS)

Bussard, R. W.; Meszaros, P.; Alexander, S.

1985-01-01

A new mechanism is proposed as a source of soft (less than 1 keV) radiation in binary pulsating X-ray sources, in the form of photon scattering which leaves the electron in an excited Landau level. In a plasma with parameters typical of such sources, the low-energy X-ray emissivity of this mechanism far exceeds that of bremsstrahlung. This copious source of soft photons is quite adequate to provide the seed photons needed to explain the power-law hard X-ray spectrum by inverse Comptonization on the hot electrons at the base of the accretion column.

Scale influence on the energy dependence of photon-proton cross sections

NASA Astrophysics Data System (ADS)

Aid, S.; Anderson, M.; Andreev, V.; Andrieu, B.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Beck, M.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Boudry, V.; Braemer, A.; Braunschweig, W.; Brisson, V.; Brückner, W.; Bruel, P.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Calvet, D.; Campbell, A. J.; Carli, T.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Cousinou, M.-C.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; de Roeck, A.; de Wolf, E. A.; Dirkmann, M.; Dixon, P.; di Nezza, P.; Dlugosz, W.; Dollfus, C.; Donovan, K. T.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Erdmann, M.; Erdmann, W.; Fahr, A. B.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gebauer, M.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Golec-Biernat, K.; Gonzalez-Pineiro, B.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Gruber, A.; Gruber, C.; Hadig, T.; Haidt, D.; Hajduk, L.; Haller, T.; Hampel, M.; Haynes, W. J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hewitt, K.; Hildesheim, W.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Höppner, M.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hütte, M.; Ibbotson, M.; Itterbeck, H.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, D. M.; Jansen, T.; Jönsson, L.; Johnson, D. P.; Jung, H.; Kalmus, P. I. P.; Kander, M.; Kant, D.; Kaschowitz, R.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kaufmann, O.; Kausch, M.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Lacour, D.; Laforge, B.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Lebedev, A.; Lehner, F.; Levonian, S.; Lindström, G.; Lindstroem, M.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Lüke, D.; Lytkin, L.; Magnussen, N.; Malinovski, E.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Metlica, F.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moeck, J.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, D.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Newton, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nowak, G.; Noyes, G. W.; Nunnemann, T.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pope, G.; Povh, B.; Prell, S.; Rabbertz, K.; Rädel, G.; Reimer, P.; Reinshagen, S.; Rick, H.; Riepenhausen, F.; Riess, S.; Rizvi, E.; Robertson, S. M.; Robmann, P.; Roloff, H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sefkow, F.; Sell, R.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Solochenko, V.; Soloviev, Y.; Specka, A.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Squinabol, F.; Steffen, P.; Steinberg, R.; Steiner, H.; Steinhart, J.; Stella, B.; Stellberger, A.; Stier, J.; Stiewe, J.; Stößlein, U.; Stolze, K.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thiebaux, C.; Thompson, G.; Todenhagen, R.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tutas, J.; Tzamariudaki, E.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; van Esch, P.; van Mechelen, P.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; West, L. R.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wobisch, M.; Wünsch, E.; ŽáČek, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; Zuber, K.; Zurnedden, M.

1997-02-01

The scale dependence of the evolution of photoproduction cross sections with the photon-proton centre of mass energyW is studied using low Q2 < 0.01 GeV2 e+p interactions collected by the H1 experiment at HERA. The value of the largest transverse momentum of a charged particle in the photon fragmentation region is used to define the hard scale. The slope of the W dependence of the cross section is observed to increase steeply with increasing transverse momentum. The result is compared to measurements of the Q2 evolution of the W dependence of the virtual photon-proton cross section. Interpretations in terms of QCD and in terms of Regge phenomenology are discussed.

Observational capabilities of solar satellite "Coronas-Photon"

NASA Astrophysics Data System (ADS)

Kotov, Yu.

Coronas-Photon mission is the third satellite of the Russian Coronas program on solar activity observation The main goal of the Coronas-Photon is the study of solar hard electromagnetic radiation in the wide energy range from UV up to high energy gamma-radiation sim 2000MeV Scientific payload for solar radiation observation consists of three type of instruments 1 monitors Natalya-2M Konus-RF RT-2 Penguin-M BRM Phoka Sphin-X Sokol for spectral and timing measurements of full solar disk radiation with timing in flare burst mode up to one msec Instruments Natalya-2M Konus-RF RT-2 will cover the wide energy range of hard X-rays and soft Gamma rays 15keV to 2000MeV and will together constitute the largest area detectors ever used for solar observations Detectors of gamma-ray monitors are based on structured inorganic scintillators with energy resolution sim 5 for nuclear gamma-line band to 35 for GeV-band PSD analysis is used for gamma neutron separation for solar neutron registration T 30MeV Penguin-M has capability to measure linear polarization of hard X-rays using azimuth are measured by Compton scattering asymmetry in case of polarization of an incident flux For X-ray and EUV monitors the scintillation phoswich detectors gas proportional counter CZT assembly and Filter-covered Si-diodes are used 2 Telescope-spectrometer TESIS for imaging solar spectroscopy in X-rays with angular resolution up to 1 in three spectral lines and RT-2 CZT assembly of CZT

Measurement of infrared optical constants with visible photons

NASA Astrophysics Data System (ADS)

Paterova, Anna; Yang, Hongzhi; An, Chengwu; Kalashnikov, Dmitry; Krivitsky, Leonid

2018-04-01

We demonstrate a new scheme for infrared spectroscopy with visible light sources and detectors. The technique relies on the nonlinear interference of correlated photons, produced via spontaneous parametric down conversion in a nonlinear crystal. Visible and infrared photons are split into two paths and the infrared photons interact with the sample under study. The photons are reflected back to the crystal, resembling a conventional Michelson interferometer. Interference of the visible photons is observed and it is dependent on the phases of all three interacting photons: pump, visible and infrared. The transmission coefficient and the refractive index of the sample in the infrared range can be inferred from the interference pattern of visible photons. The method does not require the use of potentially expensive and inefficient infrared detectors and sources, it can be applied to a broad variety of samples, and it does not require a priori knowledge of sample properties in the visible range.

Strong Photonic-Band-Gap Effect on the Spontaneous Emission in 3D Lead Halide Perovskite Photonic Crystals.

PubMed

Zhou, Xue; Li, Mingzhu; Wang, Kang; Li, Huizeng; Li, Yanan; Li, Chang; Yan, Yongli; Zhao, Yongsheng; Song, Yanlin

2018-03-25

Stimulated emission in perovskite-embedded polymer opal structures is investigated. A polymer opal structure is filled with a perovskite, and perovskite photonic crystals are prepared. The spontaneous emission of the perovskite embedded in the polymer opal structures exhibits clear signatures of amplified spontaneous emission (ASE) via gain modulation. The difference in refractive-index contrast between the perovskite and the polymer opal is large enough for retaining photonic-crystals properties. The photonic band gap has a strong effect on the fluorescence emission intensity and lifetime. The stimulated emission spectrum exhibits a narrow ASE rather than a wide fluorescence peak in the thin film. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hard X-ray spectra of neutron stars and black hole candidates

NASA Technical Reports Server (NTRS)

Durouchoux, P.; Mahoney, W.; Clenet, Y.; Ling, J.; Wallyn, P.; Wheaton, W.; Corbet, S.; Chapuis, C.

1997-01-01

The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.

White Beam Slits and Pink Beam Slits for the Hard X-ray Nanoprobe Beamline at the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, C.; Jaski, Y.; Powers, T.

2007-01-19

A new type of slit has been designed for use in the hard x-ray nanoprobe beamline at the Advanced Photon Source (APS). The design incorporates monolithic GlidCop slit bodies mounted to commercially available x-y drive systems. Long, tapered apertures with adjacent water-cooling channels intercept the x-ray beam, removing the high heat load produced by two collinear APS undulators. The apertures are L-shaped and provide both horizontal and vertical slits. The beam-defining edges, positioned at the end of the tapered surfaces, consist of two sets of tungsten blades. These blades produce an exit beam with sharp corners and assure a cleanmore » cut-off for the white beam edges. The slit assembly is designed to allow overlap of the slit edges to stop the beam.The white beam slit design accommodates 3100 W of total power with a peak power density of 763 W/mm2. The pink beam slit design accommodates 400 W of total power with a peak power density of 180 W/mm2. Detailed thermal analyses were performed to verify the slits' accuracy under full beam loading. The new concept allows beamline operations to 180 mA with a simplified design approach.« less

White beam slits and pink beam slits for the hard x-ray nanoprobe beamline at the Advanced Photon Source.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, C.; Jaski, Y.; Maser, J.

2007-01-01

A new type of slit has been designed for use in the hard x-ray nanoprobe beamline at the Advanced Photon Source (APS). The design incorporates monolithic GlidCop slit bodies mounted to commercially available x-y drive systems. Long, tapered apertures with adjacent water-cooling channels intercept the x-ray beam, removing the high heat load produced by two collinear APS undulators. The apertures are L-shaped and provide both horizontal and vertical slits. The beam-defining edges, positioned at the end of the tapered surfaces, consist of two sets of tungsten blades. These blades produce an exit beam with sharp corners and assure a cleanmore » cut-off for the white beam edges. The slit assembly is designed to allow overlap of the slit edges to stop the beam. The white beam slit design accommodates 3100 W of total power with a peak power density of 763 W/mm2. The pink beam slit design accommodates 400 W of total power with a peak power density of 180 W/mm2. Detailed thermal analyses were performed to verify the slits accuracy under full beam loading. The new concept allows beamline operations to 180 mA with a simplified design approach.« less

Energetic electrons, hard x-ray emission and MHD activity studies in the IR-T1 tokamak.

PubMed

Agah, K Mikaili; Ghoranneviss, M; Elahi, A Salar

2015-01-01

Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons.

Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osaka, Taito; Hirano, Takashi; Morioka, Yuki

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturingmore » single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. In conclusion, this is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femtoseconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.« less

Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms

DOE PAGES

Osaka, Taito; Hirano, Takashi; Morioka, Yuki; ...

2017-10-13

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturingmore » single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. In conclusion, this is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femtoseconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.« less

Estimation of photonic band gap in the hollow core cylindrical multilayer structure

NASA Astrophysics Data System (ADS)

Chourasia, Ritesh Kumar; Singh, Vivek

2018-04-01

The propagation characteristic of two hollow core cylindrical multilayer structures having high and low refractive index contrast of cladding regions have been studied and compared at two design wavelengths i.e. 1550 nm and 632.8 nm. With the help of transfer matrix method a relation between the incoming light wave and outgoing light wave has been developed using the boundary matching technique. In high refractive index contrast, small numbers of layers are sufficient to provide perfect band gap in both design wavelengths. The spectral position and width of band gap is highly depending on the optical path of incident light in all considered cases. For sensing application, the sensitivity of waveguide can be obtained either by monitoring the width of photonic band gap or by monitoring the spectral shift of photonic band gap. Change in the width of photonic band gap with the core refractive index is larger in high refractive index contrast of cladding materials. However, in the case of monitoring the spectral shift of band gap, the obtained sensitivity is large for low refractive index contrast of cladding materials and further it increases with increase of design wavelength.

Fabrication of triangular nanobeam waveguide networks in bulk diamond using single-crystal silicon hard masks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayn, I.; Mouradian, S.; Li, L.

2014-11-24

A scalable approach for integrated photonic networks in single-crystal diamond using triangular etching of bulk samples is presented. We describe designs of high quality factor (Q = 2.51 × 10{sup 6}) photonic crystal cavities with low mode volume (V{sub m} = 1.062 × (λ/n){sup 3}), which are connected via waveguides supported by suspension structures with predicted transmission loss of only 0.05 dB. We demonstrate the fabrication of these structures using transferred single-crystal silicon hard masks and angular dry etching, yielding photonic crystal cavities in the visible spectrum with measured quality factors in excess of Q = 3 × 10{sup 3}.

Ultra-compact air-mode photonic crystal nanobeam cavity integrated with bandstop filter for refractive index sensing.

PubMed

Sun, Fujun; Fu, Zhongyuan; Wang, Chunhong; Ding, Zhaoxiang; Wang, Chao; Tian, Huiping

2017-05-20

We propose and investigate an ultra-compact air-mode photonic crystal nanobeam cavity (PCNC) with an ultra-high quality factor-to-mode volume ratio (Q/V) by quadratically tapering the lattice space of the rectangular holes from the center to both ends while other parameters remain unchanged. By using the three-dimensional finite-difference time-domain method, an optimized geometry yields a Q of 7.2×10 6 and a V∼1.095(λ/n Si ) 3 in simulations, resulting in an ultra-high Q/V ratio of about 6.5×10 6 (λ/n Si ) -3 . When the number of holes on either side is 8, the cavity possesses a high sensitivity of 252 nm/RIU (refractive index unit), a high calculated Q-factor of 1.27×10 5 , and an ultra-small effective V of ∼0.758(λ/n Si ) 3 at the fundamental resonant wavelength of 1521.74 nm. Particularly, the footprint is only about 8×0.7  μm 2 . However, inevitably our proposed PCNC has several higher-order resonant modes in the transmission spectrum, which makes the PCNC difficult to be used for multiplexed sensing. Thus, a well-designed bandstop filter with weak sidelobes and broad bandwidth based on a photonic crystal nanobeam waveguide is created to connect with the PCNC to filter out the high-order modes. Therefore, the integrated structure presented in this work is promising for building ultra-compact lab-on-chip sensor arrays with high density and parallel-multiplexing capability.

Wafer-scale plasmonic and photonic crystal sensors

NASA Astrophysics Data System (ADS)

George, M. C.; Liu, J.-N.; Farhang, A.; Williamson, B.; Black, M.; Wangensteen, T.; Fraser, J.; Petrova, R.; Cunningham, B. T.

2015-08-01

200 mm diameter wafer-scale fabrication, metrology, and optical modeling results are reviewed for surface plasmon resonance (SPR) sensors based on 2-D metallic nano-dome and nano-hole arrays (NHA's) as well as 1-D photonic crystal sensors based on a leaky-waveguide mode resonance effect, with potential applications in label free sensing, surface enhanced Raman spectroscopy (SERS), and surface-enhanced fluorescence spectroscopy (SEFS). Potential markets include micro-arrays for medical diagnostics, forensic testing, environmental monitoring, and food safety. 1-D and 2-D nanostructures were fabricated on glass, fused silica, and silicon wafers using optical lithography and semiconductor processing techniques. Wafer-scale optical metrology results are compared to FDTD modeling and presented along with application-based performance results, including label-free plasmonic and photonic crystal sensing of both surface binding kinetics and bulk refractive index changes. In addition, SEFS and SERS results are presented for 1-D photonic crystal and 2-D metallic nano-array structures. Normal incidence transmittance results for a 550 nm pitch NHA showed good bulk refractive index sensitivity, however an intensity-based design with 665 nm pitch was chosen for use as a compact, label-free sensor at both 650 and 632.8 nm wavelengths. The optimized NHA sensor gives an SPR shift of about 480 nm per refractive index unit when detecting a series of 0-40% glucose solutions, but according to modeling shows about 10 times greater surface sensitivity when operating at 532 nm. Narrow-band photonic crystal resonance sensors showed quality factors over 200, with reasonable wafer-uniformity in terms of both resonance position and peak height.

Refractive index modulation in LiNbO3: MgO slab through Lamb wave

NASA Astrophysics Data System (ADS)

Prakash, Suraj; Sharma, Gaurav; Yadav, Gulab Chand; Singh, Vivek

2018-05-01

Present theoretical analysis deals with inducing refractive index contrast in Y-Z LiNbO3:MgO plate via GHz Lamb wave perturbation for photonic applications. Dispersion curves for Lamb wave in plate are plotted by employing displacement potential technique. Selecting wave parameters from dispersion curve, fundamental symmetric Lamb mode (S0) is excited in slab for 6GHz frequency. Produced displacement field by propagating S0 mode and thus developed strain is estimated to calculate refractive index modulation by applying photo-elastic relations. Modulated refractive index is of sinusoidal nature with period of modulation dependence on Lamb's wavelength. This plate having periodically modulated refractive index can be used as photonic crystal for different applications with acoustically tunable photonic band gap.

Fano resonance in anodic aluminum oxide based photonic crystals.

PubMed

Shang, Guo Liang; Fei, Guang Tao; Zhang, Yao; Yan, Peng; Xu, Shao Hui; Ouyang, Hao Miao; Zhang, Li De

2014-01-08

Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile.

Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu, Deming, E-mail: shu@aps.anl.gov; Shvyd’ko, Yuri V.; Stoupin, Stanislav

2016-07-27

A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

Infrared transparent graphene heater for silicon photonic integrated circuits.

PubMed

Schall, Daniel; Mohsin, Muhammad; Sagade, Abhay A; Otto, Martin; Chmielak, Bartos; Suckow, Stephan; Giesecke, Anna Lena; Neumaier, Daniel; Kurz, Heinrich

2016-04-18

Thermo-optical tuning of the refractive index is one of the pivotal operations performed in integrated silicon photonic circuits for thermal stabilization, compensation of fabrication tolerances, and implementation of photonic operations. Currently, heaters based on metal wires provide the temperature control in the silicon waveguide. The strong interaction of metal and light, however, necessitates a certain gap between the heater and the photonic structure to avoid significant transmission loss. Here we present a graphene heater that overcomes this constraint and enables an energy efficient tuning of the refractive index. We achieve a tuning power as low as 22 mW per free spectral range and fast response time of 3 µs, outperforming metal based waveguide heaters. Simulations support the experimental results and suggest that for graphene heaters the spacing to the silicon can be further reduced yielding the best possible energy efficiency and operation speed.

Rapidity distribution of photons from an anisotropic quark-gluon plasma

NASA Astrophysics Data System (ADS)

Bhattacharya, Lusaka; Roy, Pradip

2010-05-01

We calculate rapidity distribution of photons due to Compton and annihilation processes from quark gluon plasma with pre-equilibrium momentum-space anisotropy. We also include contributions from hadronic matter with late-stage transverse expansion. A phenomenological model has been used for the time evolution of hard momentum scale, phard(τ), and anisotropy parameter, ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of photons rapidity distribution. For example, with the fixed initial condition (FIC) free-streaming (δ=2) interpolating model we observe significant enhancement of photon rapidity distribution at fixed pT, where as for FIC collisionally broadened (δ=2/3) interpolating model the yield increases till y~1. Beyond that suppression is observed. With fixed final multiplicity (FFM) free-streaming interpolating model we predict enhancement of photon yield which is less than the case of FIC. Suppression is always observed for FFM collisionally broadened interpolating model.

Hadroproduction of t-anti-t pair with two isolated photons with PowHel

NASA Astrophysics Data System (ADS)

Kardos, A.; Trócsányi, Z.

2015-08-01

We simulate the hadroproduction of a t t bar pair in association with two isolated hard photons at 13 TeV LHC using the PowHel package. We use the generated events, stored according to the Les-Houches event format, to make predictions for differential distributions formally at the next-to-leading order (NLO) accuracy. We present predictions at the hadron level employing the cone-type isolation of the photons used by experiments. We also compare the kinematic distributions to the same distributions obtained in the t t bar H final state when the Higgs-boson decays into a photon pair, to which the process discussed here is an irreducible background.

Hard-X-Ray-Induced Multistep Ultrafast Dissociation

NASA Astrophysics Data System (ADS)

Travnikova, Oksana; Marchenko, Tatiana; Goldsztejn, Gildas; Jänkälä, Kari; Sisourat, Nicolas; Carniato, Stéphane; Guillemin, Renaud; Journel, Loïc; Céolin, Denis; Püttner, Ralph; Iwayama, Hiroshi; Shigemasa, Eiji; Piancastelli, Maria Novella; Simon, Marc

2016-05-01

Creation of deep core holes with very short (τ ≤1 fs ) lifetimes triggers a chain of relaxation events leading to extensive nuclear dynamics on a few-femtosecond time scale. Here we demonstrate a general multistep ultrafast dissociation on an example of HCl following Cl 1 s →σ* excitation. Intermediate states with one or multiple holes in the shallower core electron shells are generated in the course of the decay cascades. The repulsive character and large gradients of the potential energy surfaces of these intermediates enable ultrafast fragmentation after the absorption of a hard x-ray photon.

Integrated quantum photonic sensor based on Hong-Ou-Mandel interference.

PubMed

Basiri-Esfahani, Sahar; Myers, Casey R; Armin, Ardalan; Combes, Joshua; Milburn, Gerard J

2015-06-15

Photonic-crystal-based integrated optical systems have been used for a broad range of sensing applications with great success. This has been motivated by several advantages such as high sensitivity, miniaturization, remote sensing, selectivity and stability. Many photonic crystal sensors have been proposed with various fabrication designs that result in improved optical properties. In parallel, integrated optical systems are being pursued as a platform for photonic quantum information processing using linear optics and Fock states. Here we propose a novel integrated Fock state optical sensor architecture that can be used for force, refractive index and possibly local temperature detection. In this scheme, two coupled cavities behave as an "effective beam splitter". The sensor works based on fourth order interference (the Hong-Ou-Mandel effect) and requires a sequence of single photon pulses and consequently has low pulse power. Changes in the parameter to be measured induce variations in the effective beam splitter reflectivity and result in changes to the visibility of interference. We demonstrate this generic scheme in coupled L3 photonic crystal cavities as an example and find that this system, which only relies on photon coincidence detection and does not need any spectral resolution, can estimate forces as small as 10(-7) Newtons and can measure one part per million change in refractive index using a very low input power of 10(-10)W. Thus linear optical quantum photonic architectures can achieve comparable sensor performance to semiclassical devices.

Vasodilator Stress Single-Photon Emission Computed Tomography or Contrast Stress Echocardiography Association with Hard Cardiac Events in Suspected Coronary Artery Disease.

PubMed

Gaibazzi, Nicola; Siniscalchi, Carmine; Porter, Thomas R; Crocamo, Antonio; Basaglia, Manuela; Boffetti, Francesca; Lorenzoni, Valentina

2018-06-01

We compared the long-term outcome of subjects without prior cardiac disease who underwent either vasodilator single-photon emission computed tomography (SPECT) or contrast stress-echocardiography (cSE) for suspected coronary artery disease (CAD). Subjects who underwent vasodilator SPECT or cSE between 2008 and 2012 for suspected CAD but no history of cardiac disease were included. We retrospectively compared the association of each method with combined all-cause death and nonfatal myocardial infarction and their positive predictive value (PPV) for angiographically obstructive CAD. A total of 1,387 subjects were selected: 497 who underwent SPECT and 890 who underwent cSE. During 4 years of mean follow-up there were 78 hard events in the cSE group and 51 in the SPECT group. Event-free survival in subjects testing positive for ischemia, either with SPECT or cSE, was significantly worse both in the overall population and after propensity matching patients. In multivariable analyses, vasodilator SPECT or cSE demonstrated significant stratification capability with an ischemic test doubling (SPECT) or more than doubling (cSE) the risk of future hard events independently from other variables. PPV of vasodilator SPECT for the diagnosis of obstructive CAD was inferior to vasodilator cSE (PPV = 63% vs 89%, respectively; P < .001). Our study suggests that the associations of vasodilator SPECT or cSE with outcome are comparable, with cSE demonstrating better diagnostic PPV for CAD. The absence of ionizing radiation and anticipated lower costs from higher PPV suggest that vasodilator cSE is a valid alternative to vasodilator SPECT as a gatekeeper in subjects without a prior history of CAD. Copyright © 2018 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Theoretical and experimental investigations of asymmetric light transport in graded index photonic crystal waveguides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giden, I. H., E-mail: igiden@etu.edu.tr; Yilmaz, D.; Turduev, M.

To provide asymmetric propagation of light, we propose a graded index photonic crystal (GRIN PC) based waveguide configuration that is formed by introducing line and point defects as well as intentional perturbations inside the structure. The designed system utilizes isotropic materials and is purely reciprocal, linear, and time-independent, since neither magneto-optical materials are used nor time-reversal symmetry is broken. The numerical results show that the proposed scheme based on the spatial-inversion symmetry breaking has different forward (with a peak value of 49.8%) and backward transmissions (4.11% at most) as well as relatively small round-trip transmission (at most 7.11%) in amore » large operational bandwidth of 52.6 nm. The signal contrast ratio of the designed configuration is above 0.80 in the telecom wavelengths of 1523.5–1576.1 nm. An experimental measurement is also conducted in the microwave regime: A strong asymmetric propagation characteristic is observed within the frequency interval of 12.8 GHz–13.3 GHz. The numerical and experimental results confirm the asymmetric transmission behavior of the proposed GRIN PC waveguide.« less

Diversity, distribution of Puroindoline genes and their effect on kernel hardness in a diverse panel of Chinese wheat germplasm.

PubMed

Ma, Xiaoling; Sajjad, Muhammad; Wang, Jing; Yang, Wenlong; Sun, Jiazhu; Li, Xin; Zhang, Aimin; Liu, Dongcheng

2017-09-20

Kernel hardness, which has great influence on the end-use properties of common wheat, is mainly controlled by Puroindoline genes, Pina and Pinb. Using EcoTILLING platform, we herein investigated the allelic variations of Pina and Pinb genes and their association with the Single Kernel Characterization System (SKCS) hardness index in a diverse panel of wheat germplasm. The kernel hardness varied from 1.4 to 102.7, displaying a wide range of hardness index. In total, six Pina and nine Pinb alleles resulting in 15 genotypes were detected in 1787 accessions. The most common alleles are the wild type Pina-D1a (90.4%) and Pina-D1b (7.4%) for Pina, and Pinb-D1b (43.6%), Pinb-D1a (41.1%) and Pinb-D1p (12.8%) for Pinb. All the genotypes have hard type kernel hardness of SKCS index (>60.0), except the wild types of Pina and Pinb combination (Pina-D1a/Pinb-D1a). The most frequent genotypes in Chinese and foreign cultivars was Pina-D1a/Pinb-D1b (46.3 and 39.0%, respectively) and in Chinese landraces was Pina-D1a/Pinb-D1a (54.2%). The frequencies of hard type accessions are increasing from 35.5% in the region IV, to 40.6 and 61.4% in the regions III and II, and then to 77.0% in the region I, while those of soft type are accordingly decreasing along with the increase of latitude. Varieties released after 2000 in Beijing, Hebei, Shandong and Henan have higher average kernel hardness index than that released before 2000. The kernel hardness in a diverse panel of Chinese wheat germplasm revealed an increasing of kernel hardness generally along with the latitude across China. The wild type Pina-D1a and Pinb-D1a, and one Pinb mutant (Pinb-D1b) are the most common alleles of six Pina and nine Pinb alleles, and a new double null genotype (Pina-D1x/Pinb-D1ah) possessed relatively high SKCS hardness index. More hard type varieties were released in recent years with different prevalence of Pin-D1 combinations in different regions. This work would benefit the understanding of the selection

Measurement of refractive index profile of non-symmetric, complex silica preforms with high refractive index differences

NASA Astrophysics Data System (ADS)

Probostova, Jana; Slanicka, Jiri; Mrazek, Jan; Podrazky, Ondrej; Benda, Adam; Peterka, Pavel

2016-04-01

Refractive index profile measurement is a key instrument for characterization of optical properties of preforms, which are used for drawing of high-quality optical fibers. Common industrial optical preform analyzers have been designed for measurement of simple symmetric structures such as step-index or graded-index preforms with refractive index close to the silica (n=1.457 at 633 nm). However, these conditions are usually far from more complex structures used in fiber lasers or in fiber sensor area. Preforms for the drawing of advanced optical fibers, such as Bragg, microstructure or photonic crystal fibers, are usually constituted from stacks with non-symmetric internal structure or composed of alternating layers with high refractive index contrasts. In this paper we present comparison of refractive index profile measurements of simple as well as complex structures with high refractive index differences simulating the Bragg structures. Commercial Photon Kinetics 2600 preform analyzer was used for the refractive index profile measurements. A set of concentrically arranged silica tubes was welded to form a complex preforms. Free space between the tubes was filled by immersion with varying refractive indices to simulate the Bragg structure. Up to three tubes were used for the analysis and the refractive indices of immersion were changed from 1.4 to 1.5. When refractive index of immersion was independently measured the structure of preform was defined. Profiles of these "known" structures were compared to measured data processed by originally proposed algorithm. The work provides an extension of issues of refractive index profile measurements in non-symmetric complex silica structures by a commercial preform analyzer and proposes more convenient methods of numeric data processing.

Anti-Hermitian photodetector facilitating efficient subwavelength photon sorting.

PubMed

Kim, Soo Jin; Kang, Ju-Hyung; Mutlu, Mehmet; Park, Joonsuk; Park, Woosung; Goodson, Kenneth E; Sinclair, Robert; Fan, Shanhui; Kik, Pieter G; Brongersma, Mark L

2018-01-22

The ability to split an incident light beam into separate wavelength bands is central to a diverse set of optical applications, including imaging, biosensing, communication, photocatalysis, and photovoltaics. Entirely new opportunities are currently emerging with the recently demonstrated possibility to spectrally split light at a subwavelength scale with optical antennas. Unfortunately, such small structures offer limited spectral control and are hard to exploit in optoelectronic devices. Here, we overcome both challenges and demonstrate how within a single-layer metafilm one can laterally sort photons of different wavelengths below the free-space diffraction limit and extract a useful photocurrent. This chipscale demonstration of anti-Hermitian coupling between resonant photodetector elements also facilitates near-unity photon-sorting efficiencies, near-unity absorption, and a narrow spectral response (∼ 30 nm) for the different wavelength channels. This work opens up entirely new design paradigms for image sensors and energy harvesting systems in which the active elements both sort and detect photons.

Tunable photonic nanojet formed by generalized Luneburg lens.

PubMed

Mao, Xiurun; Yang, Yang; Dai, Haitao; Luo, Dan; Yao, Baoli; Yan, Shaohui

2015-10-05

Nanojet has been emerging as an interesting topic in variety photonics applications. In this paper, inspired by the properties of generalized Luneburg lens (GLLs), a two-dimensional photonic nanojet system has been developed, which focal distance can be tuned by engineering the refractive index profile of GLLs. Simulation and analysis results show that the maximum light intensity, transverse and longitudinal dimensions of the photonic nanojet are dependent on the focal distance of the GLLs, thereby, by simply varying the focal distance, it is possible to obtain localized photon fluxes with different power characteristics and spatial dimensions. This can be of interest for many promising applications, such as high-resolution optical detection, optical manipulation, technology of direct-write nano-patterning and nano-lithography.

Data indexing techniques for the EUVE all-sky survey

NASA Technical Reports Server (NTRS)

Lewis, J.; Saba, V.; Dobson, C.

1992-01-01

This poster describes techniques developed for manipulating large full-sky data sets for the Extreme Ultraviolet Explorer project. The authors have adapted the quatrilateralized cubic sphere indexing algorithm to allow us to efficiently store and process several types of large data sets, such as full-sky maps of photon counts, exposure time, and count rates. A variation of this scheme is used to index sparser data such as individual photon events and viewing times for selected areas of the sky, which are eventually used to create EUVE source catalogs.

Determining the confined optical length of high index vertical Si nanoforest arrays for photonic applications

NASA Astrophysics Data System (ADS)

Chaliyawala, Harsh A.; Purohit, Zeel; Khanna, Sakshum; Ray, Abhijit; Pati, Ranjan K.; Mukhopadhyay, Indrajit

2018-06-01

The structural and the optical properties of different Si nanostructures have been compared. Detailed optical properties of Si nanowires arrays of different optical lengths, fabricated by facile electroless etching technique, have been reported. The theoretical calculation of exponential sine profile at constant λ = 600 nm shows a better explanation in terms of gradient index with optical length for vertical nanowires. The observations signify the possibility of strong light trapping due to an exponential gradient towards the high index along the nanowires and the existence of dense subwavelength features. The optical admittance (Ƶ) shows a strong impact on optical distance (Z) for Z < H, owing to the electromagnetic wave interaction with the nanowires that perceive a different Ƶ at the oblique angle of incidence (AOI). In addition, the experimental reflectance data and the theoretical model for transverse electric and transverse magnetic modes predict that an optical length of 5 μm can exhibit a very low reflectance value. This indicates that the Si nanowires are polarization insensitive over a wide range of AOI (0°-80°). Moreover, Raman spectra showed a very strong light confinement effect in the first order transverse optical band with increasing etching depths. The morphological dependent resonance theory predicts a strong localized light field confinement in the lower wavelength regime for SiNWs. The effect on the strong resonant absorption modes was further correlated with the simulation results obtained by using COMSOL. The obtained results are likely to enhance the maximum absorption of SiNWs for various photonic applications.

Temperature sensor based on an isopropanol-sealed photonic crystal fiber in-line interferometer with enhanced refractive index sensitivity.

PubMed

Qiu, Sun-jie; Chen, Ye; Xu, Fei; Lu, Yan-qing

2012-03-01

We fabricate a simple, compact, and stable temperature sensor based on a liquid-sealed photonic crystal fiber (PCF) in-line nonpolarimetric modal interferometer. Different from other reported PCF devices, it does not need expensive polarimetric devices, and the liquid is sealed in one fiber. The device consists of a stub of isopropanol-filled PCF spliced between standard single-mode fibers. The temperature sensitivity (-166 pm/°C) increases over an order of magnitude compared with those of the previous sensors based on air-sealed PCF interferometers built via fusion splicing with the same mechanism. In addition, the refractive index sensitivity also increases. Higher temperature sensitivity can be realized by infiltrating some liquid having a higher thermo-optic coefficient into the microholes of the PCF. © 2012 Optical Society of America

Study on the application of Raman spectroscopy on detecting water hardness.

PubMed

Yang, Chang-Hu; Shi, Xiang-Hua; Yuan, Jian-Hui

2014-05-01

Laser Raman spectrum method was used to study the hardness index of four water samples. The ratio of bending vibration peak intensity to stretching vibration peak intensity of these water samples was measured. The results showed that as the total hardness of water decreases, so does the ratio. This offers a possible new approach to water quality analysis that is both simple and effective.

Hard Burst Emission from the Soft Gamma Repeater SGR 1900+14

NASA Technical Reports Server (NTRS)

Woods, Peter M.; Kouveliotou, Chryssa; VanParadijs, Jan; Briggs, Michael S.; Hurley, Kevin; Gogus, Ersin; Preece, Robert D.; Giblin, Timothy W.; Thompson, Christopher; Duncan, Robert C.

1999-01-01

We present evidence for burst emission from SGR 1900 + 14 with a power-law high-energy spectrum extending beyond 500 keV. Unlike previous detections of high-energy photons during bursts from soft gamma repeaters (SGRs), these emissions are not associated with extraordinarily bright flares. Not only is the emission hard, but the spectra are better fitted by D. Band's gamma-ray burst (GRB) function rather than by the traditional optically thin thermal bremsstrahlung model. We find that the spectral evolution within these hard events obeys a hardness/intensity anticorrelation. Temporally, these events are distinct from typical SGR burst emissions in that they are longer (approximately 1 s) and have relatively smooth profiles. Despite a difference in peak luminosity of approximately > 10(exp 11) between these bursts from SGR 1900 + 14 and cosmological GRBs, there are striking temporal and spectral similarities between the two kinds of bursts, aside from spectral evolution. We outline an interpretation of these events in the context of the magnetar model.

Electrically pumped edge-emitting photonic bandgap semiconductor laser

DOEpatents

Lin, Shawn-Yu; Zubrzycki, Walter J.

2004-01-06

A highly efficient, electrically pumped edge-emitting semiconductor laser based on a one- or two-dimensional photonic bandgap (PBG) structure is described. The laser optical cavity is formed using a pair of PBG mirrors operating in the photonic band gap regime. Transverse confinement is achieved by surrounding an active semiconductor layer of high refractive index with lower-index cladding layers. The cladding layers can be electrically insulating in the passive PBG mirror and waveguide regions with a small conducting aperture for efficient channeling of the injection pump current into the active region. The active layer can comprise a quantum well structure. The quantum well structure can be relaxed in the passive regions to provide efficient extraction of laser light from the active region.

Correlated Photon Dynamics in Dissipative Rydberg Media

NASA Astrophysics Data System (ADS)

Zeuthen, Emil; Gullans, Michael J.; Maghrebi, Mohammad F.; Gorshkov, Alexey V.

2017-07-01

Rydberg blockade physics in optically dense atomic media under the conditions of electromagnetically induced transparency (EIT) leads to strong dissipative interactions between single photons. We introduce a new approach to analyzing this challenging many-body problem in the limit of a large optical depth per blockade radius. In our approach, we separate the single-polariton EIT physics from Rydberg-Rydberg interactions in a serialized manner while using a hard-sphere model for the latter, thus capturing the dualistic particle-wave nature of light as it manifests itself in dissipative Rydberg-EIT media. Using this approach, we analyze the saturation behavior of the transmission through one-dimensional Rydberg-EIT media in the regime of nonperturbative dissipative interactions relevant to current experiments. Our model is able to capture the many-body dynamics of bright, coherent pulses through these strongly interacting media. We compare our model with available experimental data in this regime and find good agreement. We also analyze a scheme for generating regular trains of single photons from continuous-wave input and derive its scaling behavior in the presence of imperfect single-photon EIT.

Extraordinarily soft, medium-hard and hard Indian wheat varieties: Composition, protein profile, dough and baking properties.

PubMed

Katyal, Mehak; Singh, Narpinder; Virdi, Amardeep Singh; Kaur, Amritpal; Chopra, Nidhi; Ahlawat, Arvind Kumar; Singh, Anju Mahendru

2017-10-01

Hard wheat (HW), medium-hard wheat (MHW) and extraordinarily soft wheat (Ex-SW) varieties with grain hardness index (GHI) of 83 to 95, 72 to 80, 17 to 29 were evaluated for pasting, protein molecular weight (MW) distribution, dough rheology and baking properties. Flours from varieties with higher GHI had more protein content, ash content and paste viscosities. Ex-SW had more glutenins proportion as compared to HW and MHW. Flours from Ex-SW varieties showed lower NaSRC, WA and mixographic parameters as compared to HW and MHW. Dough from flours milled from Ex-SW had higher Intermolecular-β-sheets (IM-β-sheets) than those from MHW and HW. Muffins volume increased with decrease in GHI, Ex-SW varieties had more muffin volume and less air space. The accumulation of polypeptides (PPs) varied significantly in different varieties. Ex-SW variety (QBP12-10) showed accumulation of 98, 90, 81 and 79kDa PPs, which was unique and was different from other varieties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of Compton X-ray spectrometer for high energy resolution single-shot high-flux hard X-ray spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, Sadaoki, E-mail: kojima-s@ile.osaka-u.ac.jp, E-mail: sfujioka@ile.osaka-u.ac.jp; Ikenouchi, Takahito; Arikawa, Yasunobu

Hard X-ray spectroscopy is an essential diagnostics used to understand physical processes that take place in high energy density plasmas produced by intense laser-plasma interactions. A bundle of hard X-ray detectors, of which the responses have different energy thresholds, is used as a conventional single-shot spectrometer for high-flux (>10{sup 13} photons/shot) hard X-rays. However, high energy resolution (Δhv/hv < 0.1) is not achievable with a differential energy threshold (DET) X-ray spectrometer because its energy resolution is limited by energy differences between the response thresholds. Experimental demonstration of a Compton X-ray spectrometer has already been performed for obtaining higher energy resolutionmore » than that of DET spectrometers. In this paper, we describe design details of the Compton X-ray spectrometer, especially dependence of energy resolution and absolute response on photon-electron converter design and its background reduction scheme, and also its application to the laser-plasma interaction experiment. The developed spectrometer was used for spectroscopy of bremsstrahlung X-rays generated by intense laser-plasma interactions using a 200 μm thickness SiO{sub 2} converter. The X-ray spectrum obtained with the Compton X-ray spectrometer is consistent with that obtained with a DET X-ray spectrometer, furthermore higher certainly of a spectral intensity is obtained with the Compton X-ray spectrometer than that with the DET X-ray spectrometer in the photon energy range above 5 MeV.« less

A Test of Thick-Target Nonuniform Ionization as an Explanation for Breaks in Solar Flare Hard X-Ray Spectra

NASA Technical Reports Server (NTRS)

Holman, gordon; Dennis Brian R.; Tolbert, Anne K.; Schwartz, Richard

2010-01-01

Solar nonthermal hard X-ray (HXR) flare spectra often cannot be fitted by a single power law, but rather require a downward break in the photon spectrum. A possible explanation for this spectral break is nonuniform ionization in the emission region. We have developed a computer code to calculate the photon spectrum from electrons with a power-law distribution injected into a thick-target in which the ionization decreases linearly from 100% to zero. We use the bremsstrahlung cross-section from Haug (1997), which closely approximates the full relativistic Bethe-Heitler cross-section, and compare photon spectra computed from this model with those obtained by Kontar, Brown and McArthur (2002), who used a step-function ionization model and the Kramers approximation to the cross-section. We find that for HXR spectra from a target with nonuniform ionization, the difference (Delta-gamma) between the power-law indexes above and below the break has an upper limit between approx.0.2 and 0.7 that depends on the power-law index delta of the injected electron distribution. A broken power-law spectrum with a. higher value of Delta-gamma cannot result from nonuniform ionization alone. The model is applied to spectra obtained around the peak times of 20 flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI from 2002 to 2004 to determine whether thick-target nonuniform ionization can explain the measured spectral breaks. A Monte Carlo method is used to determine the uncertainties of the best-fit parameters, especially on Delta-gamma. We find that 15 of the 20 flare spectra require a downward spectral break and that at least 6 of these could not be explained by nonuniform ionization alone because they had values of Delta-gamma with less than a 2.5% probability of being consistent with the computed upper limits from the model. The remaining 9 flare spectra, based on this criterion, are consistent with the nonuniform ionization model.

Reversible thermochromic response based on photonic crystal structure in butterfly wing

NASA Astrophysics Data System (ADS)

Wang, Wanlin; Wang, Guo Ping; Zhang, Wang; Zhang, Di

2018-01-01

Subtle responsive properties can be achieved by the photonic crystal (PC) nanostructures of butterfly based on thermal expansion effect. The studies focused on making the sample visually distinct. However, the response is restricted by limited thermal expansion coefficients. We herein report a new class of reversible thermochromic response achieved by controlling the ambient refractive index in butterfly PC structure. The photonic ethanol-filled nanoarchitecture sample is simply assembled by sealing liquid ethanol filling Papilio ulysses butterfly wing. Volatile ethanol is used to modulate the ambient refractive index. The sample is sealed with glasses to ensure reversibility. Liquid ethanol filling butterfly wing demonstrated significant allochroic response to ambient refractive index, which can be controlled by the liquefaction and vaporization of ethanol. This design is capable of converting thermal energy into visual color signals. The mechanism of this distinct response is simulated and proven by band theory. The response properties are performed with different filled chemicals and different structure parameters. Thus, the reversible thermochromic response design might have potential use in the fields such as detection, photonic switch, displays, and so forth.

Hard X-ray spectrum of Cygnus X-1

NASA Technical Reports Server (NTRS)

Nolan, P. L.; Gruber, D. E.; Knight, F. K.; Matteson, J. L.; Rothschild, R. E.; Marshall, F. E.; Levine, A. M.; Primini, F. A.

1981-01-01

Long-term measurements of the hard X-ray spectrum from 3 keV to 8 MeV of the black-hole candidate Cygnus X-1 in its low state are reported. Observations were made from October 26 to November 18, 1977 with the A2 (Cosmic X-ray) and A4 (Hard X-ray and Low-Energy Gamma-Ray) experiments on board HEAO 1 in the spacecraft's scanning mode. The measured spectrum below 200 keV is found to agree well with previous spectra which have been fit by a model of the Compton scattering of optical or UV photons in a very hot plasma of electron temperature 32.4 keV and optical depth 3.9 or 1.6 for spherical or disk geometry, respectively. At energies above 300 keV, however, flux excess is observed which may be accounted for by a distribution of electron temperatures from 15 to about 100 keV.

Pion-photon reactions and chiral dynamics in Primakoff processes at COMPASS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedrich, Jan Michael

2016-01-22

With the COMPASS experiment at CERN, pion-photon reactions are investigated via the Primakoff effect, implying that high-energetic pions react with the quasi-real photon field surrounding the target nuclei. The production of a single hard photon in such a pion scattering at lowest momentum transfer to the nucleus is related to pion Compton scattering. From the measured cross-section shape, the pion polarisability is determined. The COMPASS measurement is in contradiction to the earlier dedicated measurements, and rather in agreement with the theoretical expectation from chiral perturbation theory. In the same data taking, reactions with neutral and charged pions in the finalmore » state are measured and analyzed. At low energy in the pion-photon centre-of-momentum system, these reactions are governed by chiral dynamics and contain information relevant for chiral perturbation theory. At higher energies, resonances are produced and their radiative coupling is investigated.« less

Predicting the Performance of Chain Saw Machines Based on Shore Scleroscope Hardness

NASA Astrophysics Data System (ADS)

Tumac, Deniz

2014-03-01

Shore hardness has been used to estimate several physical and mechanical properties of rocks over the last few decades. However, the number of researches correlating Shore hardness with rock cutting performance is quite limited. Also, rather limited researches have been carried out on predicting the performance of chain saw machines. This study differs from the previous investigations in the way that Shore hardness values (SH1, SH2, and deformation coefficient) are used to determine the field performance of chain saw machines. The measured Shore hardness values are correlated with the physical and mechanical properties of natural stone samples, cutting parameters (normal force, cutting force, and specific energy) obtained from linear cutting tests in unrelieved cutting mode, and areal net cutting rate of chain saw machines. Two empirical models developed previously are improved for the prediction of the areal net cutting rate of chain saw machines. The first model is based on a revised chain saw penetration index, which uses SH1, machine weight, and useful arm cutting depth as predictors. The second model is based on the power consumed for only cutting the stone, arm thickness, and specific energy as a function of the deformation coefficient. While cutting force has a strong relationship with Shore hardness values, the normal force has a weak or moderate correlation. Uniaxial compressive strength, Cerchar abrasivity index, and density can also be predicted by Shore hardness values.

Evidence for a Hard Ionizing Spectrum from a z = 6.11 Stellar Population

NASA Astrophysics Data System (ADS)

Mainali, Ramesh; Kollmeier, Juna A.; Stark, Daniel P.; Simcoe, Robert A.; Walth, Gregory; Newman, Andrew B.; Miller, Daniel R.

2017-02-01

We present the Magellan/FIRE detection of highly ionized C IV λ1550 and O III]λ1666 in a deep infrared spectrum of the z = 6.11 gravitationally lensed low-mass galaxy RXC J2248.7-4431-ID3, which has previously known Lyα. No corresponding emission is detected at the expected location of He II λ1640. The upper limit on He II, paired with detection of O III] and C IV, constrains possible ionization scenarios. Production of C IV and O III] requires ionizing photons of 2.5-3.5 Ryd, but once in that state their multiplet emission is powered by collisional excitation at lower energies (˜0.5 Ryd). As a pure recombination line, He II emission is powered by 4 Ryd ionizing photons. The data therefore require a spectrum with significant power at 3.5 Ryd but a rapid drop toward 4.0 Ryd. This hard spectrum with a steep drop is characteristic of low-metallicity stellar populations, and less consistent with soft AGN excitation, which features more 4 Ryd photons and hence higher He II flux. The conclusions based on ratios of metal line detections to helium non-detection are strengthened if the gas metallicity is low. RXJ2248-ID3 adds to the growing handful of reionization-era galaxies with UV emission line ratios distinct from the general z=2{--}3 population in a way that suggests hard ionizing spectra that do not necessarily originate in AGNs.

Photonic metamaterials: a new class of materials for manipulating light waves

PubMed Central

Iwanaga, Masanobu

2012-01-01

A decade of research on metamaterials (MMs) has yielded great progress in artificial electromagnetic materials in a wide frequency range from microwave to optical frequencies. This review outlines the achievements in photonic MMs that can efficiently manipulate light waves from near-ultraviolet to near-infrared in subwavelength dimensions. One of the key concepts of MMs is effective refractive index, realizing values that have not been obtained in ordinary solid materials. In addition to the high and low refractive indices, negative refractive indices have been reported in some photonic MMs. In anisotropic photonic MMs of high-contrast refractive indices, the polarization and phase of plane light waves were efficiently transformed in a well-designed manner, enabling remarkable miniaturization of linear optical devices such as polarizers, wave plates and circular dichroic devices. Another feature of photonic MMs is the possibility of unusual light propagation, paving the way for a new subfield of transfer optics. MM lenses having super-resolution and cloaking effects were introduced by exploiting novel light-propagating modes. Here, we present a new approach to describing photonic MMs definitely by resolving the electromagnetic eigenmodes. Two representative photonic MMs are addressed: the so-called fishnet MM slabs, which are known to have effective negative refractive index, and a three-dimensional MM based on a multilayer of a metal and an insulator. In these photonic MMs, we elucidate the underlying eigenmodes that induce unusual light propagations. Based on the progress of photonic MMs, the future potential and direction are discussed. PMID:27877512

Gap maps and intrinsic diffraction losses in one-dimensional photonic crystal slabs.

PubMed

Gerace, Dario; Andreani, Lucio Claudio

2004-05-01

A theoretical study of photonic bands for one-dimensional (1D) lattices embedded in planar waveguides with strong refractive index contrast is presented. The approach relies on expanding the electromagnetic field on the basis of guided modes of an effective waveguide, and on treating the coupling to radiative modes by perturbation theory. Photonic mode dispersion, gap maps, and intrinsic diffraction losses of quasi guided modes are calculated for the case of self-standing membranes as well as for silicon-on-insulator structures. Photonic band gaps in a waveguide are found to depend strongly on the core thickness and on polarization, so that the gaps for transverse electric and transverse magnetic modes most often do not overlap. Radiative losses of quasiguided modes above the light line depend in a nontrivial way on structure parameters, mode index, and wave vector. The results of this study may be useful for the design of integrated 1D photonic structures with low radiative losses.

QUANTUM NETWORKS WITH SINGLE ATOMS, PHOTONS AND PHONONS

DTIC Science & Technology

2016-10-04

methodology, the NSSEFF research required an interdisciplinary ’toolkit’ from atomic physics, quantum optics, and nano-photonics for the control ...achieve a very small non -guided decay rate, i.e. Γ′ ’ 0.5Γ0. Moreover, one can engineer flatter bands, which leads to an increase of the group index...without the need to investigate over a wide range of PCW designs with different photonic band structures. To fully control spin-exchange coefficients

Ultra-fast LuI{sub 3}:Ce scintillators for hard x-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marton, Zsolt, E-mail: zmarton@rmdinc.com; Miller, Stuart R.; Ovechkina, Elena

We have developed ultra-fast cerium-coped lutetium-iodide (LuI{sub 3}:Ce) films thermally evaporated as polycrystalline, structured scintillator using hot wall epitaxy (HWE) method. The films have shown a 13 ns decay compared to the 28 ns reported for crystals. The fast speed coupled with its high density (∼5.6 g/cm{sup 3}), high effective atomic number (59.7), and the fact that it can be vapor deposited in a columnar form makes LuI{sub 3}:Ce an attractive candidate for high frame rate, high-resolution, hard X-ray imaging. In crystal form, LuI{sub 3}:Ce has demonstrated bright (>100,000 photons/MeV) green (540 nm) emission, which is well matched to commercialmore » CCD/CMOS sensors and is critical for maintaining high signal to noise ratio in light starved applications. Here, we report on the scintillation properties of films and those for corresponding crystalline material. The vapor grown films were integrated into a high-speed CMOS imager to demonstrate high-speed radiography capability. The films were also tested at Advanced Photon Source, Argonne National Laboratory beamline 1-ID under hard X-ray irradiation. The data show a factor of four higher efficiency than the reference LuAG:Ce scintillators, high image quality, and linearity of scintillation response over a wide energy range. The films were employed to perform hard X-ray microtomography, the results of which will also be discussed.« less

On-chip photonic memory elements employing phase-change materials.

PubMed

Rios, Carlos; Hosseini, Peiman; Wright, C David; Bhaskaran, Harish; Pernice, Wolfram H P

2014-03-05

Phase-change materials integrated into nanophotonic circuits provide a flexible way to realize tunable optical components. Relying on the enormous refractive-index contrast between the amorphous and crystalline states, such materials are promising candidates for on-chip photonic memories. Nonvolatile memory operation employing arrays of microring resonators is demonstrated as a route toward all-photonic chipscale information processing. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RF Photonic Technology in Optical Fiber Links

NASA Astrophysics Data System (ADS)

Chang, William S. C.

2007-06-01

List of contributors; Introduction and preface; 1. Figures of merit and performance analysis of photonic microwave links Charles Cox and William S. C. Chang; 2. RF subcarrier links in local access networks Xiaolin Lu; 3. Analog modulation of semiconductor lasers Joachim Piprek and John E. Bowers; 4. LiNbO3 external modulators and their use in high performance analog links Gary E. Betts; 5. Broadband traveling wave modulators in LiNbO3 Marta M. Howerton and William K. Burns; 6. Multiple quantum well electroabsorption modulators for RF photonic links William S. C. Chang; 7. Polymer modulators for RF photonics Timothy Van Eck; 8. Photodiodes for high performance analog links P. K. L. Yu and Ming C. Wu; 9. Opto-electronic oscillators X. Steve Yao; 10. Photonic link techniques for microwave frequency conversion Stephen A. Pappert, Roger Helkey and Ronald T. Logan Jr; 11. Antenna-coupled millimeter-wave electro-optical modulators William B. Bridges; 12. System design and performance of wideband photonic phased array antennas Greg L. Tangonan, Willie Ng, Daniel Yap and Ron Stephens; Acknowledgements; References; Index.

Simultaneous optical/X-ray study of GS 1354-64 (=BW Cir) during hard outburst: evidence for optical cyclo-synchrotron emission from the hot accretion flow

NASA Astrophysics Data System (ADS)

Pahari, Mayukh; Gandhi, Poshak; Charles, Philip A.; Kotze, Marissa M.; Altamirano, Diego; Misra, Ranjeev

2017-07-01

We present results from simultaneous optical [South African Large Telescope (SALT)] and X-ray (Swift and INTEGRAL) observations of GS 1354-64/BW Cir during the 2015 hard state outburst. During the rising phase, optical/X-ray time series shows a strong anti-correlation with X-ray photons lagging optical. Optical and X-ray power spectra show quasi-periodic oscillations (QPOs) at a frequency of ˜18 mHz with a confidence level of at least 99 per cent. Simultaneous fitting of Swift/XRT and INTEGRAL spectra in the range 0.5-1000.0 keV shows non-thermal, power-law-dominated (>90 per cent) spectra with a hard power-law index of 1.48 ± 0.03, inner disc temperature of 0.12 ± 0.01 keV and an inner disc radius of ˜3000 km. All evidence is consistent with cyclo-synchrotron radiation in a non-thermal, hot electron cloud extending to ˜100 Schwarzschild radii being a major physical process for the origin of optical photons. At outburst peak about one month later, when the X-ray flux rises and the optical drops, the apparent features in the optical/X-ray correlation vanish and the optical auto correlation widens. Although ˜0.19 Hz QPO is observed from the X-ray power spectra, the optical variability is dominated by the broad-band noise, and the inner disc temperature increases. These results support a change in the dominant optical emission source between outburst rise and peak, consistent with a weakening of hot flow as the disc moves in.

A correlation between hard gamma-ray sources and cosmic voids along the line of sight

DOE PAGES

Furniss, A.; Sutter, P. M.; Primack, J. R.; ...

2014-11-25

We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E > 100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as “VHE-like” sources) are distributed along underdense lines of sight at the 2.4σ level. There is a less suggestive correlation for the Fermi hard source population (1.7σ). A correlation between 10-500 GeV fluxmore » and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4σ and 2.6σ, calculated from the Pearson correlation coefficients of r = 0.57 and 0.47, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity τ(E, z) ~ 5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight.« less

The pedagogical effect of a health education application for deaf and hard of hearing students in elementary schools.

PubMed

Abbasi, Masoumeh; Eslami, Saeid; Mohammadi, Mahdi; Khajouei, Reza

2017-09-01

Deaf or hard-of-hearing children experience difficulties in learning health principles. But technology has significantly improved their ability to learn. The challenge in e-learning is to design attractive applications while having an educational aspect. The aims of this study were to determine the pedagogical effectiveness of a health education application for deaf and hard of hearing students in elementary schools, and to investigate the student's perceptions in different educational grades about the educational effectiveness of the text, graphics, video clips, and animation in the application. The study design was quasi experimental and was conducted in Mashhad in 2016. Study population were deaf or hard-of-hearing students in elementary schools. The intervention included health application training to deaf and hard-of-hearing students in Mashhad. A questionnaire was used for data gathering. The pedagogical effectiveness was determined by measuring the modified Adapted Pedagogical Index. This index was created based on the characteristics of the application and study population. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney tests with Bonferroni adjustment by SPSS 22. Eighty-two students participated in the intervention. The value of modified Adapted Pedagogical Index was 0.669, indicating that the application was effective. The results of Kruskal-Wallis H and Mann-Whitney U test showed significant differences in different educational grades. (p<0.008). Using information technology can improve the education of deaf and hard-of-hearing students. Modified Adapted Pedagogical Index can be used for evaluation of non-interactive applications for elementary school children who are deaf or hard of hearing.

Topological Valley Transport in Two-dimensional Honeycomb Photonic Crystals.

PubMed

Yang, Yuting; Jiang, Hua; Hang, Zhi Hong

2018-01-25

Two-dimensional photonic crystals, in analogy to AB/BA stacking bilayer graphene in electronic system, are studied. Inequivalent valleys in the momentum space for photons can be manipulated by simply engineering diameters of cylinders in a honeycomb lattice. The inequivalent valleys in photonic crystal are selectively excited by a designed optical chiral source and bulk valley polarizations are visualized. Unidirectional valley interface states are proved to exist on a domain wall connecting two photonic crystals with different valley Chern numbers. With the similar optical vortex index, interface states can couple with bulk valley polarizations and thus valley filter and valley coupler can be designed. Our simple dielectric PC scheme can help to exploit the valley degree of freedom for future optical devices.

A next-generation in-situ nanoprobe beamline for the Advanced Photon Source

NASA Astrophysics Data System (ADS)

Maser, Jörg; Lai, Barry; Buonassisi, Tonio; Cai, Zhonghou; Chen, Si; Finney, Lydia; Gleber, Sophie-Charlotte; Harder, Ross; Jacobsen, Chris; Liu, Wenjun; Murray, Conal; Preissner, Curt; Roehrig, Chris; Rose, Volker; Shu, Deming; Vine, David; Vogt, Stefan

2013-09-01

The Advanced Photon Source is currently developing a suite of new hard x-ray beamlines, aimed primarily at the study of materials and devices under real conditions. One of the flagship beamlines of the APS Upgrade is the In-Situ Nanoprobe beamline (ISN beamline), which will provide in-situ and operando characterization of advanced energy materials and devices under change of temperature and gases, under applied fields, in 3D. The ISN beamline is designed to deliver spatially coherent x-rays with photon energies between 4 keV and 30 keV to the ISN instrument. As an x-ray source, a revolver-type undulator with two interchangeable magnetic structures, optimized to provide high brilliance throughout the range of photon energies of 4 keV - 30 keV, will be used. The ISN instrument will provide a smallest hard x-ray spot of 20 nm using diffractive optics, with sensitivity to sub-10 nm sample structures using coherent diffraction. Using nanofocusing mirrors in Kirkpatrick-Baez geometry, the ISN will also provide a focus of 50 nm with a flux of 8·1011 Photons/s at a photon energy of 10 keV, several orders of magnitude larger than what is currently available. This will allow imaging of trace amounts of most elements in the periodic table, with a sensitivity to well below 100 atoms for most metals in thin samples. It will also enable nanospectroscopic studies of the chemical state of most materials relevant to energy science. The ISN beamline will be primarily used to study inorganic and organic photovoltaic systems, advanced batteries and fuel cells, nanoelectronics devices, and materials and systems diesigned to reduce the environmental impact of combustion.

Ultra-high sensitivity Fabry-Perot interferometer gas refractive index fiber sensor based on photonic crystal fiber and Vernier effect.

PubMed

Quan, Mingran; Tian, Jiajun; Yao, Yong

2015-11-01

An ultra-high sensitivity open-cavity Fabry-Perot interferometer (FPI) gas refractive index (RI) sensor based on the photonic crystal fiber (PCF) and Vernier effect is proposed and demonstrated. The sensor is prepared by splicing a section of PCF to a section of fiber tube fused with a section of single mode fiber. The air holes running along the cladding of the PCF enable the gas to enter or leave the cavity freely. The reflection beam from the last end face of the PCF is used to generate the Vernier effect, which significantly improves the sensitivity of the sensor. Experimental results show that the proposed sensor can provide an ultra-high RI sensitivity of 30899 nm/RIU. This sensor has potential applications in fields such as gas concentration analyzing and humidity monitoring.

Octonacci photonic crystals with negative refraction index materials

NASA Astrophysics Data System (ADS)

Brandão, E. R.; Vasconcelos, M. S.; Anselmo, D. H. A. L.

2016-12-01

We investigate the optical transmission spectra for s-polarized (TE) and p-polarized (TM) waves in one-dimensional photonic quasicrystals on a quasiperiodic multilayer structure made up by alternate layers of SiO2 and metamaterials, organized by following the Octonacci sequence. Maxwell's equations and the transfer-matrix technique are used to derive the transmission spectra for the propagation of normally and obliquely incident optical fields. We assume Drude-Lorentz-type dispersive response for the dielectric permittivity and magnetic permeability of the metamaterials. For normally incident waves, we observe that the spectra does not have self-similar behavior or mirror symmetry and it also features the absence of optical band gap. Also for normally incident waves, we show regions of full transmittance when the incident angle θC = 0° in a particular frequency range.

Photonic jet with ultralong working distance by hemispheric shell.

PubMed

Hengyu, Zhu; Zaichun, Chen; Chong, Chong Tow; Minghui, Hong

2015-03-09

Micro-particle assisted nano-imaging has proven its success in the past few years since it can magnify the nano-objects, especially the metallic objects, into an image then collected by a conventional microscope. Micro-shell, which is a novel design of micro-particle in the configuration of a hemisphere with a hollow core region, is proposed and optimized in this paper in order to obtain a long photonic jet far away from its flat surface, thus increasing its working distance. Its dependence on the configuration and refractive index is investigated numerically. A micro-shell with the outer and inner radii of 5 and 2.5 µm and the refractive index of 1.5 can focus the incident light of 400 nm wavelength 2.7 µm away from the micro-shell flat surface, although the photonic jet intensity decreases to 25.8% compared to the solid hemisphere. Meanwhile, the photonic jet length of the micro-shell under the incident light of 400 nm and 1000 nm wavelengths are 1.7 µm and 4.3 µm, respectively, because its hollow core region tends to reduce the angle variation of the Poynting vectors in the photonic jet. With the long working distance and long photonic jet, the micro-shell could be used to scan over a sample to obtain a large area image when coupled with a conventional microscope, which is especially useful for the samples with the rough surfaces.

Real-Time Fluorescence Detection in Aqueous Systems by Combined and Enhanced Photonic and Surface Effects in Patterned Hollow Sphere Colloidal Photonic Crystals.

PubMed

Zhong, Kuo; Wang, Ling; Li, Jiaqi; Van Cleuvenbergen, Stijn; Bartic, Carmen; Song, Kai; Clays, Koen

2017-05-16

Hollow sphere colloidal photonic crystals (HSCPCs) exhibit the ability to maintain a high refractive index contrast after infiltration of water, leading to extremely high-quality photonic band gap effects, even in an aqueous (physiological) environment. Superhydrophilic pinning centers in a superhydrophobic environment can be used to strongly confine and concentrate water-soluble analytes. We report a strategy to realize real-time ultrasensitive fluorescence detection in patterned HSCPCs based on strongly enhanced fluorescence due to the photonic band-edge effect combined with wettability differentiation in the superhydrophobic/superhydrophilic pattern. The orthogonal nature of the two strategies allows for a multiplicative effect, resulting in an increase of two orders of magnitude in fluorescence.

Hadroproduction of t anti-t pair in association with an isolated photon at NLO accuracy matched with parton shower

NASA Astrophysics Data System (ADS)

Kardos, Adam; Trócsányi, Zoltán

2015-05-01

We simulate the hadroproduction of a -pair in association with a hard photon at LHC using the PowHel package. These events are almost fully inclusive with respect to the photon, allowing for any physically relevant isolation of the photon. We use the generated events, stored according to the Les-Houches event format, to make predictions for differential distributions formally at the next-to-leading order (NLO) accuracy and we compare these to existing predictions accurate at NLO using the smooth isolation prescription of Frixione. Our fixed-order predictions include the direct-photon contribution only. We also make predictions for distributions after full parton shower and hadronization using the standard experimental cone-isolation of the photon.

Photonic crystal surface-emitting lasers enabled by an accidental Dirac point

DOEpatents

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2014-12-02

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

Numerical investigation of the flat band Bloch modes in a 2D photonic crystal with Dirac cones

DOE PAGES

Zhang, Peng; Fietz, Chris; Tassin, Philippe; ...

2015-04-14

A numerical method combining complex-k band calculations and absorbing boundary conditions for Bloch waves is presented. We use this method to study photonic crystals with Dirac cones. We demonstrate that the photonic crystal behaves as a zero-index medium when excited at normal incidence, but that the zero-index behavior is lost at oblique incidence due to excitation of modes on the flat band. We also investigate the formation of monomodal and multimodal cavity resonances inside the photonic crystals, and the physical origins of their different line-shape features.

Polarization operator of a photon in a magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katkov, V. M., E-mail: V.M.Katkov@inp.nsk.su

2016-08-15

The polarization operator of a photon in a static uniform magnetic field has been studied at photon energies both above and below the threshold of electron–positron pair production by a photon. In the first order of the fine-structure constant α, expressions for the refractive index of a photon with a certain polarization in both low and high fields as compared to the critical field H{sub 0} = 4.41 × 10{sup 13} G have been obtained. Both the purely quantum range of photon energies, where the particles of a pair are produced at the lowest Landau levels, and the region ofmore » applicability of the semiclassical approximation in the case of the population of high energy levels have been considered. A general spectral integral formula has been obtained with divergent threshold terms separated in an explicit form.« less

The relationship between grain hardness, dough mixing parameters and bread-making quality in winter wheat.

PubMed

Salmanowicz, Bolesław P; Adamski, Tadeusz; Surma, Maria; Kaczmarek, Zygmunt; Karolina, Krystkowiak; Kuczyńska, Anetta; Banaszak, Zofia; Lugowska, Bogusława; Majcher, Małgorzata; Obuchowski, Wiktor

2012-01-01

The influence of grain hardness, determined by using molecular markers and physical methods (near-infrared (NIR) technique and particle size index-PSI) on dough characteristics, which in turn were determined with the use of a farinograph and reomixer, as well as bread-making properties were studied. The material covered 24 winter wheat genotypes differing in grain hardness. The field experiment was conducted at standard and increased levels of nitrogen fertilization. Results of molecular analyses were in agreement with those obtained by the use of physical methods for soft-grained lines. Some lines classified as hard (by physical methods) appeared to have the wild-type Pina and Pinb alleles, similar to soft lines. Differences in dough and bread-making properties between lines classified as hard and soft on the basis of molecular data appeared to be of less significance than the differences between lines classified as hard and soft on the basis of physical analyses of grain texture. Values of relative grain hardness at the increased nitrogen fertilization level were significantly higher. At both fertilization levels the NIR parameter determining grain hardness was significantly positively correlated with the wet gluten and sedimentation values, with most of the rheological parameters and bread yield. Values of this parameter correlated with quality characteristics in a higher degree than values of particle size index.

Design study of an optical cavity for a future photon collider at ILC

NASA Astrophysics Data System (ADS)

Klemz, G.; Mönig, K.; Will, I.

2006-08-01

Hard photons well above 100 GeV have to be generated in a future photon collider which essentially will be based on the infrastructure of the planned International Linear Collider (ILC). The energy of near-infrared laser photons will be boosted by Compton backscattering against a high-energy relativistic electron beam. For high effectiveness, a very powerful laser system is required that exceeds today's state-of-the-art capabilities. In this paper a design of an auxiliary passive cavity is discussed that resonantly enhances the peak-power of the laser. The properties and prospects of such a cavity are addressed on the basis of the specifications for the European TeV Energy Superconducting Linear Accelerator (TESLA) proposal. Those of the ILC are expected to be similar.

The photon PDF from high-mass Drell-Yan data at the LHC.

PubMed

Giuli, F

2017-01-01

Achieving the highest precision for theoretical predictions at the LHC requires the calculation of hard-scattering cross sections that include perturbative QCD corrections up to (N)NNLO and electroweak (EW) corrections up to NLO. Parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, [Formula: see text]. In this work a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell-Yan dilepton production at [Formula: see text] TeV is presented. This analysis is based on the xFitter framework, and has required improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results are compared with other recent QED fits and determinations of the photon PDF, consistent results are found.

Photonic crystal nanofiber air-mode cavity with high Q-factor and high sensitivity for refractive index sensing

NASA Astrophysics Data System (ADS)

Ma, Xiaoxue; Chen, Xin; Nie, Hongrui; Yang, Daquan

2018-01-01

Recently, due to its superior characteristics and simple manufacture, such as small size, low loss, high sensitivity and convenience to couple, the optical fiber sensor has become one of the most promising sensors. In order to achieve the most effective realization of light propagation by changing the structure of sensors, FOM(S •Q/λres) ,which is determined by two significant variables Q-factor and sensitivity, as a trade-off parameter should be optimized to a high value. In typical sensors, a high Q can be achieved by confining the optical field in the high refractive index dielectric region to make an interaction between analytes and evanescent field of the resonant mode. However, the ignored sensitivity is relatively low with a high Q achieved, which means that the resonant wavelength shift changes non-obviously when the refractive index increases. Meanwhile, the sensitivity also leads to a less desirable FOM. Therefore, a gradient structure, which can enhance the performance of sensors by achieving high Q and high sensitivity, has been developed by Kim et al. later. Here, by introducing parabolic-tapered structure, the light field localized overlaps strongly and sufficiently with analytes. And based on a one-dimensional photonic-crystal nanofiber air-mode cavity, a creative optical fiber sensor is proposed by combining good stability and transmission characteristics of fiber and strengths of tapered structure, realizing excellent FOM {4.7 x 105 with high Q-factors (Q{106) and high sensitivities (<700 nm/RIU).

The pedagogical effect of a health education application for deaf and hard of hearing students in elementary schools

PubMed Central

Abbasi, Masoumeh; Eslami, Saeid; Mohammadi, Mahdi; khajouei, Reza

2017-01-01

Background Deaf or hard-of-hearing children experience difficulties in learning health principles. But technology has significantly improved their ability to learn. The challenge in e-learning is to design attractive applications while having an educational aspect. Objective The aims of this study were to determine the pedagogical effectiveness of a health education application for deaf and hard of hearing students in elementary schools, and to investigate the student’s perceptions in different educational grades about the educational effectiveness of the text, graphics, video clips, and animation in the application. Methods The study design was quasi experimental and was conducted in Mashhad in 2016. Study population were deaf or hard-of-hearing students in elementary schools. The intervention included health application training to deaf and hard-of-hearing students in Mashhad. A questionnaire was used for data gathering. The pedagogical effectiveness was determined by measuring the modified Adapted Pedagogical Index. This index was created based on the characteristics of the application and study population. Statistical analysis was performed using the Kruskal-Wallis and Mann–Whitney tests with Bonferroni adjustment by SPSS 22. Results Eighty-two students participated in the intervention. The value of modified Adapted Pedagogical Index was 0.669, indicating that the application was effective. The results of Kruskal-Wallis H and Mann–Whitney U test showed significant differences in different educational grades. (p<0.008) Conclusion Using information technology can improve the education of deaf and hard-of-hearing students. Modified Adapted Pedagogical Index can be used for evaluation of non-interactive applications for elementary school children who are deaf or hard of hearing. PMID:29038697

EDITORIAL: Special issue on green photonics Special issue on green photonics

NASA Astrophysics Data System (ADS)

Boardman, Allan; Brongersma, Mark; Polman, Albert

2012-02-01

Photovoltaic (PV) cells can provide virtually unlimited amounts of energy by effectively converting sunlight into clean electrical power. Over the years, significant research and development efforts have been devoted to improving the structural and charge transport properties of the materials used in PV cells. Despite these efforts, the current energy conversion efficiencies of commercial solar cells are still substantially lower than the ultimate limits set by thermodynamics. Economic arguments in addition to the scarcity of some semiconductors and materials used in transparent conductive oxides are also driving us to use less and less material in a cell. For these reasons, it is clear that new approaches need to be found. One possible solution that is more-or-less orthogonal to previous approaches is aimed at managing the photons rather than the electrons or atoms in a cell. This type of photon management is termed Green Photonics. Nano- and micro-photonic trapping techniques are currently gaining significant attention. The use of engineered plasmonic and high refractive index structures shows tremendous potential for enhancing the light absorption per unit volume in semiconductors. Unfortunately, the design space in terms of the nanostructure sizes, shapes, and array structures is too large to allow for optimization of PV cells using brute force simulations. For this reason, new intuitive models and rapid optimization techniques for advanced light trapping technologies need to be developed. At the same time we need to come up with new, inexpensive, and scalable nanostructure fabrication and optical characterization techniques in order to realize the dream of inexpensive, high power conversion efficiency cells that make economic sense. This special issue discusses some of the exciting new approaches to light trapping that leverage the most recent advances in the field of nanophotonics. It also provides some insights into why giving the green light to green

NuSTAR Hard X-Ray Survey of the Galactic Center Region. II. X-Ray Point Sources

NASA Technical Reports Server (NTRS)

Hong, Jaesub; Mori, Kaya; Hailey, Charles J.; Nynka, Melania; Zhang, Shou; Gotthelf, Eric; Fornasini, Francesca M.; Krivonos, Roman; Bauer, Franz; Perez, Kerstin;

Photonic sensing based on variation of propagation properties of photonic crystal fibres

NASA Astrophysics Data System (ADS)

Rothwell, John H.; Flavin, Dónal A.; MacPherson, William N.; Jones, Julian D.; Knight, Jonathan C.; Russell, Philip St. J.

2006-12-01

We report on a low-coherence interferometric scheme for the measurement of the strain and temperature dependences of group delay and dispersion in short, index-guiding, 'endlessly-single-mode' photonic crystal fibre elements in the 840 nm and 1550 nm regions. Based on the measurements, we propose two schemes for simultaneous strain and temperature measurement using a single unmodified PCF element, without a requirement for any compensating components, and we project the measurement accuracies of these schemes.

Dual curved photonic crystal ring resonator based channel drop filter using two-dimensional photonic crystal structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chhipa, Mayur Kumar, E-mail: mayurchhipa1@gmail.com; Dusad, Lalit Kumar

In this paper channel drop filter (CDF) is designed using dual curved photonic crystal ring resonator (PCRR). The photonic band gap (PBG) is calculated by plane wave expansion (PWE) method and the photonic crystal (PhC) based on two dimensional (2D) square lattice periodic arrays of silicon (Si) rods in air structure have been investigated using finite difference time domain (FDTD) method. The number of rods in Z and X directions is 21 and 20 respectively with lattice constant 0.540 nm and rod radius r = 0.1 µm. The channel drop filter has been optimized for telecommunication wavelengths λ = 1.591 µm with refractivemore » indices 3.533. In the designed structure further analysis is also done by changing whole rods refractive index and it has been observed that this filter may be used for filtering several other channels also. The designed structure is useful for CWDM systems. This device may serve as a key component in photonic integrated circuits. The device is ultra compact with the overall size around 123 µm{sup 2}.« less

Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers

NASA Astrophysics Data System (ADS)

Noordegraaf, Danny; Scolari, Lara; Lægsgaard, Jesper; Rindorf, Lars; Tanggaard Alkeskjold, Thomas

2007-06-01

We demonstrate electrically and mechanically induced long period gratings (LPGs) in a photonic crystal fiber (PCF) filled with a high-index liquid crystal. The presence of the liquid crystal changes the guiding properties of the fiber from an index guiding fiber to a photonic bandgap guiding fiber - a so called liquid crystal photonic bandgap (LCPBG) fiber. Both the strength and resonance wavelength of the gratings are highly tunable. By adjusting the amplitude of the applied electric field, the grating strength can be tuned and by changing the temperature, the resonance wavelength can be tuned as well. Numerical calculations of the higher order modes of the fiber cladding are presented, allowing the resonance wavelengths to be calculated. A high polarization dependent loss of the induced gratings is also observed.

Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in p + p collisions at s = 510 GeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adare, A.; Aidala, C.; Ajitanand, N. N.

Dihadron and isolated direct photon-hadron angular correlations are measured in p+p collisions at √s=510 GeV. Correlations of charged hadrons of 0.7T<10 GeV/c with π 0 mesons of 4T<15 GeV/c or isolated direct photons of 7T direct photon or π 0. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (pmore » $$trig\\atop{T}$$). The Gaussian widths and root mean square of p out are reported as a function of the interaction hard scale p$$trig\\atop{T}$$ to investigate possible transverse-momentum-dependent evolution differences between the π 0-h ± and direct photon-h ± correlations and factorization breaking effects. The widths are found to decrease with p$$trig\\atop{T}$$, which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in p+p collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.« less

Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in p + p collisions at s = 510 GeV

DOE PAGES

Adare, A.; Aidala, C.; Ajitanand, N. N.; ...

2017-04-04

Dihadron and isolated direct photon-hadron angular correlations are measured in p+p collisions at √s=510 GeV. Correlations of charged hadrons of 0.7T<10 GeV/c with π 0 mesons of 4T<15 GeV/c or isolated direct photons of 7T direct photon or π 0. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (pmore » $$trig\\atop{T}$$). The Gaussian widths and root mean square of p out are reported as a function of the interaction hard scale p$$trig\\atop{T}$$ to investigate possible transverse-momentum-dependent evolution differences between the π 0-h ± and direct photon-h ± correlations and factorization breaking effects. The widths are found to decrease with p$$trig\\atop{T}$$, which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in p+p collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.« less

Hard X-ray imaging spectroscopy of FOXSI microflares

NASA Astrophysics Data System (ADS)

Glesener, Lindsay; Krucker, Sam; Christe, Steven; Buitrago-Casas, Juan Camilo; Ishikawa, Shin-nosuke; Foster, Natalie

2015-04-01

The ability to investigate particle acceleration and hot thermal plasma in solar flares relies on hard X-ray imaging spectroscopy using bremsstrahlung emission from high-energy electrons. Direct focusing of hard X-rays (HXRs) offers the ability to perform cleaner imaging spectroscopy of this emission than has previously been possible. Using direct focusing, spectra for different sources within the same field of view can be obtained easily since each detector segment (pixel or strip) measures the energy of each photon interacting within that segment. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload has successfully completed two flights, observing microflares each time. Flare images demonstrate an instrument imaging dynamic range far superior to the indirect methods of previous instruments like the RHESSI spacecraft.In this work, we present imaging spectroscopy of microflares observed by FOXSI in its two flights. Imaging spectroscopy performed on raw FOXSI images reveals the temperature structure of flaring loops, while more advanced techniques such as deconvolution of the point spread function produce even more detailed images.

High Precision Grids for Neutron, Hard X-Ray, and Gamma-Ray Imaging Systems

NASA Technical Reports Server (NTRS)

Campbell, Jonathan W. (Inventor)

2002-01-01

Fourier telescopes permit observations over a very broad band of energy. They generally include synthetic spatial filtering structures, known as multilayer grids or grid pairs consisting of alternate layers of absorbing and transparent materials depending on whether neutrons or photons are being imaged. For hard x-rays and gamma rays high (absorbing) and low (transparent) atomic number elements, termed high-Z and low-Z materials may be used. Fabrication of these multilayer grid structures is not without its difficulties. Herein the alternate layers of the higher material and the lower material are inserted in a polyhedron, transparent to photons of interest, through an open face of the polyhedron. The inserted layers are then uniformly compressed to form a multilayer grid.

Integrated photonics for fiber optic based temperature sensing

NASA Astrophysics Data System (ADS)

Evenblij, R. S.; van Leest, T.; Haverdings, M. B.

2017-09-01

One of the promising space applications areas for fibre sensing is high reliable thermal mapping of metrology structures for effects as thermal deformation, focal plane distortion, etc. Subsequently, multi-point temperature sensing capability for payload panels and instrumentation instead of, or in addition to conventional thermo-couple technology will drastically reduce electrical wiring and sensor materials to minimize weight and costs. Current fiber sensing technologies based on solid state ASPIC (Application Specific Photonic Integrated Circuits) technology, allow significant miniaturization of instrumentation and improved reliability. These imperative aspects make the technology candidate for applications in harsh environments such as space. One of the major aspects in order to mature ASPIC technology for space is assessment on radiation hardness. This paper describes the results of radiation hardness experiments on ASPIC including typical multipoint temperature sensing and thermal mapping capabilities.

Method to create gradient index in a polymer

DOEpatents

Dirk, Shawn M; Johnson, Ross Stefan; Boye, Robert; Descour, Michael R; Sweatt, William C; Wheeler, David R; Kaehr, Bryan James

2014-10-14

Novel photo-writable and thermally switchable polymeric materials exhibit a refractive index change of .DELTA.n.gtoreq.1.0 when exposed to UV light or heat. For example, lithography can be used to convert a non-conjugated precursor polymer to a conjugated polymer having a higher index-of-refraction. Further, two-photon lithography can be used to pattern high-spatial frequency structures.

Manipulating Light and Matter with Photonic Structures: Numerical Investigations on Photonic Crystals and Optical Forces

NASA Astrophysics Data System (ADS)

Zhang, Peng

The highly developed nano-fabrication techniques allow light to be modulated with photonic structures in a more intensive way. These photonic structures involve photonic crystals, metals supporting surface plasmon polaritons, metamaterials, etc. In this thesis work, three different ways for light manipulation are numerically investigated. First, the light propagation is modulated using a photonic crystal with Dirac cones. It is demonstrated that the zero-index behavior of this photonic crystal which happens for normal incident waves, is lost at oblique incidence. A new method combining complex-k band calculations and absorbing boundary conditions for Bloch modes is developed to analyze the Bloch mode interaction in details. Second, the mechanic states of graphene are modulated through the optical gradient force. This force is induced by the coupled surface plasmons on the double graphene sheets and is greatly enhanced in comparison to the regular waveguides. By applying different strengths of forces in accordance to the input power, the mechanic state transition is made possible, accompanied by an abrupt change in the transmission and reflection spectra. Third, the helicity/chirality of light is studied to modulate the lateral force on a small particle. A left-hand material slab which supports coherent TE ad TM plasmons simultaneously is introduced. By mixing the TE and TM surface plasmons with different relative phases, the lateral force on a chiral particle can be changed, which will be beneficial for chiral particle sorting.

Design and process development of a photonic crystal polymer biosensor for point-of-care diagnostics

NASA Astrophysics Data System (ADS)

Dortu, F.; Egger, H.; Kolari, K.; Haatainen, T.; Furjes, P.; Fekete, Z.; Bernier, D.; Sharp, G.; Lahiri, B.; Kurunczi, S.; Sanchez, J.-C.; Turck, N.; Petrik, P.; Patko, D.; Horvath, R.; Eiden, S.; Aalto, T.; Watts, S.; Johnson, N. P.; De La Rue, R. M.; Giannone, D.

2011-07-01

In this work, we report advances in the fabrication and anticipated performance of a polymer biosensor photonic chip developed in the European Union project P3SENS (FP7-ICT4-248304). Due to the low cost requirements of point-ofcare applications, the photonic chip is fabricated from nanocomposite polymeric materials, using highly scalable nanoimprint- lithography (NIL). A suitable microfluidic structure transporting the analyte solutions to the sensor area is also fabricated in polymer and adequately bonded to the photonic chip. We first discuss the design and the simulated performance of a high-Q resonant cavity photonic crystal sensor made of a high refractive index polyimide core waveguide on a low index polymer cladding. We then report the advances in doped and undoped polymer thin film processing and characterization for fabricating the photonic sensor chip. Finally the development of the microfluidic chip is presented in details, including the characterisation of the fluidic behaviour, the technological and material aspects of the 3D polymer structuring and the stable adhesion strategies for bonding the fluidic and the photonic chips, with regards to the constraints imposed by the bioreceptors supposedly already present on the sensors.

Direct-Photon Spectra and Anisotropic Flow in Heavy Ion Collisions from Holography

NASA Astrophysics Data System (ADS)

Iatrakis, Ioannis; Kiritsis, Elias; Shen, Chun; Yang, Di-Lun

2017-03-01

The thermal-photon emission from strongly coupled gauge theories at finite temperature is calculated by using holographic models for QCD in the Veneziano limit (V-QCD). These emission rates are then embedded in hydrodynamic simulations combined with prompt photons from hard scattering and the thermal photons from hadron gas to analyze the spectra and anisotropic flow of direct photons at RHIC and LHC. The results from different sources responsible for the thermal photons in the quark gluon plasma (QGP) including the weakly coupled QGP (wQGP) from perturbative calculations, strongly coupled N = 4 super Yang-Mills (SYM) plasma (as a benchmark for reference), and Gubser's phenomenological model mimicking the strongly coupled QGP (sQGP) are then compared. It is found that the direct-photon spectra are enhanced in the strongly coupled scenario compared with the ones in the wQGP, especially at intermediate and high momenta, which improve the agreements with data. Moreover, by using IP-glassma initial states, both the elliptic flow and triangular flow of direct photons are amplified at high momenta (pT > 2.5 GeV) for V-QCD, while they are suppressed at low momenta compared to wQGP. The distinct results in holography stem from the blue-shift of emission rates in strong coupling. In addition, the spectra and flow in small collision systems were evaluated for future comparisons. It is found that thermal photons from the deconfined phase are substantial to reconcile the spectra and flow at high momenta.

Photonic Crystal Sensors Based on Porous Silicon

PubMed Central

Pacholski, Claudia

2013-01-01

Porous silicon has been established as an excellent sensing platform for the optical detection of hazardous chemicals and biomolecular interactions such as DNA hybridization, antigen/antibody binding, and enzymatic reactions. Its porous nature provides a high surface area within a small volume, which can be easily controlled by changing the pore sizes. As the porosity and consequently the refractive index of an etched porous silicon layer depends on the electrochemial etching conditions photonic crystals composed of multilayered porous silicon films with well-resolved and narrow optical reflectivity features can easily be obtained. The prominent optical response of the photonic crystal decreases the detection limit and therefore increases the sensitivity of porous silicon sensors in comparison to sensors utilizing Fabry-Pérot based optical transduction. Development of porous silicon photonic crystal sensors which allow for the detection of analytes by the naked eye using a simple color change or the fabrication of stacked porous silicon photonic crystals showing two distinct optical features which can be utilized for the discrimination of analytes emphasize its high application potential. PMID:23571671

Active phase correction of high resolution silicon photonic arrayed waveguide gratings

DOE PAGES

Gehl, M.; Trotter, D.; Starbuck, A.; ...

2017-03-10

Arrayed waveguide gratings provide flexible spectral filtering functionality for integrated photonic applications. Achieving narrow channel spacing requires long optical path lengths which can greatly increase the footprint of devices. High index contrast waveguides, such as those fabricated in silicon-on-insulator wafers, allow tight waveguide bends which can be used to create much more compact designs. Both the long optical path lengths and the high index contrast contribute to significant optical phase error as light propagates through the device. Thus, silicon photonic arrayed waveguide gratings require active or passive phase correction following fabrication. We present the design and fabrication of compact siliconmore » photonic arrayed waveguide gratings with channel spacings of 50, 10 and 1 GHz. The largest device, with 11 channels of 1 GHz spacing, has a footprint of only 1.1 cm 2. Using integrated thermo-optic phase shifters, the phase error is actively corrected. We present two methods of phase error correction and demonstrate state-of-the-art cross-talk performance for high index contrast arrayed waveguide gratings. As a demonstration of possible applications, we perform RF channelization with 1 GHz resolution. In addition, we generate unique spectral filters by applying non-zero phase offsets calculated by the Gerchberg Saxton algorithm.« less

Active phase correction of high resolution silicon photonic arrayed waveguide gratings.

PubMed

Gehl, M; Trotter, D; Starbuck, A; Pomerene, A; Lentine, A L; DeRose, C

2017-03-20

Arrayed waveguide gratings provide flexible spectral filtering functionality for integrated photonic applications. Achieving narrow channel spacing requires long optical path lengths which can greatly increase the footprint of devices. High index contrast waveguides, such as those fabricated in silicon-on-insulator wafers, allow tight waveguide bends which can be used to create much more compact designs. Both the long optical path lengths and the high index contrast contribute to significant optical phase error as light propagates through the device. Therefore, silicon photonic arrayed waveguide gratings require active or passive phase correction following fabrication. Here we present the design and fabrication of compact silicon photonic arrayed waveguide gratings with channel spacings of 50, 10 and 1 GHz. The largest device, with 11 channels of 1 GHz spacing, has a footprint of only 1.1 cm². Using integrated thermo-optic phase shifters, the phase error is actively corrected. We present two methods of phase error correction and demonstrate state-of-the-art cross-talk performance for high index contrast arrayed waveguide gratings. As a demonstration of possible applications, we perform RF channelization with 1 GHz resolution. Additionally, we generate unique spectral filters by applying non-zero phase offsets calculated by the Gerchberg Saxton algorithm.

Unidirectional Wave Propagation in Low-Symmetric Colloidal Photonic-Crystal Heterostructures.

PubMed

Yannopapas, Vassilios

2015-03-19

We show theoretically that photonic crystals consisting of colloidal spheres exhibit unidirectional wave propagation and one-way frequency band gaps without breaking time-reversal symmetry via, e.g., the application of an external magnetic field or the use of nonlinear materials. Namely, photonic crystals with low symmetry such as the monoclinic crystal type considered here as well as with unit cells formed by the heterostructure of different photonic crystals show significant unidirectional electromagnetic response. In particular, we show that the use of scatterers with low refractive-index contrast favors the formation of unidirectional frequency gaps which is the optimal route for achieving unidirectional wave propagation.

Fine tuning of optical signals in nanoporous anodic alumina photonic crystals by apodized sinusoidal pulse anodisation.

PubMed

Santos, Abel; Law, Cheryl Suwen; Chin Lei, Dominique Wong; Pereira, Taj; Losic, Dusan

2016-11-03

In this study, we present an advanced nanofabrication approach to produce gradient-index photonic crystal structures based on nanoporous anodic alumina. An apodization strategy is for the first time applied to a sinusoidal pulse anodisation process in order to engineer the photonic stop band of nanoporous anodic alumina (NAA) in depth. Four apodization functions are explored, including linear positive, linear negative, logarithmic positive and logarithmic negative, with the aim of finely tuning the characteristic photonic stop band of these photonic crystal structures. We systematically analyse the effect of the amplitude difference (from 0.105 to 0.840 mA cm -2 ), the pore widening time (from 0 to 6 min), the anodisation period (from 650 to 950 s) and the anodisation time (from 15 to 30 h) on the quality and the position of the characteristic photonic stop band and the interferometric colour of these photonic crystal structures using the aforementioned apodization functions. Our results reveal that a logarithmic negative apodisation function is the most optimal approach to obtain unprecedented well-resolved and narrow photonic stop bands across the UV-visible-NIR spectrum of NAA-based gradient-index photonic crystals. Our study establishes a fully comprehensive rationale towards the development of unique NAA-based photonic crystal structures with finely engineered optical properties for advanced photonic devices such as ultra-sensitive optical sensors, selective optical filters and all-optical platforms for quantum computing.

Application of Rapid Visco Analyser (RVA) viscograms and chemometrics for maize hardness characterisation.

PubMed

Guelpa, Anina; Bevilacqua, Marta; Marini, Federico; O'Kennedy, Kim; Geladi, Paul; Manley, Marena

2015-04-15

It has been established in this study that the Rapid Visco Analyser (RVA) can describe maize hardness, irrespective of the RVA profile, when used in association with appropriate multivariate data analysis techniques. Therefore, the RVA can complement or replace current and/or conventional methods as a hardness descriptor. Hardness modelling based on RVA viscograms was carried out using seven conventional hardness methods (hectoliter mass (HLM), hundred kernel mass (HKM), particle size index (PSI), percentage vitreous endosperm (%VE), protein content, percentage chop (%chop) and near infrared (NIR) spectroscopy) as references and three different RVA profiles (hard, soft and standard) as predictors. An approach using locally weighted partial least squares (LW-PLS) was followed to build the regression models. The resulted prediction errors (root mean square error of cross-validation (RMSECV) and root mean square error of prediction (RMSEP)) for the quantification of hardness values were always lower or in the same order of the laboratory error of the reference method. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of a Hard X-ray Beam Position Monitor for Insertion Device Beams at the APS

NASA Astrophysics Data System (ADS)

Decker, Glenn; Rosenbaum, Gerd; Singh, Om

2006-11-01

Long-term pointing stability requirements at the Advanced Photon Source (APS) are very stringent, at the level of 500 nanoradians peak-to-peak or better over a one-week time frame. Conventional rf beam position monitors (BPMs) close to the insertion device source points are incapable of assuring this level of stability, owing to mechanical, thermal, and electronic stability limitations. Insertion device gap-dependent systematic errors associated with the present ultraviolet photon beam position monitors similarly limit their ability to control long-term pointing stability. We report on the development of a new BPM design sensitive only to hard x-rays. Early experimental results will be presented.

In vivo brain imaging using a portable 3.9 gram two-photon fluorescence microendoscope

NASA Astrophysics Data System (ADS)

Flusberg, Benjamin A.; Jung, Juergen C.; Cocker, Eric D.; Anderson, Erik P.; Schnitzer, Mark J.

2005-09-01

We introduce a compact two-photon fluorescence microendoscope based on a compound gradient refractive index endoscope probe, a DC micromotor for remote adjustment of the image plane, and a flexible photonic bandgap fiber for near distortion-free delivery of ultrashort excitation pulses. The imaging head has a mass of only 3.9 g and provides micrometer-scale resolution. We used portable two-photon microendoscopy to visualize hippocampal blood vessels in the brains of live mice.

Two-photon interference of temporally separated photons.

PubMed

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-10-06

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms.

Two-photon interference of temporally separated photons

PubMed Central

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-01-01

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms. PMID:27708380

Inference of the electron temperature in ICF implosions from the hard X-ray spectral continuum

NASA Astrophysics Data System (ADS)

Kagan, Grigory; Landen, O. L.; Svyatsky, D.; Sio, H.; Kabadi, N. V.; Simpson, R. A.; Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Shah, R. C.; Joshi, T. R.; Hakel, P.; Weber, T. E.; Rinderknecht, H. G.; Thorn, D.; Schneider, M.; Bradley, D.; Kilkenny, J.

2017-10-01

The NIF Continuum Spectrometer, scheduled to be first deployed in Fall of 2017, will infer the imploded core electron temperature from the free-free continuum self-emission spectra of photons with energies of 20 to 30 keV. However, this hard X-ray radiation is emitted by the tail of the electron distribution, which likely deviates from Maxwellian and thus obscures interpretation of the data. We investigate resulting modifications to the X-ray spectra. The logarithmic slope of the spectrum from the more realistic, non-thermal tail of the electron distribution is found to decrease more rapidly at higher photon energies, as compared to the perfectly Maxwellian case. Interpreting the spectrum with assumption of Maxwellian electrons enforced is shown to give an electron temperature that is lower than the actual one. Conversely, due to its connection with the non-thermal features in the electron distribution, hard X-ray emission can provide unprecedented information about kinetic processes in the hot DT core. This work was performed under the auspices of the U.S. Dept. of Energy by the Los Alamos National Security, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396.

Flexible single-crystal silicon nanomembrane photonic crystal cavity.

PubMed

Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

2014-12-23

Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2×10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation.

Design of thin-film photonic crystal waveguides

NASA Astrophysics Data System (ADS)

Silvestre, E.; Pottage, J. M.; Russell, P. St. J.; Roberts, P. J.

2000-08-01

We present numerical designs for single-mode leak-free photonic crystal waveguides exhibiting strongly anisotropic spatial and temporal dispersion. These structures may be produced quite simply by drilling regular arrays of holes into thin films of high refractive index, and permit the realization of highly compact optical elements and wavelength division multiplexing devices.

Low-light-level image super-resolution reconstruction based on iterative projection photon localization algorithm

NASA Astrophysics Data System (ADS)

Ying, Changsheng; Zhao, Peng; Li, Ye

2018-01-01

The intensified charge-coupled device (ICCD) is widely used in the field of low-light-level (LLL) imaging. The LLL images captured by ICCD suffer from low spatial resolution and contrast, and the target details can hardly be recognized. Super-resolution (SR) reconstruction of LLL images captured by ICCDs is a challenging issue. The dispersion in the double-proximity-focused image intensifier is the main factor that leads to a reduction in image resolution and contrast. We divide the integration time into subintervals that are short enough to get photon images, so the overlapping effect and overstacking effect of dispersion can be eliminated. We propose an SR reconstruction algorithm based on iterative projection photon localization. In the iterative process, the photon image is sliced by projection planes, and photons are screened under the constraints of regularity. The accurate position information of the incident photons in the reconstructed SR image is obtained by the weighted centroids calculation. The experimental results show that the spatial resolution and contrast of our SR image are significantly improved.

The photon PDF from high-mass Drell–Yan data at the LHC

DOE PAGES

Giuli, F.

2017-06-15

Achieving the highest precision for theoretical predictions at the LHC requires the calculation of hard-scattering cross sections that include perturbative QCD corrections up to (N)NNLO and electroweak (EW) corrections up to NLO. Parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, xγ(x,Q2) . In this work a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell–Yan dilepton production atmore » $$\\sqrt{s}$$=8 TeV is presented. This analysis is based on the xFitter framework, and has required improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results are compared with other recent QED fits and determinations of the photon PDF, consistent results are found.« less

SPECTRAL ANALYSIS IN ORBITAL/SUPERORBITAL PHASE SPACE AND HINTS OF SUPERORBITAL VARIABILITY IN THE HARD X-RAYS OF LS I +61°303

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jian; Torres, Diego F.; Zhang, Shu

2014-04-10

We present an INTEGRAL spectral analysis in the orbital/superorbital phase space of LS I +61°303. A hard X-ray spectrum with no cutoff is observed at all orbital/superorbital phases. The hard X-ray index is found to be uncorrelated with the radio index (non-simultaneously) measured at the same orbital and superorbital phases. In particular, the absence of an X-ray spectrum softening during periods of negative radio index does not favor a simple interpretation of the radio index variations in terms of a microquasar's changes of state. We uncover hints of superorbital variability in the hard X-ray flux, in phase with the superorbitalmore » modulation in soft X-rays. An orbital phase drift of the radio peak flux and index along the superorbital period is observed in the radio data. We explore its influence on a previously reported double-peak structure of a radio orbital light curve, and present it as a plausible explanation.« less

Method and apparatus for micromachining using hard X-rays

DOEpatents

Siddons, D.P.; Johnson, E.D.; Guckel, H.; Klein, J.L.

1997-10-21

An X-ray source such as a synchrotron which provides a significant spectral content of hard X-rays is used to expose relatively thick photoresist such that the portions of the photoresist at an exit surface receive at least a threshold dose sufficient to render the photoresist susceptible to a developer, while the entrance surface of the photoresist receives an exposure which does not exceed a power limit at which destructive disruption of the photoresist would occur. The X-ray beam is spectrally shaped to substantially eliminate lower energy photons while allowing a substantial flux of higher energy photons to pass through to the photoresist target. Filters and the substrate of the X-ray mask may be used to spectrally shape the X-ray beam. Machining of photoresists such as polymethylmethacrylate to micron tolerances may be obtained to depths of several centimeters, and multiple targets may be exposed simultaneously. The photoresist target may be rotated and/or translated in the beam to form solids of rotation and other complex three-dimensional structures. 21 figs.

Method and apparatus for micromachining using hard X-rays

DOEpatents

Siddons, David Peter; Johnson, Erik D.; Guckel, Henry; Klein, Jonathan L.

1997-10-21

An X-ray source such as a synchrotron which provides a significant spectral content of hard X-rays is used to expose relatively thick photoresist such that the portions of the photoresist at an exit surface receive at least a threshold dose sufficient to render the photoresist susceptible to a developer, while the entrance surface of the photoresist receives an exposure which does not exceed a power limit at which destructive disruption of the photoresist would occur. The X-ray beam is spectrally shaped to substantially eliminate lower energy photons while allowing a substantial flux of higher energy photons to pass through to the photoresist target. Filters and the substrate of the X-ray mask may be used to spectrally shape the X-ray beam. Machining of photoresists such as polymethylmethacrylate to micron tolerances may be obtained to depths of several centimeters, and multiple targets may be exposed simultaneously. The photoresist target may be rotated and/or translated in the beam to form solids of rotation and other complex three-dimensional structures.

Very low-refractive-index optical thin films consisting of an array of SiO2 nanorods

NASA Astrophysics Data System (ADS)

Xi, J.-Q.; Kim, Jong Kyu; Schubert, E. F.; Ye, Dexian; Lu, T.-M.; Lin, Shawn-Yu; Juneja, Jasbir S.

2006-03-01

The refractive-index contrast in dielectric multilayer structures, optical resonators, and photonic crystals is an important figure of merit that creates a strong demand for high-quality thin films with a low refractive index. A SiO2 nanorod layer with low refractive index of n=1.08, to our knowledge the lowest ever reported in thin-film materials, is grown by oblique-angle electron-beam deposition of SiO2. A single-pair distributed Bragg reflector employing a SiO2 nanorod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-refractive-index films for applications in photonic structures and devices.

NuSTAR Hard X-Ray Observation of the Gamma-Ray Binary Candidate HESS J1832-093

NASA Astrophysics Data System (ADS)

Mori, Kaya; Gotthelf, E. V.; Hailey, Charles J.; Hord, Ben J.; de Oña Wilhelmi, Emma; Rahoui, Farid; Tomsick, John A.; Zhang, Shuo; Hong, Jaesub; Garvin, Amani M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

2017-10-01

We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832-093, which is coincident with the supernova remnant G22.7-0.2, using the Nuclear Spectroscopic Telescope Array. Non-thermal X-ray emission from XMMU J183245-0921539, the X-ray source associated with HESS J1832-093, is detected up to ˜30 keV and is well-described by an absorbed power-law model with a best-fit photon index {{Γ }}=1.5+/- 0.1. A re-analysis of archival Chandra and XMM-Newton data finds that the long-term X-ray flux increase of XMMU J183245-0921539 is {50}-20+40 % (90% C.L.), much less than previously reported. A search for a pulsar spin period or binary orbit modulation yields no significant signal to a pulse fraction limit of {f}p< 19 % in the range 4 ms < P< 40 ks. No red noise is detected in the FFT power spectrum to suggest active accretion from a binary system. While further evidence is required, we argue that the X-ray and gamma-ray properties of XMMU J183245-0921539 are most consistent with a non-accreting binary generating synchrotron X-rays from particle acceleration in the shock formed as a result of the pulsar and stellar wind collision. We also report on three nearby hard X-ray sources, one of which may be associated with diffuse emission from a fast-moving supernova fragment interacting with a dense molecular cloud.

The Variable Crab Nebula: Evidence for a Connection between GeV flares and Hard X-ray Variations

NASA Astrophysics Data System (ADS)

Wilson-Hodge, Colleen A.; Kust Harding, Alice; Hays, Elizabeth A.; Cherry, Michael L.; Case, Gary L.; Finger, Mark H.; Jenke, Peter; Zhang, Xiao-Ling

2016-04-01

In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.

The Variable Crab Nebula: Evidence for a Connection Between GeV Flares and Hard X-ray Variations

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Harding, A. K.; Hays, E. A.; Cherry, M. L.; Case, G. L.; Finger, M. H.; Jenke, P.; Zhang, X.

2016-01-01

In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.

2009 America's Civic Health Index: Civic Health in Hard Times

ERIC Educational Resources Information Center

Center for Information and Research on Civic Learning and Engagement (CIRCLE), 2009

2009-01-01

Since 2006, the National Conference on Citizenship (NCoC), in partnership with the Civic Indicators Working Group, has published annual reports called "America's Civic Health Index." These reports have informed Americans about leading indicators of the nation's civic health and motivated citizens, leaders and policymakers to strengthen…

X-RAY VARIABILITY AND HARDNESS OF ESO 243-49 HLX-1: CLEAR EVIDENCE FOR SPECTRAL STATE TRANSITIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Servillat, Mathieu; Farrell, Sean A.; Lin Dacheng

2011-12-10

The ultraluminous X-ray (ULX) source ESO 243-49 HLX-1, which reaches a maximum luminosity of 10{sup 42} erg s{sup -1} (0.2-10 keV), currently provides the strongest evidence for the existence of intermediate-mass black holes (IMBHs). To study the spectral variability of the source, we conduct an ongoing monitoring campaign with the Swift X-ray Telescope (XRT), which now spans more than two years. We found that HLX-1 showed two fast rise and exponential decay type outbursts in the Swift XRT light curve with increases in the count rate of a factor {approx}40 separated by 375 {+-} 13 days. We obtained new XMM-Newtonmore » and Chandra dedicated pointings that were triggered at the lowest and highest luminosities, respectively. From spectral fitting, the unabsorbed luminosities ranged from 1.9 Multiplication-Sign 10{sup 40} to 1.25 Multiplication-Sign 10{sup 42} erg s{sup -1}. We confirm here the detection of spectral state transitions from HLX-1 reminiscent of Galactic black hole binaries (GBHBs): at high luminosities, the X-ray spectrum showed a thermal state dominated by a disk component with temperatures of 0.26 keV at most, and at low luminosities the spectrum is dominated by a hard power law with a photon index in the range 1.4-2.1, consistent with a hard state. The source was also observed in a state consistent with the steep power-law state, with a photon index of {approx}3.5. In the thermal state, the luminosity of the disk component appears to scale with the fourth power of the inner disk temperature, which supports the presence of an optically thick, geometrically thin accretion disk. The low fractional variability (rms of 9% {+-} 9%) in this state also suggests the presence of a dominant disk. The spectral changes and long-term variability of the source cannot be explained by variations of the beaming angle and are not consistent with the source being in a super-Eddington accretion state as is proposed for most ULX sources with lower luminosities. All this

HX-POL - A Balloon-Bourne Hard X-Ray Polarimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krawczynski, H.; De Geronimo, G.; Garson, A., III, Martin, J.

2009-12-09

We report on the design and estimated performance of a balloon-borne hard X-ray polarimeter called HX-POL. The experiment uses a combination of Si and Cadmium Zinc Telluride detectors to measure the polarization of 50 keV-400 keV X-rays from cosmic sources through the dependence of the angular distribution of Compton scattered photons on the polarization direction. On a one-day balloon flight, HX-POL would allow us to measure the polarization of bright Crab-like sources for polarization degrees well below 10%. On a longer (15-30 day) flight from Australia or Antarctica, HX-POL would be be able to measure the polarization of bright galacticmore » X-ray sources down to polarization degrees of a few percent. Hard X-ray polarization measurements provide unique venues for the study of particle acceleration processes by compact objects and relativistic outflows. In this paper, we discuss the overall instrument design and performance. Furthermore, we present results from laboratory tests of the Si and CZT detectors.« less

Narrow-line Seyfert 1 galaxies at hard X-rays

NASA Astrophysics Data System (ADS)

Panessa, F.; de Rosa, A.; Bassani, L.; Bazzano, A.; Bird, A.; Landi, R.; Malizia, A.; Miniutti, G.; Molina, M.; Ubertini, P.

2011-11-01

Narrow-line Seyfert 1 (NLSy1) galaxies are a peculiar class of type 1 active galactic nuclei (broad-line Seyfert 1 galaxies, hereinafter BLSy1). The X-ray properties of individual objects belonging to this class are often extreme and associated with accretion at high Eddington ratios. Here, we present a study on a sample of 14 NLSy1 galaxies selected at hard X-rays (>20 keV) from the fourth INTEGRAL/IBIS catalogue. The 20-100 keV IBIS spectra show hard-X-ray photon indices flatly distributed (Γ20-100 keV ranging from ˜1.3 to ˜3.6) with an average value of <Γ20-100 keV>= 2.3 ± 0.7, compatible with a sample of hard-X-ray BLSy1 average slopes. Instead, NLSy1 galaxies show steeper spectral indices with respect to BLSy1 galaxies when broad-band spectra are considered. Indeed, we combine XMM-Newton and Swift/XRT with INTEGRAL/IBIS data sets to obtain a wide energy spectral coverage (0.3-100 keV). A constraint on the high energy cut-off and on the reflection component is achieved only in one source, SWIFT J2127.4+5654 (Ecut-off˜ 50 keV, R= 1.0+0.5- 0.4). Hard-X-ray-selected NLSy1 galaxies do not display particularly strong soft excess emission, while absorption fully or partially covering the continuum is often measured as well as Fe line emission features. Variability is a common trait in this sample, both at X-rays and at hard X-rays. The fraction of NLSy1 galaxies in the hard-X-ray sky is likely to be ˜15 per cent, in agreement with estimates derived in optically selected NLSy1 samples. We confirm the association of NLSy1 galaxies with small black hole masses with a peak at 107 M⊙ in the distribution; however, hard-X-ray NLSy1 galaxies seem to occupy the lower tail of the Eddington ratio distribution of classical NLSy1 galaxies. Based on observations obtained with the INTEGRAL/IBIS, XMM-Newton and Swift/XRT.

Study and analysis of filtering characteristics of 1D photonic crystal

NASA Astrophysics Data System (ADS)

Juyal, Rohan; Suthar, Bhuvneshwer; Kumar, Arun

2018-05-01

Propagation of electromagnetic wave have been studied and analyzed through 1D photonic crystal. 1D photonic band gap material with low and high refractive index material has been chosen for this study. Band structure and reflectivity of this 1D structure has been calculated using transmission matrix method (TMM). Study and analysis of the band structure and reflectivity of this structure shows that this structure may work as an optical filter.

All-digital full waveform recording photon counting flash lidar

NASA Astrophysics Data System (ADS)

Grund, Christian J.; Harwit, Alex

2010-08-01

Current generation analog and photon counting flash lidar approaches suffer from limitation in waveform depth, dynamic range, sensitivity, false alarm rates, optical acceptance angle (f/#), optical and electronic cross talk, and pixel density. To address these issues Ball Aerospace is developing a new approach to flash lidar that employs direct coupling of a photocathode and microchannel plate front end to a high-speed, pipelined, all-digital Read Out Integrated Circuit (ROIC) to achieve photon-counting temporal waveform capture in each pixel on each laser return pulse. A unique characteristic is the absence of performance-limiting analog or mixed signal components. When implemented in 65nm CMOS technology, the Ball Intensified Imaging Photon Counting (I2PC) flash lidar FPA technology can record up to 300 photon arrivals in each pixel with 100 ps resolution on each photon return, with up to 6000 range bins in each pixel. The architecture supports near 100% fill factor and fast optical system designs (f/#<1), and array sizes to 3000×3000 pixels. Compared to existing technologies, >60 dB ultimate dynamic range improvement, and >104 reductions in false alarm rates are anticipated, while achieving single photon range precision better than 1cm. I2PC significantly extends long-range and low-power hard target imaging capabilities useful for autonomous hazard avoidance (ALHAT), navigation, imaging vibrometry, and inspection applications, and enables scannerless 3D imaging for distributed target applications such as range-resolved atmospheric remote sensing, vegetation canopies, and camouflage penetration from terrestrial, airborne, GEO, and LEO platforms. We discuss the I2PC architecture, development status, anticipated performance advantages, and limitations.

Controlling graphene plasmons with a zero-index metasurface.

PubMed

Lin, Lihui; Lu, Yanxin; Yuan, Mengmeng; Shi, Fenghua; Xu, Haixia; Chen, Yihang

2017-11-30

Graphene plasmons, owing to their diverse applications including electro-optical modulation, optical sensing, spectral photometry and tunable lighting at the nanoscale, have recently attracted much attention. One key challenge in advancing this field is to precisely control the propagation of graphene plasmons. Here, we propose an on-chip integrated platform to engineer the wave front of the graphene plasmons through a metasurface with a refractive index of zero. We demonstrate that a well-designed graphene/photonic-crystal metasurface can possess conical plasmonic dispersion at the Brillouin zone center with a triply degenerate state at the Dirac frequency, giving rise to the zero-effective-index of graphene plasmons. Plane-wave-emission and focusing effects of the graphene plasmons are achieved by tailoring such a zero-index metasurface. In addition to the tunable Dirac point frequency enabled by the electrical tuning of the graphene Fermi level, our highly integrated system also provides stable performance even when defects exist. This actively controllable on-chip platform can potentially be useful for integrated photonic circuits and devices.

Characterization of photonic colloidal crystals in real and reciprocal space

NASA Astrophysics Data System (ADS)

Thijssen, J. H. J.

2007-05-01

In this thesis, we present experimental work on the characterization of photonic colloidal crystals in real and reciprocal space. Photonic crystals are structures in which the refractive index varies periodically in space on the length scale of the wavelength of light. Self-assembly of colloidal particles is a promising route towards three-dimensional (3-D) photonic crystals. However, fabrication of photonic band-gap materials remains challenging, so calculations that predict their optical properties are indispensable. Our photonic band-structure calculations on binary Laves phases have led to a proposed route towards photonic colloidal crystals with a band gap in the visible region. Furthermore, contrary to results in literature, we found that there is no photonic band gap for inverse BCT crystals. Finally, optical spectra of colloidal crystals were analyzed using band-structure calculations. Self-assembled photonic crystals are fabricated in multiple steps. Each of these steps can significantly affect the 3-D structure of the resulting crystal. X-rays are an excellent probe of the internal structure of photonic crystals, even if the refractive-index contrast is large. In Chapter 3, we demonstrate that an angular resolution of 0.002 mrad is achievable at a third-generation synchrotron using compound refractive optics. As a result, the position and the width of Bragg reflections in 2D diffraction patterns can be resolved, even for lattice spacings larger than a micrometer (corresponding to approximately 0.1 mrad). X-ray diffraction patterns and electron-microscopy images are used in Chapter 4 to determine the orientation of hexagonal layers in convective-assembly colloidal crystals. Quantitative analysis revealed that, in our samples, the layers were not exactly hexagonal and the stacking sequence was that of face-centered cubic (FCC) crystals, though stacking faults may have been present. In Chapter 5, binary colloidal crystals of organic spheres (polystyrene

EDITORIAL: Photonic Crystal Devices

NASA Astrophysics Data System (ADS)

Bhattacharya, Pallab K.

2007-05-01

The engineering of electromagnetic modes at optical frequencies in artificial dielectric structures with periodic and random variation of the refractive index, enabling control of the radiative properties of the materials and photon localization, was first proposed independently by Yablonovitch and John in 1987. It is possible to control the flow of light in the periodic dielectric structures, known as photonic crystals (PC). As light waves scatter within the photonic crystal, destructive interference cancels out light of certain wavelengths, thereby forming a photonic bandgap, similar to the energy bandgap for electron waves in a semiconductor. Photons whose energies lie within the gap cannot propagate through the periodic structure. This property can be used to make a low-loss cavity. If a point defect, such as one or more missing periods, is introduced into the periodic structure a region is obtained within which the otherwise forbidden wavelengths can be locally trapped. This property can be used to realize photonic microcavities. Similarly, a line of defects can serve as a waveguide. While the realization of three-dimensional (3D) photonic crystals received considerable attention initially, planar two-dimensional (2D) structures are currently favoured because of their relative ease of fabrication. 2D photonic crystal structures provide most of the functionality of 3D structures. These attributes have generated worldwide research and development of sub-μm and μm size active and passive photonic devices such as single-mode and non- classical light sources, guided wave devices, resonant cavity detection, and components for optical communication. More recently, photonic crystal guided wave devices are being investigated for application in microfludic and biochemical sensing. Photonic crystal devices have been realized with bulk, quantum well and quantum dot active regions. The Cluster of articles in this issue of Journal of Physics D: Applied Physics provides a

Photonic slab heterostructures based on opals

NASA Astrophysics Data System (ADS)

Palacios-Lidon, Elisa; Galisteo-Lopez, Juan F.; Juarez, Beatriz H.; Lopez, Cefe

2004-09-01

In this paper the fabrication of photonic slab heterostructures based on artificial opals is presented. The innovated method combines high-quality thin-films growing of opals and silica infiltration by Chemical Vapor Deposition through a multi-step process. By varying structure parameters, such as lattice constant, sample thickness or refractive index, different heterostructures have been obtained. The optical study of these systems, carried out by reflectance and transmittance measurements, shows that the prepared samples are of high quality further confirmed by Scanning Electron Microscopy micrographs. The proposed novel method for sample preparation allows a high control of the involved structure parameters, giving the possibility of tunning their photonic behavior. Special attention in the optical response of these materials has been addressed to the study of planar defects embedded in opals, due to their importance in different photonic fields and future technological applications. Reflectance and transmission measurements show a sharp resonance due to localized states associated with the presence of planar defects. A detailed study of the defect mode position and its dependance on defect thickness and on the surrounding photonic crystal is presented as well as evidence showing the scalability of the problem. Finally, it is also concluded that the proposed method is cheap and versatile allowing the preparation of opal-based complex structures.

Numerical study on characteristic of two-dimensional metal/dielectric photonic crystals

NASA Astrophysics Data System (ADS)

Zong, Yi-Xin; Xia, Jian-Bai; Wu, Hai-Bin

2017-04-01

An improved plan-wave expansion method is adopted to theoretically study the photonic band diagrams of two-dimensional (2D) metal/dielectric photonic crystals. Based on the photonic band structures, the dependence of flat bands and photonic bandgaps on two parameters (dielectric constant and filling factor) are investigated for two types of 2D metal/dielectric (M/D) photonic crystals, hole and cylinder photonic crystals. The simulation results show that band structures are affected greatly by these two parameters. Flat bands and bandgaps can be easily obtained by tuning these parameters and the bandgap width may reach to the maximum at certain parameters. It is worth noting that the hole-type photonic crystals show more bandgaps than the corresponding cylinder ones, and the frequency ranges of bandgaps also depend strongly on these parameters. Besides, the photonic crystals containing metallic medium can obtain more modulation of photonic bands, band gaps, and large effective refractive index, etc. than the dielectric/dielectric ones. According to the numerical results, the needs of optical devices for flat bands and bandgaps can be met by selecting the suitable geometry and material parameters. Project supported by the National Basic Research Program of China (Grant No. 2011CB922200) and the National Natural Science Foundation of China (Grant No. 605210010).

High-Efficiency and High-Color-Rendering-Index Semitransparent Polymer Solar Cells Induced by Photonic Crystals and Surface Plasmon Resonance.

PubMed

Shen, Ping; Wang, Guoxin; Kang, Bonan; Guo, Wenbin; Shen, Liang

2018-02-21

Semitransparent polymer solar cells (ST-PSCs) show attractive potential in power-generating windows or building-integrated photovoltaics. However, the development of ST-PSCs is lagging behind opaque PSCs because of the contradiction between device efficiency and transmission. Herein, Ag/Au alloy nanoparticles and photonic crystals (PCs) were simultaneously introduced into ST-PSCs, acting compatibly as localized surface plasmon resonances and distributed Bragg reflectors to enhance light absorption and transmission. As a result, ST-PSCs based on a hybrid PTB7-Th:PC 71 BM active layer contribute an efficiency as high as 7.13 ± 0.15% and an average visible transmission beyond 20%, which are superior to most of the reported results. Furthermore, PCs can partly compensate valley range of transmission by balancing reflection and transmission regions, yielding a high color rendering index of 95. We believe that the idea of two light management methods compatibly enhancing the performance of ST-PSCs can offer a promising path to develop photovoltaic applications.

A Search for Point Sources of EeV Photons

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Criss, A.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fuji, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, A. J.; Matthews, J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Peters, C.; Petrera, S.; Petrolini, A.; Petrov, Y.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Cabo, I.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schulz, A.; Schulz, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Thao, N. T.; Theodoro, V. M.; Tiffenberg, J.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Whelan, B. J.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Auger Collaboration102, The Pierre

2014-07-01

Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from -85° to +20°, in an energy range from 1017.3 eV to 1018.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of -2, is 0.06 eV cm-2 s-1, and no celestial direction exceeds 0.25 eV cm-2 s-1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galaxy.

Photon Recollision Probability: a Useful Concept for Cross Scale Consistency Check between Leaf Area Index and Foliage Clumping Products

NASA Astrophysics Data System (ADS)

Pisek, J.

2017-12-01

Clumping index (CI) is the measure of foliage aggregation relative to a random distribution of leaves in space. CI is an important factor for the correct quantification of true leaf area index (LAI). Global and regional scale CI maps have been generated from various multi-angle sensors based on an empirical relationship with the normalized difference between hotspot and darkspot (NDHD) index (Chen et al., 2005). Ryu et al. (2011) suggested that accurate calculation of radiative transfer in a canopy, important for controlling gross primary productivity (GPP) and evapotranspiration (ET) (Baldocchi and Harley, 1995), should be possible by integrating CI with incoming solar irradiance and LAI from MODIS land and atmosphere products. It should be noted that MODIS LAI/FPAR product uses internal non-empirical, stochastic equations for parameterization of foliage clumping. This raises a question if integration of the MODIS LAI product with empirically-based CI maps does not introduce any inconsistencies. Here, the consistency is examined independently through the `recollision probability theory' or `p-theory' (Knyazikhin et al., 1998) along with raw LAI-2000/2200 Plant Canopy Analyzer (PCA) data from > 30 sites, surveyed across a range of vegetation types. The theory predicts that the amount of radiation scattered by a canopy should depend only on the wavelength and the spectrally invariant canopy structural parameter p. The parameter p is linked to the foliage clumping (Stenberg et al., 2016). Results indicate that integration of the MODIS LAI product with empirically-based CI maps is feasible. Importantly, for the first time it is shown that it is possible to obtain p values for any location solely from Earth Observation data. This is very relevant for future applications of photon recollision probability concept for global and local monitoring of vegetation using Earth Observation data.

Characteristics of strain-sensitive photonic crystal cavities in a flexible substrate.

PubMed

No, You-Shin; Choi, Jae-Hyuck; Kim, Kyoung-Ho; Park, Hong-Gyu

2016-11-14

High-index semiconductor photonic crystal (PhC) cavities in a flexible substrate support strong and tunable optical resonances that can be used for highly sensitive and spatially localized detection of mechanical deformations in physical systems. Here, we report theoretical studies and fundamental understandings of resonant behavior of an optical mode excited in strain-sensitive rod-type PhC cavities consisting of high-index dielectric nanorods embedded in a low-index flexible polymer substrate. Using the three-dimensional finite-difference time-domain simulation method, we calculated two-dimensional transverse-electric-like photonic band diagrams and the three-dimensional dispersion surfaces near the first Γ-point band edge of unidirectionally strained PhCs. A broken rotational symmetry in the PhCs modifies the photonic band structures and results in the asymmetric distributions and different levels of changes in normalized frequencies near the first Γ-point band edge in the reciprocal space, which consequently reveals strain-dependent directional optical losses and selected emission patterns. The calculated electric fields, resonant wavelengths, and quality factors of the band-edge modes in the strained PhCs show an excellent agreement with the results of qualitative analysis of modified dispersion surfaces. Furthermore, polarization-resolved time-averaged Poynting vectors exhibit characteristic dipole-like emission patterns with preferentially selected linear polarizations, originating from the asymmetric band structures in the strained PhCs.

High-resolution hard x-ray spectroscopy of high-temperature plasmas using an array of quantum microcalorimeters.

PubMed

Thorn, Daniel B; Gu, Ming F; Brown, Greg V; Beiersdorfer, Peter; Porter, F Scott; Kilbourne, Caroline A; Kelley, Richard L

2008-10-01

Quantum microcalorimeters show promise in being able to fully resolve x-ray spectra from heavy highly charged ions, such as would be found in hot plasmas with temperatures in excess of 50 keV. Quantum microcalorimeter arrays are able to achieve this as they have a high-resolving power and good effective quantum efficiency for hard x-ray photons up to 60 keV. To demonstrate this, we present a measurement using an array of thin HgTe quantum microcalorimeters to measure the K-shell spectrum of hydrogenlike through carbonlike praseodymium (Z=57). With this device we are able to attain a resolving power, E/DeltaE, of 1000 at a photon energy of 37 keV.

Hard X-ray tests of the unified model for an ultraviolet-detected sample of Seyfert 2 galaxies

NASA Technical Reports Server (NTRS)

Mulchaey, John S.; Myshotzky, Richard F.; Weaver, Kimberly A.

1992-01-01

An ultraviolet-detected sample of Seyfert 2 galaxies shows heavy photoelectric absorption in the hard X-ray band. The presence of UV emission combined with hard X-ray absorption argues strongly for a special geometry which must have the general properties of the Antonucci and Miller unified model. The observations of this sample are consistent with the picture in which the hard X-ray photons are viewed directly through the obscuring matter (molecular torus?) and the optical, UV, and soft X-ray continuum are seen in scattered light. The large range in X-ray column densities implies that there must be a large variation in intrinsic thicknesses of molecular tori, an assumption not found in the simplest of unified models. Furthermore, constraints based on the cosmic X-ray background suggest that some of the underlying assumptions of the unified model are wrong.

A sampling study on rock properties affecting drilling rate index (DRI)

NASA Astrophysics Data System (ADS)

Yenice, Hayati; Özdoğan, Mehmet V.; Özfırat, M. Kemal

2018-05-01

Drilling rate index (DRI) developed in Norway is a very useful index in determining the drillability of rocks and even in performance prediction of hard rock TBMs and it requires special laboratory test equipment. Drillability is one of the most important subjects in rock excavation. However, determining drillability index from physical and mechanical properties of rocks is very important for practicing engineers such as underground excavation, drilling operations in open pit mining, underground mining and natural stone production. That is why many researchers have studied concerned with drillability to find the correlations between drilling rate index (DRI) and penetration rate, influence of geological properties on drillability prediction in tunneling, correlations between rock properties and drillability. In this study, the relationships between drilling rate index (DRI) and some physico-mechanical properties (Density, Shore hardness, uniaxial compressive strength (UCS, σc), Indirect tensile strength (ITS, σt)) of three different rock groups including magmatic, sedimentary and metamorphic were evaluated using both simple and multiple regression analysis. This study reveals the effects of rock properties on DRI according to different types of rocks. In simple regression, quite high correlations were found between DRI and uniaxial compressive strength (UCS) and also between DRI and indirect tensile strength (ITS) values. Multiple regression analyses revealed even higher correlations when compared to simple regression. Especially, UCS, ITS, Shore hardness (SH) and the interactions between them were found to be very effective on DRI values.

Silicon-photonic interferometric biosensor using active phase demodulation

NASA Astrophysics Data System (ADS)

Marin, Y.; Toccafondo, V.; Velha, P.; Scarano, S.; Tirelli, S.; Nottola, A.; Jeong, Y.; Jeon, H. P.; Minunni, M.; Di Pasquale, F.; Oton, C. J.

2018-02-01

Silicon photonics is becoming a consolidated technology, mainly in the telecom/datacom sector, but with a great potential in the chemical and biomedical sensor market too, mainly due to its CMOS compatibility, which allows massfabrication of huge numbers of miniaturized devices at a very low cost per chip. Integrated photonic sensors, typically based on resonators, interferometers, or periodic structures, are easy to multiplex as the light is confined in optical waveguides. In this work, we present a silicon-photonic sensor capable of measuring refractive index and chemical binding of biomolecules on the surface, using a low-cost phase interrogation scheme. The sensor consists of a pair of balanced Mach-Zehnder interferometers with interaction lengths of 2.5 mm and 22 mm, wound to a sensing area of only 500 μm x500 μm. The phase interrogation is performed with a fixed laser and an active phase demodulation approach based on a phase generated carrier (PGC) technique using a phase demodulator integrated within the chip. No laser tuning is required, and the technique can extract the univocal phase value with no sensitivity fading. The detection only requires a photo-receiver per interferometer, analog-to-digital conversion, and simple processing performed in real-time. We present repeatable and linear refractive index measurements, with a detection limit down to 4.7·10-7 RIU. We also present sensing results on a chemically-functionalized sample, where anti-BSA to BSA (bovine serum albumin) binding curves are clearly visible for concentrations down to 5 ppm. Considering the advantages of silicon photonics, this device has great potential over several applications in the chemical/biochemical sensing industry.

Three-photon N00N states generated by photon subtraction from double photon pairs.

PubMed

Kim, Heonoh; Park, Hee Su; Choi, Sang-Kyung

2009-10-26

We describe an experimental demonstration of a novel three-photon N00N state generation scheme using a single source of photons based on spontaneous parametric down-conversion (SPDC). The three-photon entangled state is generated when a photon is subtracted from a double pair of photons and detected by a heralding counter. Interference fringes measured with an emulated three-photon detector reveal the three-photon de Broglie wavelength and exhibit visibility > 70% without background subtraction.

CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuhar, Matej; Krucker, Säm; Battaglia, Marina

A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and Helioseismic and Magnetic Imager. We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 Å summed over the hard X-ray flare ribbons with an integration time of 45 s around the peak hard-X ray time. We find a good correlation between hard X-raymore » fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ∼50 keV. At higher electron energies the correlation decreases gradually while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy ∼50 keV are the main source for white light production.« less

Electrical tuning of three-dimensional photonic crystals using polymer dispersed liquid crystals

NASA Astrophysics Data System (ADS)

McPhail, Dennis; Straub, Martin; Gu, Min

2005-01-01

Electrically tunable three-dimensional photonic crystals with a tunable wavelength range of over 70nm of stop gaps between 3 and 4μm have been generated in a liquid crystal-polymer composite. The photonic crystals were fabricated by femtosecond-laser direct writing of void channels in an inverse woodpile configuration with 20 layers providing an extinction of infrared light transmission of 70% in the stacking direction. Stable structures could be manufactured up to a liquid crystal concentration of 24%. Applying a direct voltage of several hundred volts in the stacking direction of the photonic crystal changes the alignment of the liquid crystal directors and hence the average refractive index of the structure. This mechanism permits the direct tuning of the photonic stop gap.

NuSTAR Search for Hard X-ray Emission from the Star Formation Regions in Sh2-104

NASA Astrophysics Data System (ADS)

Gotthelf, Eric V.

2016-04-01

We present NuSTAR hard X-ray observations of Sh2-104, a compact Hii region containing several young massive stellar clusters (YMSCs). We have detected distinct hard X-ray sources coincident with localized VERITAS TeV emission recently resolved from the giant gamma-ray complex MGRO J2019+37 in the Cygnus region. Faint, diffuse X-ray emission coincident with the eastern YMSC in Sh2-104 is likely the result of colliding winds of component stars. Just outside the radio shell of Sh2-104 lies 3XMM J201744.7+365045 and nearby nebula NuSTAR J201744.3+364812, whose properties are most consistent with extragalactic objects. The combined XMM-Newton and NuSTAR spectrum of 3XMM J201744.7+365045 is well-fit to an absorbed power-law model with NH = (3.1+/-1.0)E22 1/cm^2 and photon index Gamma = 2.1+/-0.1. Based on possible long-term flux variation and lack of detected pulsations (<43% modulation), this object is likely a background AGN rather than a Galactic pulsar. The spectrum of the NuSTAR nebula shows evidence of an emission line at E = 5.6 keV suggesting an optically obscured galaxy cluster at z = 0.19+/-0.02 (d = 800 Mpc) and Lx = 1.2E44 erg/s. Follow-up Chandra observations of Sh2-104 will help identify the nature of the X-ray sources and their relation to MGRO J2019+37.

Photon correlation in single-photon frequency upconversion.

PubMed

Gu, Xiaorong; Huang, Kun; Pan, Haifeng; Wu, E; Zeng, Heping

2012-01-30

We experimentally investigated the intensity cross-correlation between the upconverted photons and the unconverted photons in the single-photon frequency upconversion process with multi-longitudinal mode pump and signal sources. In theoretical analysis, with this multi-longitudinal mode of both signal and pump sources system, the properties of the signal photons could also be maintained as in the single-mode frequency upconversion system. Experimentally, based on the conversion efficiency of 80.5%, the joint probability of simultaneously detecting at upconverted and unconverted photons showed an anti-correlation as a function of conversion efficiency which indicated the upconverted photons were one-to-one from the signal photons. While due to the coherent state of the signal photons, the intensity cross-correlation function g(2)(0) was shown to be equal to unity at any conversion efficiency, agreeing with the theoretical prediction. This study will benefit the high-speed wavelength-tunable quantum state translation or photonic quantum interface together with the mature frequency tuning or longitudinal mode selection techniques.

Inverse opal photonic crystal of chalcogenide glass by solution processing.

PubMed

Kohoutek, Tomas; Orava, Jiri; Sawada, Tsutomu; Fudouzi, Hiroshi

2011-01-15

Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and low-temperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As(30)S(70) chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Δn ~ 0.84 near λ=770 nm) and the inverse opal As-S photonic structure (Δn ~ 1.26 near λ=660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Δn ~ 0.434 near λ=600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated "inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors. Copyright © 2010 Elsevier Inc. All rights reserved.

Deterministic photon-emitter coupling in chiral photonic circuits.

PubMed

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Deterministic photon-emitter coupling in chiral photonic circuits

NASA Astrophysics Data System (ADS)

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Single photon source with individualized single photon certifications

NASA Astrophysics Data System (ADS)

Migdall, Alan L.; Branning, David A.; Castelletto, Stefania; Ware, M.

2002-12-01

As currently implemented, single-photon sources cannot be made to produce single photons with high probability, while simultaneously suppressing the probability of yielding two or more photons. Because of this, single photon sources cannot really produce single photons on demand. We describe a multiplexed system that allows the probabilities of producing one and more photons to be adjusted independently, enabling a much better approximation of a source of single photons on demand. The scheme uses a heralded photon source based on parametric downconversion, but by effectively breaking the trigger detector area into multiple regions, we are able to extract more information about a heralded photon than is possible with a conventional arrangement. This scheme allows photons to be produced along with a quantitative 'certification' that they are single photons. Some of the single-photon certifications can be significantly better than what is possible with conventional downconversion sources, as well as being better than faint laser sources. With such a source of more tightly certified single photons, it should be possible to improve the maximum secure bit rate possible over a quantum cryptographic link. We present an analysis of the relative merits of this method over the conventional arrangement.

All-optical on-chip sensor for high refractive index sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yazhao; Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft; Salemink, H. W. M., E-mail: H.Salemink@science.ru.nl

2015-01-19

A highly sensitive sensor design based on two-dimensional photonic crystal cavity is demonstrated. The geometric structure of the cavity is modified to gain a high quality factor, which enables a sensitive refractive index sensing. A group of slots with optimized parameters is created in the cavity. The existence of the slots enhances the light-matter interactions between confined photons and analytes. The interactions result in large wavelength shifts in the transmission spectra and are denoted by high sensitivities. Experiments show that a change in refractive index of Δn ∼ 0.12 between water and oil sample 1 causes a spectral shift of 23.5 nm, andmore » the spectral shift between two oil samples is 5.1 nm for Δn ∼ 0.039. These results are in good agreement with simulations, which are 21.3 and 7.39 nm for the same index changes.« less

Realizing and characterizing chiral photon flow in a circuit quantum electrodynamics necklace.

PubMed

Wang, Yan-Pu; Wang, Wei; Xue, Zheng-Yuan; Yang, Wan-Li; Hu, Yong; Wu, Ying

2015-02-10

Gauge theory plays the central role in modern physics. Here we propose a scheme of implementing artificial Abelian gauge fields via the parametric conversion method in a necklace of superconducting transmission line resonators (TLRs) coupled by superconducting quantum interference devices (SQUIDs). The motivation is to synthesize an extremely strong effective magnetic field for charge-neutral bosons which can hardly be achieved in conventional solid-state systems. The dynamic modulations of the SQUIDs can induce effective magnetic fields for the microwave photons in the TLR necklace through the generation of the nontrivial hopping phases of the photon hopping between neighboring TLRs. To demonstrate the synthetic magnetic field, we study the realization and detection of the chiral photon flow dynamics in this architecture under the influence of decoherence. Taking the advantages of its simplicity and flexibility, this parametric scheme is feasible with state-of-the-art technology and may pave an alternative way for investigating the gauge theories with superconducting quantum circuits. We further propose a quantitative measure for the chiral property of the photon flow. Beyond the level of qualitative description, the dependence of the chiral flow on external pumping parameters and cavity decay is characterized.

Optical control of light propagation in photonic crystal based on electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Dan, Wang; Jin-Ze, Wu; Jun-Xiang, Zhang

2016-06-01

A kind of photonic crystal structure with modulation of the refractive index is investigated both experimentally and theoretically for exploiting electromagnetically induced transparency (EIT). The combination of EIT with periodically modulated refractive index medium gives rise to high efficiency reflection as well as forbidden transmission in a three-level atomic system coupled by standing wave. We show an accurate theoretical simulation via transfer-matrix theory, automatically accounting for multilayer reflections, thus fully demonstrate the existence of photonic crystal structure in atomic vapor. Project supported by the National Natural Science Foundation of China (Grant No. 11574188) and the Project for Excellent Research Team of the National Natural Science Foundation of China (Grant No. 61121064).

Investigation of 2D photonic crystal structure based channel drop filter using quad shaped photonic crystal ring resonator for CWDM system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chhipa, Mayur Kumar, E-mail: mayurchhipa1@gmail.com; Dusad, Lalit Kumar; Rajasthan Technical University, Kota, Rajasthan

In this paper, the design & performance of two dimensional (2-D) photonic crystal structure based channel drop filter is investigated using quad shaped photonic crystal ring resonator. In this paper, Photonic Crystal (PhC) based on square lattice periodic arrays of Gallium Indium Phosphide (GaInP) rods in air structure have been investigated using Finite Difference Time Domain (FDTD) method and photonic band gap is being calculated using Plane Wave Expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength λ= 1571 nm by varying the rods lattice constant. The number of rods in Z and X directions is 21 andmore » 20, with lattice constant 0.540 nm it illustrates that the arrangement of Gallium Indium Phosphide (GaInP) rods in the structure which gives the overall size of the device around 11.4 µm × 10.8 µm. The designed filter gives good dropping efficiency using 3.298, refractive index. The designed structure is useful for CWDM systems. This device may serve as a key component in photonic integrated circuits. The device is ultra compact with the overall size around 123 µm{sup 2}.« less

Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions.

PubMed

Chattaraj, Pratim K; Ayers, Paul W; Melin, Junia

2007-08-07

Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition.

"Photonic lantern" spectral filters in multi-core Fiber.

PubMed

Birks, T A; Mangan, B J; Díez, A; Cruz, J L; Murphy, D F

2012-06-18

Fiber Bragg gratings are written across all 120 single-mode cores of a multi-core optical Fiber. The Fiber is interfaced to multimode ports by tapering it within a depressed-index glass jacket. The result is a compact multimode "photonic lantern" filter with astrophotonic applications. The tapered structure is also an effective mode scrambler.

Safe and simple detection of sparse hydrogen by Pd-Au alloy/air based 1D photonic crystal sensor

NASA Astrophysics Data System (ADS)

Mitra, S.; Biswas, T.; Chattopadhyay, R.; Ghosh, J.; Bysakh, S.; Bhadra, S. K.

2016-11-01

A simple integrated hydrogen sensor using Pd-Au alloy/air based one dimensional photonic crystal with an air defect layer is theoretically modeled. Structural parameters of the photonic crystal are delicately scaled to generate photonic band gap frequencies in a visible spectral regime. An optimized defect thickness permits a localized defect mode operating at a frequency within the photonic band gap region. Hydrogen absorption causes modification in the band gap characteristics due to variation of refractive index and lattice parameters of the alloy. As a result, the transmission peak appeared due to the resonant defect state gets shifted. This peak shifting is utilized to detect sparse amount of hydrogen present in the surrounding environment. A theoretical framework is built to calculate the refractive index profile of hydrogen loaded alloy using density functional theory and Bruggeman's effective medium approximation. The calculated refractive index variation of Pd3Au alloy film due to hydrogen loading is verified experimentally by measuring the reflectance characteristics. Lattice expansion properties of the alloy are studied through X-ray diffraction analyses. The proposed structure shows about 3 nm red shift of the transmission peak for a rise of 1% atomic hydrogen concentration in the alloy.

Hierarchically structured photonic crystals for integrated chemical separation and colorimetric detection.

PubMed

Fu, Qianqian; Zhu, Biting; Ge, Jianping

2017-02-16

A SiO 2 colloidal photonic crystal film with a hierarchical porous structure is fabricated to demonstrate an integrated separation and colorimetric detection of chemical species for the first time. This new photonic crystal based thin layer chromatography process requires no dyeing, developing and UV irradiation compared to the traditional TLC. The assembling of mesoporous SiO 2 particles via a supersaturation-induced-precipitation process forms uniform and hierarchical photonic crystals with micron-scale cracks and mesopores, which accelerate the diffusion of developers and intensify the adsorption/desorption between the analytes and silica for efficient separation. Meanwhile, the chemical substances infiltrated to the voids of photonic crystals cause an increase of the refractive index and a large contrast of structural colors towards the unloaded part, so that the sample spots can be directly recognized with the naked eye before and after separation.

Controllable light diffraction in woodpile photonic crystals filled with liquid crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Chih-Hua; Zeng, Hao; Wiersma, Diederik S.

2015-01-12

An approach to switching between different patterns of light beams transmitted through the woodpile photonic crystals filled with liquid crystals is proposed. The phase transition between the nematic and isotropic liquid crystal states leads to an observable variation of the spatial pattern transmitted through the photonic structure. The transmission profiles in the nematic phase also show polarization sensibility due to refractive index dependence on the field polarization. The experimental results are consistent with a numerical calculation by Finite Difference Time Domain method.

Slow-light transmission with high group index and large normalized delay bandwidth product through successive defect rods on intrinsic photonic crystal waveguide

NASA Astrophysics Data System (ADS)

Elshahat, Sayed; Khan, Karim; Yadav, Ashish; Bibbò, Luigi; Ouyang, Zhengbiao

2018-07-01

We proposed a strategy with successive cavities as energy reservoirs of electromagnetic energy and light-speed reducers introduced in the first and second rows of rods on the walls of an intrinsic photonic crystal waveguide (PCW) for slow-light transmission in the PCW concerning applications for optical communication, optical computation and optical signal processing. Subsequently, plane-wave expansion method (PWE) is used for studying slow-light properties and finite-difference time-domain (FDTD) method to demonstrate the slow-light propagating property of our proposed structure. We obtained group index as exceedingly large as 6123 with normalized delay bandwidth product (NDBP) as high as 0.48. We designed a facile but more generalized structure that may provide a vital theoretical basis for further enhancing the storage capacity properties of slow light with wideband and high NDBP.

Diffractive hard photoproduction at HERA and evidence for the gluon content of the pomeron

NASA Astrophysics Data System (ADS)

Derrick, M.; Krakauer, D.; Magill, S.; Mikunas, D.; Musgrave, B.; Repond, J.; Stanek, R.; Talaga, R. L.; Zhang, H.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Cara Romeo, G.; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Contin, A.; Corradi, M.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Zamora Garcia, Y.; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckert, M.; Feld, L.; Frey, A.; Geerts, M.; Grothe, M.; Hartmann, H.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mengel, S.; Mollen, J.; Paul, E.; Pfeiffer, M.; Rembser, Ch; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Capua, M.; Garfagnini, A.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Cartiglia, N.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Zhu, Q.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zajaç, J.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Beier, H.; Bienlein, J. K.; Coldewey, C.; Deppe, O.; Desler, K.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Glasman, C.; Göttlicher, P.; Große-Knetter, J.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Iga, Y.; Johnson, K.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Monteiro, T.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Surrow, B.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Zeuner, W.; Zhou, J. F.; Grabosch, H. J.; Kharchilava, A.; Leich, A.; Mattingly, M. C. K.; Meyer, A.; Schlenstedt, S.; Wulff, N.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; De Pasquale, S.; Votano, L.; Bamberger, A.; Eisenhardt, S.; Freidhof, A.; Söldner-Rembold, S.; Schroeder, J.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, J. I.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Hagge, L.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Zetsche, F.; Bacon, T. C.; Bruemmer, N.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. Y. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Fernandez, J. P.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Martinez, M.; del Peso, J.; Puga, J.; Terron, J.; de Trocóniz, J. F.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Yu. A.; Kobrin, V. D.; Korzhavina, I. A.; Kuzmin, V. A.; Lukina, O. Yu; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Kamps, M.; Kooijman, P.; Kruse, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Lindemann, L.; McFall, J. D.; Nath, C.; Noyes, V. A.; Quadt, A.; Tickner, J. R.; Uijterwaal, H.; Walczak, R.; Waters, D. S.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; De Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Marini, G.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Dubbs, T.; Heusch, C.; Van Hook, M.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Williams, D. C.; Biltzinger, J.; Seifert, R. J.; Schwarzer, O.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nakamitsu, Y.; Yamauchi, K.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Polenz, S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprazak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Karshon, U.; Revel, D.; Zer-Zion, D.; Ali, I.; Badgett, W. F.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Vaiciulis, A.; Wodarczyk, M.; Tsurugai, T.; Bhadra, S.; Cardy, M. L.; Fagerstroem, C.-P.; Frisken, W. R.; Furutani, K. M.; Khakzad, M.; Schmidke, W. B.; ZEUS Collaboration

1995-02-01

Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction ep → jet + X with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies ETjet > 8 GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale ˜ ( ETjet) 2. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30% and 80% of the momentum of the pomeron carried by partons is due to hard gluons.

The 2015 hard-state only outburst of GS 1354-64

NASA Astrophysics Data System (ADS)

Stiele, H.; Kong, A. K. H.

2016-07-01

Since its outburst in 1997, GS 1354-64 stayed in quiescence. In 2015 June, renewed activity of GS 1354-64 was observed. Based on our analysis of energy spectra and timing properties obtained from Swift/X-ray telescope monitoring data, we found that GS 1354-64 stayed in the hard state during the entire outburst. Such a hard state only (or `failed' outburst) has also been observed in 1997. In addition, we analysed an XMM-Newton observation taken on August 6th. We compared variability on long and short time-scales using covariance ratio and found that the ratio showed a decrease towards lower energies instead of the increase that has been found in other black hole X-ray binaries. There are now two sources (H1743-322 and GS 1354-64) that do not show an increase towards lower energies in their covariance ratio. Both sources have been observed during `failed' outbursts and showed photon indices much harder than what is usually observed in black hole X-ray binaries.

Refractive index sensing characteristics of carbon nanotube-deposited photonic crystal fiber SPR sensor

NASA Astrophysics Data System (ADS)

Jing, Jian-Ying; Wang, Qi; Wang, Bo-Tao

2018-07-01

In this paper, the carbon nanotubes (CNTs)-deposited Au film photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor (CNTs/Au-PCF sensor) and CNTs-deposited Ag film PCF SPR sensor (CNTs/Ag-PCF sensor) were developed and utilized to conduct a series of experiments for the refractive index sensing characteristics study of the CNTs-deposited SPR sensors. The PCF, spliced between two sections of multimode fibers (MMFs), was coated with a metal (Au or Ag) film and then deposited with CNTs for further sensing. CNTs coating can enhance the confined electric field intensity surrounding the sensing layer, making the SPR sensor more sensitive to the changes in the ambient medium. Compared with conventional Au film PCF SPR sensor (Au-PCF sensor), the sensitivity of CNTs/Au-PCF sensor increases by 1016.09 nm/RIU. Compared with conventional Ag film PCF SPR sensor (Ag-PCF sensor), the sensitivity of CNTs/Ag-PCF sensor increases by 709.22 nm/RIU. Therefore, we find that CNTs have a more significant effect on the Au-PCF sensor than the Ag-PCF sensor. The experimental measurements results agreed well with the simulation results. Furthermore, CNTs have high surface-to-volume ratio and extremely excellent biocompatibility. Bovine serum albumin (BSA) was employed as the target analyte to evaluate the feasibility of the CNTs/Au-PCF sensor for the detection of biomolecules, and the sensor exhibits higher sensitivity (8.18 nm/(mg/mL)), lower limit of detection (LOD) (2.5 μg/mL), and faster response time (8 s) than the Au-PCF sensor. Such CNTs-deposited SPR sensors with high sensitivities and fast response present highly promising potential for application in the field of biochemistry.

Hard X-Ray-emitting Black Hole Fed by Accretion of Low Angular Momentum Matter

NASA Astrophysics Data System (ADS)

Igumenshchev, Igor V.; Illarionov, Andrei F.; Abramowicz, Marek A.

1999-05-01

Observed spectra of active galactic nuclei and luminous X-ray binaries in our Galaxy suggest that both hot (~109 K) and cold (~106 K) plasma components exist close to the central accreting black hole. The hard X-ray component of the spectra is usually explained by Compton upscattering of optical/UV photons from optically thick cold plasma by hot electrons. Observations also indicate that some of these objects are quite efficient in converting gravitational energy of accretion matter into radiation. Existing theoretical models have difficulties in explaining the two plasma components and high intensity of hard X-rays. Most of the models assume that the hot component emerges from the cold one because of some kind of instability, but no one offers a satisfactory physical explanation for this. Here we propose a solution to these difficulties that reverses what was imagined previously: in our model, the hot component forms first and afterward it cools down to form the cold component. In our model, the accretion flow initially has a small angular momentum, and thus it has a quasi-spherical geometry at large radii. Close to the black hole, the accreting matter is heated up in shocks that form because of the action of the centrifugal force. The hot postshock matter is very efficiently cooled down by Comptonization of low-energy photons and condensates into a thin and cool accretion disk. The thin disk emits the low-energy photons which cool the hot component. All the properties of our model, in particular the existence of hot and cold components, follow from an exact numerical solution of standard hydrodynamical equations--we postulate no unknown processes operating in the flow. In contrast to the recently discussed advection-dominated accretion flow, the particular type of accretion flow considered in this Letter is both very hot and quite radiatively efficient.

Low-index discontinuity terahertz waveguides

NASA Astrophysics Data System (ADS)

Nagel, Michael; Marchewka, Astrid; Kurz, Heinrich

2006-10-01

A new type of dielectric THz waveguide based on recent approaches in the field of integrated optics is presented with theoretical and experimental results. Although the guiding mechanism of the low-index discontinuity (LID) THz waveguide is total internal reflection, the THz wave is predominantly confined in the virtually lossless low-index air gap within a high-index dielectric waveguide due to the continuity of electric flux density at the dielectric interface. Attenuation, dispersion and single-mode confinement properties of two LID structures are discussed and compared with other THz waveguide solutions. The new approach provides an outstanding combination of high mode confinement and low transmission losses currently not realizable with any other metal-based or photonic crystal approach. These exceptional properties might enable the breakthrough of novel integrated THz systems or endoscopy applications with sub-wavelength resolution.

Two-photon absorption by spectrally shaped entangled photons

NASA Astrophysics Data System (ADS)

Oka, Hisaki

2018-03-01

We theoretically investigate two-photon excitation by spectrally shaped entangled photons with energy anticorrelation in terms of how the real excitation of an intermediate state affects two-photon absorption by entangled photons. Spectral holes are introduced in the entangled photons around the energy levels of an intermediate state so that two-step excitation via the real excitation of the intermediated state can be suppressed. Using a three-level atomic system as an example, we show that the spectral holes well suppress the real excitation of the intermediate state and recover two-photon absorption via a virtual state. Furthermore, for a short pulse close to a monocycle, we show that the excitation efficiency by the spectrally shaped entangled photons can be enhanced a thousand times as large as that by uncorrelated photons.

Magneto-photonic crystal microcavities based on magnetic nanoparticles embedded in Silica matrix

NASA Astrophysics Data System (ADS)

Hocini, Abdesselam; Moukhtari, Riad; Khedrouche, Djamel; Kahlouche, Ahmed; Zamani, Mehdi

2017-02-01

Using the three-dimensional finite difference time domain method (3D FDTD) with perfectly matched layers (PML), optical and magneto-optical properties of two-dimensional magneto-photonic crystals micro-cavity is studied. This micro-cavity is fabricated by SiO2/ZrO2 or SiO2/TiO2 matrix doped with magnetic nanoparticles, in which the refractive index varied in the range of 1.51-1.58. We demonstrate that the Q factor for the designed cavity increases as the refractive index increases, and we find that the Q factor decreases as the volume fraction VF% due to off-diagonal elements increases. These magnetic microcavities may serve as a fundamental structure in a variety of ultra compact magneto photonic devices such as optical isolators, circulators and modulators in the future.

First report on the association of drinking water hardness and endothelial function in children and adolescents.

PubMed

Poursafa, Parinaz; Kelishadi, Roya; Amin, Mohammad Mehdi; Hashemi, Mohammad; Amin, Maryam

2014-08-29

This study aims to investigate the relationship of water hardness and its calcium and magnesium content with endothelial function in a population-based sample of healthy children and adolescents. This case-control study was conducted in 2012 among 90 individuals living in two areas with moderate and high water hardness in Isfahan County, Iran. The flow-mediated dilatation (FMD) of the brachial artery and the serum levels of soluble adhesion molecules (sICAM-1, sVCAM-1) were measured as surrogate markers of endothelial function, and high-sensitivity C-reactive protein (hs-CRP), as a marker of inflammation. Data of 89 participants (51% boys, mean age 14.75 (2.9) years) were complete. Those participants living in the area with high water hardness had higher FMD, hs-CRP, and soluble adhesion molecules (sICAM-1, sVCAM-1) than their counterparts living in the area with moderate water hardness. Multiple linear regression analysis showed that after adjustment for confounding factors of age, gender, body mass index, healthy eating index and physical activity level, total water hardness, as well as water content of calcium and magnesium, had a significant positive relationship with FMD. The corresponding associations were inverse and significant with soluble adhesion molecules (p < 0.05). This study, which to the best of our knowledge is the first of its kind in the pediatric age group, suggests that water hardness, as well as its calcium and magnesium content, may have a protective role against early stages of atherosclerosis in children and adolescents.

Amended Results for Hard X-Ray Emission by Non-thermal Thick Target Recombination in Solar Flares

NASA Astrophysics Data System (ADS)

Reep, J. W.; Brown, J. C.

2016-06-01

Brown & Mallik and the corresponding corrigendum Brown et al. presented expressions for non-thermal recombination (NTR) in the collisionally thin- and thick-target regimes, claiming that the process could account for a substantial part of the hard X-ray continuum in solar flares usually attributed entirely to thermal and non-thermal bremsstrahlung (NTB). However, we have found the thick-target expression to become unphysical for low cut-offs in the injected electron energy spectrum. We trace this to an error in the derivation, derive a corrected version that is real-valued and continuous for all photon energies and cut-offs, and show that, for thick targets, Brown et al. overestimated NTR emission at small photon energies. The regime of small cut-offs and large spectral indices involve large (reducing) correction factors but in some other thick-target parameter regimes NTR/NTB can still be of the order of unity. We comment on the importance of these results to flare and microflare modeling and spectral fitting. An empirical fit to our results shows that the peak NTR contribution comprises over half of the hard X-ray signal if δ ≳ 6{≤ft(\\tfrac{{E}0c}{4{keV}}\\right)}0.4.

Tuning single-photon sources for telecom multi-photon experiments.

PubMed

Greganti, Chiara; Schiansky, Peter; Calafell, Irati Alonso; Procopio, Lorenzo M; Rozema, Lee A; Walther, Philip

2018-02-05

Multi-photon state generation is of great interest for near-future quantum simulation and quantum computation experiments. To-date spontaneous parametric down-conversion is still the most promising process, even though two major impediments still exist: accidental photon noise (caused by the probabilistic non-linear process) and imperfect single-photon purity (arising from spectral entanglement between the photon pairs). In this work, we overcome both of these difficulties by (1) exploiting a passive temporal multiplexing scheme and (2) carefully optimizing the spectral properties of the down-converted photons using periodically-poled KTP crystals. We construct two down-conversion sources in the telecom wavelength regime, finding spectral purities of > 91%, while maintaining high four-photon count rates. We use single-photon grating spectrometers together with superconducting nanowire single-photon detectors to perform a detailed characterization of our multi-photon source. Our methods provide practical solutions to produce high-quality multi-photon states, which are in demand for many quantum photonics applications.

The NuSTAR view on Hard-TeV BL Lacs

NASA Astrophysics Data System (ADS)

Costamante, L.; Bonnoli, G.; Tavecchio, F.; Ghisellini, G.; Tagliaferri, G.; Khangulyan, D.

2018-05-01

Hard-TeV BL Lacs are a new type of blazars characterized by a hard intrinsic TeV spectrum, locating the peak of their gamma-ray emission in the spectral energy distribution (SED) above 2-10 TeV. Such high energies are problematic for the Compton emission, using a standard one-zone leptonic model. We study six examples of this new type of BL Lacs in the hard X-ray band with NuSTAR. Together with simultaneous observations with the Neil Gehrels Swift Observatory, we fully constrain the peak of the synchrotron emission in their SED, and test the leptonic synchrotron self-Compton (SSC) model. We confirm the extreme nature of 5 objects also in the synchrotron emission. We do not find evidence of additional emission components in the hard X-ray band. We find that a one-zone SSC model can in principle reproduce the extreme properties of both peaks in the SED, from X-ray up to TeV energies, but at the cost of i) extreme electron energies with very low radiative efficiency, ii) conditions heavily out of equipartition (by 3 to 5 orders of magnitude), and iii) not accounting for the simultaneous UV data, which then should belong to a different emission component, possibly the same as the far-IR (WISE) data. We find evidence of this separation of the UV and X-ray emission in at least two objects. In any case, the TeV electrons must not "see" the UV or lower-energy photons, even if coming from different zones/populations, or the increased radiative cooling would steepen the VHE spectrum.

The NuSTAR view on hard-TeV BL Lacs

NASA Astrophysics Data System (ADS)

Costamante, L.; Bonnoli, G.; Tavecchio, F.; Ghisellini, G.; Tagliaferri, G.; Khangulyan, D.

2018-07-01

Hard-TeV BL Lacs are a new type of blazars characterized by a hard intrinsic TeV spectrum, locating the peak of their gamma-ray emission in the spectral energy distribution (SED) above 2-10 TeV. Such high energies are problematic for the Compton emission, using a standard one-zone leptonic model. We study six examples of this new type of BL Lacs in the hard X-ray band with NuSTAR. Together with simultaneous observations with the Neil Gehrels Swift Observatory, we fully constrain the peak of the synchrotron emission in their SED, and test the leptonic synchrotron self-Compton (SSC) model. We confirm the extreme nature of five objects also in the synchrotron emission. We do not find evidence of additional emission components in the hard X-ray band. We find that a one-zone SSC model can in principle reproduce the extreme properties of both peaks in the SED, from X-ray up to TeV energies, but at the cost of (i) extreme electron energies with very low radiative efficiency, (ii) conditions heavily out of equipartition (by three to five orders of magnitude), and (iii) not accounting for the simultaneous UV data, which then should belong to a different emission component, possibly the same as the far-IR (WISE) data. We find evidence of this separation of the UV and X-ray emission in at least two objects. In any case, the TeV electrons must not `see' the UV or lower energy photons, even if coming from different zones/populations, or the increased radiative cooling would steepen the very high energies spectrum.

Numerical study of photon migration in the presence of a void region using the radiative transfer and diffusion equations

NASA Astrophysics Data System (ADS)

Miyakawa, Erina; Fujii, Hiroyuki; Hattori, Kiyohito; Tatekura, Yuki; Kobayashi, Kazumichi; Watanabe, Masao

2016-12-01

Diffuse optical tomography (DOT), which is still under development, has a potential to enable non-invasive diagnoses of thyroid cancers in the human neck using the near-infrared light. This modality needs a photon migration model because scattered light is used. There are two types of photon migration models: the radiative transport equation (RTE) and diffusion equation (DE). The RTE can describe photon migration in the human neck with accuracy, while the DE enables an efficient calculation. For developing the accurate and efficient model of photon migration, it is crucial to investigate a condition where the DE holds in a scattering medium including a void region under the refractive-index mismatch at the void boundary because the human neck has a trachea (void region) and the refractive indices are different between the human neck and trachea. Hence, in this paper, we compare photon migration using the RTE with that using the DE in the medium. The numerical results show that the DE is valid under the refractive-index match at the void boundary even though the void region is near the source and detector positions. Under the refractive-index mismatch at the boundary, the numerical results using the DE disagree with those using the RTE when the void region is near the source and detector positions. This is probably because the anisotropy of the light scattering remains around the void boundary.

Full utilization of semi-Dirac cones in photonics

NASA Astrophysics Data System (ADS)

Yasa, Utku G.; Turduev, Mirbek; Giden, Ibrahim H.; Kurt, Hamza

2018-05-01

In this study, realization and applications of anisotropic zero-refractive-index materials are proposed by exposing the unit cells of photonic crystals that exhibit Dirac-like cone dispersion to rotational symmetry reduction. Accidental degeneracy of two Bloch modes in the Brillouin zone center of two-dimensional C2-symmetric photonic crystals gives rise to the semi-Dirac cone dispersion. The proposed C2-symmetric photonic crystals behave as epsilon-and-mu-near-zero materials (ɛeff≈ 0 , μeff≈ 0 ) along one propagation direction, but behave as epsilon-near-zero material (ɛeff≈ 0 , μeff≠ 0 ) for the perpendicular direction at semi-Dirac frequency. By extracting the effective medium parameters of the proposed C4- and C2-symmetric periodic media that exhibit Dirac-like and semi-Dirac cone dispersions, intrinsic differences between isotropic and anisotropic materials are investigated. Furthermore, advantages of utilizing semi-Dirac cone materials instead of Dirac-like cone materials in photonic applications are demonstrated in both frequency and time domains. By using anisotropic transmission behavior of the semi-Dirac materials, photonic application concepts such as beam deflectors, beam splitters, and light focusing are proposed. Furthermore, to the best of our knowledge, semi-Dirac cone dispersion is also experimentally demonstrated for the first time by including negative, zero, and positive refraction states of the given material.

Inkjet-Printed Nanocavities on a Photonic Crystal Template.

PubMed

Brossard, Frederic S F; Pecunia, Vincenzo; Ramsay, Andrew J; Griffiths, Jonathan P; Hugues, Maxime; Sirringhaus, Henning

2017-12-01

The last decade has witnessed the rapid development of inkjet printing as an attractive bottom-up microfabrication technology due to its simplicity and potentially low cost. The wealth of printable materials has been key to its widespread adoption in organic optoelectronics and biotechnology. However, its implementation in nanophotonics has so far been limited by the coarse resolution of conventional inkjet-printing methods. In addition, the low refractive index of organic materials prevents the use of "soft-photonics" in applications where strong light confinement is required. This study introduces a hybrid approach for creating and fine tuning high-Q nanocavities, involving the local deposition of an organic ink on the surface of an inorganic 2D photonic crystal template using a commercially available high-resolution inkjet printer. The controllability of this approach is demonstrated by tuning the resonance of the printed nanocavities by the number of printer passes and by the fabrication of photonic crystal molecules with controllable splitting. The versatility of this method is evidenced by the realization of nanocavities obtained by surface deposition on a blank photonic crystal. A new method for a free-form, high-density, material-independent, and high-throughput fabrication technique is thus established with a manifold of opportunities in photonic applications. © 2017 Hitachi Cambridge Laboratory. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NuSTAR and XMM-Newton Observations of the Hard X- Ray Spectrum of Centaurus A

NASA Technical Reports Server (NTRS)

Furst, F.; Muller, C.; Madsen, K. K.; Lanz, L.; Rivers, E.; Brightman, M.; Arevalo, P.; Balokovic, M.; Beuchert, T.; Zhang, W.

2016-01-01

We present simultaneous XMM-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with subarcminute resolution at X-ray energies above 10 keV for the first time, but found no evidence for an extended source or other off-nuclear point sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power law with a photon index Gamma = 1.8150 +/- 0.005 and a fluorescent Fe Kaline in good agreement with literature values. The spectrum is greater than 1 MeV. A thermal Comptonization continuum describes the data well, with parameters that agree with values measured by INTEGRAL, in particular an electron temperature kTe between approximately 100-300 keV and seed photon input temperatures between 5 and 50 eV. We do not find evidence for reflection or a broad iron line and put stringent upper limits of R is less than 0.01 on the reflection fraction and accretion disk illumination. We use archival Chandra data to estimate the contribution from diffuse emission, extra-nuclear point sources, and the outer X-ray jet to the observed NuSTAR and XMM-Newton X-ray spectra and find the contribution to be negligible. We discuss different scenarios for the physical origin of the observed hard X-ray spectrum and conclude that the inner disk is replaced by an advection-dominated accretion flow or that the X-rays are dominated by synchrotron self-Compton emission from the inner regions of the radio jet or a combination thereof.

Two-Dimensional Photonic Crystals for Sensitive Microscale Chemical and Biochemical Sensing

PubMed Central

Miller, Benjamin L.

2015-01-01

Photonic crystals – optical devices able to respond to changes in the refractive index of a small volume of space – are an emerging class of label-free chemical-and bio-sensors. This review focuses on one class of photonic crystal, in which light is confined to a patterned planar material layer of sub-wavelength thickness. These devices are small (on the order of tens to 100s of microns square), suitable for incorporation into lab-on-a-chip systems, and in theory can provide exceptional sensitivity. We introduce the defining characteristics and basic operation of two-dimensional photonic crystal sensors, describe variations of their basic design geometry, and summarize reported detection results from chemical and biological sensing experiments. PMID:25563402

The Evolution of GX 339-4 in the Low-hard State as Seen by NuSTAR and Swift

NASA Astrophysics Data System (ADS)

Wang-Ji, Jingyi; García, Javier A.; Steiner, James F.; Tomsick, John A.; Harrison, Fiona A.; Bambi, Cosimo; Petrucci, Pierre-Olivier; Ferreira, Jonathan; Chakravorty, Susmita; Clavel, Maïca

2018-03-01

We analyze 11 Nuclear Spectroscopic Telescope Array and Swift observations of the black hole X-ray binary GX 339–4 in the hard state, 6 of which were taken during the end of the 2015 outburst and 5 during a failed outburst in 2013. These observations cover luminosities from 0.5% to 5% of the Eddington luminosity. Implementing the most recent version of the reflection model relxillCp, we perform simultaneous spectral fits on both data sets to track the evolution of the properties in the accretion disk, including the inner edge radius, the ionization, and the temperature of the thermal emission. We also constrain the photon index and electron temperature of the primary source (the “corona”). We observe a maximum truncation radius of 37 R g in the preferred fit for the 2013 data set, and a marginal correlation between the level of truncation and luminosity. We also explore a self-consistent model under the framework of coronal Comptonization, and find consistent results regarding the disk truncation in the 2015 data, providing a more physical preferred fit for the 2013 observations.

Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics.

PubMed

D'Angelo, Francesco; Mics, Zoltán; Bonn, Mischa; Turchinovich, Dmitry

2014-05-19

Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6 and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultra-broadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science.

Negative refraction angular characterization in one-dimensional photonic crystals.

PubMed

Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

2011-04-06

Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs. By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone. Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

Semi-analytical model for a slab one-dimensional photonic crystal

NASA Astrophysics Data System (ADS)

Libman, M.; Kondratyev, N. M.; Gorodetsky, M. L.

2018-02-01

In our work we justify the applicability of a dielectric mirror model to the description of a real photonic crystal. We demonstrate that a simple one-dimensional model of a multilayer mirror can be employed for modeling of a slab waveguide with periodically changing width. It is shown that this width change can be recalculated to the effective refraction index modulation. The applicability of transfer matrix method of reflection properties calculation was demonstrated. Finally, our 1-D model was employed to analyze reflection properties of a 2-D structure - a slab photonic crystal with a number of elliptic holes.

Flatland Photonics: Circumventing Diffraction with Planar Plasmonic Architectures

NASA Astrophysics Data System (ADS)

Dionne, Jennifer Anne

On subwavelength scales, photon-matter interactions are limited by diffraction. The diffraction limit restricts the size of optical devices and the resolution of conventional microscopes to wavelength-scale dimensions, severely hampering our ability to control and probe subwavelength-scale optical phenomena. Circumventing diffraction is now a principle focus of integrated nanophotonics. Surface plasmons provide a particularly promising approach to sub-diffraction-limited photonics. Surface plasmons are hybrid electron-photon modes confined to the interface between conductors and transparent materials. Combining the high localization of electronic waves with the propagation properties of optical waves, plasmons can achieve extremely small mode wavelengths and large local electromagnetic field intensities. Through their unique dispersion, surface plasmons provide access to an enormous phase space of refractive indices and propagation constants that can be readily tuned with material or geometry. In this thesis, we explore both the theory and applications of dispersion in planar plasmonic architectures. Particular attention is given to the modes of metallic core and plasmon slot waveguides, which can span positive, near-zero, and even negative indices. We demonstrate how such basic plasmonic geometries can be used to develop a suite of passive and active plasmonic components, including subwavelength waveguides, color filters, negative index metamaterials, and optical MOS field effect modulators. Positive index modes are probed by near- and far-field techniques, revealing plasmon wavelengths as small as one-tenth of the excitation wavelength. Negative index modes are characterized through direct visualization of negative refraction. By fabricating prisms comprised of gold, silicon nitride, and silver multilayers, we achieve the first experimental demonstration of a negative index material at visible frequencies, with potential applications for sub

THE ROLE OF KELVIN–HELMHOLTZ INSTABILITY FOR PRODUCING LOOP-TOP HARD X-RAY SOURCES IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Xia; Yuan, Ding; Xia, Chun

We propose a model for the formation of loop-top hard X-ray (HXR) sources in solar flares through the inverse Compton mechanism, scattering the surrounding soft X-ray (SXR) photons to higher energy HXR photons. We simulate the consequences of a flare-driven energy deposit in the upper chromosphere in the impulsive phase of single loop flares. The consequent chromosphere evaporation flows from both footpoints reach speeds up to hundreds of kilometers per second, and we demonstrate how this triggers Kelvin–Helmholtz instability (KHI) in the loop top, under mildly asymmetric conditions, or more toward the loop flank for strongly asymmetric cases. The KHImore » vortices further fragment the magnetic topology into multiple magnetic islands and current sheets, and the hot plasma within leads to a bright loop-top SXR source region. We argue that the magnetohydrodynamic turbulence that appears at the loop apex could be an efficient accelerator of non-thermal particles, which the island structures can trap at the loop-top. These accelerated non-thermal particles can upscatter the surrounding thermal SXR photons emitted by the extremely hot evaporated plasma to HXR photons.« less

Is there a relation between priapism occurring after penile doppler ultrasonography and international erectile function index score and erection hardness score levels?

PubMed Central

Sönmez, Mehmet Giray; Öztürk, Ahmet

2017-01-01

Objective The relation between Erection Hardness Score (EHS) and The International Erectile Function Index (IIEF) Questionnaire- Erectile Function Domain Score (IIEF-EF score) used in erectile dysfunction (ED) evaluation and the prevalence of priapism after penile Doppler ultrasonography (PDU) was examined in this study. Material and methods A total of 62 patients who had PDU were included in the study. Patients were divided into two groups; there were 33 patients in IIEF-EF score ≤10, EHS <2 group (Group 1) and 29 patients in IIEF-EF score >10, EHS ≥2 group (Group 2). The two groups separated according to their scores were compared for age, body mass index (BMI), prevalence of priapism, vascular comorbidities and duration of erection. Results When compared to Group 2, median age, rate of vascular comorbidities rate and BMI were detected to be higher in Group 1 with IIEF-EF score ≤10 and EHS <2. But contrary to age and rate of vascular comorbidities (p=0.035, p=0.049 respectively), higher BMI was detected to be statistically insignificant (p=0.093). Duration of erection, IIEF-EF score and number of cases with priapism were significantly higher in Group 2 with IIEF-EF score >10 and EHS ≥2 (p<0.001, p=0.027, p=0.049 respectively). Conclusion High IIEF-EF and EHS scores, younger ages and lower rates of vascular comorbidities in patients from whom PDU was demanded increase the prevalence of priapism. PMID:29201505

Is there a relation between priapism occurring after penile doppler ultrasonography and international erectile function index score and erection hardness score levels?

PubMed

Sönmez, Mehmet Giray; Öztürk, Ahmet

2017-12-01

The relation between Erection Hardness Score (EHS) and The International Erectile Function Index (IIEF) Questionnaire- Erectile Function Domain Score (IIEF-EF score) used in erectile dysfunction (ED) evaluation and the prevalence of priapism after penile Doppler ultrasonography (PDU) was examined in this study. A total of 62 patients who had PDU were included in the study. Patients were divided into two groups; there were 33 patients in IIEF-EF score ≤10, EHS <2 group (Group 1) and 29 patients in IIEF-EF score >10, EHS ≥2 group (Group 2). The two groups separated according to their scores were compared for age, body mass index (BMI), prevalence of priapism, vascular comorbidities and duration of erection. When compared to Group 2, median age, rate of vascular comorbidities rate and BMI were detected to be higher in Group 1 with IIEF-EF score ≤10 and EHS <2. But contrary to age and rate of vascular comorbidities (p=0.035, p=0.049 respectively), higher BMI was detected to be statistically insignificant (p=0.093). Duration of erection, IIEF-EF score and number of cases with priapism were significantly higher in Group 2 with IIEF-EF score >10 and EHS ≥2 (p<0.001, p=0.027, p=0.049 respectively). High IIEF-EF and EHS scores, younger ages and lower rates of vascular comorbidities in patients from whom PDU was demanded increase the prevalence of priapism.

Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits

PubMed Central

Wang, Zheng; Xu, Xiaochuan; Fan, Donglei; Wang, Yaguo; Subbaraman, Harish; Chen, Ray T.

2016-01-01

Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits. In this work, we propose a geometrical tuning art, which realizes a pre-distorted refractive index profile in SWG waveguide bends. The pre-distorted refractive index profile can effectively reduce the mode mismatch and radiation loss simultaneously, thus significantly reduce the bend loss. This geometry tuning art has been numerically optimized and experimentally demonstrated in present study. Through such tuning, the average insertion loss of a 5 μm SWG waveguide bend is reduced drastically from 5.43 dB to 1.10 dB per 90° bend for quasi-TE polarization. In the future, the proposed scheme will be utilized to enhance performance of a wide range of SWG waveguide based photonics devices. PMID:27145872

Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits.

PubMed

Wang, Zheng; Xu, Xiaochuan; Fan, Donglei; Wang, Yaguo; Subbaraman, Harish; Chen, Ray T

2016-05-05

Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits. In this work, we propose a geometrical tuning art, which realizes a pre-distorted refractive index profile in SWG waveguide bends. The pre-distorted refractive index profile can effectively reduce the mode mismatch and radiation loss simultaneously, thus significantly reduce the bend loss. This geometry tuning art has been numerically optimized and experimentally demonstrated in present study. Through such tuning, the average insertion loss of a 5 μm SWG waveguide bend is reduced drastically from 5.43 dB to 1.10 dB per 90° bend for quasi-TE polarization. In the future, the proposed scheme will be utilized to enhance performance of a wide range of SWG waveguide based photonics devices.

Low-loss curved subwavelength grating waveguide based on index engineering

NASA Astrophysics Data System (ADS)

Wang, Zheng; Xu, Xiaochuan; Fan, D. L.; Wang, Yaoguo; Chen, Ray T.

2016-03-01

Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to its freedom to tune a few important waveguide properties such as dispersion and refractive index. Devices based on SWG waveguide have demonstrated impressive performances compared to those of conventional waveguides. However, the large loss of SWG waveguide bends jeopardizes their applications in integrated photonics circuits. In this work, we propose that a predistorted refractive index distribution in SWG waveguide bends can effectively decrease the mode mismatch noise and radiation loss simultaneously, and thus significantly reduce the bend loss. Here, we achieved the pre-distortion refractive index distribution by using trapezoidal silicon pillars. This geometry tuning approach is numerically optimized and experimentally demonstrated. The average insertion loss of a 5 μm SWG waveguide bend can be reduced drastically from 5.58 dB to 1.37 dB per 90° bend for quasi-TE polarization. In the future, the proposed approach can be readily adopted to enhance performance of an array of SWG waveguide-based photonics devices.

The Role of Inverse Compton Scattering in Solar Coronal Hard X-Ray and γ-Ray Sources

NASA Astrophysics Data System (ADS)

Chen, Bin; Bastian, T. S.

2012-05-01

Coronal hard X-ray (HXR) and continuum γ-ray sources associated with the impulsive phase of solar flares have been the subject of renewed interest in recent years. They have been interpreted in terms of thin-target, non-thermal bremsstrahlung emission. This interpretation has led to rather extreme physical requirements in some cases. For example, in one case, essentially all of the electrons in the source must be accelerated to non-thermal energies to account for the coronal HXR source. In other cases, the extremely hard photon spectra of the coronal continuum γ-ray emission suggest that the low-energy cutoff of the electron energy distribution lies in the MeV energy range. Here, we consider the role of inverse Compton scattering (ICS) as an alternate emission mechanism in both the ultra- and mildly relativistic regimes. It is known that relativistic electrons are produced during powerful flares; these are capable of upscattering soft photospheric photons to HXR and γ-ray energies. Previously overlooked is the fact that mildly relativistic electrons, generally produced in much greater numbers in flares of all sizes, can upscatter extreme-ultraviolet/soft X-ray photons to HXR energies. We also explore ICS on anisotropic electron distributions and show that the resulting emission can be significantly enhanced over an isotropic electron distribution for favorable viewing geometries. We briefly review results from bremsstrahlung emission and reconsider circumstances under which non-thermal bremsstrahlung or ICS would be favored. Finally, we consider a selection of coronal HXR and γ-ray events and find that in some cases the ICS is a viable alternative emission mechanism.

Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agio, Mario

2002-12-31

This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group.more » The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected to model a photonic-crystal combiner for an integrated multi-wavelength-source laser.« less

Characterizing the radial content of orbital-angular-momentum photonic states impaired by weak-to-strong atmospheric turbulence.

PubMed

Chen, Chunyi; Yang, Huamin

2016-08-22

The changes in the radial content of orbital-angular-momentum (OAM) photonic states described by Laguerre-Gaussian (LG) modes with a radial index of zero, suffering from turbulence-induced distortions, are explored by numerical simulations. For a single-photon field with a given LG mode propagating through weak-to-strong atmospheric turbulence, both the average LG and OAM mode densities are dependent only on two nondimensional parameters, i.e., the Fresnel ratio and coherence-width-to-beam-radius (CWBR) ratio. It is found that atmospheric turbulence causes the radially-adjacent-mode mixing, besides the azimuthally-adjacent-mode mixing, in the propagated photonic states; the former is relatively slighter than the latter. With the same Fresnel ratio, the probabilities that a photon can be found in the zero-index radial mode of intended OAM states in terms of the relative turbulence strength behave very similarly; a smaller Fresnel ratio leads to a slower decrease in the probabilities as the relative turbulence strength increases. A photon can be found in various radial modes with approximately equal probability when the relative turbulence strength turns great enough. The use of a single-mode fiber in OAM measurements can result in photon loss and hence alter the observed transition probability between various OAM states. The bit error probability in OAM-based free-space optical communication systems that transmit photonic modes belonging to the same orthogonal LG basis may depend on what digit is sent.

Combined effect of smoking habits and occupational exposure to hard metal on total IgE antibodies.

PubMed

Shirakawa, T; Kusaka, Y; Morimoto, K

1992-06-01

A survey was made within a population of workers (n = 706) exposed to hard metal dust (an alloy including cobalt), an agent known to cause occupational allergy. Twenty-seven (4 percent) of 733 workers were eliminated from consideration in this study because of atopic status identified prior to starting work in the plant. Using a Phadebas PRIST, the subjects' total IgE levels were determined and related to their smoking and exposure status. Nonexposed male smokers (n = 135) had a higher geometric mean IgE level (39.7 IU/ml) than did nonexposed subjects who had never smoked (33.1 IU/ml; n = 99); those with a higher Brinkman index (greater than 300), a smoking index obtained by multiplying the number of cigarettes per day by the duration of smoking in years, had significantly (p less than 0.05) decreased IgE levels. Although ex-smokers (n = 72) had a higher geometric mean IgE level (73.3 IU/ml) than did those who had never smoked, their serum IgE level declined with age since the time they quit smoking, regardless of their hard metal exposure status. Hard metal (cobalt) exposure may play a significant role as an adjuvant in the production of total IgE. A multivariate analysis demonstrated that hard metal exposure and a smoking habit together arithmetically (p less than 0.05) increased total IgE levels. These two factors may be preventable risk factors for occupational allergy in hard metal workers.

Hard X-ray Microscopic Images of the Human Hair

NASA Astrophysics Data System (ADS)

Goo, Jawoong; Jeon, Soo Young; Oh, Tak Heon; Hong, Seung Phil; Yon, Hwa Shik; Lee, Won-Soo

2007-01-01

The better visualization of the human organs or internal structure is challenging to the physicist and physicians. It can lead to more understanding of the morphology, pathophysiology and the diagnosis. Conventionally used methods to investigate cells or architectures, show limited value due to sample processing procedures and lower resolution. In this respect, Zernike type phase contrast hard x-ray microscopy using 6.95keV photon energy has advantages. We investigated hair fibers of the normal healthy persons. Coherence based phase contrast images revealed three distinct structures of hair, medulla, cortex, and cuticular layer. Some different detailed characters of each sample were noted. And further details would be shown and these results would be utilized as basic data of morphologic study of human hair.

Investigation of the Wave Propagation of Vector Modes of Light in a Spherically Symmetric Refractive Index Profile

NASA Astrophysics Data System (ADS)

Pozderac, Preston; Leary, Cody

We investigated the solutions to the Helmholtz equation in the case of a spherically symmetric refractive index using three different methods. The first method involves solving the Helmholtz equation for a step index profile and applying further constraints contained in Maxwell's equations. Utilizing these equations, we can simultaneously solve for the electric and magnetic fields as well as the allowed energies of photons propagating in this system. The second method applies a perturbative correction to these energies, which surfaces when deriving a Helmholtz type equation in a medium with an inhomogeneous refractive index. Applying first order perturbation theory, we examine how the correction term affects the energy of the photon. In the third method, we investigate the effects of the above perturbation upon solutions to the scalar Helmholtz equation, which are separable with respect to its polarization and spatial degrees of freedom. This work provides insights into the vector field structure of a photon guided by a glass microsphere.

Physics of Hard Spheres Experiment: Significant and Quantitative Findings Made

NASA Technical Reports Server (NTRS)

Doherty, Michael P.

2000-01-01

Direct examination of atomic interactions is difficult. One powerful approach to visualizing atomic interactions is to study near-index-matched colloidal dispersions of microscopic plastic spheres, which can be probed by visible light. Such spheres interact through hydrodynamic and Brownian forces, but they feel no direct force before an infinite repulsion at contact. Through the microgravity flight of the Physics of Hard Spheres Experiment (PHaSE), researchers have sought a more complete understanding of the entropically driven disorder-order transition in hard-sphere colloidal dispersions. The experiment was conceived by Professors Paul M. Chaikin and William B. Russel of Princeton University. Microgravity was required because, on Earth, index-matched colloidal dispersions often cannot be density matched, resulting in significant settling over the crystallization period. This settling makes them a poor model of the equilibrium atomic system, where the effect of gravity is truly negligible. For this purpose, a customized light-scattering instrument was designed, built, and flown by the NASA Glenn Research Center at Lewis Field on the space shuttle (shuttle missions STS 83 and STS 94). This instrument performed both static and dynamic light scattering, with sample oscillation for determining rheological properties. Scattered light from a 532- nm laser was recorded either by a 10-bit charge-coupled discharge (CCD) camera from a concentric screen covering angles of 0 to 60 or by sensitive avalanche photodiode detectors, which convert the photons into binary data from which two correlators compute autocorrelation functions. The sample cell was driven by a direct-current servomotor to allow sinusoidal oscillation for the measurement of rheological properties. Significant microgravity research findings include the observation of beautiful dendritic crystals, the crystallization of a "glassy phase" sample in microgravity that did not crystallize for over 1 year in 1g

CMOS-compatible photonic devices for single-photon generation

NASA Astrophysics Data System (ADS)

Xiong, Chunle; Bell, Bryn; Eggleton, Benjamin J.

2016-09-01

Sources of single photons are one of the key building blocks for quantum photonic technologies such as quantum secure communication and powerful quantum computing. To bring the proof-of-principle demonstration of these technologies from the laboratory to the real world, complementary metal-oxide-semiconductor (CMOS)-compatible photonic chips are highly desirable for photon generation, manipulation, processing and even detection because of their compactness, scalability, robustness, and the potential for integration with electronics. In this paper, we review the development of photonic devices made from materials (e.g., silicon) and processes that are compatible with CMOS fabrication facilities for the generation of single photons.

Intramuscular changes of soft and hard areas after low-level static contraction of the masseter muscle and the correlations with muscle hardness and increase in water content: evaluations with sonographic elastography and magnetic resonance imaging.

PubMed

Ariji, Yoshiko; Nakayama, Miwa; Taguchi, Akira; Gotoh, Akihiko; Kise, Yoshitaka; Katsumata, Aakitoshi; Kurita, Kenichi; Ariji, Eiichiro

2013-09-01

To investigate the intramuscular changes on sonographic elastography (SE) after low-level static contraction of the masseter muscle, and to clarify the relationship with the total hardness and edematous change. Ten healthy volunteers performed sustained bilateral biting at 20% of maximal voluntary contraction for 10 min. The SE and magnetic resonance (MR) scans of the masseter muscles were performed before, immediately after, and 10 min after exercise. The masseter muscle elasticity index (MEI) ratio, muscle thickness, and intramuscular soft and hard areas distribution were evaluated on SE images. The signal to noise ratio (SNR), indicating the water content, was measured on MR images. The soft area ratio showed significant correlations with the water content expressed as SNR. The hard area ratio showed significant correlations with the total muscle hardness expressed as the MEI ratio. Intramuscular soft and hard areas could be used both clinically and experimentally. Copyright © 2013 Elsevier Inc. All rights reserved.

First NuSTAR Observations of the BL Lac-Type Blazar PKS 2155-304: Constraints on the Jet Content and Distribution of Radiating Particles

NASA Technical Reports Server (NTRS)

Madejski, G. M.; Nalewajko, K.; Madsen, K. K.; Chiang, J.; Balokovic, M.; Paneque, D.; Furniss, A. K.; Hayashida, M.; Urry, C. M.; Sikora, M.;

First NuSTAR Observations of the BL Lac-type Blazar PKS 2155-304: Constraints on the Jet Content and Distribution of Radiating Particles

NASA Astrophysics Data System (ADS)

Madejski, G. M.; Nalewajko, K.; Madsen, K. K.; Chiang, J.; Baloković, M.; Paneque, D.; Furniss, A. K.; Hayashida, M.; Urry, C. M.; Sikora, M.; Ajello, M.; Blandford, R. D.; Harrison, F. A.; Sanchez, D.; Giebels, B.; Stern, D.; Alexander, D. M.; Barret, D.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Forster, K.; Giommi, P.; Grefenstette, B.; Hailey, C.; Hornstrup, A.; Kitaguchi, T.; Koglin, J. E.; Mao, P. H.; Miyasaka, H.; Mori, K.; Perri, M.; Pivovaroff, M. J.; Puccetti, S.; Rana, V.; Westergaard, N. J.; Zhang, W. W.; Zoglauer, A.

2016-11-01

We report the first hard X-ray observations with NuSTAR of the BL Lac-type blazar PKS 2155-304, augmented with soft X-ray data from XMM-Newton and γ-ray data from the Fermi Large Area Telescope, obtained in 2013 April when the source was in a very low flux state. A joint NuSTAR and XMM spectrum, covering the energy range 0.5-60 keV, is best described by a model consisting of a log-parabola component with curvature β ={0.3}-0.1+0.2 and a (local) photon index 3.04 ± 0.15 at photon energy of 2 keV, and a hard power-law tail with photon index 2.2 ± 0.4. The hard X-ray tail can be smoothly joined to the quasi-simultaneous γ-ray spectrum by a synchrotron self-Compton component produced by an electron distribution with index p = 2.2. Assuming that the power-law electron distribution extends down to γ min = 1 and that there is one proton per electron, an unrealistically high total jet power of L p ˜ 1047 erg s-1 is inferred. This can be reduced by two orders of magnitude either by considering a significant presence of electron-positron pairs with lepton-to-proton ratio {n}{{e}+{{e}}-}/{n}{{p}}˜ 30, or by introducing an additional, low-energy break in the electron energy distribution at the electron Lorentz factor γ br1 ˜ 100. In either case, the jet composition is expected to be strongly matter-dominated.

The new HMI beamline MAGS: an instrument for hard X-ray diffraction at BESSY.

PubMed

Dudzik, Esther; Feyerherm, Ralf; Diete, Wolfgang; Signorato, Riccardo; Zilkens, Christopher

2006-11-01

The Hahn-Meitner-Institute Berlin is operating the new hard X-ray diffraction beamline MAGS at the Berlin synchrotron radiation source BESSY. The beamline is intended to complement the existing neutron instrumentation at the Berlin Neutron Scattering Centre. The new beamline uses a 7 T multipole wiggler to produce photon fluxes in the 10(11)-10(12) photons s(-1) (100 mA)(-1) (0.1% bandwidth)(-1) range at energies from 4 to 30 keV at the experiment. It has active bendable optics to provide flexible horizontal and vertical focusing and to compensate the large heat load from the wiggler source. The experimental end-station consists of a six-circle Huber diffractometer which can be used with an additional (polarization) analyser and different sample environments. The beamline is intended for single-crystal diffraction and resonant magnetic scattering experiments for the study of ordering phenomena, phase transitions and materials science.

Development of grating-based x-ray Talbot interferometry at the advanced photon source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marathe, Shashidhara; Xiao Xianghui; Wojcik, Michael J.

2012-07-31

We report on the ongoing effort to develop hard x-ray Talbot interferometry at the Advanced Photon Source (APS), Argonne National Laboratory, USA. We describe the design of the interferometer and preliminary results obtained at 25 keV using a feather and a phantom sample lithographically fabricated of gold. We mention the future developmental goals and applications of this technique as a metrology tool for x-ray optics and beam wavefront characterization.

The Si/CdTe semiconductor camera of the ASTRO-H Hard X-ray Imager (HXI)

NASA Astrophysics Data System (ADS)

Sato, Goro; Hagino, Kouichi; Watanabe, Shin; Genba, Kei; Harayama, Atsushi; Kanematsu, Hironori; Kataoka, Jun; Katsuragawa, Miho; Kawaharada, Madoka; Kobayashi, Shogo; Kokubun, Motohide; Kuroda, Yoshikatsu; Makishima, Kazuo; Masukawa, Kazunori; Mimura, Taketo; Miyake, Katsuma; Murakami, Hiroaki; Nakano, Toshio; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Onishi, Mitsunobu; Saito, Shinya; Sato, Rie; Sato, Tamotsu; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takahashi, Tadayuki; Takeda, Shin`ichiro; Yuasa, Takayuki

2016-09-01

The Hard X-ray Imager (HXI) is one of the instruments onboard the ASTRO-H mission [1-4] to be launched in early 2016. The HXI is the focal plane detector of the hard X-ray reflecting telescope that covers an energy range from 5 to 80 keV. It will execute observations of astronomical objects with a sensitivity for point sources as faint as 1/100,000 of the Crab nebula at > 10 keV. The HXI camera - the imaging part of the HXI - is realized by a hybrid semiconductor detector system that consists of silicon (Si) and cadmium telluride (CdTe) semiconductor detectors. Here, we present the final design of the HXI camera and report on the development of the flight model. The camera is composed of four layers of Double-sided Silicon Strip Detectors (DSSDs) and one layer of CdTe Double-sided Strip Detector (CdTe-DSD), each with an imaging area of 32 mm×32 mm. The strip pitch of the Si and CdTe sensors is 250 μm, and the signals from all 1280 strips are processed by 40 Application Specified Integrated Circuits (ASICs) developed for the HXI. The five layers of sensors are vertically stacked with a 4 mm spacing to increase the detection efficiency. The thickness of the sensors is 0.5 mm for the Si, and 0.75 mm for the CdTe. In this configuration, soft X-ray photons will be absorbed in the Si part, while hard X-ray photons will go through the Si part and will be detected in the CdTe part. The design of the sensor trays, peripheral circuits, power connections, and readout schemes are also described. The flight models of the HXI camera have been manufactured, tested and installed in the HXI instrument and then on the satellite.

A population of isolated hard X-ray sources near the supernova remnant Kes 69

NASA Astrophysics Data System (ADS)

Bocchino, F.; Bykov, A. M.; Chen, Y.; Krassilchtchikov, A. M.; Levenfish, K. P.; Miceli, M.; Pavlov, G. G.; Uvarov, Yu. A.; Zhou, X.

2012-05-01

Recent X-ray observations of the supernova remnant (SNR) IC 443 interacting with molecular clouds detected a new population of hard X-ray sources related to the remnant itself, which has been proposed to be fast ejecta fragments propagating within the dense environment. Encouraged by these studies, we obtained a deep XMM-Newton observation of the SNR Kes 69, which also shows signs of a shock-cloud interaction. We report on the detection of 18 hard X-ray sources in the field of Kes 69, which is a number sognificantly higher than expected for the Galactic source population in the field. The sources are spatially correlated with CO emission from the cloud in the remnant environment. The spectra of 3 of the 18 sources can be described as hard power-laws with photon indices smaller than two plus line emission associated with K-shell transitions. We discuss the two most promising scenarios for the interpretation of the sources, namely fast ejecta fragments (as in IC 443) and cataclysmic variables. While most of the observational evidence is consistent with the former interpretation, we cannot rule out the latter.

Multi-photon absorption limits to heralded single photon sources

PubMed Central

Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

2013-01-01

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

Non-Poissonian photon statistics from macroscopic photon cutting materials.

PubMed

de Jong, Mathijs; Meijerink, Andries; Rabouw, Freddy T

2017-05-24

In optical materials energy is usually extracted only from the lowest excited state, resulting in fundamental energy-efficiency limits such as the Shockley-Queisser limit for single-junction solar cells. Photon-cutting materials provide a way around such limits by absorbing high-energy photons and 'cutting' them into multiple low-energy excitations that can subsequently be extracted. The occurrence of photon cutting or quantum cutting has been demonstrated in a variety of materials, including semiconductor quantum dots, lanthanides and organic dyes. Here we show that photon cutting results in bunched photon emission on the timescale of the excited-state lifetime, even when observing a macroscopic number of optical centres. Our theoretical derivation matches well with experimental data on NaLaF 4 :Pr 3+ , a material that can cut deep-ultraviolet photons into two visible photons. This signature of photon cutting can be used to identify and characterize new photon-cutting materials unambiguously.

Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in p +p collisions at √{s } =510 GeV

NASA Astrophysics Data System (ADS)

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alexander, J.; Alfred, M.; Andrieux, V.; Aoki, K.; Apadula, N.; Aramaki, Y.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Ayuso, C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bai, X.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Black, D.; Blau, D. S.; Boer, M.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Buesching, H.; Bumazhnov, V.; Butler, C.; Butsyk, S.; Campbell, S.; Canoa Roman, V.; Cervantes, R.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Christiansen, P.; Chujo, T.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Cronin, N.; Crossette, N.; Csanád, M.; Csörgő, T.; Danley, T. W.; Datta, A.; Daugherity, M. S.; David, G.; Deblasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Ding, L.; Dion, A.; Dixit, D.; Do, J. H.; D'Orazio, L.; Drapier, O.; Drees, A.; Drees, K. A.; Dumancic, M.; Durham, J. M.; Durum, A.; Elder, T.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Eyser, K. O.; Fadem, B.; Fan, W.; Feege, N.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fukao, Y.; Fukuda, Y.; Fusayasu, T.; Gainey, K.; Gal, C.; Gallus, P.; Garg, P.; Garishvili, A.; Garishvili, I.; Ge, H.; Giordano, F.; Glenn, A.; Gong, X.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gu, Y.; Gunji, T.; Guragain, H.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamilton, H. F.; Han, S. Y.; Hanks, J.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; Hayano, R.; He, X.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hill, K.; Hollis, R. S.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Ichihara, T.; Ikeda, Y.; Imai, K.; Imazu, Y.; Imrek, J.; Inaba, M.; Iordanova, A.; Isenhower, D.; Isinhue, A.; Ito, Y.; Ivanishchev, D.; Jacak, B. V.; Jeon, S. J.; Jezghani, M.; Ji, Z.; Jia, J.; Jiang, X.; Johnson, B. M.; Joo, E.; Joo, K. S.; Jorjadze, V.; Jouan, D.; Jumper, D. S.; Kamin, J.; Kanda, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapukchyan, D.; Kapustinsky, J.; Karthas, S.; Kawall, D.; Kazantsev, A. V.; Key, J. A.; Khachatryan, V.; Khandai, P. K.; Khanzadeev, A.; Kihara, K.; Kijima, K. M.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.-J.; Kim, H.-J.; Kim, M. H.; Kim, M.; Kim, Y.-J.; Kim, Y. K.; Kincses, D.; Kistenev, E.; Klatsky, J.; Kleinjan, D.; Kline, P.; Koblesky, T.; Kofarago, M.; Komkov, B.; Koster, J.; Kotchetkov, D.; Kotov, D.; Krizek, F.; Kudo, S.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lallow, E. O.; Lebedev, A.; Lee, D. M.; Lee, G. H.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S.; Lee, S. H.; Leitch, M. J.; Leitgab, M.; Leung, Y. H.; Lewis, B.; Lewis, N. A.; Li, X.; Li, X.; Lim, S. H.; Liu, L. D.; Liu, M. X.; Loggins, V.-R.; Loggins, V.-R.; Lovasz, K.; Lynch, D.; Maguire, C. F.; Majoros, T.; Makdisi, Y. I.; Makek, M.; Malaev, M.; Manion, A.; Manko, V. I.; Mannel, E.; Masuda, H.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Meles, A.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Mihalik, D. E.; Miller, A. J.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Mitsuka, G.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Mohapatra, S.; Montuenga, P.; Moon, T.; Morrison, D. P.; Morrow, S. I. M.; Moskowitz, M.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Mwai, A.; Nagae, T.; Nagai, K.; Nagamiya, S.; Nagashima, K.; Nagashima, T.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Netrakanti, P. K.; Nihashi, M.; Niida, T.; Nouicer, R.; Novák, T.; Novitzky, N.; Novotny, R.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Oide, H.; Okada, K.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ottino, G. J.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J. S.; Park, S.; Park, S. K.; Pate, S. F.; Patel, L.; Patel, M.; Peng, J.-C.; Peng, W.; Perepelitsa, D. V.; Perera, G. D. N.; Peressounko, D. Yu.; Perezlara, C. E.; Perry, J.; Petti, R.; Phipps, M.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Pun, A.; Purschke, M. L.; Qu, H.; Rak, J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Richford, D.; Rinn, T.; Riveli, N.; Roach, D.; Rolnick, S. D.; Rosati, M.; Rowan, Z.; Rubin, J. G.; Runchey, J.; Ryu, M. S.; Safonov, A. S.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, K.; Sato, S.; Sawada, S.; Schaefer, B.; Schmoll, B. K.; Schmoll, B. K.; Sedgwick, K.; Seele, J.; Seidl, R.; Sekiguchi, Y.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shaver, A.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shioya, T.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Singh, B. K.; Singh, C. P.; Singh, V.; Skolnik, M.; Slunečka, M.; Smith, K. L.; Snowball, M.; Solano, S.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Steinberg, P.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Stone, M. R.; Sugitate, T.; Sukhanov, A.; Sumita, T.; Sun, J.; Syed, S.; Sziklai, J.; Takahara, A.; Takeda, A.; Taketani, A.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarnai, G.; Tennant, E.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Torii, H.; Towell, C. L.; Towell, M.; Towell, R.; Towell, R. S.; Tserruya, I.; Ueda, Y.; Ujvari, B.; van Hecke, H. W.; Vargyas, M.; Vazquez-Carson, S.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Virius, M.; Vrba, V.; Vukman, N.; Vznuzdaev, E.; Wang, X. R.; Wang, Z.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Whitaker, S.; Wolin, S.; Wong, C. P.; Woody, C. L.; Wysocki, M.; Xia, B.; Xu, C.; Xu, Q.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yamamoto, H.; Yanovich, A.; Yin, P.; Yokkaichi, S.; Yoo, J. H.; Yoon, I.; You, Z.; Younus, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Zharko, S.; Zhou, S.; Zou, L.; Phenix Collaboration

2017-04-01

Dihadron and isolated direct photon-hadron angular correlations are measured in p +p collisions at √{s }=510 GeV . Correlations of charged hadrons of 0.7 photons of 7 photon or π0. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (pTtrig ). The Gaussian widths and root mean square of pout are reported as a function of the interaction hard scale pTtrig to investigate possible transverse-momentum-dependent evolution differences between the π0-h± and direct photon-h± correlations and factorization breaking effects. The widths are found to decrease with pTtrig , which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in p +p collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.

Deterministically swapping frequency-bin entanglement from photon-photon to atom-photon hybrid systems

NASA Astrophysics Data System (ADS)

Ou, Bao-Quan; Liu, Chang; Sun, Yuan; Chen, Ping-Xing

2018-02-01

Inspired by the recent developments of the research on the atom-photon quantum interface and energy-time entanglement between single-photon pulses, we are motivated to study the deterministic protocol for the frequency-bin entanglement of the atom-photon hybrid system, which is analogous to the frequency-bin entanglement between single-photon pulses. We show that such entanglement arises naturally in considering the interaction between a frequency-bin entangled single-photon pulse pair and a single atom coupled to an optical cavity, via straightforward atom-photon phase gate operations. Its anticipated properties and preliminary examples of its potential application in quantum networking are also demonstrated. Moreover, we construct a specific quantum entanglement witness tool to detect such extended frequency-bin entanglement from a reasonably general set of separable states, and prove its capability theoretically. We focus on the energy-time considerations throughout the analysis.

Neuromorphic photonic networks using silicon photonic weight banks.

PubMed

Tait, Alexander N; de Lima, Thomas Ferreira; Zhou, Ellen; Wu, Allie X; Nahmias, Mitchell A; Shastri, Bhavin J; Prucnal, Paul R

2017-08-07

Photonic systems for high-performance information processing have attracted renewed interest. Neuromorphic silicon photonics has the potential to integrate processing functions that vastly exceed the capabilities of electronics. We report first observations of a recurrent silicon photonic neural network, in which connections are configured by microring weight banks. A mathematical isomorphism between the silicon photonic circuit and a continuous neural network model is demonstrated through dynamical bifurcation analysis. Exploiting this isomorphism, a simulated 24-node silicon photonic neural network is programmed using "neural compiler" to solve a differential system emulation task. A 294-fold acceleration against a conventional benchmark is predicted. We also propose and derive power consumption analysis for modulator-class neurons that, as opposed to laser-class neurons, are compatible with silicon photonic platforms. At increased scale, Neuromorphic silicon photonics could access new regimes of ultrafast information processing for radio, control, and scientific computing.

Photonic-crystal fiber as a multifunctional optical sensor and sample collector.

PubMed

Konorov, Stanislav; Zheltikov, Aleksei; Scalora, Michael

2005-05-02

Two protocols of optical sensing realized with the same photonic-crystal fiber are compared. In the first protocol, diode-laser radiation is delivered to a sample through the central core of a dual-cladding photonic-crystal fiber with a diameter of a few micrometers, while the large-diameter fiber cladding serves to collect the fluorescent response from the sample and to guide it to a detector in the backward direction. In the second scheme, liquid sample is collected by a microcapillary array in the fiber cladding and is interrogated by laser radiation guided in the fiber modes. For sample fluids with refractive indices exceeding the refractive index of the fiber material, fluid channels in photonic-crystal fibers can guide laser light by total internal reflection, providing an 80% overlap of interrogating radiation with sample fluid.

Two-photon equivalent weighting of spatial excimer laser beam profiles

NASA Astrophysics Data System (ADS)

Eva, Eric; Bauer, Harry H.; Metzger, K.; Pfeiffer, A.

2001-04-01

Damage in optical materials for semiconductor lithography applications caused by exposure to 248 or 193 nm light is usually two-photon driven, hence it is a nonlinear function of incident intensity. Materials should be tested with flat- topped temporal and spatial laser beam profiles to facilitate interpretation of data, but in reality this is hard to achieve. Sandstrom provided a formula that approximates any given temporal pulse shape with a two- photon equivalent rectangular pulse (Second Symposium on 193 nm Lithography, Colorado Springs 1997). Known as the integral-square pulse duration, this definition has been embraced as an industry standard. Originally faced with the problem of comparing results obtained with pseudo-Gaussian spatial profiles to literature data, we found that a general solution for arbitrarily inhomogeneous spatial beam profiles exists which results in a definition much similar to Sandstrom's. In addition, we proved the validity of our approach in experiments with intentionally altered beam profiles.

Tunable two-dimensional photonic crystals using liquid crystal infiltration

NASA Astrophysics Data System (ADS)

Leonard, S. W.; Mondia, J. P.; van Driel, H. M.; Toader, O.; John, S.; Busch, K.; Birner, A.; Gösele, U.; Lehmann, V.

2000-01-01

The photonic band gap of a two-dimensional photonic crystal is continuously tuned using the temperature dependent refractive index of a liquid crystal. Liquid crystal E7 was infiltrated into the air pores of a macroporous silicon photonic crystal with a triangular lattice pitch of 1.58 μm and a band gap wavelength range of 3.3-5.7 μm. After infiltration, the band gap for the H polarized field shifted dramatically to 4.4-6.0 μm while that of the E-polarized field collapsed. As the sample was heated to the nematic-isotropic phase transition temperature of the liquid crystal (59 °C), the short-wavelength band edge of the H gap shifted by as much as 70 nm while the long-wavelength edge was constant within experimental error. Band structure calculations incorporating the temperature dependence of the liquid crystal birefringence can account for our results and also point to an escaped-radial alignment of the liquid crystal in the nematic phase.

The Effects of Low- and High-Energy Cutoffs on Solar Flare Microwave and Hard X-Ray Spectra

NASA Technical Reports Server (NTRS)

Holman, G. D.; Oegerle, William (Technical Monitor)

2002-01-01

Microwave and hard x-ray spectra provide crucial information about energetic electrons and their environment in solar flares. These spectra are becoming better determined with the Owens Valley Solar Array (OVSA) and the recent launch of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The proposed Frequency Agile Solar Radiotelescope (FASR) promises even greater advances in radio observations of solar flares. Both microwave and hard x-ray spectra are sensitive to cutoffs in the electron distribution function. The determination of the high-energy cutoff from these spectra establishes the highest electron energies produced by the acceleration mechanism, while determination of the low-energy cutoff is crucial to establishing the total energy in accelerated electrons. This paper will show computations of the effects of both high- and low-energy cutoffs on microwave and hard x-ray spectra. The optically thick portion of a microwave spectrum is enhanced and smoothed by a low-energy cutoff, while a hard x-ray spectrum is flattened below the cutoff energy. A high-energy cutoff steepens the microwave spectrum and increases the wavelength at which the spectrum peaks, while the hard x-ray spectrum begins to steepen at photon energies roughly an order of magnitude below the electron cutoff energy. This work discusses how flare microwave and hard x-ray spectra can be analyzed together to determine these electron cutoff energies. This work is supported in part by the NASA Sun-Earth Connection Program.

Vernier-like super resolution with guided correlated photon pairs.

PubMed

Nespoli, Matteo; Goan, Hsi-Sheng; Shih, Min-Hsiung

2016-01-11

We describe a dispersion-enabled, ultra-low power realization of super-resolution in an integrated Mach-Zehnder interferometer. Our scheme is based on a Vernier-like effect in the coincident detection of frequency correlated, non-degenerate photon pairs at the sensor output in the presence of group index dispersion. We design and simulate a realistic integrated refractive index sensor in a silicon nitride on silica platform and characterize its performance in the proposed scheme. We present numerical results showing a sensitivity improvement upward of 40 times over a traditional sensing scheme. The device we design is well within the reach of modern semiconductor fabrication technology. We believe this is the first metrology scheme that uses waveguide group index dispersion as a resource to attain super-resolution.

Photonic structures based on hybrid nanocomposites

NASA Astrophysics Data System (ADS)

Husaini, Saima

In this thesis, photonic structures embedded with two types of nanomaterials, (i) quantum dots and (ii) metal nanoparticles are studied. Both of these exhibit optical and electronic properties different from their bulk counterpart due to their nanoscale physical structure. By integrating these nanomaterials into photonic structures, in which the electromagnetic field can be confined and controlled via modification of geometry and composition, we can enhance their linear and nonlinear optical properties to realize functional photonic structures. Before embedding quantum dots into photonic structures, we study the effect of various host matrices and fabrication techniques on the optical properties of the colloidal quantum dots. The two host matrices of interest are SU8 and PMMA. It is shown that the emission properties of the quantum dots are significantly altered in these host matrices (especially SU8) and this is attributed to a high rate of nonradiative quenching of the dots. Furthermore, the effects of fabrication techniques on the optical properties of quantum dots are also investigated. Finally a microdisk resonator embedded with quantum dots is fabricated using soft lithography and luminescence from the quantum dots in the disk is observed. We investigate the absorption and effective index properties of silver nanocomposite films. It is shown that by varying the fill factor of the metal nanoparticles and fabrication parameters such as heating time, we can manipulate the optical properties of the metal nanocomposite. Optimizing these parameters, a silver nanocomposite film with a 7% fill factor is prepared. A one-dimensional photonic crystal consisting of alternating layers of the silver nanocomposite and a polymer (Polymethyl methacrylate) is fabricated using spin coating and its linear and nonlinear optical properties are investigated. Using reflectivity measurements we demonstrate that the one-dimensional silver-nanocomposite-dielectric photonic crystal

A HARD X-RAY POWER-LAW SPECTRAL CUTOFF IN CENTAURUS X-4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakrabarty, Deepto; Nowak, Michael A.; Tomsick, John A.

2014-12-20

The low-mass X-ray binary (LMXB) Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1×10{sup 33} D{sub kpc}{sup 2} erg s{sup –1}, with ≅60% in the thermalmore » component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. We show that thermal Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with kT{sub e} = 18 keV, which can be understood as arising either in a hot layer above the neutron star atmosphere or in a radiatively inefficient accretion flow. The power-law cutoff energy may be set by the degree of Compton cooling of the bremsstrahlung electrons by thermal seed photons from the neutron star surface. Lower thermal luminosities should lead to higher (possibly undetectable) cutoff energies. We compare Cen X-4's behavior with PSR J1023+0038, IGR J18245–2452, and XSS J12270–4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity.« less

Silicon photonics: Design, fabrication, and characterization of on-chip optical interconnects

NASA Astrophysics Data System (ADS)

Hsieh, I.-Wei

In recent years, the research field of silicon photonics has been developing rapidly from a concept to a demonstrated technology, and has gathered much attention from both academia and industry communities. Its many potential applications in long-haul telecommunication, mid-range data-communication, on-chip optical interconnection networks, and nano-scale sensing as well as its compatibility with electronic integrated circuits have driven much effort in realizing silicon photonics both as a disruptive technology for existing markets and as an enabling technology for new ones. Despite the promising future of silicon photonics, many fundamental issues still remain to be understood---both in the linear- and nonlinear-optical regimes. There are also many engineering challenges to make silicon photonics the gold standard in photonic integrated circuits. In this thesis, we focus on the design, fabrication, and characterization of active and passive silicon-on-insulator (SOI) photonic devices. The SOI material system differs from most conventional optical material platforms because of its high-refractive-index-contrast, which enables engineers to design very compact integrated photonic networks with sub-micron transverse waveguide dimensions and sharp bends. On the other hand, because most analytical formulas for designing waveguide devices are valid only in low-index-contrast cases, SOI photonic devices need to be analyzed numerically for accurate results. The second chapter of this thesis describes some common numerical methods such as Beam Propagation Method (BPM) and Finite Element Method (FEM) for waveguide-design simulations, and presents two design studies based on these methods. The compatibility of silicon photonic integrated circuits with conventional CMOS fabrication technology is another important aspect that distinguishes silicon photonics from others such as III-V materials and lithium niobate. However, the requirements for fabricating silicon photonic

Photon time-interval statistics applied to the analysis of laser heterodyne signal with photon counter

NASA Astrophysics Data System (ADS)

Liu, Lisheng; Zhang, Heyong; Guo, Jin; Zhao, Shuai; Wang, Tingfeng

2012-08-01

In this paper, we report a mathematical derivation of probability density function (PDF) of time-interval between two successive photoelectrons of the laser heterodyne signal, and give a confirmation of the theoretical result by both numerical simulation and an experiment. The PDF curve of the beat signal displays a series of fluctuations, the period and amplitude of which are respectively determined by the beat frequency and the mixing efficiency. The beat frequency is derived from the frequency of fluctuations accordingly when the PDF curve is measured. This frequency measurement method still works while the traditional Fast Fourier Transform (FFT) algorithm hardly derives the correct peak value of the beat frequency in the condition that we detect 80 MHz beat signal with 8 Mcps (counts per-second) photons count rate, and this indicates an advantage of the PDF method.

Evaluation of HardSys/HardDraw, An Expert System for Electromagnetic Interactions Modelling

DTIC Science & Technology

1993-05-01

interactions ir complex systems. This report gives a description of HardSys/HardDraw and reviews the main concepts used in its design. Various aspects of its ...HardDraw, an expert system for the modelling of electromagnetic interactions in complex systems. It consists of two main components: HardSys and HardDraw...HardSys is the advisor part of the expert system. It is knowledge-based, that is it contains a database of models and properties for various types of

Hard X-Ray Emission from SH 2-104: A NuSTAR Search for Gamma-Ray Counterparts

NASA Technical Reports Server (NTRS)

Gotthelf, E. V.; Mori, K.; Aliu, E.; Paredes, J. M.; Tomsick, J. A.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Hailey, C. J.; Harrison, F. A.;

Hard X-Ray Emission from Sh 2-104: A NuSTAR Search for Gamma-Ray Counterparts

NASA Astrophysics Data System (ADS)

Gotthelf, E. V.; Mori, K.; Aliu, E.; Paredes, J. M.; Tomsick, J. A.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Hailey, C. J.; Harrison, F. A.; Hong, J. S.; Rahoui, F.; Stern, D.; Zhang, W. W.

2016-07-01

We present NuSTAR hard X-ray observations of Sh 2-104, a compact H II region containing several young massive stellar clusters (YMSCs). We have detected distinct hard X-ray sources coincident with localized VERITAS TeV emission recently resolved from the giant gamma-ray complex MGRO J2019+37 in the Cygnus region. Fainter, diffuse X-rays coincident with the eastern YMSC in Sh2-104 likely result from the colliding winds of a component star. Just outside the radio shell of Sh 2-104 lies 3XMM J201744.7+365045 and a nearby nebula, NuSTAR J201744.3+364812, whose properties are most consistent with extragalactic objects. The combined XMM-Newton and NuSTAR spectrum of 3XMM J201744.7+365045 is well-fit to an absorbed power-law model with {N}{{H}}=(3.1+/- 1.0)× {10}22 cm-2 and a photon index {{Γ }}=2.1+/- 0.1. Based on possible long-term flux variation and the lack of detected pulsations (≤43% modulation), this object is likely a background active galactic nucleus rather than a Galactic pulsar. The spectrum of the NuSTAR nebula shows evidence of an emission line at E = 5.6 keV, suggesting an optically obscured galaxy cluster at z = 0.19 ± 0.02 (d = 800 Mpc) and L X = 1.2 × 1044 erg s-1. Follow-up Chandra observations of Sh 2-104 will help identify the nature of the X-ray sources and their relation to MGRO J2019+37. We also show that the putative VERITAS excess south of Sh 2-104, is most likely associated with the newly discovered Fermi pulsar PSR J2017+3625 and not the H II region.

Circularly polarized guided modes in dielectrically chiral photonic crystal fiber.

PubMed

Li, Junqing; Su, Qiyao; Cao, Yusheng

2010-08-15

The effect of dielectric chirality on the polarization states and mode indices of guided modes in photonic crystal fiber (PCF) is investigated by a modified plane-wave expansion (PWE) method. Using a solid-core chiral PCF as a numerical example, we show that circular polarization is the eigenstate of the fundamental mode. Mode index divergence between right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) states is demonstrated. Chirality's effect on mode index and circular birefringence (CB) in such a PCF is found to be similar to that in bulk chiral media.

Linear and nonlinear properties of photonic crystal fibers filled with nematic liquid crystals

NASA Astrophysics Data System (ADS)

Brzdąkiewicz, K. A.; Laudyn, U. A.; Karpierz, M. A.; Woliński, T. R.; Wójcik, J.

2006-12-01

We investigate linear and nonlinear light propagation in the photonic crystal fibers infiltrated with nematic liquid crystals. Such a photonic structure, with periodic modulation of refractive index, which could be additionally controlled by the temperature and by the optical power, allows for the study of discrete optical phenomena. Our theoretical investigations, carried out with the near infrared wavelength of 830 nm, for both focusing and defocusing Kerr-type nonlinearity, show the possibility of the transverse light localization, which can result in the discrete soliton generation. In addition, we present the preliminary experimental results on the linear light propagation in the photonic crystal fiber with the glycerin-water solution and 6CHBT nematics, as the guest materials.

Negative Refraction Angular Characterization in One-Dimensional Photonic Crystals

PubMed Central

Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

2011-01-01

Background Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs. Methodology/Principal Findings By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone. Conclusions/Significance Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications. PMID:21494332

Searching for photon-sector Lorentz violation using gravitational-wave detectors

NASA Astrophysics Data System (ADS)

Kostelecký, V. Alan; Melissinos, Adrian C.; Mewes, Matthew

2016-10-01

We study the prospects for using interferometers in gravitational-wave detectors as tools to search for photon-sector violations of Lorentz symmetry. Existing interferometers are shown to be exquisitely sensitive to tiny changes in the effective refractive index of light occurring at frequencies around and below the microhertz range, including at the harmonics of the frequencies of the Earth's sidereal rotation and annual revolution relevant for tests of Lorentz symmetry. We use preliminary data obtained by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2006-2007 to place constraints on coefficients for Lorentz violation in the photon sector exceeding current limits by about four orders of magnitude.

Tunable properties of light propagation in photonic liquid crystal fibers

NASA Astrophysics Data System (ADS)

Szaniawska, K.; Nasilowski, T.; Woliński, T. R.; Thienpont, H.

2006-12-01

Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].

Glass-embedded two-dimensional silicon photonic crystal devices with a broad bandwidth waveguide and a high quality nanocavity.

PubMed

Jeon, Seung-Woo; Han, Jin-Kyu; Song, Bong-Shik; Noda, Susumu

2010-08-30

To enhance the mechanical stability of a two-dimensional photonic crystal slab structure and maintain its excellent performance, we designed a glass-embedded silicon photonic crystal device consisting of a broad bandwidth waveguide and a nanocavity with a high quality (Q) factor, and then fabricated the structure using spin-on glass (SOG). Furthermore, we showed that the refractive index of the SOG could be tuned from 1.37 to 1.57 by varying the curing temperature of the SOG. Finally, we demonstrated a glass-embedded heterostructured cavity with an ultrahigh Q factor of 160,000 by adjusting the refractive index of the SOG.

Multidimensional microstructured photonic device based on all-solid waveguide array fiber and magnetic fluid

NASA Astrophysics Data System (ADS)

Miao, Yinping; Ma, Xixi; He, Yong; Zhang, Hongmin; Yang, Xiaoping; Yao, Jianquan

2017-01-01

An all-solid waveguide array fiber (WAF) is one kind of special microstructured optical fiber in which the higher-index rods are periodically distributed in a low-index silica host to form the transverse two-dimensional photonic crystal. In this paper, one kind of multidimensional microstructured optical fiber photonic device is proposed by using electric arc discharge method to fabricate periodic tapers along the fiber axis. By tuning the applied magnetic field intensity, the propagation characteristics of the all-solid WAF integrated with magnetic fluid are periodically modulated in both radial and axial directions. Experimental results show that the wavelength changes little while the transmission loss increases for an applied magnetic field intensity range from 0 to 500 Oe. The magnetic field sensitivity is 0.055 dB/Oe within the linear range from 50 to 300 Oe. Meanwhile, the all-solid WAF has very similar thermal expansion coefficient for both high- and low-refractive index glasses, and thermal drifts have a little effect on the mode profile. The results show that the temperature-induced transmission loss is <0.3 dB from 26°C to 44°C. Further tuning coherent coupling of waveguides and controlling light propagation, the all-solid WAF would be found great potential applications to develop new micro-nano photonic devices for optical communications and optical sensing applications.

Photon statistics in scintillation crystals

NASA Astrophysics Data System (ADS)

Bora, Vaibhav Joga Singh

Scintillation based gamma-ray detectors are widely used in medical imaging, high-energy physics, astronomy and national security. Scintillation gamma-ray detectors are eld-tested, relatively inexpensive, and have good detection eciency. Semi-conductor detectors are gaining popularity because of their superior capability to resolve gamma-ray energies. However, they are relatively hard to manufacture and therefore, at this time, not available in as large formats and much more expensive than scintillation gamma-ray detectors. Scintillation gamma-ray detectors consist of: a scintillator, a material that emits optical (scintillation) photons when it interacts with ionization radiation, and an optical detector that detects the emitted scintillation photons and converts them into an electrical signal. Compared to semiconductor gamma-ray detectors, scintillation gamma-ray detectors have relatively poor capability to resolve gamma-ray energies. This is in large part attributed to the "statistical limit" on the number of scintillation photons. The origin of this statistical limit is the assumption that scintillation photons are either Poisson distributed or super-Poisson distributed. This statistical limit is often dened by the Fano factor. The Fano factor of an integer-valued random process is dened as the ratio of its variance to its mean. Therefore, a Poisson process has a Fano factor of one. The classical theory of light limits the Fano factor of the number of photons to a value greater than or equal to one (Poisson case). However, the quantum theory of light allows for Fano factors to be less than one. We used two methods to look at the correlations between two detectors looking at same scintillation pulse to estimate the Fano factor of the scintillation photons. The relationship between the Fano factor and the correlation between the integral of the two signals detected was analytically derived, and the Fano factor was estimated using the measurements for SrI2:Eu, YAP

Ferrofluid Photonic Dipole Contours

NASA Astrophysics Data System (ADS)

Snyder, Michael; Frederick, Jonathan

2008-03-01

Understanding magnetic fields is important to facilitate magnetic applications in diverse fields in industry, commerce, and space exploration to name a few. Large electromagnets can move heavy loads of metal. Magnetic materials attached to credit cards allow for fast, accurate business transactions. And the Earth's magnetic field gives us the colorful auroras observed near the north and south poles. Magnetic fields are not visible, and therefore often hard to understand or characterize. This investigation describes and demonstrates a novel technique for the visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been constructed to facilitate the imaging of magnetic field lines [1,2,3,4]. We deduce that magnetically induced photonic band gap arrays similar to electrostatic liquid crystal operation are responsible for the photographed images and seek to mathematically prove the images are of exact dipole nature. We also note by comparison that our photographs are very similar to solar magnetic Heliosphere photographs.

Dual CARS and SHG image acquisition scheme that combines single central fiber and multimode fiber bundle to collect and differentiate backward and forward generated photons

PubMed Central

Weng, Sheng; Chen, Xu; Xu, Xiaoyun; Wong, Kelvin K.; Wong, Stephen T. C.

2016-01-01

In coherent anti-Stokes Raman scattering (CARS) and second harmonic generation (SHG) imaging, backward and forward generated photons exhibit different image patterns and thus capture salient intrinsic information of tissues from different perspectives. However, they are often mixed in collection using traditional image acquisition methods and thus are hard to interpret. We developed a multimodal scheme using a single central fiber and multimode fiber bundle to simultaneously collect and differentiate images formed by these two types of photons and evaluated the scheme in an endomicroscopy prototype. The ratio of these photons collected was calculated for the characterization of tissue regions with strong or weak epi-photon generation while different image patterns of these photons at different tissue depths were revealed. This scheme provides a new approach to extract and integrate information captured by backward and forward generated photons in dual CARS/SHG imaging synergistically for biomedical applications. PMID:27375938

Light-induced switching in pDTE-FICO 1D photonic structures

NASA Astrophysics Data System (ADS)

Kriegel, Ilka; Scotognella, Francesco

2018-03-01

We propose the design of 1D photonic crystals and microcavities in which fluorine-indium codoped cadmium oxide (FICO) nanocrystal based layers and layers of diarylethene-based polyester (pDTE) are alternated or embedded in a microcavity. The irradiation with UV light results in two different behaviours: (i) it dopes the FICO nanocrystals inducing a blue shift of their plasmonic resonances; (ii) it changes the real part of the refractive index of the photochromic pDTE polymer. These two behaviours are combined in the proposed photonic structures and can be useful for switchable filters and cavities for light emission.

Two-photon spectroscopy of excitons with entangled photons.

PubMed

Schlawin, Frank; Mukamel, Shaul

2013-12-28

The utility of quantum light as a spectroscopic tool is demonstrated for frequency-dispersed pump-probe, integrated pump-probe, and two-photon fluorescence signals which show Ramsey fringes. Simulations of the frequency-dispersed transmission of a broadband pulse of entangled photons interacting with a three-level model of matter reveal how the non-classical time-bandwidth properties of entangled photons can be used to disentangle congested spectra, and reveal otherwise unresolved features. Quantum light effects are most pronounced at weak intensities when entangled photon pairs are well separated, and are gradually diminished at higher intensities when different photon pairs overlap.

Two-photon spectroscopy of excitons with entangled photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlawin, Frank, E-mail: Frank.Schlawin@physik.uni-freiburg.de; Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Straße 3, 79108 Freiburg; Mukamel, Shaul, E-mail: smukamel@uci.edu

The utility of quantum light as a spectroscopic tool is demonstrated for frequency-dispersed pump-probe, integrated pump-probe, and two-photon fluorescence signals which show Ramsey fringes. Simulations of the frequency-dispersed transmission of a broadband pulse of entangled photons interacting with a three-level model of matter reveal how the non-classical time-bandwidth properties of entangled photons can be used to disentangle congested spectra, and reveal otherwise unresolved features. Quantum light effects are most pronounced at weak intensities when entangled photon pairs are well separated, and are gradually diminished at higher intensities when different photon pairs overlap.

Aperiodic Mo/Si multilayers for hard x-rays

DOE PAGES

Pardini, Tom; Alameda, Jennifer; Platonov, Yuriy; ...

2016-08-04

In this work we have developed aperiodic Molybdenum/Silicon (Mo/Si) multilayers (MLs) to reflect 16.25 keV photons at a grazing angle of incidence of 0.6° ± 0.05°. To the best of our knowledge this is the first time this material system has been used to fabricate aperiodic MLs for hard x-rays. At these energies new hurdles arise. First of all a large number of bilayers is required to reach saturation. This poses a challenge from the manufacturing point of view, as thickness control of each ML period becomes paramount. The latter is not well defined a priori, due to the thicknessmore » of the interfacial silicide layers which has been observed to vary as a function of Mo and Si thickness. Additionally an amorphous-to-crystalline transition for Mo must be avoided in order maintain reasonably low roughness at the interfaces. This transition is well within the range of thicknesses pertinent to this study. Despite these difficulties our data demonstrates that we achieved reasonably flat ML response across the angular acceptance of ± 0.05°, with an experimentally confirmed average reflectivity of 28%. Such a ML prescription is well suited for applications in the field of hard x-ray imaging of highly diverging sources.« less

Observation of extraordinary transmission in deep UV region from aluminum film coated two dimensional photonic crystals

NASA Astrophysics Data System (ADS)

Venkatesh, A.; Piragash Kumar, R. M.; Moorthy, V. H. S.

2018-05-01

We report the first observation of extraordinary transmission of deep-UV light (λ = 289nm) through 20nm aluminum film coated two-dimensional photonic crystals. The two-dimensional photonic crystals are made of self-assembled hexagonally arranged monolayer of 200 nm polystyrene spheres fabricated using drop casting method. The high quality photonic crystal exhibits a well-defined photonic band gap of 4.59 eV (λ = 270nm) and the aluminum coated two-dimensional photonic crystal displays extraordinary transmission in the deep-UV region at λ = 289 nm. The fabricated aluminum nanostructure produces a sensitivity of 42nm/RIU and 57nm/RIU when the refractive index of the surrounding medium is changed from 1 (= air) to 1.36 (= ethanol) and 1.49 (=toluene), respectively. Therefore, the aluminum film coated two-dimensional photonic crystals could be utilized to fabricate cost-effective and ultrasensitive chemical sensors.

New Constraints on the Hard Ionizing Photon Budget and the Lifetime and Obscuration of Quasars During the Epoch of Helium Reionization

NASA Astrophysics Data System (ADS)

Davies, Frederick

2017-08-01

The epoch of helium reionization was a major milestone in the history of the Universe, a direct consequence of supermassive black hole growth and the cumulative output of hard ionizing photons by quasars. Our observations of the He II Ly-alpha forest with HST/COS in 26 quasar sightlines show strong fluctuations at z 3, consistent with our state-of-the-art simulations of the He II reionization epoch. However, our detection of transmission at z > 3.5 is inconsistent with all He II reionization models. Resolving this puzzle requires an extensive parameter study of He II reionization, which we propose to carry out using our fast, efficient simulations. The He II Ly-alpha forest is also sensitive to the effect of quasar radiation illuminating the intergalactic medium, known as the proximity effect. We have performed an ambitious ground-based imaging and spectroscopic survey for z 3 quasars in the foreground of HeII sightlines observed with HST/COS, and statistically detected the transverse proximity effect for the first time. The strength of this effect depends on both the quasar lifetime and the opening angle of quasar emission (or the fraction of obscured quasars), and we propose to use our He II reionization simulations to interpret this new measurement. Finally, the line-of-sight proximity effect due to the background quasar provides an independent constraint on the quasar lifetime. Our preliminary comparison of He II spectra to our radiative transfer simulations suggests a quasar lifetime > 10 Myr. We propose to use our He II reionization simulations to model this diverse set of observations and fully capitalize on the far-UV legacy of HST.

Fifty Years of the Index to Dental Literature: A Critical Appraisal

PubMed Central

1971-01-01

The year 1971 marks the fiftieth anniversary of the Index to Dental Literature. The Index had a slow and stormy birth, with twenty-three years of hard work put in until the first volume was issued. The first Index is described and the changes in its contents and format are traced through the years until its production in 1965 by the National Library of Medicine. The current Index is analyzed with attention paid to nomenclature, classification scheme, quality of the index entries and cross references. The results of a survey of regular users of the Index are interpreted, and suggestions gleaned for the improvement of this most useful tool in dental research. Images PMID:4947815

Creating aperiodic photonic structures by synthesized Mathieu-Gauss beams

NASA Astrophysics Data System (ADS)

Vasiljević, Jadranka M.; Zannotti, Alessandro; Timotijević, Dejan V.; Denz, Cornelia; Savić, Dragana M. Jović

2017-08-01

We demonstrate a kind of aperiodic photonic structure realized using the interference of multiple Mathieu-Gauss beams. Depending on the beam configurations, their mutual distances, angles of rotation, or phase relations we are able to observe different classes of such aperiodic optically induced refractive index structures. Our experimental approach is based on the optical induction in a single parallel writing process.

Three-dimensional ordered particulate structures: Method to retrieve characteristics from photonic band gap data

NASA Astrophysics Data System (ADS)

Miskevich, Alexander A.; Loiko, Valery A.

2015-01-01

A method to retrieve characteristics of ordered particulate structures, such as photonic crystals, is proposed. It is based on the solution of the inverse problem using data on the photonic band gap (PBG). The quasicrystalline approximation (QCA) of the theory of multiple scattering of waves and the transfer matrix method (TMM) are used. Retrieval of the refractive index of particles is demonstrated. Refractive indices of the artificial opal particles are estimated using the published experimental data.

Ultrahigh refractive index chalcogenide based copolymers for infrared optics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Anderson, Laura E.; Namnabat, Soha; Char, Kookheon; Glass, Richard; Norwood, Robert A.; Pyun, Jeffrey

2016-09-01

Current trends in technology development demand increased miniaturization and higher level integration of electronic and photonic components. Such needs arise in emerging imaging systems, optoelectronic devices, optical interconnects and photonic integrated circuits. Compact, integrated photonics requires high refractive index materials, which primarily comprise crystalline and amorphous semiconductors, as well as chalcogenide glasses, which can possess refractive indices higher than 4 and good infrared transparency. There is currently no high refractive index (n 2 or above) that has the low cost production and ease of processing available in optical polymers. Such polymers would potentially cover applications that are not convenient or possible with crystalline and vitreous semiconductors. Examples of such applications include micro lens arrays for image sensors, optical adhesives for bonding and antireflection coatings, and high contrast optical waveguides. While much of the focus has been in the telecommunications transparency regions, significant new opportunities exist for a polymer which is capable of transmitting efficiently in the MWIR region. While there are polymers that have been synthesized with refractive indices as high as 1.75, these polymers are generally conjugated and incorporate heteroatoms such as sulfur or metals, and generally have complex and expensive syntheses. Here we report on new chalcogenide based copolymers with very high refractive index (n 2) that also have good optical transmission properties in the near-, short- and mid-wave infrared up to 5µm. These polymers are rich in sulfur, have low hydrogen content and were made using inverse vulcanization.

Photon nonlinear mixing in subcarrier multiplexed quantum key distribution systems.

PubMed

Capmany, José

2009-04-13

We provide, for the first time to our knowledge, an analysis of the influence of nonlinear photon mixing on the end to end quantum bit error rate (QBER) performance of subcarrier multiplexed quantum key distribution systems. The results show that negligible impact is to be expected for modulation indexes in the range of 2%.

gPhoton: The GALEX Photon Data Archive

NASA Astrophysics Data System (ADS)

Million, Chase; Fleming, Scott W.; Shiao, Bernie; Seibert, Mark; Loyd, Parke; Tucker, Michael; Smith, Myron; Thompson, Randy; White, Richard L.

2016-12-01

gPhoton is a new database product and software package that enables analysis of GALEX ultraviolet data at the photon level. The project’s stand-alone, pure-Python calibration pipeline reproduces the functionality of the original mission pipeline to reduce raw spacecraft data to lists of time-tagged, sky-projected photons, which are then hosted in a publicly available database by the Mikulski Archive at Space Telescope. This database contains approximately 130 terabytes of data describing approximately 1.1 trillion sky-projected events with a timestamp resolution of five milliseconds. A handful of Python and command-line modules serve as a front end to interact with the database and to generate calibrated light curves and images from the photon-level data at user-defined temporal and spatial scales. The gPhoton software and source code are in active development and publicly available under a permissive license. We describe the motivation, design, and implementation of the calibration pipeline, database, and tools, with emphasis on divergence from prior work, as well as challenges created by the large data volume. We summarize the astrometric and photometric performance of gPhoton relative to the original mission pipeline. For a brief example of short time-domain science capabilities enabled by gPhoton, we show new flares from the known M-dwarf flare star CR Draconis. The gPhoton software has permanent object identifiers with the ASCL (ascl:1603.004) and DOI (doi:10.17909/T9CC7G). This paper describes the software as of version v1.27.2.

gPhoton: THE GALEX PHOTON DATA ARCHIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Million, Chase; Fleming, Scott W.; Shiao, Bernie

gPhoton is a new database product and software package that enables analysis of GALEX ultraviolet data at the photon level. The project’s stand-alone, pure-Python calibration pipeline reproduces the functionality of the original mission pipeline to reduce raw spacecraft data to lists of time-tagged, sky-projected photons, which are then hosted in a publicly available database by the Mikulski Archive at Space Telescope. This database contains approximately 130 terabytes of data describing approximately 1.1 trillion sky-projected events with a timestamp resolution of five milliseconds. A handful of Python and command-line modules serve as a front end to interact with the database andmore » to generate calibrated light curves and images from the photon-level data at user-defined temporal and spatial scales. The gPhoton software and source code are in active development and publicly available under a permissive license. We describe the motivation, design, and implementation of the calibration pipeline, database, and tools, with emphasis on divergence from prior work, as well as challenges created by the large data volume. We summarize the astrometric and photometric performance of gPhoton relative to the original mission pipeline. For a brief example of short time-domain science capabilities enabled by gPhoton, we show new flares from the known M-dwarf flare star CR Draconis. The gPhoton software has permanent object identifiers with the ASCL (ascl:1603.004) and DOI (doi:10.17909/T9CC7G). This paper describes the software as of version v1.27.2.« less

Photonic Bandgaps in Photonic Molecules

NASA Technical Reports Server (NTRS)

Smith, David D.; Chang, Hongrok; Gates, Amanda L.; Fuller, Kirk A.; Gregory, Don A.; Witherow, William K.; Paley, Mark S.; Frazier, Donald O.; Curreri, Peter A. (Technical Monitor)

2002-01-01

This talk will focus on photonic bandgaps that arise due to nearly free photon and tight-binding effects in coupled microparticle and ring-resonator systems. The Mie formulation for homogeneous spheres is generalized to handle core/shell systems and multiple concentric layers in a manner that exploits an analogy with stratified planar systems, thereby allowing concentric multi-layered structures to be treated as photonic bandgap (PBG) materials. Representative results from a Mie code employing this analogy demonstrate that photonic bands arising from nearly free photon effects are easily observed in the backscattering, asymmetry parameter, and albedo for periodic quarter-wave concentric layers, though are not readily apparent in extinction spectra. Rather, the periodicity simply alters the scattering profile, enhancing the ratio of backscattering to forward scattering inside the bandgap, in direct analogy with planar quarter-wave multilayers. PBGs arising from tight-binding may also be observed when the layers (or rings) are designed such that the coupling between them is weak. We demonstrate that for a structure consisting of N coupled micro-resonators, the morphology dependent resonances split into N higher-Q modes, in direct analogy with other types of oscillators, and that this splitting ultimately results in PBGs which can lead to enhanced nonlinear optical effects.

Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits

DOE PAGES

Wang, Zheng; Xu, Xiaochuan; Fan, Donglei; ...

2016-05-05

Here, subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits. In this work, we propose a geometrical tuning art, which realizes a pre-distorted refractive index profile in SWG waveguide bends. The pre-distorted refractive index profile can effectively reduce the mode mismatch and radiation loss simultaneously, thus significantlymore » reduce the bend loss. This geometry tuning art has been numerically optimized and experimentally demonstrated in present study. Through such tuning, the average insertion loss of a 5 μm SWG waveguide bend is reduced drastically from 5.43 dB to 1.10 dB per 90° bend for quasi-TE polarization. In the future, the proposed scheme will be utilized to enhance performance of a wide range of SWG waveguide based photonics devices.« less

Monitoring system for testing the radiation hardness of a KINTEX-7 FPGA

NASA Astrophysics Data System (ADS)

Cojocariu, L. N.; Placinta, V. M.; Dumitru, L.

2016-03-01

A much more efficient Ring Imaging Cherenkov sub-detector system will be rebuilt in the second long shutdown of Large Hadron Collider for the LHCb experiment. Radiation-hard electronic components together with Commercial Off-The-Shelf ones will be used in the new Cherenkov photon detection system architecture. An irradiation program was foreseen to determine the radiation tolerance for the new electronic devices, including a Field Programmable Gate Array from KINTEX-7 family of XILINX. An automated test bench for online monitoring of the XC7K70T KINTEX-7 device operation in radiation conditions was designed and implemented by the LHCb Romanian group.

Bioinspired Thermoresponsive Photonic Polymers with Hierarchical Structures and Their Unique Properties.

PubMed

Lu, Tao; Zhu, Shenmin; Ma, Jun; Lin, Jinyou; Wang, Wanlin; Pan, Hui; Tian, Feng; Zhang, Wang; Zhang, Di

2015-10-01

Thermoresponsive photonic materials having hierarchical structures are created by combining a template of Morpho butterfly wings with poly(N-isopropylacrylamide) (PNIPAM) through a chemical bonding and polymerization route. These materials show temperature-induced color tunability. Through reacting with both NIPAM monomers and the amino groups of chitosan in wing scales, glutaraldehyde workes as a bridge by creating chemical bonding between the biotemplate and the PNIPAM. The corresponding reflection peaks red-shift with increase in temperature-an opposite phenomenon to previous studies, demonstrating a thermoresponsive photonic property. This unique phenomenon is caused by the refractive index change due to the volume change of PNIPAM during the temperature rising. This work sets up an efficient strategy for the fabrication of stimuli-responsive photonic materials with hierarchical structures toward extensive applications in science and technology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bond-orientational analysis of hard-disk and hard-sphere structures.

PubMed

Senthil Kumar, V; Kumaran, V

2006-05-28

We report the bond-orientational analysis results for the thermodynamic, random, and homogeneously sheared inelastic structures of hard-disks and hard-spheres. The thermodynamic structures show a sharp rise in the order across the freezing transition. The random structures show the absence of crystallization. The homogeneously sheared structures get ordered at a packing fraction higher than the thermodynamic freezing packing fraction, due to the suppression of crystal nucleation. On shear ordering, strings of close-packed hard-disks in two dimensions and close-packed layers of hard-spheres in three dimensions, oriented along the velocity direction, slide past each other. Such a flow creates a considerable amount of fourfold order in two dimensions and body-centered-tetragonal (bct) structure in three dimensions. These transitions are the flow analogs of the martensitic transformations occurring in metals due to the stresses induced by a rapid quench. In hard-disk structures, using the bond-orientational analysis we show the presence of fourfold order. In sheared inelastic hard-sphere structures, even though the global bond-orientational analysis shows that the system is highly ordered, a third-order rotational invariant analysis shows that only about 40% of the spheres have face-centered-cubic (fcc) order, even in the dense and near-elastic limits, clearly indicating the coexistence of multiple crystalline orders. When layers of close-packed spheres slide past each other, in addition to the bct structure, the hexagonal-close-packed (hcp) structure is formed due to the random stacking faults. Using the Honeycutt-Andersen pair analysis and an analysis based on the 14-faceted polyhedra having six quadrilateral and eight hexagonal faces, we show the presence of bct and hcp signatures in shear ordered inelastic hard-spheres. Thus, our analysis shows that the dense sheared inelastic hard-spheres have a mixture of fcc, bct, and hcp structures.

Design of a diamond-crystal monochromator for the LCLS hard x-ray self-seeding project

NASA Astrophysics Data System (ADS)

Shu, D.; Shvyd'ko, Y.; Amann, J.; Emma, P.; Stoupin, S.; Quintana, J.

2013-03-01

As the result of collaborations between the Advanced Photon Source (APS), Argonne National Laboratory, and the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory, we have designed and constructed a diamond crystal monochromator for the LCLS hard x-ray self-seeding project. The novel monochromator is ultrahigh-vacuum compatible to meet the LCLS linear accelerator vacuum environmental requirement. A special graphite holder was designed for strain-free mount of the 110-μm thin synthetic diamond crystal plate provided by Technological Institute for Super-hard and Novel Carbon Materials of Russia (TISNCM). An in-vacuum multi-axis precision positioning mechanism is designed to manipulate the thin-film diamond holder with resolutions and stabilities required by the hard x-ray self-seeding physics. Optical encoders, limit switches, and hardware stops are established in the mechanism to ensure system reliability and to meet the accelerator personal and equipment safety interlock requirements. Molybdenum shields are installed in the monochromator to protect the encoders and associated electronics from radiation damage. Mechanical specifications, designs, and preliminary test results of the diamond monochromator are presented in this paper.

Two-photon interference of polarization-entangled photons in a Franson interferometer.

PubMed

Kim, Heonoh; Lee, Sang Min; Kwon, Osung; Moon, Han Seb

2017-07-18

We present two-photon interference experiments with polarization-entangled photon pairs in a polarization-based Franson-type interferometer. Although the two photons do not meet at a common beamsplitter, a phase-insensitive Hong-Ou-Mandel type two-photon interference peak and dip fringes are observed, resulting from the two-photon interference effect between two indistinguishable two-photon probability amplitudes leading to a coincidence detection. A spatial quantum beating fringe is also measured for nondegenerate photon pairs in the same interferometer, although the two-photon states have no frequency entanglement. When unentangled polarization-correlated photons are used as an input state, the polarization entanglement is successfully recovered through the interferometer via delayed compensation.

Three-Dimensional Self-Assembled Photonic Crystal Waveguide

NASA Astrophysics Data System (ADS)

Baek, Kang-Hyun

Photonic crystals (PCs), two- or three-dimensionally periodic, artificial, and dielectric structures, have a specific forbidden band for electromagnetic waves, referred to as photonic bandgap (PBG). The PBG is analogous to the electronic bandgap in natural crystal structures with periodic atomic arrangement. A well-defined and embedded planar, line, or point defect within the PCs causes a break in its structural periodicity, and introduces a state in the PBG for light localization. It offers various applications in integrated optics and photonics including optical filters, sharp bending light guides and very low threshold lasers. Using nanofabrication processes, PCs of the 2-D slab-type and 3-D layer-by-layer structures have been investigated widely. Alternatively, simple and low-cost self-assembled PCs with full 3-D PBG, inverse opals, have been suggested. A template with face centered cubic closed packed structure, opal, may initially be built by self-assembly of colloidal spheres, and is selectively removed after infiltrating high refractive index materials into the interstitials of spheres. In this dissertation, the optical waveguides utilizing the 3-D self-assembled PCs are discussed. The waveguides were fabricated by microfabrication technology. For high-quality colloidal silica spheres and PCs, reliable synthesis, self-assembly, and characterization techniques were developed. Its theoretical and experimental demonstrations are provided and correlated. They suggest that the self-assembled PCs with PBG are feasible for the applications in integrated optics and photonics.

Photonic time crystals.

PubMed

Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia

2017-12-07

When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.

First flight of SMASH, the SwRI Miniature Assembly for Solar Hard X-rays

NASA Astrophysics Data System (ADS)

Caspi, Amir; Laurent, Glenn Thomas; Shoffner, Michael; Higuera Caubilla, David; Meurisse, Jeremie; Smith, Kelly; Shih, Albert Y.; Saint-Hilaire, Pascal; DeForest, Craig; Mansour, Nagi N.; Hathaway, David H.

2016-05-01

The SwRI Miniature Assembly for Solar Hard X-rays (SMASH) was successfully flown from Antarctica in January (19-30) 2016, as a piggy-back instrument on the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) high altitude balloon payload. SMASH is a technological demonstration of a new miniaturized hard X-ray (HXR) detector for use on CubeSats and other small spacecraft, including the proposed CubeSat Imaging X-ray Solar Spectrometer (CubIXSS).HXRs are the observational signatures of energetic processes on the Sun, including plasma heating and particle acceleration. One of the goals of CubIXSS will be to address the question of how plasma is heated during solar flares, including the relationship between thermal plasma and non-thermal particles. SMASH demonstrated the space-borne application of the commercial off-the-shelf Amptek X123-CdTe, a miniature cadmium telluride photon-counting HXR spectrometer. The CdTe detector has a physical area of 25 mm^2 and 1 mm fully-depleted thickness, with a ~100 micron Be window; with on-board thermoelectric cooling and pulse pile-up rejection, it is sensitive to solar photons from ~5 to ~100 keV with ~0.5-1.0 keV FWHM resolution. Photons are accumulated into histogram spectra with customizable energy binning and integration time. With modest resource requirements (~1/8 U, ~200 g, ~2.5 W) and low cost (~$10K), the X123-CdTe is an attractive solution for HXR measurements from budget- and resource-limited platforms such as CubeSats. SMASH flew two identical X123-CdTe detectors for redundancy and increased collecting area; the supporting electronics (power, CPU) were largely build-to-print using the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat design.We review the SMASH mission, design, and detector performance during the 12-day Antarctic flight. We present current progress on our data analysis of observed solar flares, and discuss future applications of the space-qualified X123-CdTe detector, including the CubIXSS mission

Disposable photonic integrated circuits for evanescent wave sensors by ultra-high volume roll-to-roll method.

PubMed

Aikio, Sanna; Hiltunen, Jussi; Hiitola-Keinänen, Johanna; Hiltunen, Marianne; Kontturi, Ville; Siitonen, Samuli; Puustinen, Jarkko; Karioja, Pentti

2016-02-08

Flexible photonic integrated circuit technology is an emerging field expanding the usage possibilities of photonics, particularly in sensor applications, by enabling the realization of conformable devices and introduction of new alternative production methods. Here, we demonstrate that disposable polymeric photonic integrated circuit devices can be produced in lengths of hundreds of meters by ultra-high volume roll-to-roll methods on a flexible carrier. Attenuation properties of hundreds of individual devices were measured confirming that waveguides with good and repeatable performance were fabricated. We also demonstrate the applicability of the devices for the evanescent wave sensing of ambient refractive index. The production of integrated photonic devices using ultra-high volume fabrication, in a similar manner as paper is produced, may inherently expand methods of manufacturing low-cost disposable photonic integrated circuits for a wide range of sensor applications.

Programmable Phase Transitions in a Photonic Microgel System: Linking Soft Interactions to a Temporal pH Gradient.

PubMed

Go, Dennis; Rommel, Dirk; Chen, Lisa; Shi, Feng; Sprakel, Joris; Kuehne, Alexander J C

2017-02-28

Soft amphoteric microgel systems exhibit a rich phase behavior. Crystalline phases of these material systems are of interest because they exhibit photonic stop-gaps, giving rise to iridescent color. Such microgel systems are promising for applications in soft, switchable, and programmable photonic filters and devices. We here report a composite microgel system consisting of a hard and fluorescently labeled core and a soft, amphoteric microgel shell. At pH above the isoelectric point (IEP), these colloids easily crystallize into three-dimensional colloidal assemblies. By adding a cyclic lactone to the system, the temporal pH profile can be controlled, and the microgels can be programmed to melt, while they lose charge. When the microgels gain the opposite charge, they recrystallize into assemblies of even higher order. We provide a model system to study the dynamic phase behavior of soft particles and their switchable and programmable photonic effects.

Design of integrated all optical digital to analog converter (DAC) using 2D photonic crystals

NASA Astrophysics Data System (ADS)

Moniem, Tamer A.; El-Din, Eman S.

2017-11-01

A novel design of all optical 3 bit digital to analog (DAC) converter will be presented in this paper based on 2 Dimension photonic crystals (PhC). The proposed structure is based on the photonic crystal ring resonators (PCRR) with combining the nonlinear Kerr effect on the PCRR. The total size of the proposed optical 3 bit DAC is equal to 44 μm × 37 μm of 2D square lattice photonic crystals of silicon rods with refractive index equal to 3.4. The finite different time domain (FDTD) and Plane Wave Expansion (PWE) methods are used to back the overall operation of the proposed optical DAC.

Parallel photonic information processing at gigabyte per second data rates using transient states

NASA Astrophysics Data System (ADS)

Brunner, Daniel; Soriano, Miguel C.; Mirasso, Claudio R.; Fischer, Ingo

2013-01-01

The increasing demands on information processing require novel computational concepts and true parallelism. Nevertheless, hardware realizations of unconventional computing approaches never exceeded a marginal existence. While the application of optics in super-computing receives reawakened interest, new concepts, partly neuro-inspired, are being considered and developed. Here we experimentally demonstrate the potential of a simple photonic architecture to process information at unprecedented data rates, implementing a learning-based approach. A semiconductor laser subject to delayed self-feedback and optical data injection is employed to solve computationally hard tasks. We demonstrate simultaneous spoken digit and speaker recognition and chaotic time-series prediction at data rates beyond 1Gbyte/s. We identify all digits with very low classification errors and perform chaotic time-series prediction with 10% error. Our approach bridges the areas of photonic information processing, cognitive and information science.

Signal photon flux generated by high-frequency relic gravitational waves

NASA Astrophysics Data System (ADS)

Li, Xin; Wang, Sai; Wen, Hao

2016-08-01

The power spectrum of primordial tensor perturbations increases rapidly in the high frequency region if the spectral index n t > 0. It is shown that the amplitude of relic gravitational waves h t(5 × 109 Hz) varies from 10-36 to 10-25 while n t varies from -6.25 × 10-3 to 0.87. A high frequency gravitational wave detector proposed by F.-Y. Li detects gravitational waves through observing the perturbed photon flux that is generated by interaction between relic gravitational waves and electromagnetic field. It is shown that the perturbative photon flux (5 × 109 Hz) varies from 1.40 × 10-4 s-1 to 2.85 × 107 s-1 while n t varies from -6.25 × 10-3 to 0.87. Correspondingly, the ratio of the transverse perturbative photon flux to the background photon flux varies from 10-28 to 10-16. Supported by National Natural Science Foundation of China (11305181,11322545,11335012) and Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF181CJ1)

Near-Infrared Trigged Stimulus-Responsive Photonic Crystals with Hierarchical Structures.

PubMed

Lu, Tao; Pan, Hui; Ma, Jun; Li, Yao; Zhu, Shenmin; Zhang, Di

2017-10-04

Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe 3 O 4 nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout. It is noteworthy that the whole process is durable and stable mainly owing to the chemical bonding formed between PNIPAM and the biotemplate. We envision that this biologically inspired approach could be utilized in a broad range of applications and would have a great impact on various monitoring processes and medical sensing.

Searching for photon-sector Lorentz violation using gravitational-wave detectors

DOE PAGES

Kostelecký, V. Alan; Melissinos, Adrian C.; Mewes, Matthew

2016-08-04

Here, we study the prospects for using interferometers in gravitational-wave detectors as tools to search for photon-sector violations of Lorentz symmetry. Existing interferometers are shown to be exquisitely sensitive to tiny changes in the effective refractive index of light occurring at frequencies around and below the microhertz range, including at the harmonics of the frequencies of the Earth's sidereal rotation and annual revolution relevant for tests of Lorentz symmetry. We use preliminary data obtained by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2006-2007 to place constraints on coefficients for Lorentz violation in the photon sector exceeding current limits by aboutmore » four orders of magnitude.« less

Generation of higher odd harmonics in a defective photonic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramanujam, N. R., E-mail: wilsonpra@yahoo.co.in; Wilson, K. S. Joseph

2015-06-24

A photonic crystal (AB){sup 2}(DB)(AB){sup 2} with high refractive index medium as silicon and low refractive medium as air is considered. Using the transfer matrix method, the transmission properties as a function of wavelength with photonic band gaps has been obtained. We are able to demonstrate the generation of third, fifth, seventh and ninth harmonics in the present work. We show that if the air medium is removed in the defect, the defect modes are generated but not harmonics. It can be designed to have a frequency conversion, and have a potential for becoming the basis for the next generationmore » of optical devices.« less

Photonic band gap in isotropic hyperuniform disordered solids with low dielectric contrast.

PubMed

Man, Weining; Florescu, Marian; Matsuyama, Kazue; Yadak, Polin; Nahal, Geev; Hashemizad, Seyed; Williamson, Eric; Steinhardt, Paul; Torquato, Salvatore; Chaikin, Paul

2013-08-26

We report the first experimental demonstration of a TE-polarization photonic band gap (PBG) in a 2D isotropic hyperuniform disordered solid (HUDS) made of dielectric media with a dielectric index contrast of 1.6:1, very low for PBG formation. The solid is composed of a connected network of dielectric walls enclosing air-filled cells. Direct comparison with photonic crystals and quasicrystals permitted us to investigate band-gap properties as a function of increasing rotational isotropy. We present results from numerical simulations proving that the PBG observed experimentally for HUDS at low index contrast has zero density of states. The PBG is associated with the energy difference between complementary resonant modes above and below the gap, with the field predominantly concentrated in the air or in the dielectric. The intrinsic isotropy of HUDS may offer unprecedented flexibilities and freedom in applications (i. e. defect architecture design) not limited by crystalline symmetries.

THz photonic wireless links with 16-QAM modulation in the 375-450 GHz band.

PubMed

Jia, Shi; Yu, Xianbin; Hu, Hao; Yu, Jinlong; Guan, Pengyu; Da Ros, Francesco; Galili, Michael; Morioka, Toshio; Oxenløwe, Leif K

2016-10-17

We propose and experimentally demonstrate THz photonic wireless communication systems with 16-QAM modulation in the 375-450 GHz band. The overall throughput reaches as high as 80 Gbit/s by exploiting four THz channels with 5 Gbaud 16-QAM baseband modulation per channel. We create a coherent optical frequency comb (OFC) for photonic generation of multiple THz carriers based on photo-mixing in a uni-travelling carrier photodiode (UTC-PD). The OFC configuration also allows us to generate reconfigurable THz carriers with low phase noise. The multiple-channel THz radiation is received by using a Schottky mixer based electrical receiver after 0.5 m free-space wireless propagation. 2-channel (40 Gbit/s) and 4-channel (80 Gbit/s) THz photonic wireless links with 16-QAM modulation are reported in this paper, and the bit error rate (BER) performance for all channels in both cases is below the hard decision forward error correction (HD-FEC) threshold of 3.8e-3 with 7% overhead. In addition, we also successfully demonstrate hybrid photonic wireless transmission of 40 Gbit/s 16-QAM signal at carrier frequencies of 400 GHz and 425 GHz over 30 km standard single mode fiber (SSMF) between the optical baseband signal transmitter and the THz wireless transmitter with negligible induced power penalty.

Bright nanowire single photon source based on SiV centers in diamond

DOE PAGES

Marseglia, L.; Saha, K.; Ajoy, A.; ...

2018-01-01

The practical implementation of quantum technologies such as quantum commu- nication and quantum cryptography relies on the development of indistinguishable, robust, and bright single photon sources that works at room temperature. The silicon- vacancy (SiV -) center in diamond has emerged as a possible candidate for a single photon source with all these characteristics. Unfortunately, due to the high refraction index mismatch between diamond and air, color centers in diamond show low photon out-coupling. This drawback can be overcome by fabrication of photonic structures that improve the in-coupling of excitation laser to the diamond defect as well as the out-couplingmore » emission from the color centers. An additional shortcoming is due to the random localization of native defects in the diamond sample. Here we demonstrate deterministic implantation of Si ions with high conversion effciency to single SiV -, targeted to fabricated nanowires. The co-localization of single SiV - defects with the nanostructures yields a ten times higher light coupling effciency as compared to single SiV - in the bulk. This result, with its intrinsic scalability, enables a new class of devices for integrated photonics and quantum information processing.« less

Gradient polymer network liquid crystal with a large refractive index change.

PubMed

Ren, Hongwen; Xu, Su; Wu, Shin-Tson

2012-11-19

A simple approach for preparing gradient polymer network liquid crystal (PNLC) with a large refractive index change is demonstrated. To control the effective refractive index at a given cell position, we applied a voltage to a homogeneous cell containing LC/diacrylate monomer mixture to generate the desired tilt angle and then stabilize the LC orientation with UV-induced polymer network. By varying the applied voltage along with the cells' movement, a PNLC with a gradient refractive index distribution is obtained. In comparison with conventional approaches using patterned photomask or electrode, our method offers following advantages: large refractive index change, freedom to design specific index profile, and large panel capability. Potential applications include tunable-focus lenses, prism gratings, phase modulators, and other adaptive photonic devices.

Inverse opal photonic crystals with photonic band gaps in the visible and near-infrared

NASA Astrophysics Data System (ADS)

Jarvis, Brandon C.; Gilleland, Cody L.; Renfro, Tim; Gutierrez, Jose; Parikh, Kunjal; Glosser, R.; Landon, Preston B.

2005-08-01

Colloidal silica spheres with 200nm, 250nm, and 290nm diameters were self-assembled with single crystal crystallites 4-5mm wide and 10-15mm long. Larger spheres with diameters between 1000-2300nm were self-assembled with single crystal crystallites up to 1.5mm wide and 2mm long. The silica opals self-assembled vertically along the [100] direction of the face centered cubic lattice resulting in self-templated opals. Inverse opal photonic crystals with a partial band gap possessing a maximum in the near infrared at 3.8μm were constructed from opal templates composed of 2300nm diameter spheres with chalcogenide Ge33As12Se55 (AMTIR-1), a transparent glass in the near infrared with high refractive index. Inverse gold and gold/ polypropylene composite photonic crystals were fabricated from synthetic opal templates composed of 200-290nm silica spheres. The reflectance spectra and electrical conductance of the resulting structures is presented. Gold was infiltrated into opal templates as gold chloride and heat converted to metallic gold. Opals partially infiltrated with gold were co-infiltrated with polypropylene plastic for mechanical support prior to removal of the silica template with hydrofluoric acid.

Measurements of the spatial structure and directivity of 100 KeV photon sources in solar flares using PVO and ISEE-3 spacecraft

NASA Technical Reports Server (NTRS)

Anderson, Kinsey A.

1991-01-01

The objective of this grant was to measure the spatial structure and directivity of the hard X-ray and low energy gamma-ray (100 keV-2 MeV) continuum sources in solar flares using stereoscopic observations made with spectrometers aboard the Pioneer Venus Orbiter (PVO) and Third International Sun Earth Explorer (ISEE-3) spacecraft. Since the hard X-ray emission is produced by energetic electrons through the bremsstrahlung process, the observed directivity can be directly related to the 'beaming' of electrons accelerated during the flare as they propagate from the acceleration region in the corona to the chromosphere/transition region. Some models (e.g., the thick-target model) predict that most of the impulsive hard X-ray/low energy gamma-ray source is located in the chromosphere, the effective height of the X-ray source above the photosphere increasing with the decrease in the photon energy. This can be verified by determining the height-dependence of the photon source through stereoscopic observations of those flares which are partially occulted from the view of one of the two spacecraft. Thus predictions about beaming of electrons as well as their spatial distributions could be tested through the analysis proposed under this grant.

The Relationship Between Grain Hardness, Dough Mixing Parameters and Bread-Making Quality in Winter Wheat

PubMed Central

Salmanowicz, Bolesław P.; Adamski, Tadeusz; Surma, Maria; Kaczmarek, Zygmunt; Karolina, Krystkowiak; Kuczyńska, Anetta; Banaszak, Zofia; Ługowska, Bogusława; Majcher, Małgorzata; Obuchowski, Wiktor

2012-01-01

The influence of grain hardness, determined by using molecular markers and physical methods (near-infrared (NIR) technique and particle size index—PSI) on dough characteristics, which in turn were determined with the use of a farinograph and reomixer, as well as bread-making properties were studied. The material covered 24 winter wheat genotypes differing in grain hardness. The field experiment was conducted at standard and increased levels of nitrogen fertilization. Results of molecular analyses were in agreement with those obtained by the use of physical methods for soft-grained lines. Some lines classified as hard (by physical methods) appeared to have the wild-type Pina and Pinb alleles, similar to soft lines. Differences in dough and bread-making properties between lines classified as hard and soft on the basis of molecular data appeared to be of less significance than the differences between lines classified as hard and soft on the basis of physical analyses of grain texture. Values of relative grain hardness at the increased nitrogen fertilization level were significantly higher. At both fertilization levels the NIR parameter determining grain hardness was significantly positively correlated with the wet gluten and sedimentation values, with most of the rheological parameters and bread yield. Values of this parameter correlated with quality characteristics in a higher degree than values of particle size index. PMID:22605973

Development of the hard x-ray monitor onboard WF-MAXI

NASA Astrophysics Data System (ADS)

Arimoto, Makoto; Yatsu, Yoichi; Kawai, Nobuyuki; Ikeda, Hirokazu; Harayama, Atsushi; Takeda, Shin'ichiro; Takahashi, Tadayuki; Tomida, Hiroshi; Ueno, Shiro; Kimura, Masashi; Mihara, Tatehiro; Serino, Motoko; Tsunemi, Hiroshi; Yoshida, Atsumasa; Sakamoto, Takanori; Kohmura, Tadayoshi; Negoro, Hitoshi; Ueda, Yoshihiro

2014-07-01

WF-MAXI is a mission to detect and localize X-ray transients with short-term variability as gravitational-wave (GW) candidates including gamma-ray bursts, supernovae etc. We are planning on starting observations by WF-MAXI to be ready for the initial operation of the next generation GW telescopes (e.g., KAGRA, Advanced LIGO etc.). WF-MAXI consists of two main instruments, Soft X-ray Large Solid Angle Camera (SLC) and Hard X-ray Monitor (HXM) which totally cover 0.7 keV to 1 MeV band. HXM is a multi-channel array of crystal scintillators coupled with APDs observing photons in the hard X-ray band with an effective area of above 100 cm2. We have developed an analog application specific integrated circuit (ASIC) dedicated for the readout of 32-channel APDs' signals using 0.35 μm CMOS technology based on Open IP project and an analog amplifier was designed to achieve a low-noise readout. The developed ASIC showed a low-noise performance of 2080 e- + 2.3 e-/pF at root mean square and with a reverse-type APD coupled to a Ce:GAGG crystal a good FWHM energy resolution of 6.9% for 662 keV -rays.

Effect of MMF stub on the sensitivity of a photonic crystal fiber interferometer sensor at 1550 nm

NASA Astrophysics Data System (ADS)

Dhara, P.; Singh, Vinod K.

2015-01-01

A simple photonic crystal fiber (PCF) based Mach-Zehnder interferometric sensor is reported for sensing the refractive index and level of liquid. The sensing head is formed by all-fiber in-line single mode-multi mode-photonic crystal-single mode fiber structure using the fusion splicing method. The interferometric pattern, observed in the PCF interferometer using monochromatic source and temperature sensing arrangement, is novel and reported for the first time to the best of our knowledge. The refractive index sensitivity of the interferometric device is increased by using multimode fiber. The output intensity at the end of lead-out single mode fiber decreases with increase in refractive index of surrounding. The index sensitivities of the interferometric devices are 440.32 μw/RIU, 267.48 μw/RIU and 195.36 μw/RIU with sensing length 2.10 cm, 5.50 cm and 7.20 cm respectively. A 7.20 cm longed PCF sensor exhibits liquid level sensitivities -1.032 μw/cm, -1.197 μw/cm, and -1.489 μw/cm for three different liquid respectively.

Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

NASA Technical Reports Server (NTRS)

Furst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Ghandi, P.; Zhang, William W.

2016-01-01

We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339-4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from approx. 1.69 to approx. 1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from approx. 0.68 to approx. 1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of approx. 100 Mass compared to the Sun, which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

Solar Flare Hard X-ray Spikes Observed by RHESSI: a Statistical Study

NASA Astrophysics Data System (ADS)

Cheng, Jianxia; Qiu, J.; Ding, M.; Wang, H.

2013-07-01

Hard X-ray (HXR) spikes refer to fine time structures on timescales of seconds to milliseconds in high-energy HXR emission profiles during solar flare eruptions. We present a preliminary statistical investigation of temporal and spectral properties of HXR spikes. Using a three-sigma spike selection rule, we detected 184 spikes in 94 out of 322 flares with significant counts at given photon energies, which were detected from demodulated HXR light curves obtained by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). About one fifth of these spikes are also detected at photon energies higher than 100 keV. The statistical properties of the spikes are as follows. (1) HXR spikes are produced in both impulsive flares and long-duration flares with nearly the same occurrence rates. Ninety percent of the spikes occur during the rise phase of the flares, and about 70% occur around the peak times of the flares. (2) The time durations of the spikes vary from 0.2 to 2 s, with the mean being 1.0 s, which is not dependent on photon energies. The spikes exhibit symmetric time profiles with no significant difference between rise and decay times.(3) Among the most energetic spikes, nearly all of them have harder count spectra than their underlying slow-varying components. There is also a weak indication that spikes exhibiting time lags in high-energy emissions tend to have harder spectra than spikes with time lags in low-energy emissions.

Resonantly Enhanced Betatron Hard X-rays from Ionization Injected Electrons in a Laser Plasma Accelerator

PubMed Central

Huang, K.; Li, Y. F.; Li, D. Z.; Chen, L. M.; Tao, M. Z.; Ma, Y.; Zhao, J. R.; Li, M. H.; Chen, M.; Mirzaie, M.; Hafz, N.; Sokollik, T.; Sheng, Z. M.; Zhang, J.

2016-01-01

Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell electrons of nitrogen into the accelerating bucket. A total photon yield of 8 × 108/shot and 108 photons with energy greater than 110 keV is obtained. The yield is 10 times higher than that achieved with self-injection mode in helium under similar laser parameters. The simulation suggests that ionization-injected electrons are quickly accelerated to the driving laser region and are subsequently driven into betatron resonance. The present scheme enables the single-stage betatron radiation from LWFA to be extended to bright γ-ray radiation, which is beyond the capability of 3rd generation synchrotrons. PMID:27273170

Resonant photonic States in coupled heterostructure photonic crystal waveguides.

PubMed

Cox, Jd; Sabarinathan, J; Singh, Mr

2010-02-09

In this paper, we study the photonic resonance states and transmission spectra of coupled waveguides made from heterostructure photonic crystals. We consider photonic crystal waveguides made from three photonic crystals A, B and C, where the waveguide heterostructure is denoted as B/A/C/A/B. Due to the band structure engineering, light is confined within crystal A, which thus act as waveguides. Here, photonic crystal C is taken as a nonlinear photonic crystal, which has a band gap that may be modified by applying a pump laser. We have found that the number of bound states within the waveguides depends on the width and well depth of photonic crystal A. It has also been found that when both waveguides are far away from each other, the energies of bound photons in each of the waveguides are degenerate. However, when they are brought close to each other, the degeneracy of the bound states is removed due to the coupling between them, which causes these states to split into pairs. We have also investigated the effect of the pump field on photonic crystal C. We have shown that by applying a pump field, the system may be switched between a double waveguide to a single waveguide, which effectively turns on or off the coupling between degenerate states. This reveals interesting results that can be applied to develop new types of nanophotonic devices such as nano-switches and nano-transistors.

Direct virtual photon production in Au+Au collisions at s N N = 200   GeV

DOE PAGES

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; ...

2017-04-27

Here we report the direct virtual photon invariant yields in the transverse momentum ranges 1< pT <3GeV/c and 5ee < 0.28GeV/c 2 for 0–80% minimum-bias Au+Au collisions atmore » $$\\sqrt{s}$$$_ {NN}$$ = 200GeV. A clear excess in the invariant yield compared to the nuclear overlap function T AA scaled p+p reference is observed in the p T range 1T <3GeV/c. For p T >6GeV/c the production follows T AA scaling. In conclusion, model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield.« less

Hard-X-Ray/Soft-Gamma-Ray Imaging Sensor Assembly for Astronomy

NASA Technical Reports Server (NTRS)

Myers, Richard A.

2008-01-01

An improved sensor assembly has been developed for astronomical imaging at photon energies ranging from 1 to 100 keV. The assembly includes a thallium-doped cesium iodide scintillator divided into pixels and coupled to an array of high-gain avalanche photodiodes (APDs). Optionally, the array of APDs can be operated without the scintillator to detect photons at energies below 15 keV. The array of APDs is connected to compact electronic readout circuitry that includes, among other things, 64 independent channels for detection of photons in various energy ranges, up to a maximum energy of 100 keV, at a count rate up to 3 kHz. The readout signals are digitized and processed by imaging software that performs "on-the-fly" analysis. The sensor assembly has been integrated into an imaging spectrometer, along with a pair of coded apertures (Fresnel zone plates) that are used in conjunction with the pixel layout to implement a shadow-masking technique to obtain relatively high spatial resolution without having to use extremely small pixels. Angular resolutions of about 20 arc-seconds have been measured. Thus, for example, the imaging spectrometer can be used to (1) determine both the energy spectrum of a distant x-ray source and the angular deviation of the source from the nominal line of sight of an x-ray telescope in which the spectrometer is mounted or (2) study the spatial and temporal development of solar flares, repeating - ray bursters, and other phenomena that emit transient radiation in the hard-x-ray/soft- -ray region of the electromagnetic spectrum.