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Sample records for lcls-s1 optical transition

  1. Patterning via optical saturable transitions

    NASA Astrophysics Data System (ADS)

    Cantu, Precious

    For the past 40 years, optical lithography has been the patterning workhorse for the semiconductor industry. However, as integrated circuits have become more and more complex, and as device geometries shrink, more innovative methods are required to meet these needs. In the far-field, the smallest feature that can be generated with light is limited to approximately half the wavelength. This, so called far-field diffraction limit or the Abbe limit (after Prof. Ernst Abbe who first recognized this), effectively prevents the use of long-wavelength photons >300nm from patterning nanostructures <100nm. Even with a 193nm laser source and extremely complicated processing, patterns below ˜20nm are incredibly challenging to create. Sources with even shorter wavelengths can potentially be used. However, these tend be much more expensive and of much lower brightness, which in turn limits their patterning speed. Multi-photon reactions have been proposed to overcome the diffraction limit. However, these require very large intensities for modest gain in resolution. Moreover, the large intensities make it difficult to parallelize, thus limiting the patterning speed. In this dissertation, a novel nanopatterning technique using wavelength-selective small molecules that undergo single-photon reactions, enabling rapid top-down nanopatterning over large areas at low-light intensities, thereby allowing for the circumvention of the far-field diffraction barrier is developed and experimentally verified. This approach, which I refer to as Patterning via Optical Saturable Transitions (POST) has the potential for massive parallelism, enabling the creation of nanostructures and devices at a speed far surpassing what is currently possible with conventional optical lithographic techniques. The fundamental understanding of this technique goes beyond optical lithography in the semiconductor industry and is applicable to any area that requires the rapid patterning of large-area two or three

  2. Enhanced optical transmission at the cutoff transition.

    PubMed

    Laux, E; Genet, C; Ebbesen, T W

    2009-04-27

    The phenomenon of extraordinary transmission in the optical regime for circular hole arrays in optically thick metal films is studied as a function of hole size and depth. In the limit of small holes compared to the depth, the transmission properties follow a waveguide type behavior. By describing the transmission process as resulting from the interference between a resonant and a non-resonant contribution, a transition is clearly revealed through the specific spectral variations of the resonance at a given hole depth. This transition is associated to a change in the attenuation through the hole as its size increases, and corresponds to the optimal condition for surface plasmon excitation.

  3. Turbulent Transitions in Optical Wave Propagation

    NASA Astrophysics Data System (ADS)

    Pierangeli, D.; Di Mei, F.; Di Domenico, G.; Agranat, A. J.; Conti, C.; DelRe, E.

    2016-10-01

    We report the direct observation of the onset of turbulence in propagating one-dimensional optical waves. The transition occurs as the disordered hosting material passes from being linear to one with extreme nonlinearity. As the response grows, increased wave interaction causes a modulational unstable quasihomogeneous flow to be superseded by a chaotic and spatially incoherent one. Statistical analysis of high-resolution wave behavior in the turbulent regime unveils the emergence of concomitant rogue waves. The transition, observed in a photorefractive ferroelectric crystal, introduces a new and rich experimental setting for the study of optical wave turbulence and information transport in conditions dominated by large fluctuations and extreme nonlinearity.

  4. Interband optical transitions in ellipsoidal shaped nanoparticles

    NASA Astrophysics Data System (ADS)

    Kereselidze, Tamaz; Tchelidze, Tamar; Devdariani, Alexander

    2017-04-01

    The optical properties of crystalline semiconductor nanoparticles with ellipsoidal shape are investigated and discussed as a function of the shape-anisotropy parameter. The optical transition-matrix elements are calculated in the dipole approximation using perturbation theory and with a direct diagonalization of the appropriate Hamiltonian. The matrix elements involving the ground and first excited states are monotonic functions of the shape-anisotropy parameter, whereas matrix elements involving the highly excited states have zeros and extrema that are reflected in the behaviour of the corresponding transition probabilities. Moreover, some matrix elements involving the excited states have discontinuity. We demonstrate that, nanoparticles with ellipsoidal shape can be grown with the infrared as well as ultraviolet features.

  5. Optical angular momentum: Multipole transitions and photonics

    SciTech Connect

    Andrews, David L.

    2010-03-15

    The premise that multipolar decay should produce photons uniquely imprinted with a measurably corresponding angular momentum is shown in general to be untrue. To assume a one-to-one correlation between the transition multipoles involved in source decay and detector excitation is to impose a generally unsupportable one-to-one correlation between the multipolar form of emission transition and a multipolar character for the detected field. It is specifically proven impossible to determine without ambiguity, by use of any conventional detector, and for any photon emitted through the nondipolar decay of an atomic excited state, a unique multipolar character for the transition associated with its generation. Consistent with the angular quantum uncertainty principle, removal of a detector from the immediate vicinity of the source produces a decreasing angular uncertainty in photon propagation direction, reflected in an increasing range of integer values for the measured angular momentum. In such a context it follows that when the decay of an electronic excited state occurs by an electric quadrupolar transition, for example, any assumption that the radiation so produced is conveyed in the form of 'quadrupole photons' is experimentally unverifiable. The results of the general proof based on irreducible tensor analysis invite experimental verification, and they signify certain limitations on quantum optical data transmission.

  6. Theory of optical transitions in curved chromophores

    NASA Astrophysics Data System (ADS)

    Barford, William; Marcus, Max

    2016-09-01

    Using first order perturbation theory in the Born-Oppenheimer regime of the Frenkel-Holstein model, we develop a theory for the optical transitions in curved chromophores of π-conjugated polymers. Our key results are that for absorption, A, and emission, I, polarized parallel to the 0-0 transition, I01/I00 ≃ A01/A00 = S(N), where S(N) = S(1)/IPR is the effective Huang-Rhys parameter for a chromophore of N monomers and IPR is the inverse participation ratio. In contrast, absorption and emission polarized perpendicular to the 0-0 transition acquires vibronic intensity via the Herzberg-Teller effect. This intensity generally increases as the curvature increases and consequently I01/I00 increases (where I01 is the total 0-1 emission intensity). This effect is enhanced for long chromophores and in the anti-adiabatic regime. We show via DMRG calculations that this theory works well in the adiabatic regime relevant to π-conjugated polymers, i.e., ħ ω/|J| ≲ 0.2.

  7. Resolved Atomic Interaction Sidebands in an Optical Clock Transition

    DTIC Science & Technology

    2011-06-24

    Resolved Atomic Interaction Sidebands in an Optical Clock Transition M. Bishof,1 Y. Lin,1 M.D. Swallows,1 A.V. Gorshkov,2 J. Ye,1 and A.M. Rey1 1JILA...Institute of Technology, Pasadena, California 91125, USA (Received 4 February 2011; published 22 June 2011) We report the observation of resolved atomic ...interaction sidebands (ISB) in the 87Sr optical clock transition when atoms at microkelvin temperatures are confined in a two-dimensional optical lattice

  8. Black Hole Advective Accretion Disks with Optical Depth Transition

    SciTech Connect

    Artemove, Y.V.; Bisnovatyi-Kogan, G.S.; Igumenshchev, I.V.; Novikov, I.D.

    2006-02-01

    We have constructed numerically global solutions of advective accretion disks around black holes that describe a continuous transition between the effectively optically thick outer and optically thin inner disk regions. We have concentrated on models of accretion flows with large mass accretion rates, and we have employed a bridging formula for radiative losses at high and low effective optical depths.

  9. All-optical OXC transition strategy from WDM optical network to elastic optical network.

    PubMed

    Chen, Xin; Li, Juhao; Guo, Bingli; Zhu, Paikun; Tang, Ruizhi; Chen, Zhangyuan; He, Yongqi

    2016-02-22

    Elastic optical network (EON) has been proposed recently as a spectrum-efficient optical layer to adapt to rapidly-increasing traffic demands instead of current deployed wavelength-division-multiplexing (WDM) optical network. In contrast with conventional WDM optical cross-connect (OXCs) based on wavelength selective switches (WSSs), the EON OXCs are based on spectrum selective switches (SSSs) which are much more expensive than WSSs, especially for large-scale switching architectures. So the transition cost from WDM OXCs to EON OXCs is a major obstacle to realizing EON. In this paper, we propose and experimentally demonstrate a transition OXC (TOXC) structure based on 2-stage cascading switching architectures, which make full use of available WSSs in current deployed WDM OXCs to reduce number and port count of required SSSs. Moreover, we propose a contention-aware spectrum allocation (CASA) scheme for EON built with the proposed TOXCs. We show by simulation that the TOXCs reduce the network capital expenditure transiting from WDM optical network to EON about 50%, with a minor traffic blocking performance degradation and about 10% accommodated traffic number detriment compared with all-SSS EON OXC architectures.

  10. Aqueous medium induced optical transitions in cerium oxide nanoparticles

    SciTech Connect

    Inerbaev, Talgat M.; Karakoti, Ajay S.; Kuchibhatla, S. V. N. T.; Kumar, Amit; Masunov, Artem E.; Seal, Sudipta

    2015-03-07

    Experimental and theoretical investigations were performed to investigate the effect of water on optical properties of nanoceria as a function of Ce3+ concentration. Theoretical studies based on density functional plane-wave calculations reveal that the indirect optical transitions in bare ceria nanoparticles are red-shifted with an increase in the concentration of Ce3+. However, ceria nanoparticles model with adsorbed water molecules show a blue shift in the indirect optical spectra under identical conditions. Direct optical transitions are almost independent of Ce3+ concentration but show a pronounced blue shift in the aqueous environment relative to the bare nanoparticles. The theoretical study is consistent with our experimental observation in difference of shift behaviour in bare and aqueous suspended ceria nanoparticles. This change from red- to blue-shift in indirect optical transitions is associated with the polarization effect of water molecules on f-electron states.

  11. Physics: Optical transition seen in antihydrogen

    NASA Astrophysics Data System (ADS)

    Ulmer, Stefan

    2017-01-01

    Precise measurements of antimatter systems might cast light on why the Universe is dominated by matter. The observation of a transition in an antihydrogen atom heralds the next wave of high-precision antimatter studies. See Letter p.506

  12. Electronic structure and optical transition of semiconductor nanocrystallites

    NASA Astrophysics Data System (ADS)

    Xia, Jian-Bai; Cheah, K. W.

    1997-11-01

    The electronic states and optical transition properties of three semiconductor nanocrystallites, Si, GaAs, and ZnSe, are studied using the empirical pseudopotential homojunction model. The energy levels, wave functions, optical transition matrix elements, and lifetimes are obtained for quadratic prisms with widths from 11 to 27 Å. It is found that the three kinds of prism have different quantum confinement properties. For Si prisms, the energy gaps vary with the equivalent diameter d as 0953-8984/9/45/013/img1, in agreement with previous theoretical calculations. For the same d the energy gaps are slightly different for different shapes: large for the prism with large aspect ratio; small for the prism with small aspect ratio. The exponent of d depends on the boundary barrier height, i.e. the extent of penetration of the wave function into the vacuum. The wave function of the LUMO states consists mainly of bulk X states. The optical transition matrix elements are much smaller than those of direct transition, and increase with decreasing width. The corresponding lifetimes decrease from the millisecond range to the microsecond range, and the change is abrupt depending on the symmetry and composition of the wave function of the LUMO and HOMO states. For GaAs prisms, the energy gap is also pseudo-direct, but the optical transition matrix elements are larger than those of Si prisms by two orders of magnitude for the same width. For ZnSe prisms, the energy gap is always direct, and the optical transition matrix elements are comparable with those of direct energy gap bulk semiconductors. In some cases the symmetry of the HOMO state changes, resulting in an abrupt decrease of the transition matrix element. The calculated lifetimes of the Si prism and the positions of PL peaks are in agreement with experimental results for porous Si.

  13. Optical Control of Spin Polarization in Monolayer Transition Metal Dichalcogenides.

    PubMed

    Chen, Xi; Yan, Tengfei; Zhu, Bairen; Yang, Siyuan; Cui, Xiaodong

    2017-02-28

    Optical excitation could generate electrons' spin polarization in some semiconductors with the control of the field polarization. In this article, we report a series of spin-resolved photocurrent experiments on monolayer tungsten disulfide. The experiments demonstrate that the optical excitations with the same helicity could generate opposite spin polarization around the Fermi level by tuning the excitation energy. The mechanism lies in the valley-dependent optical selection rules, the giant spin-orbit coupling, and spin-valley locking in monolayer transition metal dichalcogenides (TMDs). These exotic features make monolayer TMDs promising candidates for conceptual semiconductor-based spintronics.

  14. Isotropically sensitive optical filter employing atomic resonance transitions

    DOEpatents

    Marling, John B.

    1981-01-01

    An ultra-high Q isotropically sensitive optical filter or optical detector employing atomic resonance transitions. More specifically, atomic resonance transitions utilized in conjunction with two optical bandpass filters provide an optical detector having a wide field of view (.about.2.pi. steradians) and very narrow acceptance bandwidth approaching 0.01 A. A light signal to be detected is transmitted through an outer bandpass filter into a resonantly absorbing atomic vapor, the excited atomic vapor then providing a fluorescence signal at a different wavelength which is transmitted through an inner bandpass filter. The outer and inner bandpass filters have no common transmission band, thereby resulting in complete blockage of all optical signals that are not resonantly shifted in wavelength by the intervening atomic vapor. Two embodiments are disclosed, one in which the light signal raises atoms contained in the atomic vapor from the ground state to an excited state from which fluorescence occurs, and the other in which a pump laser is used to raise the atoms in the ground state to a first excited state from which the light signal then is resonantly absorbed, thereby raising the atoms to a second excited state from which fluorescence occurs. A specific application is described in which an optical detector according to the present invention can be used as an underwater detector for light from an optical transmitter which could be located in an orbiting satellite.

  15. Hyper-Ramsey spectroscopy of optical clock transitions

    SciTech Connect

    Yudin, V. I.; Taichenachev, A. V.; Oates, C. W.; Barber, Z. W.; Lemke, N. D.; Ludlow, A. D.; Sterr, U.; Lisdat, Ch.; Riehle, F.

    2010-07-15

    We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase, and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be radically suppressed (by two to four orders of magnitude) in comparison with the usual Ramsey method (using two equal pulses) as well as with single-pulse Rabi spectroscopy. Atom interferometers and optical clocks based on two-photon transitions, heavily forbidden transitions, or magnetically induced spectroscopy could significantly benefit from this method. In the latter case, these frequency shifts can be suppressed considerably below a fractional level of 10{sup -17}. Moreover, our approach opens the door for high-precision optical clocks based on direct frequency comb spectroscopy.

  16. Optical & Infrared Spectroscopy of Transiting Exoplanets

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Tinetti, G.

    2010-10-01

    Two types of spectra can be measured from transiting extrasolar planets. The primary eclipse provides a transmission spectra of the exoplanet's limb as the planet passes in front of the star. These data probe the gas and particle composition of the atmosphere, as well as the atmospheric scale height. The secondary eclipse measures the emission of mainly the planet's dayside atmosphere from the planet plus star's emission minus the emission of star alone, when it eclipses the planet. These data probe the temperature and composition structure of the exoplanet. Only in the past 3 years, have infrared transmission and emission spectroscopy revealed the presence of the primary carbon and oxygen species (CH4, CO2, CO, and H2O). Efforts to constrain the abundances of these molecules are hindered by degenerate effects of the temperature and composition in the emission spectra. Transmission spectra, while less sensitive to the atmospheric temperatures, are difficult to interpret because the composition derived depends delicately on the assumed radius at a specified pressure level. This talk will discuss the correlations in the degenerate solutions that result from the radiative transfer analyses of both emission and transmission spectroscopy. The physical implications of these correlations are assessed in order to determine the temperature and composition structure of extrasolar planets, and their significance with respect to the exoplanet's chemistry and dynamics.

  17. Isotropically sensitive optical filter employing atomic resonance transitions

    DOEpatents

    Marling, J.B.

    An ultra-high Q isotropically sensitive optical filter or optical detector is disclosed employing atomic resonance transitions. More specifically, atomic resonance transitions utilized in conjunction with two optical bandpass filters provide an optical detector having a wide field of view (approx. 2 ..pi.. steradians) and very narrow acceptance bandwidth approaching 0.01A. A light signal to be detected is transmitted through an outer bandpass filter into a resonantly absorbing atomic vapor, the excited atomic vapor than providing a fluorescence signal at a different wavelength which is transmitted through an inner bandpass filters have no common transmission band, therby resulting in complete blockage of all optical signals that are not resonantly shifted in wavelength by the intervening atomic vapor. Two embodiments are disclosed, one in which the light signal raises atoms contained in the atomic vapor from the ground state to an excited state from which fluorescence occurs, and the other in which a pump laser is used to raise the atoms in the ground state to a first excited state from which the light signal then is resonantly absorbed, thereby raising the atoms to a second excited state from which fluorescence occurs. A specific application is described in which an optical detector according to the present invention can be located in an orbiting satellite.

  18. Optical properties of transition metal oxide quantum wells

    SciTech Connect

    Lin, Chungwei; Posadas, Agham; Choi, Miri; Demkov, Alexander A.

    2015-01-21

    Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/SrTiO{sub 3}/SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered.

  19. Optical properties of transition metal oxide quantum wells

    NASA Astrophysics Data System (ADS)

    Lin, Chungwei; Posadas, Agham; Choi, Miri; Demkov, Alexander A.

    2015-01-01

    Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/SrTiO3/SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered.

  20. Optical Properties in Non-equilibrium Phase Transitions

    SciTech Connect

    Ao, T; Ping, Y; Widmann, K; Price, D F; Lee, E; Tam, H; Springer, P T; Ng, A

    2006-01-05

    An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.

  1. Spectroscopy of intraband optical transitions in anisotropic semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Turkov, Vadim K.; Baimuratov, Anvar S.; Rukhlenko, Ivan D.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-09-01

    We propose a new type of optical spectroscopy of anisotropic semiconductor nanocrystals, which is based on the welldeveloped stationary pump-probe technique, where the pump and probe fields are absorbed upon, respectively, interband and intraband transitions of the nanocrystals' electronic subsystem. We develop a general theory of intraband absorption based on the density matrix formalism. This theory can be applied to study degenerate eigenstates of electrons in semiconductor nanocrystals of different shapes and dimentions. We demonstrate that the angular dependence of intraband absorption by nonspherical nanocrystals enables investigating their shape and orientation, as well as the symmetry of quantum states excited by the probe field and selection rules of electronic transitions.

  2. Resolved Atomic Interaction Sidebands in an Optical Clock Transition

    SciTech Connect

    Bishof, M.; Lin, Y.; Swallows, M. D.; Ye, J.; Rey, A. M.; Gorshkov, A. V.

    2011-06-24

    We report the observation of resolved atomic interaction sidebands (ISB) in the {sup 87}Sr optical clock transition when atoms at microkelvin temperatures are confined in a two-dimensional optical lattice. The ISB are a manifestation of the strong interactions that occur between atoms confined in a quasi-one-dimensional geometry and disappear when the confinement is relaxed along one dimension. The emergence of ISB is linked to the recently observed suppression of collisional frequency shifts. At the current temperatures, the ISB can be resolved but are broad. At lower temperatures, ISB are predicted to be substantially narrower and useful spectroscopic tools in strongly interacting alkaline-earth gases.

  3. Clock Shifts of Optical Transitions in Ultracold Atomic Gases

    SciTech Connect

    Yu Zhenhua; Pethick, C. J.

    2010-01-08

    We calculate the shift, due to interatomic interactions, of an optical transition in an atomic Fermi gas trapped in an optical lattice, as in recent experiments of Campbell et al.[Science 324, 360 (2009)]. Using a pseudospin formalism to describe the density matrix of atoms, we derive a Bloch equation which incorporates both spatial inhomogeneity of the probe laser field and interatomic interactions. Expressions are given for the frequency shift as a function of pulse duration, detuning of the probe laser, and the spatial dependence of the electric field of the probe beam. In the low temperature semiclassical regime, we find that the magnitude of the shift is proportional to the temperature.

  4. Older Persons’ Transitions in Care (OPTIC): a study protocol

    PubMed Central

    2012-01-01

    Background Changes in health status, triggered by events such as infections, falls, and geriatric syndromes, are common among nursing home (NH) residents and necessitate transitions between NHs and Emergency Departments (EDs). During transitions, residents frequently experience care that is delayed, unnecessary, not evidence-based, potentially unsafe, and fragmented. Furthermore, a high proportion of residents and their family caregivers report substantial unmet needs during transitions. This study is part of a program of research whose overall aim is to improve quality of care for frail older adults who reside in NHs. The purpose of this study is to identify successful transitions from multiple perspectives and to identify organizational and individual factors related to transition success, in order to inform improvements in care for frail elderly NH residents during transitions to and from acute care. Specific objectives are to: 1. define successful and unsuccessful elements of transitions from multiple perspectives; 2. develop and test a practical tool to assess transition success; 3. assess transition processes in a discrete set of transfers in two study sites over a one year period; 4. assess the influence of organizational factors in key practice locations, e.g., NHs, emergency medical services (EMS), and EDs, on transition success; and 5. identify opportunities for evidence-informed management and quality improvement decisions related to the management of NH – ED transitions. Methods/Design This is a mixed-methods observational study incorporating an integrated knowledge translation (IKT) approach. It uses data from multiple levels (facility, care unit, individual) and sources (healthcare providers, residents, health records, and administrative databases). Discussion Key to study success is operationalizing the IKT approach by using a partnership model in which the OPTIC governance structure provides for team decision-makers and researchers to participate

  5. Optical characterization of phase transitions in pure polymers and blends

    SciTech Connect

    Mannella, Gianluca A.; Brucato, Valerio; La Carrubba, Vincenzo

    2015-12-17

    To study the optical properties of polymeric samples, an experimental apparatus was designed on purpose and set up. The sample is a thin film enclosed between two glass slides and a PTFE frame, with a very thin thermocouple placed on sample for direct temperature measurement. This sample holder was placed between two aluminum slabs, equipped with a narrow slit for optical measurements and with electrical resistances for temperature control. Sample was enlightened by a laser diode, whereas transmitted light was detected with a photodiode. Measurements were carried out on polyethylene-terephtalate (PET) and two different polyamides, tested as pure polymers and blends. The thermal history imposed to the sample consisted in a rapid heating from ambient temperature to a certain temperature below the melting point, a stabilization period, and then a heating at constant rate. After a second stabilization period, the sample was cooled. The data obtained were compared with DSC measurements performed with the same thermal history. In correspondence with transitions detected via DSC (e.g. melting, crystallization and cold crystallization), the optical signal showed a steep variation. In particular, crystallization resulted in a rapid decrease of transmitted light, whereas melting gave up an increase of light transmitted by the sample. Further variations in transmitted light were recorded for blends, after melting: those results may be related to other phase transitions, e.g. liquid-liquid phase separation. All things considered, the apparatus can be used to get reliable data on phase transitions in polymeric systems.

  6. Optical characterization of phase transitions in pure polymers and blends

    NASA Astrophysics Data System (ADS)

    Mannella, Gianluca A.; Brucato, Valerio; La Carrubba, Vincenzo

    2015-12-01

    To study the optical properties of polymeric samples, an experimental apparatus was designed on purpose and set up. The sample is a thin film enclosed between two glass slides and a PTFE frame, with a very thin thermocouple placed on sample for direct temperature measurement. This sample holder was placed between two aluminum slabs, equipped with a narrow slit for optical measurements and with electrical resistances for temperature control. Sample was enlightened by a laser diode, whereas transmitted light was detected with a photodiode. Measurements were carried out on polyethylene-terephtalate (PET) and two different polyamides, tested as pure polymers and blends. The thermal history imposed to the sample consisted in a rapid heating from ambient temperature to a certain temperature below the melting point, a stabilization period, and then a heating at constant rate. After a second stabilization period, the sample was cooled. The data obtained were compared with DSC measurements performed with the same thermal history. In correspondence with transitions detected via DSC (e.g. melting, crystallization and cold crystallization), the optical signal showed a steep variation. In particular, crystallization resulted in a rapid decrease of transmitted light, whereas melting gave up an increase of light transmitted by the sample. Further variations in transmitted light were recorded for blends, after melting: those results may be related to other phase transitions, e.g. liquid-liquid phase separation. All things considered, the apparatus can be used to get reliable data on phase transitions in polymeric systems.

  7. Stimulated emission on impurity – band optical transitions in semiconductors

    SciTech Connect

    Bekin, N A; Shastin, V N

    2015-02-28

    This paper examines conditions for population inversion and amplification in the terahertz range using impurity – band electron transitions in semiconductors and semiconductor structures. Our estimates indicate that stimulated emission on such transitions under optical excitation of impurities can be obtained in a semiconductor with a sufficiently high doping level if electron heating is restricted. At a CO{sub 2} laser pump power density near 0.2 MW cm{sup -2} (photon energy of 117 meV), the gain in n-GaAs may exceed the loss by 50 cm{sup -1} provided the electron gas temperature does not exceed 40 K. We analyse the influence of the carrier effective mass and doping compensation on the gain coefficient and briefly discuss the use of resonance tunnelling for obtaining stimulated emission on impurity – band transitions in quantum cascade heterostructures. (terahertz radiation)

  8. Optical Sensor for Characterizing the Phase Transition in Salted Solutions

    PubMed Central

    Claverie, Rémy; Fontana, Marc D.; Duričković, Ivana; Bourson, Patrice; Marchetti, Mario; Chassot, Jean-Marie

    2010-01-01

    We propose a new optical sensor to characterize the solid-liquid phase transition in salted solutions. The probe mainly consists of a Raman spectrometer that extracts the vibrational properties from the light scattered by the salty medium. The spectrum of the O – H stretching band was shown to be strongly affected by the introduction of NaCl and the temperature change as well. A parameter SD defined as the ratio of the integrated intensities of two parts of this band allows to study the temperature and concentration dependences of the phase transition. Then, an easy and efficient signal processing and the exploitation of a modified Boltzmann equation give information on the phase transition. Validations were done on solutions with varying concentration of NaCl. PMID:22319327

  9. Transition-metal-nitride films for optical applications

    NASA Astrophysics Data System (ADS)

    Ribbing, Carl-Gustaf; Roos, Arne

    1997-10-01

    The three transition metal nitrides TiN, ZrN and HfN have remarkably high stability due to their bonding: a mixture of covalent and ionic contributions. The optical properties of these nitride compounds are free-electron like to a surprisingly large extent, in particular in comparison with the corresponding carbides. It is argued that the interband optical excitations of the d-electrons are restricted by selection rules, resulting in a Drude like behavior of these d-electron compounds. Hitherto, one of the main optical applications has been as opaque, wear-resistant replacements for gold-coatings. This review includes the efforts to study, understand and enhance the optical selectivity of group IVB transition metal nitrides as the selective surface in high temperature thermal solar absorbers, as the metal layer in LE-coatings on energy-efficient or solar control windows and as a Langmuir probe coating. The reflectance edge is not in the optimum position for absorber applications and attempts to shift it with alloying were unsuccessful. Recent development of inhomogeneous, cermet- type nitrides hold some promise. The LE-coatings will not reach as high selectivity as the current noble metal based multilayers, but many find use in aggressive environments because of their excellent stability.

  10. Direct band gap carbon superlattices with efficient optical transition

    NASA Astrophysics Data System (ADS)

    Oh, Young Jun; Kim, Sunghyun; Lee, In-Ho; Lee, Jooyoung; Chang, K. J.

    2016-02-01

    We report pure carbon-based superlattices that exhibit direct band gaps and excellent optical absorption and emission properties at the threshold energy. The structures are nearly identical to that of cubic diamond except that defective layers characterized by five- and seven-membered rings are intercalated in the diamond lattice. The direct band gaps lie in the range of 5.6-5.9 eV, corresponding to wavelengths of 210-221 nm. The dipole matrix elements of direct optical transition are comparable to that of GaN, suggesting that the superlattices are promising materials as an efficient deep ultraviolet light emitter. Molecular dynamics simulations show that the superlattices are thermally stable even at a high temperature of 2000 K. We provide a possible route to the synthesis of superlattices through wafer bonding of diamond (100) surfaces.

  11. Optical lattice polarization effects on hyperpolarizability of atomic clock transitions.

    PubMed

    Taichenachev, A V; Yudin, V I; Ovsiannikov, V D; Pal'chikov, V G

    2006-10-27

    The light-induced frequency shift due to hyperpolarizability (i.e., terms of second-order in intensity) is studied for a forbidden optical transition, J = 0 --> J = 0. A simple universal dependence on the field ellipticity is obtained. This result allows minimization of the second-order light shift with respect to the field polarization for optical lattices operating at a magic wavelength (at which the first-order shift vanishes). We show the possibility for the existence of a magic elliptical polarization, for which the second-order frequency shift vanishes. The optimal polarization of the lattice field can be either linear, circular, or magic elliptical. The obtained results could improve the accuracy of lattice-based atomic clocks.

  12. Evolution of molecular crystal optical phonons near structural phase transitions

    NASA Astrophysics Data System (ADS)

    Michki, Nigel; Niessen, Katherine; Xu, Mengyang; Markelz, Andrea

    Molecular crystals are increasingly important photonic and electronic materials. For example organic semiconductors are lightweight compared to inorganic semiconductors and have inexpensive scale up processing with roll to roll printing. However their implementation is limited by their environmental sensitivity, in part arising from the weak intermolecular interactions of the crystal. These weak interactions result in optical phonons in the terahertz frequency range. We examine the evolution of intermolecular interactions near structural phase transitions by measuring the optical phonons as a function of temperature and crystal orientation using terahertz time-domain spectroscopy. The measured orientation dependence of the resonances provides an additional constraint for comparison of the observed spectra with the density functional calculations, enabling us to follow specific phonon modes. We observe crystal reorganization near 350 K for oxalic acid as it transforms from dihydrate to anhydrous form. We also report the first THz spectra for the molecular crystal fructose through its melting point.

  13. On the character of the optical transitions in closed-shell transition metal oxides doped with Bi(3).

    PubMed

    Amer, M; Boutinaud, P

    2017-01-18

    A criterion is introduced to achieve the assignment of the optical features observed in the excitation spectra of Bi(3+) ions incorporated in closed-shell transition metal oxides. The model is based on the calculation of the energy associated with the lowest (1)S0 → (3)P1 intra-ionic transition of Bi(3+) (A-like transition), the metal-to-metal charge transfer (D-like transition) and the Stokes shift of the corresponding emission.

  14. Coherent Magnetic Response at Optical Frequencies Using Atomic Transitions

    NASA Astrophysics Data System (ADS)

    Brewer, Nicholas R.; Buckholtz, Zachary N.; Simmons, Zachary J.; Mueller, Eli A.; Yavuz, Deniz D.

    2017-01-01

    In optics, the interaction of atoms with the magnetic field of light is almost always ignored since its strength is many orders of magnitude weaker compared to the interaction with the electric field. In this article, by using a magnetic-dipole transition within the 4 f shell of europium ions, we show a strong interaction between a green laser and an ensemble of atomic ions. The electrons move coherently between the ground and excited ionic levels (Rabi flopping) by interacting with the magnetic field of the laser. By measuring the Rabi flopping frequency as the laser intensity is varied, we report the first direct measurement of a magnetic-dipole matrix element in the optical region of the spectrum. Using density-matrix simulations of the ensemble, we infer the generation of coherent magnetization with magnitude 5.5 ×10-3 A /m , which is capable of generating left-handed electromagnetic waves of intensity 1 nW /cm2 . These results open up the prospect of constructing left-handed materials using sharp transitions of atoms.

  15. Resolution of Transverse Electron Beam Measurements using Optical Transition Radiation

    SciTech Connect

    Ischebeck, Rasmus; Decker, Franz-Josef; Hogan, Mark; Iverson, Richard H.; Krejcik, Patrick; Lincoln, Melissa; Siemann, Robert H.; Walz, Dieter; Clayton, Chris E.; Huang, Chengkun; Lu, Wei; Deng, Suzhi; Oz, Erdem; /Southern California U.

    2005-06-22

    In the plasma wakefield acceleration experiment E-167, optical transition radiation is used to measure the transverse profile of the electron bunches before and after the plasma acceleration. The distribution of the electric field from a single electron does not give a point-like distribution on the detector, but has a certain extension. Additionally, the resolution of the imaging system is affected by aberrations. The transverse profile of the bunch is thus convolved with a point spread function (PSF). Algorithms that deconvolve the image can help to improve the resolution. Imaged test patterns are used to determine the modulation transfer function of the lens. From this, the PSF can be reconstructed. The Lucy-Richardson algorithm is used to deconvolute this PSF from test images.

  16. Optical transition radiation interferometry for the A0 photoinjector

    SciTech Connect

    Kazakevich, G.; Edwards, H.; Fliller, R.; Nagaitsev, S.; Ruan, J.; Thurman-Keup, R.; /Fermilab

    2008-06-01

    Optical Transition Radiation Interferometry (OTRI) is a promising diagnostic technique and has been successfully developed and used for investigation of relativistic beams. For mid-energy accelerators the technique is traditionally based on thin polymer films (the first one is being transparent for visible light), which causes beam multiple scattering of about 1 mrad. A disadvantage of those films is unacceptable vacuum properties for photoinjectors and accelerators using superconducting cavities. We have studied the application of thin mica sheets for the OTRI diagnostics at the A0 Photoinjector in comparison with 2.5 {micro}m thick Mylar films. This diagnostic is also applicable for the ILCTA-NML accelerator test facility that is planned at Fermilab. This report discusses the experimental setups of the OTR interferometer for the A0 Photoinjector and presents comparisons of simulations and measurements obtained using Mylar and mica-based interferometers.

  17. Vibrational states and optical transitions in hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Johannsen, P. G.

    1998-03-01

    Proton energies in hydrogen bonds are mostly calculated using a double Morse potential (the DMP model). This form, however, does not reproduce the experimentally observed correlation between the proton stretching frequency and the bond length in an extended bond-length region sufficiently well. An alternative potential is proposed in the present paper. The quantum states of this non-symmetric double-well potential are calculated numerically using the Numerov (Fox-Goodwin) algorithm. It is shown that the optical spectra of hydrogen bonds in various substances can be well approximated on the basis of the transition frequencies and intensities predicted by the present model. For weakly interacting OH impurities in 0953-8984/10/10/008/img1, the overtone spectrum and line intensities are well reproduced, whereas the line broadenings and the decrease of the fundamental stretching frequencies in intermediate and strong hydrogen bonds are traced back to the influence of the reduced height of the central barrier. The model is also extrapolated to the range of symmetric hydrogen bonds, and the calculated transition frequencies are discussed with respect to most recent infra-red experiments on ice under strong compression. A possible artificial infra-red signal from strained diamond anvils is thereby noted.

  18. Determination of the liquid crystals phase transition temperatures using optical rotation effect

    NASA Astrophysics Data System (ADS)

    Niu, Xiao-ling; Liu, Wei-guo; Liu, Peng; Cai, Chang-long

    2011-11-01

    Using optical rotation effect, a sensitive, simple optical analytical system is developed for determining the phase transition temperatures of liquid crystals (LCs). When a monochromatic polarized light passes through LCs sample and analyzer, the light intensity changes with temperature. Especially, during the phase transition process, the intensity varies greatly due to optical rotation effect. The variation of light intensity versus variation of temperature curve shows the phase transition temperatures of LCs clearly. The phase transition temperatures of three cholesteric liquid crystals (ChLCs) and a nematic liquid crystals (NLCs) were detected by this method, and compared with those of the differential scanning calorimetry (DSC) and polarized light microscope (PLM) methods.

  19. Optical lattice polarization effects on magnetically induced optical atomic clock transitions

    SciTech Connect

    Taichenachev, A. V.; Yudin, V. I.; Oates, C. W.

    2007-08-15

    We derive the frequency shift for a forbidden optical transition J=0{yields}J{sup '}=0 caused by the simultaneous actions of an elliptically polarized lattice field and a static magnetic field. We find that a simple configuration of lattice and magnetic fields leads to a cancellation of this shift to first order in lattice intensity and magnetic field. In this geometry, the second-order lattice intensity shift can be minimized as well by use of optimal lattice polarization. Suppression of these shifts could considerably enhance the performance of the next generation of atomic clocks.

  20. Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

    NASA Astrophysics Data System (ADS)

    Misiewicz, J.; Kudrawiec, R.

    2012-06-01

    The authors present the application of contactless electroreflectance (CER) spectroscopy to study optical transitions in low dimensional semiconductor structures including quantum wells (QWs), step-like QWs, quantum dots (QDs), quantum dashes (QDashes), QDs and QDashes embedded in a QW, and QDashes coupled with a QW. For QWs optical transitions between the ground and excited states as well as optical transitions in QW barriers and step-like barriers have been clearly observed in CER spectra. Energies of these transitions have been compared with theoretical calculations and in this way the band structure has been determined for the investigated QWs. For QD and QDash structures optical transitions in QDs and QDashes as well as optical transitions in the wetting layer have been identified. For QDs and QDashes surrounded by a QW, in addition to energies of QD and QDash transitions, energies of optical transitions in the surrounded QW have been measured and the band structure has been determined for the surrounded QW. Finally some differences, which can be observed in CER and photo-reflectance spectra, have been presented and discussed for selected QW and QD structures.

  1. Theory of optical transitions in conjugated polymers. I. Ideal systems

    SciTech Connect

    Barford, William; Marcus, Max

    2014-10-28

    We describe a theory of linear optical transitions in conjugated polymers. The theory is based on three assumptions. The first is that the low-lying excited states of conjugated polymers are Frenkel excitons coupled to local normal modes, described by the Frenkel-Holstein model. Second, we assume that the relevant parameter regime is ℏω ≪ J, i.e., the adiabatic regime, and thus the Born-Oppenheimer factorization of the electronic and nuclear degrees of freedom is generally applicable. Finally, we assume that the Condon approximation is valid, i.e., the exciton-polaron wavefunction is essentially independent of the normal modes. Using these assumptions we derive an expression for an effective Huang-Rhys parameter for a chain (or chromophore) of N monomers, given by S(N) = S(1)/IPR, where S(1) is the Huang-Rhys parameter for an isolated monomer. IPR is the inverse participation ratio, defined by IPR = (∑{sub n}|Ψ{sub n}|{sup 4}){sup −1}, where Ψ{sub n} is the exciton center-of-mass wavefunction. Since the IPR is proportional to the spread of the exciton center-of-mass wavefunction, this is a key result, as it shows that S(N) decreases with chain length. As in molecules, in a polymer S(N) has two interpretations. First, ℏωS(N) is the relaxation energy of an excited state caused by its coupling to the normal modes. Second, S(N) appears in the definition of an effective Franck-Condon factor, F{sub 0v}(N) = S(N){sup v}exp ( − S(N))/v! for the vth vibronic manifold. We show that the 0 − 0 and 0 − 1 optical intensities are proportional to F{sub 00}(N) and F{sub 01}(N), respectively, and thus the ratio of the 0 − 1 to 0 − 0 absorption and emission intensities are proportional to S(N). These analytical results are checked by extensive DMRG calculations and found to be generally valid, particularly for emission. However, for large chain lengths higher-lying quasimomentum exciton states become degenerate with the lowest vibrational excitation of the

  2. Delocalizing transition in one-dimensional condensates in optical lattices due to inhomogeneous interactions

    SciTech Connect

    Bludov, Yu. V.; Brazhnyi, V. A.; Konotop, V. V.

    2007-08-15

    It is shown that inhomogeneous nonlinear interactions in a Bose-Einstein condensate loaded in an optical lattice can result in a delocalizing transition in one dimension, which sharply contrasts to the known behavior of discrete and periodic systems with homogeneous nonlinearity. The transition can be originated either by decreasing the amplitude of the linear periodic potential or by the change of the mean value of the periodic nonlinearity. The dynamics of the delocalizing transition is studied.

  3. Non-local Optical Topological Transitions and Critical States in Electromagnetic Metamaterials

    PubMed Central

    Ishii, Satoshi; Narimanov, Evgenii

    2015-01-01

    Just as the topology of the Fermi surface defines the properties of the free electrons in metals and semiconductors, the geometry of the iso-frequency surface in the phase space of the propagating electromagnetic waves, determines the optical properties of the corresponding optical materials. Furthermore, in the direct analog to the Lifshitz transition in condensed matter physics, a change in the topology of iso-frequency surface has a dramatic effect on the emission, propagation and scattering of the electromagnetic waves. Here, we uncover a new class of such optical topological transitions in metamaterials, induced by the non-locality of the electromagnetic response inherent to these composites. PMID:26670600

  4. Energy spectrum and optical transitions in C80 fullerene isomers

    NASA Astrophysics Data System (ADS)

    Lobanov, B. V.; Murzashev, A. I.

    2013-04-01

    The energy spectra of all isomers of the C80 fullerene have been calculated in terms of the Schubin-Wonsowskii-Hubbard model. On this basis, their optical absorption spectra have also been calculated. The optical absorption spectra calculated for the endohedral Ca@C80, Ba@C80, and Sr@C80 fullerenes with the I h symmetry agree well with the experimental data. This circumstance allows us to conclude that the optical absorption spectra of other isomers (for which experimental data are unavailable) obtained in this work can be used for their identification.

  5. Quantitative identification of dynamical transitions in a semiconductor laser with optical feedback

    NASA Astrophysics Data System (ADS)

    Quintero-Quiroz, C.; Tiana-Alsina, J.; Romà, J.; Torrent, M. C.; Masoller, C.

    2016-11-01

    Identifying transitions to complex dynamical regimes is a fundamental open problem with many practical applications. Semi- conductor lasers with optical feedback are excellent testbeds for studying such transitions, as they can generate a rich variety of output signals. Here we apply three analysis tools to quantify various aspects of the dynamical transitions that occur as the laser pump current increases. These tools allow to quantitatively detect the onset of two different regimes, low-frequency fluctuations and coherence collapse, and can be used for identifying the operating conditions that result in specific dynamical properties of the laser output. These tools can also be valuable for analyzing regime transitions in other complex systems.

  6. Feasibility study of optical boundary layer transition detection method

    NASA Technical Reports Server (NTRS)

    Azzazy, M.; Modarress, D.; Trolinger, J. D.

    1986-01-01

    A high sensitivity differential interferometer was developed to locate the region where the boundary layer flow undergoes transition from laminar to turbulent. Two laboratory experimental configurations were used to evaluate the performance of the interferometer: open shear layer, and low speed wind tunnel turbulent spot configuration. In each experiment, small temperature fluctuations were introduced as the signal source. Simultaneous cold wire measurements were compared with the interferometer data. The comparison shows that the interferometer is sensitive to very weak phase variations in the order of 0.001 the laser wavelength. An attempt to detect boundary layer transition over a flat plate at NASA-Langley Unitary Supersonic Wind Tunnel using the interferometer system was performed. The phase variations during boundary layer transition in the supersonic wind tunnel were beyond the minimum signal-to-noise level of the instrument.

  7. Doubly Magic Optical Trapping for Cs Atom Hyperfine Clock Transitions

    NASA Astrophysics Data System (ADS)

    Carr, A. W.; Saffman, M.

    2016-10-01

    We analyze doubly magic trapping of Cs hyperfine transitions including previously neglected contributions from the ground state hyperpolarizability and the interaction of the laser light and a static magnetic field. Extensive numerical searches do not reveal any doubly magic trapping conditions for any pair of hyperfine states. However, including the hyperpolarizability reveals light intensity insensitive traps for a wide range of wavelengths at specific intensities. We then investigate the use of bichromatic trapping light fields. Deploying a bichromatic scheme, we demonstrate doubly magic red and blue detuned traps for pairs of states separated by one or two single photon transitions.

  8. Three-Dimensional Analysis of Optical Transition Radiation

    DTIC Science & Technology

    1988-12-01

    may be observed from the front face of the foil and is called backward transition radiation siliCe it is reflected back fLou- the foil. Transition...reflection coefficients. The Lorentz factor , aPI the velocity / are defined E -1+ KE , (2.3) and ~= - (2.4) The parallel and perpendicular reflection...Re[(-y-N2Z/ax)W(Z)+ax (2/ )l/2] , (2.8) where Z is defined as (I +i0)/a, ax as the rms beam angle of divergence projected into the observation plane

  9. Sub-micrometer transverse beam size diagnostics using optical transition radiation

    NASA Astrophysics Data System (ADS)

    Kruchinin, K.; Aryshev, A.; Karataev, P.; Bolzon, B.; Lefevre, T.; Mazzoni, S.; Shevelev, M.; Boogert, S. T.; Nevay, L. J.; Terunuma, N.; Urakawa, J.

    2014-05-01

    Optical transition radiation (OTR) arising when a relativistic charged particle crosses a boundary between two media with different optical properties is widely used as a tool for diagnostics of particle beams in modern accelerator facilities. The resolution of the beam profile monitors based on OTR depends on different effects of the optical system such as spherical and chromatic aberrations and diffraction. In this paper we present a systematic study of the different optical effects influencing the OTR beam profile monitor resolution. Obtained results have shown that such monitors can be used for sub-micrometer beam profile diagnostics. Further improvements and studies of the monitor are discussed.

  10. Optically decomposed near-band-edge structure and excitonic transitions in Ga2S3

    PubMed Central

    Ho, Ching-Hwa; Chen, Hsin-Hung

    2014-01-01

    The band-edge structure and band gap are key parameters for a functional chalcogenide semiconductor to its applications in optoelectronics, nanoelectronics, and photonics devices. Here, we firstly demonstrate the complete study of experimental band-edge structure and excitonic transitions of monoclinic digallium trisulfide (Ga2S3) using photoluminescence (PL), thermoreflectance (TR), and optical absorption measurements at low and room temperatures. According to the experimental results of optical measurements, three band-edge transitions of EA = 3.052 eV, EB = 3.240 eV, and EC = 3.328 eV are respectively determined and they are proven to construct the main band-edge structure of Ga2S3. Distinctly optical-anisotropic behaviors by orientation- and polarization-dependent TR measurements are, respectively, relevant to distinguish the origins of the EA, EB, and EC transitions. The results indicated that the three band-edge transitions are coming from different origins. Low-temperature PL results show defect emissions, bound-exciton and free-exciton luminescences in the radiation spectra of Ga2S3. The below-band-edge transitions are respectively characterized. On the basis of experimental analyses, the optical property of near-band-edge structure and excitonic transitions in the monoclinic Ga2S3 crystal is revealed. PMID:25142550

  11. Optically pumped NMR: Revealing spin-dependent Landau level transitions in GaAs

    NASA Astrophysics Data System (ADS)

    Ramaswamy, K.; Mui, S.; Crooker, S. A.; Pan, X.; Sanders, G. D.; Stanton, C. J.; Hayes, S. E.

    2010-08-01

    We show that high-resolution optically pumped NMR (OPNMR) studies can reveal spin-dependent optical transitions between valence- and conduction-band Landau levels in bulk semiconductors such as GaAs. The OPNMR signal intensity exhibits oscillations as a function of pump photon energy that evolve with magnetic field. In contrast to standard polarized magnetoabsorption measurements, OPNMR is sensitive to the polarization of the photoexcited electron spins (i.e., the difference between spin-up and spin-down electron populations rather than the sum). This allows one to clearly resolve the spin dependence of optical transitions that might normally be obscured in conventional magnetoabsorption studies. The data are in good agreement with theoretical calculations of the transitions from the spin-split light-hole Landau levels in the valence band to the conduction-band Landau levels of GaAs.

  12. Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

    SciTech Connect

    Maxwell, Timothy John

    2012-01-01

    Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

  13. Robust Light State by Quantum Phase Transition in Non-Hermitian Optical Materials

    PubMed Central

    Zhao, Han; Longhi, Stefano; Feng, Liang

    2015-01-01

    Robust light transport is the heart of optical information processing, leading to the search for robust light states by topological engineering of material properties. Here, it is shown that quantum phase transition, rather than topology, can be strategically exploited to design a novel robust light state. We consider an interface between parity-time (PT) symmetric media with different quantum phases and use complex Berry phase to reveal the associated quantum phase transition and topological nature. While the system possesses the same topological order within different quantum phases, phase transition from PT symmetry to PT breaking across the interface in the synthetic non-Hermitian metamaterial system facilitates novel interface states, which are robust against a variety of gain/loss perturbations and topological impurities and disorder. The discovery of the robust light state by quantum phase transition may promise fault-tolerant light transport in optical communications and computing. PMID:26592765

  14. Coherent control of a strongly driven silicon vacancy optical transition in diamond

    PubMed Central

    Zhou, Yu; Rasmita, Abdullah; Li, Ke; Xiong, Qihua; Aharonovich, Igor; Gao, Wei-bo

    2017-01-01

    The ability to prepare, optically read out and coherently control single quantum states is a key requirement for quantum information processing. Optically active solid-state emitters have emerged as promising candidates with their prospects for on-chip integration as quantum nodes and sources of coherent photons connecting these nodes. Under a strongly driving resonant laser field, such quantum emitters can exhibit quantum behaviour such as Autler–Townes splitting and the Mollow triplet spectrum. Here we demonstrate coherent control of a strongly driven optical transition in silicon vacancy centre in diamond. Rapid optical detection of photons enabled the observation of time-resolved coherent Rabi oscillations and the Mollow triplet spectrum. Detection with a probing transition further confirmed Autler–Townes splitting generated by a strong laser field. The coherence time of the emitted photons is comparable to its lifetime and robust under a very strong driving field, which is promising for the generation of indistinguishable photons. PMID:28218237

  15. Coherent control of a strongly driven silicon vacancy optical transition in diamond

    NASA Astrophysics Data System (ADS)

    Zhou, Yu; Rasmita, Abdullah; Li, Ke; Xiong, Qihua; Aharonovich, Igor; Gao, Wei-Bo

    2017-02-01

    The ability to prepare, optically read out and coherently control single quantum states is a key requirement for quantum information processing. Optically active solid-state emitters have emerged as promising candidates with their prospects for on-chip integration as quantum nodes and sources of coherent photons connecting these nodes. Under a strongly driving resonant laser field, such quantum emitters can exhibit quantum behaviour such as Autler-Townes splitting and the Mollow triplet spectrum. Here we demonstrate coherent control of a strongly driven optical transition in silicon vacancy centre in diamond. Rapid optical detection of photons enabled the observation of time-resolved coherent Rabi oscillations and the Mollow triplet spectrum. Detection with a probing transition further confirmed Autler-Townes splitting generated by a strong laser field. The coherence time of the emitted photons is comparable to its lifetime and robust under a very strong driving field, which is promising for the generation of indistinguishable photons.

  16. New trends in the optical and electronic applications of polymers containing transition-metal complexes.

    PubMed

    Liu, Shu-Juan; Chen, Yang; Xu, Wen-Juan; Zhao, Qiang; Huang, Wei

    2012-04-13

    Polymers containing transition-metal complexes exhibit excellent optical and electronic properties, which are different from those of polymers with a pure organic skeleton and combine the advantages of both polymers and metal complexes. Hence, research about this class of polymers has attracted more and more interest in recent years. Up to now, a number of novel polymers containing transition-metal complexes have been exploited, and significant advances in their optical and electronic applications have been achieved. In this article, we summarize some new research trends in the applications of this important class of optoelectronic polymers, such as chemo/biosensors, electronic memory devices and photovoltaic devices.

  17. Inner-shell magnetic dipole transition in Tm atoms: A candidate for optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Sukachev, D.; Fedorov, S.; Tolstikhina, I.; Tregubov, D.; Kalganova, E.; Vishnyakova, G.; Golovizin, A.; Kolachevsky, N.; Khabarova, K.; Sorokin, V.

    2016-08-01

    We consider a narrow magneto-dipole transition in the 169Tm atom at the wavelength of 1.14 μ m as a candidate for a two-dimensional-optical lattice clock. Calculating dynamic polarizabilities of the two clock levels [Xe] 4 f136 s2(J =7 /2 ) and [Xe] 4 f136 s2(J =5 /2 ) in the spectral range from 250 to 1200 nm, we find a "magic" wavelength for the optical lattice at 807 nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction, and other effects which can perturb the transition frequency are calculated. The transition at 1.14 μ m demonstrates low sensitivity to the BBR shift corresponding to 8 ×10-17 in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than 5 ×10-18 in fractional units. By direct excitation of the 1.14 μ m transition in Tm atoms loaded into an optical dipole trap, we set the lower limit for the lifetime of the upper clock level [Xe] 4 f136 s2(J =5 /2 ) of 112 ms which corresponds to a natural spectral linewidth narrower than 1.4 Hz. The polarizability of the Tm ground state was measured by the excitation of parametric resonances in the optical dipole trap at 532 nm.

  18. Superlubric-pinned Aubry transition of two dimensional monolayers in optical lattices

    NASA Astrophysics Data System (ADS)

    Mandelli, Davide; Vanossi, Andrea; Manini, Nicola; Tosatti, Erio

    Two-dimensional (2D) crystalline colloidal monolayers sliding over a laser-induced optical lattice ``corrugation'' potential emulate friction between ideal crystal surfaces. Static friction is always present when the monolayer and the optical lattices are commensurate, but when they are incommensurate the presence or absence of static friction depends upon the system parameters. In 1D, at the Aubry dynamical phase transition the static friction goes continuously from zero (superlubricity) to finite as the periodic corrugation strength is increased. We look for the Aubry-like transition in the more realistic 2D case of a monolayer in an incommensurate periodic potential using molecular dynamics simulations. Results confirm a clear and sharp 2D superlubric-pinned transition upon increasing corrugation strength. Unlike the 1D Aubry transition which is continuous, the 2D transition is first-order, with a jump of static friction. At the 2D Aubry transition there is no change of symmetry, a sudden rise of the colloid-colloid interaction energy, and a compensating drop of the colloid-corrugation energy. The observability of the superlubric-pinned colloid transition is proposed and discussed. This work has been supported by ERC Advanced Grant N. 320796 MODPHYSFRICT.

  19. Optical properties of transition metal oxide quantum wells

    NASA Astrophysics Data System (ADS)

    Demkov, Alexander; Choi, Miri; Butcher, Matthew; Rodriguez, Cesar; He, Qian; Posadas, Agham; Borisevich, Albina; Zollner, Stefan; Lin, Chungwei; Ortmann, Elliott

    2015-03-01

    We report on the investigation of SrTiO3/LaAlO3 quantum wells (QWs) grown by molecular beam epitaxy (MBE) on LaAlO3 substrate. Structures with different QW thicknesses ranging from two to ten unit cells were grown and characterized using x-ray photoemission spectroscopy, reflection high-energy electron diffraction (RHEED), scanning transmission electron microscopy (STEM). Optical properties (complex dielectric function) were measured by spectroscopic ellipsometry (SE) in the range of 1.0 eV to 6.0 eV at room temperature. We observed that the absorption edge was blue-shifted by approximately 0.39 eV as the STO quantum well thickness was reduced to two unit cells (uc). Density functional theory and tight-binding are used to model the optical response of these heterostructures. Our results demonstrate that the energy level of the first sub-band can be controlled by the QW thickness in a complex oxide material. We acknowledge support from Air Force Office of Scientific Research (FA9550-12-10494).

  20. GRIN optics with transition elements in gel-silica matrices

    NASA Astrophysics Data System (ADS)

    Kunetz, James M.; West, Jon K.; Hench, Larry L.

    1992-12-01

    Sol-gel technology is providing a viable alternative path towards developing doped optical components via impregnation of Type VI gel silica using a vapor or liquid phase. Past work presented an optical technique for determining quantitative mass transport properties of Cr3+ ions within the water filled porous phase of Type VI silica. Ion influx is measured by integrating the strong absorption bands produced by the chromium in the visible region. Diffusion coefficients are determined for an array of pore properties (radius, volume, surface area) as well as solution concentrations. Diffusion coefficients are calculated to be 2.0 X 10-8 cm2/sec for the most restricted case and approach 1.6 X 10-6 cm2/sec, the bulk liquid diffusion coefficient, as the ratio of diffusing solute diameter to the pore diameter decreases. Final chromium distributions are determined using electron microprobe x-ray. Higher chromium distributions are found on surfaces of the gels from which solvent is restricted from evaporating. Sample geometries affect the percent change of concentration across the cross-section.

  1. Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms

    PubMed Central

    Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.

    2015-01-01

    Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877

  2. Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms.

    PubMed

    Zhang, S Y; Wu, J T; Zhang, Y L; Leng, J X; Yang, W P; Zhang, Z G; Zhao, J Y

    2015-10-13

    Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios.

  3. Very high resolution optical transition radiation imaging system: Comparison between simulation and experiment

    NASA Astrophysics Data System (ADS)

    Bolzon, B.; Aryshev, A.; Aumeyr, T.; Boogert, S.; Karataev, P.; Kruchinin, K. O.; Lefevre, T.; Mazzoni, S.; Nevay, L.; Shevelev, M.; Terunuma, N.; Urakawa, J.; Welsch, C. P.

    2015-08-01

    Optical transition radiation (OTR) has become a commonly used method for 2D beam imaging measurements. In the Accelerator Test Facility 2 (ATF2) at KEK, beam sizes smaller than the OTR point spread function have been measured. Simulations of the OTR imaging system have been performed using the ZEMAX software to study the effects of optical errors such as aberrations, diffraction, and misalignments of optical components. This paper presents a comparison of simulations of the OTR point spread function with experimental data obtained at ATF2. It shows how the quantification and control of optical errors impacts on optimizing the resolution of the system. We also show that the OTR point spread function needs to be predicted accurately to optimize any optical system and to predict the error made on measurement.

  4. Simultaneous infrared and optical observations of the transiting debris cloud around WD 1145+017

    NASA Astrophysics Data System (ADS)

    Zhou, G.; Kedziora-Chudczer, L.; Bailey, J.; Marshall, J. P.; Bayliss, D. D. R.; Stockdale, C.; Nelson, P.; Tan, T. G.; Rodriguez, J. E.; Tinney, C. G.; Dragomir, D.; Colon, K.; Shporer, A.; Bento, J.; Sefako, R.; Horne, K.; Cochran, W.

    2016-12-01

    We present multiwavelength photometric monitoring of WD 1145+017, a white dwarf exhibiting periodic dimming events interpreted to be the transits of orbiting, disintegrating planetesimals. Our observations include the first set of near-infrared light curves for the object, obtained on multiple nights over the span of 1 month, and recorded multiple transit events with depths varying between ˜20 and 50 per cent. Simultaneous near-infrared and optical observations of the deepest and longest duration transit event were obtained on two epochs with the Anglo-Australian Telescope and three optical facilities, over the wavelength range of 0.5-1.2 μm. These observations revealed no measurable difference in transit depths for multiple photometric pass bands, allowing us to place a 2σ lower limit of 0.8 μm on the grain size in the putative transiting debris cloud. This conclusion is consistent with the spectral energy distribution of the system, which can be fit with an optically thin debris disc with minimum particle sizes of 10^{+5}_{-3} μm.

  5. Magnetic field-induced spectroscopy of forbidden optical transitions with application to lattice-based optical atomic clocks.

    PubMed

    Taichenachev, A V; Yudin, V I; Oates, C W; Hoyt, C W; Barber, Z W; Hollberg, L

    2006-03-03

    We develop a method of spectroscopy that uses a weak static magnetic field to enable direct optical excitation of forbidden electric-dipole transitions that are otherwise prohibitively weak. The power of this scheme is demonstrated using the important application of optical atomic clocks based on neutral atoms confined to an optical lattice. The simple experimental implementation of this method--a single clock laser combined with a dc magnetic field--relaxes stringent requirements in current lattice-based clocks (e.g., magnetic field shielding and light polarization), and could therefore expedite the realization of the extraordinary performance level predicted for these clocks. We estimate that a clock using alkaline-earth-like atoms such as Yb could achieve a fractional frequency uncertainty of well below 10(-17) for the metrologically preferred even isotopes.

  6. Exciton scattering approach for branched conjugated molecules and complexes. IV. Transition dipoles and optical spectra

    NASA Astrophysics Data System (ADS)

    Li, Hao; Malinin, Sergey V.; Tretiak, Sergei; Chernyak, Vladimir Y.

    2010-03-01

    The electronic excitation energies and transition dipole moments are the essential ingredients to compute an optical spectrum of any molecular system. Here we extend the exciton scattering (ES) approach, originally developed for computing excitation energies in branched conjugated molecules, to the calculation of the transition dipole moments. The ES parameters that characterize contributions of molecular building blocks to the total transition dipole can be extracted from the quantum-chemical calculations of the excited states in simple molecular fragments. Using these extracted parameters, one can then effortlessly calculate the oscillator strengths and optical spectra of various large molecular structures. We illustrate application of this extended ES approach using an example of phenylacetylene-based molecules. Absorption spectra predicted by the ES approach show close agreement with the results of the reference quantum-chemical calculations.

  7. Magnetic-dipole transitions in highly charged ions as a basis of ultraprecise optical clocks.

    PubMed

    Yudin, V I; Taichenachev, A V; Derevianko, A

    2014-12-05

    We evaluate the feasibility of using magnetic-dipole (M1) transitions in highly charged ions as a basis of an optical atomic clockwork of exceptional accuracy. We consider a range of possibilities, including M1 transitions between clock levels of the same fine-structure and hyperfine-structure manifolds. In highly charged ions these transitions lie in the optical part of the spectra and can be probed with lasers. The most direct advantage of our proposal comes from the low degeneracy of clock levels and the simplicity of atomic structure in combination with negligible quadrupolar shift. We demonstrate that such clocks can have projected fractional accuracies below the 10^{-20}-10^{-21} level for all common systematic effects, such as blackbody radiation, Zeeman, ac-Stark, and quadrupolar shifts.

  8. Dual-axis vapor cell for simultaneous laser frequency stabilization on disparate optical transitions

    SciTech Connect

    Jayakumar, Anupriya Plotkin-Swing, Benjamin; Jamison, Alan O.; Gupta, Subhadeep

    2015-07-15

    We have developed a dual-axis ytterbium (Yb) vapor cell and used it to simultaneously address the two laser cooling transitions in Yb at wavelengths 399 nm and 556 nm, featuring the disparate linewidths of 2π × 29 MHz and 2π × 182 KHz, respectively. By utilizing different optical paths for the two wavelengths, we simultaneously obtain comparable optical densities suitable for saturated absorption spectroscopy for both the transitions and keep both the lasers frequency stabilized over several hours. We demonstrate that by appropriate control of the cell temperature profile, two atomic transitions differing in relative strength across a large range of over three orders of magnitude can be simultaneously addressed, making the device adaptable to a variety of spectroscopic needs. We also show that our observations can be understood with a simple theoretical model of the Yb vapor.

  9. The impact of quantum dot filling on dual-band optical transitions via intermediate quantum states

    SciTech Connect

    Wu, Jiang; Passmore, Brandon; Manasreh, M. O.

    2015-08-28

    InAs/GaAs quantum dot infrared photodetectors with different doping levels were investigated to understand the effect of quantum dot filling on both intraband and interband optical transitions. The electron filling of self-assembled InAs quantum dots was varied by direct doping of quantum dots with different concentrations. Photoresponse in the near infrared and middle wavelength infrared spectral region was observed from samples with low quantum dot filling. Although undoped quantum dots were favored for interband transitions with the absence of a second optical excitation in the near infrared region, doped quantum dots were preferred to improve intraband transitions in the middle wavelength infrared region. As a result, partial filling of quantum dot was required, to the extent of maintaining a low dark current, to enhance the dual-band photoresponse through the confined electron states.

  10. Single-shot electro-optic sampling of coherent transition radiation at the A0 Photoinjector

    SciTech Connect

    Maxwell, T.J.; Ruan, J.; Piot, P.; Thurman-Keup, R.; /Fermilab

    2011-08-01

    Future collider applications and present high-gradient laser plasma wakefield accelerators operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. Potential applications in shot-to-shot, non-interceptive diagnostics continue to be pursued for live beam monitoring of collider and pump-probe experiments. Related to our developing work with electro-optic imaging, we present results on single-shot electro-optic sampling of the coherent transition radiation from bunches generated at the A0 photoinjector.

  11. Optical Strong Coupling between near-Infrared Metamaterials and Intersubband Transitions in III-Nitride Heterostructures

    DOE PAGES

    Benz, Alexander; Campione, Salvatore; Moseley, Michael W.; ...

    2014-08-25

    We present the design, realization, and characterization of optical strong light–matter coupling between intersubband transitions within a semiconductor heterostructures and planar metamaterials in the near-infrared spectral range. The strong light–matter coupling entity consists of a III-nitride intersubband superlattice heterostructure, providing a two-level system with a transition energy of ~0.8 eV (λ ~1.55 μm) and a planar “dogbone” metamaterial structure. Furthermore, as the bare metamaterial resonance frequency is varied across the intersubband resonance, a clear anticrossing behavior is observed in the frequency domain. We found that this strongly coupled entity could enable the realization of electrically tunable optical filters, a newmore » class of efficient nonlinear optical materials, or intersubband-based light-emitting diodes.« less

  12. Optical Strong Coupling between near-Infrared Metamaterials and Intersubband Transitions in III-Nitride Heterostructures

    SciTech Connect

    Benz, Alexander; Campione, Salvatore; Moseley, Michael W.; Wierer, Jonathan J.; Allerman, Andrew A.; Wendt, Joel R.; Brener, Igal

    2014-08-25

    We present the design, realization, and characterization of optical strong light–matter coupling between intersubband transitions within a semiconductor heterostructures and planar metamaterials in the near-infrared spectral range. The strong light–matter coupling entity consists of a III-nitride intersubband superlattice heterostructure, providing a two-level system with a transition energy of ~0.8 eV (λ ~1.55 μm) and a planar “dogbone” metamaterial structure. Furthermore, as the bare metamaterial resonance frequency is varied across the intersubband resonance, a clear anticrossing behavior is observed in the frequency domain. We found that this strongly coupled entity could enable the realization of electrically tunable optical filters, a new class of efficient nonlinear optical materials, or intersubband-based light-emitting diodes.

  13. Current-modulated optical properties of vanadium dioxide thin films in the phase transition region

    SciTech Connect

    Zhang, Shuyan; Kats, Mikhail A.; Cui, Yanjie; Zhou, You; Yao, Yu; Ramanathan, Shriram; Capasso, Federico

    2014-11-24

    Vanadium dioxide (VO{sub 2}) is a correlated electron material which undergoes an insulator-metal transition proximal to room temperature. The large change of optical properties across this phase transition is promising for tunable optical and optoelectronic devices especially at infrared frequencies. We demonstrate the ability to locally tune the optical properties on the micron scale through a simple design consisting of two electrodes patterned on a VO{sub 2} thin film. By current injection between the electrodes, a localized conducting path (metallic phase) can be formed within the insulating background. The width of the conducting path can be controlled by varying the applied current. Fourier transform infrared imaging shows that this current-modulated reflectance changes significantly over a distance on the order of the wavelength in the mid-infrared spectral range.

  14. Optical frequency measurement of the 1S-3S two-photon transition in hydrogen

    NASA Astrophysics Data System (ADS)

    Arnoult, O.; Nez, F.; Julien, L.; Biraben, F.

    2010-11-01

    This article reports the first optical frequency measurement of the 1S-3S transition in hydrogen. The excitation of this transition occurs at a wavelength of 205 nm which is obtained with two frequency doubling stages of a titanium sapphire laser at 820 nm. Its frequency is measured with an optical frequency comb. The second-order Doppler effect is evaluated from the observation of the motional Stark effect due to a transverse magnetic field perpendicular to the atomic beam. The measured value of the 1S_{1/2}( F = 1)-3S1/2( F = 1) frequency splitting is 2 922 742 936.729(13) MHz with a relative uncertainty of 4.5 × 10-12. After the measurement of the 1S-2S frequency, this result is the most precise of the optical frequencies in hydrogen.

  15. Synthesis and study of optical properties of transition metals doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Ramasamy, V.; Praba, K.; Murugadoss, G.

    2012-10-01

    ZnS and transition metal (Mn, Co, Ni, Cu, Ag and Cd) doped ZnS were synthesized using chemical precipitation method in an air atmosphere. The structural and optical properties were studied using various techniques. The X-ray diffraction (XRD) analysis show that the particles are in cubic structure. The mean size of the nanoparticles calculated through Scherrer equation is in the range of 4-6.1 nm. Elemental dispersive (EDX) analysis of doped samples reveals the presence of doping ions. The scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies show that the synthesized particles are in spherical shape. Optical characterization of both undoped and doped samples was carried out by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The absorption spectra of all the samples are blue shifted from the bulk ZnS. An optimum doping level of the transition metals for enhanced PL properties are found through optical study.

  16. High temperature phase transitions and critical exponents of Samarium orthoferrite determined by in situ optical ellipsometry

    NASA Astrophysics Data System (ADS)

    Berini, B.; Fouchet, A.; Popova, E.; Scola, J.; Dumont, Y.; Franco, N.; da Silva, R. M. C.; Keller, N.

    2012-03-01

    Determining phase transitions has always been a great challenge in material science due to their important fundamental and technological aspects. Recently, iron-based perovskites (RFeO3), exhibiting phase transitions at high temperatures, have attracted much interest for their functional properties at room temperature, such as multiferroicity (BiFeO3) and ultrafast spin dynamics (TmFeO3). In this family of materials, Samarium orthoferrite (SmFeO3) is a weak ferromagnet, ordering at high temperatures and exhibiting an intrinsic spin reorientation transition above room temperature, which is "hidden" in macroscopic magnetization measurements in polycrystalline samples. In the present article, we show that the related magnetic high temperature phase transitions can be studied through their dielectric functions by spectroscopic ellipsometry in situ and without any need for an applied external magnetic field. The presence of this intrinsic spin reorientation transition is demonstrated for textured SmFeO3 films and we have determined a critical exponent of β = 0.45 ± 0.01 for the magnetic phase transition, coherently from optical, magneto-optical, and structural investigations.

  17. Pauli Blocking Versus Electrostatic Attenuation of Optical Transition Intensities in Charged PbSe Quantum Dots

    SciTech Connect

    An, J. M.; Franceschetti, A.; Zunger, A.

    2007-01-01

    Quantum dots can be charged selectively by electrons or holes. This leads to changes in the intensity of interband and intraband optical transitions. Using atomistic pseudopotential calculations, we show that (1) when carriers are injected into dot-interior quantum-confined states, the intensity of interband transitions that have those states as their initial or final states is attenuated ('Pauli blocking') and (2) when carriers are injected into localized states near the surface of the dots, the electrostatic field set up by these charges attenuates all optically allowed interband transitions. We describe and explain these two mechanisms of intensity attenuation in the case of charged PbSe quantum dots. In addition, this study reveals a new assignment of the peaks in the absorption spectrum. The absorption spectrum of charged PbSe dots was previously interpreted assuming that all injected electrons reside in dot-interior states. This assumption has led to the suggestion that the second absorption peak originates from S{sub h}-P{sub e} and P{sub h}-S{sub e} optical transitions, despite the fact that such transitions are expected to be dipole forbidden. Our results show that the observed bleaching of absorption peaks upon electron or hole charging does not imply that the S{sub h}-P{sub e} or P{sub h}-S{sub e} transitions are allowed. Instead, the observed bleaching sequence is consistent with charging of both dot-interior and surface-localized states and with the assignment of the second absorption peak to the allowed P{sub h}-P{sub e} transition.

  18. Metal-insulator transition in epitaxial NdNiO3 thin film: A structural, electrical and optical study

    NASA Astrophysics Data System (ADS)

    Shao, Tao; Qi, Zeming; Wang, Yuyin; Li, Yuanyuan; Yang, Mei; Hu, Chuansheng

    2017-03-01

    NdNiO3 thin film has been prepared by pulsed laser deposition on LaAlO3 (001) single crystalline substrate. Temperature-dependent resistivity measurement shows a sharp metal-insulator transition in such thin film. The phase transition temperature can be tuned from 90 K to 121 K by changing the thickness of thin film. The structure evolution during phase transition is studied by Raman spectroscopy. Optical conductivity reveals that the variation carrier density in the process of phase transition. The results of structural, electrical and optical studies provide useful insights to understand the mechanism of metal-insulator transition of NdNiO3 thin film.

  19. Optical and Near-UV Observations of the Transiting Extrasolar Planet TrES-4b

    NASA Astrophysics Data System (ADS)

    Smith, Carter-Thaxton; Turner, J.; Carleton, T.; Crawford, B.; Guvenen, B.; Hardegree-Ullman, K.; Small, L.; Towner, A. P.; Walker-LaFollette, A.; Henz, T.

    2013-01-01

    Using the Steward Observatory 61” Kuiper Telescope, The University of Arizona Astronomy Club conducted photometric observations of the transiting extrasolar planet TrES-4b as part of the Exoplanet Observation Project. Observations were made in the Bessell U, Harris B, and Harris R filters. Initial observations were made in 2009, with follow up observations in 2011. Basic data reduction and photometry was done using IRAF and determination of transit parameters was done using Transit Analysis Package (TAP) and JKTEBOP transit modeling code. We present an updated planetary mass, radius, density, surface gravity, Safronov number, equilibrium temperature, orbital distance, and orbital inclination for TrES-4b. In addition, we also searched for asymmetries between the near-UV and optical light curves. This project, started in spring 2009, has introduced many undergraduate students to research and given them valuable experience with data reduction and observation techniques.

  20. Band structure and optical transitions in LaFeO3: theory and experiment.

    PubMed

    Scafetta, Mark D; Cordi, Adam M; Rondinelli, James M; May, Steven J

    2014-12-17

    The optical absorption properties of LaFeO(3) (LFO) have been calculated using density functional theory and experimentally measured from several high quality epitaxial films using variable angle spectroscopic ellipsometry. We have analyzed the calculated absorption spectrum using different Tauc models and find the model based on a direct-forbidden transition gives the best agreement with the ab initio band gap energies and band dispersions. We have applied this model to the experimental data and determine the band gap of epitaxial LFO to be ∼2.34 eV, with a slight dependence on strain state. This approach has also been used to analyze the higher indirect transition at ∼3.4 eV. Temperature dependent ellipsometry measurements further confirm our theoretical analysis of the nature of the transitions. This works helps to provide a general approach for accurate determination of band gaps and transition energies in complex oxide materials.

  1. Quantitative identification of dynamical transitions in a semiconductor laser with optical feedback

    PubMed Central

    Quintero-Quiroz, C.; Tiana-Alsina, J.; Romà, J.; Torrent, M. C.; Masoller, C.

    2016-01-01

    Identifying transitions to complex dynamical regimes is a fundamental open problem with many practical applications. Semi- conductor lasers with optical feedback are excellent testbeds for studying such transitions, as they can generate a rich variety of output signals. Here we apply three analysis tools to quantify various aspects of the dynamical transitions that occur as the laser pump current increases. These tools allow to quantitatively detect the onset of two different regimes, low-frequency fluctuations and coherence collapse, and can be used for identifying the operating conditions that result in specific dynamical properties of the laser output. These tools can also be valuable for analyzing regime transitions in other complex systems. PMID:27857229

  2. Third-Order Nonlinear Optic and Optical Limiting Properties of a Mn(iii) Transition Metal Complex

    NASA Astrophysics Data System (ADS)

    Karakas, Asli; Elmali, Ayhan; Yahsi, Yasemin; Kara, Hulya

    N,N‧-bis(5-bromosalicylidene)propane-1,2-diamine-O,O‧,N,N‧)-manganese(III) chloride transition metal complex has been synthesized and characterized by elemental analysis and UV-vis spectroscopy. Its crystal structure has been determined using X-ray diffraction analysis. To provide an insight into the optical limiting (OL) behavior of the title compound, the third-order nonlinear optical (NLO) properties, one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been theoretically investigated by means of the time-dependent Hartree-Fock (TDHF), AM1 and configuration interaction (CI) methods, respectively. According to ab initio calculation results, the examined molecule exhibits second hyperpolarizabilities (γ) with non-zero values at the positions of TPA peaks, implying microscopic third-order optical nonlinearity. The maximum OPA wavelengths recorded by linear optical experiment and quantum mechanical computations are estimated in the UV region to be shorter than 400 nm, showing good optical transparency to the visible light. The TPA cross-sections (δ(ω)) at λ max(2) values indicate that the synthesized compound might possess OL phenomena, which are in accord with the experimental observations on the manganese complexes in the literature.

  3. Quantum confinement effects on optical transitions in nanodiamonds containing nitrogen vacancies

    NASA Astrophysics Data System (ADS)

    Petrone, Alessio; Goings, Joshua J.; Li, Xiaosong

    2016-10-01

    Colored nitrogen-vacancy (NV) centers in nanosize diamonds (d ˜5 nm) are promising probe materials because their optical transitions are sensitive to mechanical, vibrational, and spin changes in the surroundings. Here, a linear response time-dependent density functional theory approach is used to describe the optical transitions in several NV-doped diamond quantum dots (QDs) in order to investigate size effects on the absorption spectra. By computing the full optical spectrum up to band-to-band transitions, we analyze both the localized "pinned" midgap and the charge-transfer excitations for an isolated reduced NV center. Subband charge-transfer excitations are shown to be size dependent, involving the excitation of the dopant s p3 electrons to the diamond conduction band. Additionally, the NV-doped systems exhibit characteristic s p3-s p3 excitations whose experimental energies are reproduced well and do not depend on QD size. However, the NV position and global cluster symmetry can affect the amount of the energy splitting of the vertical excitation energies of the midgap transitions.

  4. All-optical materials design of chiral edge modes in transition-metal dichalcogenides

    SciTech Connect

    Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas P.

    2016-10-10

    Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. As a result, we develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.

  5. All-optical materials design of chiral edge modes in transition-metal dichalcogenides

    PubMed Central

    Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas P.

    2016-01-01

    Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. We develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details. PMID:27721504

  6. All-optical materials design of chiral edge modes in transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas P.

    2016-10-01

    Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping--instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. We develop an ab initio strategy to understand non-equilibrium Floquet-Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.

  7. Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials

    PubMed Central

    Kaipurath, R. M.; Pietrzyk, M.; Caspani, L.; Roger, T.; Clerici, M.; Rizza, C.; Ciattoni, A.; Di Falco, A.; Faccio, D.

    2016-01-01

    Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial. PMID:27292270

  8. Giant Zeeman shifts in the optical transitions of yttrium iron garnet thin films

    NASA Astrophysics Data System (ADS)

    Vidyasagar, R.; Alves Santos, O.; Holanda, J.; Cunha, R. O.; Machado, F. L. A.; Ribeiro, P. R. T.; Rodrigues, A. R.; Mendes, J. B. S.; Azevedo, A.; Rezende, S. M.

    2016-09-01

    We report the observation of giant Zeeman shifts in the optical transitions of high-quality very thin films of yttrium iron garnet (YIG) grown by rf sputtering on gadolinium gallium garnet substrates. The optical absorption profile measured with magneto-optical absorption spectroscopy shows dual optical transition in the UV-visible frequency region attributed to transitions from the O-2p valence band to the Fe-3d conduction band and from the O-2p valence band to Fe-2p53d6 excitonic states at the Γ-symmetry point of the YIG band structure. The application of a static magnetic field of only 0.6 kOe produces giant Zeeman shifts of ˜100 meV in the YIG band structure and ˜60 meV in the excitonic states corresponding to effective g-factors on the order of 104. The giant Zeeman effects are attributed to changes in energy levels by the large exchange fields of the Fe-3d orbitals during the magnetization process.

  9. Optical Limiting and Theoretical Modelling of Layered Transition Metal Dichalcogenide Nanosheets

    PubMed Central

    Dong, Ningning; Li, Yuanxin; Feng, Yanyan; Zhang, Saifeng; Zhang, Xiaoyan; Chang, Chunxia; Fan, Jintai; Zhang, Long; Wang, Jun

    2015-01-01

    Nonlinear optical property of transition metal dichalcogenide (TMDC) nanosheet dispersions, including MoS2, MoSe2, WS2, and WSe2, was performed by using Z-scan technique with ns pulsed laser at 1064 nm and 532 nm. The results demonstrate that the TMDC dispersions exhibit significant optical limiting response at 1064 nm due to nonlinear scattering, in contrast to the combined effect of both saturable absorption and nonlinear scattering at 532 nm. Selenium compounds show better optical limiting performance than that of the sulfides in the near infrared. A liquid dispersion system based theoretical modelling is proposed to estimate the number density of the nanosheet dispersions, the relationship between incident laser fluence and the size of the laser generated micro-bubbles, and hence the Mie scattering-induced broadband optical limiting behavior in the TMDC dispersions. PMID:26415562

  10. Communication: Generalization of Koopmans’ theorem to optical transitions in the Hubbard model of graphene nanodots

    SciTech Connect

    Sheng, Weidong; Luo, Kaikai; Zhou, Aiping

    2015-01-14

    Koopmans’ theorem implies that the Hartree-Fock quasiparticle gap in a closed-shell system is equal to its single-particle energy gap. In this work, the theorem is generalized to optical transitions in the Hubbard model of graphene nanodots. Based on systematic configuration interaction calculations, it is proposed that the optical gap of a closed-shell graphene system within the Hubbard model is equal to its tight-binding single-particle energy gap in the absence of electron correlation. In these systems, the quasiparticle energy gap and exciton binding energy are found to be dominated by the long-range Coulomb interaction, and thus, both become small when only on-site Hubbard interactions are present. Moreover, the contributions of the quasiparticle and excitonic effects to the optical gap are revealed to nearly cancel each other, which results in an unexpected overlap of the optical and single-particle gaps of the graphene systems.

  11. A micromachined thermo-optical light modulator based on semiconductor-to-metal phase transition

    NASA Astrophysics Data System (ADS)

    Jiang, Lijun

    In this research, a micromachined thermo-optical light modulator was realized based on the semiconductor-to-metal phase transition of vanadium dioxide (VO2) thin film. VO2 undergoes a reversible phase transition at approximately 68°C, which is accompanied with drastic changes in its electrical and optical properties. The sharp electrical resistivity change can be as great as five orders. Optically, VO2 film will switch from a transparent semiconductor phase to a reflective metal phase upon the phase transition. The light modulator in this research exploits this phase transition related optical switching by using surface micromachined low-thermal-mass pixels to achieve good thermal isolations, which ensures that each pixel can be individually switched without cross talking. In operation, the pixel temperature was controlled by integrated resistor on each pixel or spatially addressed thermal radiation sources. Active VO2 thin film was synthesized by thermal oxidation of e-beam evaporated vanadium metal film. The oxidized film exhibits a phase transition at ˜65°C with a hysteresis of about 15°C. A transmittance switching from ˜90% to ˜30% in the near infrared and a reflectance switching from ˜50% to ˜15% in the visible have been achieved. The surface microstructure was studied and correlated to its optical properties. A study on the hysteresis loop reveals that the VO2 can be repetitively switched between the "on" and "off" states. The micromachined thermal isolation pixel was a bridge-like silicon dioxide platform suspended with narrow supporting legs. The pixel design was optimized with both thermal and optical simulations. The VO2 light modulator was fabricated by surface micromachining based on dry processing. Silicon dioxide was deposited on a polyimide sacrificial layer by PECVD and patterned to form the structural pixel. Vanadium film was e-beam evaporated and patterned with lift-off process. It was thermally oxidized into VO2 at 390°C. The thermal

  12. First-Principles Investigations of the Phase Transition and Optical Properties of Solid Oxygen

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Hui; Duan, De-Fang; Wang, Lian-Cheng; Zhu, Chun-Ye; Cui, Tian

    2010-12-01

    Using density-functional-theory calculations, a monoclinic metallic post-ζ phase (space group C2/c) is predicted at 215 GPa. The calculated phonon dispersion curves suggest that this structure is stable at least up to 310 GPa. Oxygen remains a molecular crystal and there is no dissociation in the related pressure range. Moreover, it is found that the phase transition from ζ to post-ζ phase is attributed to phonon softening. The significant change in the optical properties can be used to identify the phase transition.

  13. Photo field-emission spectroscopy of optical transitions in the band structure of rhenium

    NASA Astrophysics Data System (ADS)

    Radoń, T.; Kleint, Ch.

    1984-09-01

    Photo field-emission (PFE) current-voltage curves of clean and barium covered rhenium have been determined with an argon ion laser and phase sensitive detection. Field strength and work function were obtained from Fowler-Nordheim plots of the field emission currents. According to a two-step PFE model the knees of the PFE characteristics are ascribed to optical transitions in the Brillouin zone near the Fermi level. Most of the observed excitations could be correlated to direct transitions in the rhenium band structure as calculated by Mattheiss including spin-orbit coupling.

  14. Coherence-enhanced optical determination of the 229Th isomeric transition.

    PubMed

    Liao, Wen-Te; Das, Sumanta; Keitel, Christoph H; Pálffy, Adriana

    2012-12-28

    The impact of coherent light propagation on the excitation and fluorescence of thorium nuclei in a crystal lattice environment is investigated theoretically. We find that in the forward direction, the fluorescence signal exhibits characteristic intensity modulations dominated by a sped-up initial decay signal that is orders of magnitude faster. This feature can be exploited for the optical determination of the isomeric transition energy. In order to obtain a unmistakable signature of the isomeric nuclear fluorescence, we put forward a novel scheme for the direct measurement of the transition energy via electromagnetically modified nuclear forward scattering involving two fields that couple to three nuclear states.

  15. Microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells

    SciTech Connect

    Budker, D.; Hollberg, L.; Kitching, J.; Kimball, D.F.; Pustelny, S.; Yashchuk, V.V.

    2005-01-01

    Using laser optical pumping, widths and frequency shifts are determined for microwave transitions between ground-state hyperfine components of {sup 85}Rb and {sup 87}Rb atoms contained in vapor cells with alkane antirelaxation coatings. The results are compared with data on Zeeman relaxation obtained in nonlinear magneto-optical rotation experiments, a comparison important for quantitative understanding of spin-relaxation mechanisms in coated cells. By comparing cells manufactured over a 40-year period we demonstrate the long-term stability of coated cells, an important property for atomic clocks and magnetometers.

  16. A novel method for sub-micrometer transverse electron beam size measurements using optical transition radiation

    NASA Astrophysics Data System (ADS)

    Aryshev, A.; Boogert, S. T.; Howell, D.; Karataev, P.; Terunuma, N.; Urakawa, J.

    2010-06-01

    Optical Transition Radiation (OTR) appearing when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in various facilities worldwide. The resolution of the monitor is defined by so-called Point Spread Function (PSF), source distribution generated by a single electron and projected by an optical system onto a screen. In this paper we represent the development of a novel sub-micrometre electron beam profile monitor based on the measurements of the PSF structure. The first experimental results are presented and future plans on the optimization of the monitor are discussed

  17. Microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells

    SciTech Connect

    Budker, Dmitry; Hollberg. Leo; Kimball, Derek F.; Kitching J.; Pustelny Szymon; Yashchuk, Valeriy V.

    2004-08-12

    Using laser optical pumping, widths and frequency shifts are determined for microwave transitions between ground-state hyperfine components of {sup 85}Rb and {sup 87}Rb atoms contained in vapor cells with alkane anti-relaxation coatings. The results are compared with data on Zeeman relaxation obtained in nonlinear magneto-optical rotation (NMOR) experiments, a comparison important for quantitative understanding of spin-relaxation mechanisms in coated cells. By comparing cells manufactured over a forty-year period we demonstrate the long-term stability of coated cells, an important property for atomic clocks and magnetometers.

  18. Investigation of microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells

    SciTech Connect

    Budker, D.; Hollberg, L.; Kimball, D.F.; Kitching, J.; Pustclny, S.; Robinson, H.G.; Yashchuk, V.V.

    2004-06-04

    Using laser optical pumping, widths and frequency shifts are determined for microwave transitions between the components of the ground-state hyperfine structure for {sup 85}Rb and {sup 87}Rb atoms contained in vapor cells with alkane anti-relaxation coatings. The results are compared with data on Zeeman relaxation obtained in nonlinear magneto-optical rotation (NMOR) experiments, a comparison important for quantitative understanding of spin-relaxation mechanisms in coated cells. By comparing cells manufactured over a forty-year period we demonstrate the long-term stability of coated cells, which may be useful for atomic clocks and magnetometers.

  19. Simple magneto-optic transition metal models for time-domain simulations.

    PubMed

    Wolff, Christian; Rodríguez-Oliveros, Rogelio; Busch, Kurt

    2013-05-20

    Efficient modelling of the magneto-optic effects of transition metals such as nickel, cobalt and iron is a topic of growing interest within the nano-optics community. In this paper, we present a general discussion of appropriate material models for the linear dielectric properties for such metals, provide parameter fits and formulate the anisotropic response in terms of auxiliary differential equations suitable for time-domain simulations. We validate both our material models and their implementation by comparing numerical results obtained with the Discontinuous Galerkin time-domain (DGTD) method to analytical results and previously published experimental data.

  20. Optically controlled polarizer using a ladder transition for high speed Stokesmetric Imaging and Quantum Zeno Effect based optical logic.

    PubMed

    Krishnamurthy, Subramanian; Wang, Y; Tu, Y; Tseng, S; Shahriar, M S

    2013-10-21

    We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S(1/2),F = 1->5P(1/2),F = 1,2->6S(1/2),F = 1,2 transitions is excited by a Ti:Sapphire laser locked to a saturated absorption signal, representing the control beam. A tunable fiber laser at ~1323 nm is used to excite the upper leg of the transitions, representing the signal beam. When the control beam is linearly polarized, it produces an excitation of the intermediate level with a particular orientation of the angular momentum. Under ideal conditions, this orientation is transparent to the signal beam if it has the same polarization as the control beam and is absorbed when it is polarized orthogonally. We also present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, and identify means to improve the performance of the polarizer. A novel algorithm to compute the evolution of large scale quantum system enabled us to perform this computation, which may have been considered too cumbersome to carry out previously. We describe how such a polarizer may serve as a key component for high-speed Stokesmetric imaging. We also show how such a polarizer, combined with an optically controlled waveplate, recently demonstrated by us, can be used to realize a high speed optical logic gate by making use of the Quantum Zeno Effect. Finally, we describe how such a logic gate can be realized at an ultra-low power level using a tapered nanofiber embedded in a vapor cell.

  1. Effective optical Faraday rotations of semiconductor EuS nanocrystals with paramagnetic transition-metal ions.

    PubMed

    Hasegawa, Yasuchika; Maeda, Masashi; Nakanishi, Takayuki; Doi, Yoshihiro; Hinatsu, Yukio; Fujita, Koji; Tanaka, Katsuhisa; Koizumi, Hitoshi; Fushimi, Koji

    2013-02-20

    Novel EuS nanocrystals containing paramagnetic Mn(II), Co(II), or Fe(II) ions have been reported as advanced semiconductor materials with effective optical rotation under a magnetic field, Faraday rotation. EuS nanocrystals with transition-metal ions, EuS:M nanocrystals, were prepared by the reduction of the Eu(III) dithiocarbamate complex tetraphenylphosphonium tetrakis(diethyldithiocarbamate)europium(III) with transition-metal complexes at 300 °C. The EuS:M nanocrystals thus prepared were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroanalysis (ICP-AES), and a superconducting quantum interference device (SQUID) magnetometer. Enhanced Faraday rotations of the EuS:M nanocrystals were observed around 550 nm, and their enhanced spin polarization was estimated using electron paramagnetic resonance (EPR) measurements. In this report, the magneto-optical relationship between the Faraday rotation efficiency and spin polarization is discussed.

  2. Optical and magnetic properties of transition-metal ions in tetrahedral and octahedral compounds

    NASA Astrophysics Data System (ADS)

    Li, Huifang; Wang, Huaiqian; Kuang, Xiaoyu

    2011-10-01

    This paper presents the complete energy matrix of the 3d2 system containing the electron-electron interaction, the ligand-field interaction, the spin-orbit coupling interaction, and the Zeeman interaction, in which the optical spectra and g-factor of V3+and Ti2+ ions in the series of tetrahedral AIIBVI (AII=Zn, Cd, BVI=S, Se, Te) semiconductor materials are determined. In the investigation of the optical and magnetic properties of these transition-metal ions in the tetrahedral coordination complexes, we compared the data obtained from the transition-metal ions in the tetrahedral coordination complexes with those obtained from the corresponding ions in the octahedral ones, and found that the tetrahedral complexes have weaker crystal-field strength, inverse energy level ordering and stronger covalence effect.

  3. Bending light via adiabatic optical transition in longitudinally modulated photonic lattices.

    PubMed

    Han, Bin; Xu, Lei; Dou, Yiling; Xu, Jingjun; Zhang, Guoquan

    2015-10-29

    Bending light in a controllable way is desired in various applications such as beam steering, navigating and cloaking. Different from the conventional way to bend light by refractive index gradient, transformation optics or special beams through wavefront design such as Airy beams and surface plasmons, we proposed a mechanism to bend light via resonant adiabatic optical transition between Floquet-Bloch (FB) modes from different FB bands in longitudinally modulated photonic lattices. The band structure of longitudinally modulated photonic lattices was calculated by employing the concept of quasi-energy based on the Floquet-Bloch theory, showing the existence of band discontinuities at specific resonant points which cannot be revealed by the coupled-mode theory. Interestingly, different FB bands can be seamlessly connected at these resonant points in longitudinally modulated photonic lattices driven by adiabatically varying the longitudinal modulation period along the propagation direction, which stimulates the adiabatic FB mode transition between different FB bands.

  4. Electronic wave functions and optical transitions in (In,Ga)As/GaP quantum dots

    NASA Astrophysics Data System (ADS)

    Robert, C.; Pereira Da Silva, K.; Nestoklon, M. O.; Alonso, M. I.; Turban, P.; Jancu, J.-M.; Even, J.; Carrère, H.; Balocchi, A.; Koenraad, P. M.; Marie, X.; Durand, O.; Goñi, A. R.; Cornet, C.

    2016-08-01

    We study the complex electronic band structure of low In content InGaAs/GaP quantum dots. A supercell extended-basis tight-binding model is used to simulate the electronic and the optical properties of a pure GaAs/GaP quantum dot modeled at the atomic level. Transitions between hole states confined into the dots and several XZ-like electronic states confined by the strain field in the GaP barrier are found to play the main role on the optical properties. Especially, the calculated radiative lifetime for such indirect transitions is in good agreement with the photoluminescence decay time measured in time-resolved photoluminescence in the µs range. Photoluminescence experiments under hydrostatic pressure are also presented. The redshift of the photoluminescence spectrum with pressure is also in good agreement with the nature of the electronic confined states simulated with the tight-binding model.

  5. Tunable optical transition in polymeric carbon nitrides synthesized via bulk thermal condensation

    NASA Astrophysics Data System (ADS)

    Tyborski, T.; Merschjann, C.; Orthmann, S.; Yang, F.; Lux-Steiner, M.-Ch; Schedel-Niedrig, Th

    2012-04-01

    Polymeric derivatives of dicyandiamide were synthesized via a bulk thermal condensation method, using a range of process temperatures between 400 and 610 °C. The obtained carbon nitride powders exhibit an optical transition in the UV-green range that has been assigned to the direct bandgap of a semiconductor-like material. Within this context, the apparent bandgap is linearly tunable with increasing process temperatures, showing a temperature coefficient of - 1.7(1) meV K-1 between 2.5 and 3.0 eV. The obtained results show a predominant optical transition within the tri-s-triazine unit of the polymer, with a bathochromic shift originating from a gradually increasing degree of polymerization.

  6. Anisotropy in the optical properties of bulk and layered transition metal dichalcogenide ReS2

    NASA Astrophysics Data System (ADS)

    Das, Suvadip; Pradhan, Nihar; Garcia, Carlos; Rhodes, Daniel; McGill, Stephen; Balicas, Luis; Manousakis, Efstratios

    Unlike most transition metal dichalcogenides, ReS2 in the distorted 1T' phase, is a direct gap semiconductor. We measured the temperature dependent photoluminescence in both bulk and layered ReS2 and examined the evolution of the peaks with the number of layers. We obtained strong signatures of optical anisotropy in the absorption spectroscopy and photocurrent response which makes this material a potential candidate for optoelectronic applications. Many body calculations including electron-hole interactions as implemented in the GW+BSE approach, agrees with the strong anisotropy in the optical properties of bulk and monolayer ReS2. A shift in the excitonic peaks by about 0.8 eV introduced by solving the Bethe-Salpeter equation indicates strong contribution from excitonic bound states in this transition metal dichalcogenide.

  7. Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes

    NASA Astrophysics Data System (ADS)

    Trushin, Maxim; Kelleher, Edmund J. R.; Hasan, Tawfique

    2016-10-01

    We develop an analytical model to describe sub-band-gap optical absorption in two-dimensional semiconducting transition metal dichalcogenide (s-TMD) nanoflakes. The material system represents an array of few-layer molybdenum disulfide crystals, randomly orientated in a polymer matrix. We propose that optical absorption involves direct transitions between electronic edge states and bulk bands, depends strongly on the carrier population, and is saturable with sufficient fluence. For excitation energies above half the band gap, the excess energy is absorbed by the edge-state electrons, elevating their effective temperature. Our analytical expressions for the linear and nonlinear absorption could prove useful tools in the design of practical photonic devices based on s-TMDs.

  8. Bending light via adiabatic optical transition in longitudinally modulated photonic lattices

    PubMed Central

    Han, Bin; Xu, Lei; Dou, Yiling; Xu, Jingjun; Zhang, Guoquan

    2015-01-01

    Bending light in a controllable way is desired in various applications such as beam steering, navigating and cloaking. Different from the conventional way to bend light by refractive index gradient, transformation optics or special beams through wavefront design such as Airy beams and surface plasmons, we proposed a mechanism to bend light via resonant adiabatic optical transition between Floquet-Bloch (FB) modes from different FB bands in longitudinally modulated photonic lattices. The band structure of longitudinally modulated photonic lattices was calculated by employing the concept of quasi-energy based on the Floquet-Bloch theory, showing the existence of band discontinuities at specific resonant points which cannot be revealed by the coupled-mode theory. Interestingly, different FB bands can be seamlessly connected at these resonant points in longitudinally modulated photonic lattices driven by adiabatically varying the longitudinal modulation period along the propagation direction, which stimulates the adiabatic FB mode transition between different FB bands. PMID:26511890

  9. Fine tuning of optical transition energy of twisted bilayer graphene via interlayer distance modulation

    NASA Astrophysics Data System (ADS)

    del Corro, Elena; Peña-Alvarez, Miriam; Sato, Kentaro; Morales-Garcia, Angel; Bousa, Milan; Mračko, Michal; Kolman, Radek; Pacakova, Barbara; Kavan, Ladislav; Kalbac, Martin; Frank, Otakar

    2017-02-01

    Twisted bilayer graphene (tBLG) represents a family of unique materials with optoelectronic properties tuned by the rotation angle between the two layers. The presented work shows an additional way of tweaking the electronic structure of tBLG by modifying the interlayer distance, for example by a small uniaxial out-of-plane compression. We have focused on the optical transition energy, which shows a clear dependence on the interlayer distance, both experimentally and theoretically.

  10. Effect of an excited-state optical transition on the linewidth enhancement factor of quantum dot lasers

    SciTech Connect

    Zhukov, A. E. Savelyev, A. V.; Maximov, M. V.; Shernyakov, Yu. M.; Arakcheeva, E. M.; Zubov, F. I.; Krasivichev, A. A.; Kryzhanovskaya, N. V.

    2012-02-15

    An analytical expression is derived for the linewidth enhancement factor of a quantum-dot laser, which makes it possible to describe its dependence on optical loss and photon density in an explicit form. The model accounts for refractive index variations at the ground-state optical transition due to gain/absorption variations upon the first excited-state transition in quantum dots. It is shown that a decrease in optical loss, an increase in saturated gain, and an increase in the energy separation between the excited-state and ground-state transitions results in a decrease in the {alpha} factor both at and above the lasing threshold.

  11. All-optical materials design of chiral edge modes in transition-metal dichalcogenides

    DOE PAGES

    Claassen, Martin; Jia, Chunjing; Moritz, Brian; ...

    2016-10-10

    Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitionsmore » from one to two chiral edge modes on sweeping from red to blue detuning. As a result, we develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.« less

  12. Spectrophotometric method for optical band gap and electronic transitions determination of semiconductor materials

    NASA Astrophysics Data System (ADS)

    Sangiorgi, Nicola; Aversa, Lucrezia; Tatti, Roberta; Verucchi, Roberto; Sanson, Alessandra

    2017-02-01

    The optical band gap energy and the electronic processes involved are important parameters of a semiconductor material and it is therefore important to determine their correct values. Among the possible methods, the spectrophotometric is one of the most common. Several methods can be applied to determine the optical band gap energy and still now a defined consensus on the most suitable one has not been established. A highly diffused and accurate optical method is based on Tauc relationship, however to apply this equation is necessary to know the nature of the electronic transitions involved commonly related to the coefficient n. For this purpose, a spectrophotometric technique was used and we developed a graphical method for electronic transitions and band gap energy determination for samples in powder form. In particular, the n coefficient of Tauc equation was determined thorough mathematical elaboration of experimental results on TiO2 (anatase), ZnO, and SnO2. The results were used to calculate the band gap energy values and then compared with the information obtained by Ultraviolet Photoelectron Spectroscopy (UPS). This approach provides a quick and accurate method for band gap determination through n coefficient calculation. Moreover, this simple but reliable method can be used to evaluate the nature of electronic transition that occurs in a semiconductor material in powder form.

  13. Using a Semiconductor-to-Metal Transition to Control Optical Transmission through Subwavelength Hole Arrays

    DOE PAGES

    Donev, E. U.; Suh, J. Y.; Lopez, R.; ...

    2008-01-01

    We describe a simple configuration in which the extraordinary optical transmission effect through subwavelength hole arrays in noble-metal films can be switched by the semiconductor-to-metal transition in an underlying thin film of vanadium dioxide. In these experiments, the transition is brought about by thermal heating of the bilayer film. The surprising reverse hysteretic behavior of the transmission through the subwavelength holes in the vanadium oxide suggest that this modulation is accomplished by a dielectric-matching condition rather than plasmon coupling through the bilayer film. The results of this switching, including the wavelength dependence, are qualitatively reproduced by a transfer matrix model.more » The prospects for effecting a similar modulation on a much faster time scale by using ultrafast laser pulses to trigger the semiconductor-to-metal transition are also discussed.« less

  14. Phase transitions in ensembles of solitons induced by an optical pumping or a strong electric field

    NASA Astrophysics Data System (ADS)

    Karpov, P.; Brazovskii, S.

    2016-09-01

    The latest trend in studies of modern electronically and/or optically active materials is to provoke phase transformations induced by high electric fields or by short (femtosecond) powerful optical pulses. The systems of choice are cooperative electronic states whose broken symmetries give rise to topological defects. For typical quasi-one-dimensional architectures, those are the microscopic solitons taking from electrons the major roles as carriers of charge or spin. Because of the long-range ordering, the solitons experience unusual super-long-range forces leading to a sequence of phase transitions in their ensembles: the higher-temperature transition of the confinement and the lower one of aggregation into macroscopic walls. Here we present results of an extensive numerical modeling for ensembles of both neutral and charged solitons in both two- and three-dimensional systems. We suggest a specific Monte Carlo algorithm preserving the number of solitons, which substantially facilitates the calculations, allows to extend them to the three-dimensional case and to include the important long-range Coulomb interactions. The results confirm the first confinement transition, except for a very strong Coulomb repulsion, and demonstrate a pattern formation at the second transition of aggregation.

  15. Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition.

    PubMed

    Ryckman, Judson D; Hallman, Kent A; Marvel, Robert E; Haglund, Richard F; Weiss, Sharon M

    2013-05-06

    Vanadium dioxide (VO(2)) is a promising reconfigurable optical material and has long been a focus of condensed matter research owing to its distinctive semiconductor-to-metal phase transition (SMT), a feature that has stimulated recent development of thermally reconfigurable photonic, plasmonic, and metamaterial structures. Here, we integrate VO(2) onto silicon photonic devices and demonstrate all-optical switching and reconfiguration of ultra-compact broadband Si-VO(2) absorption modulators (L < 1 μm) and ring-resonators (R ~ λ(0)). Optically inducing the SMT in a small, ~0.275 μm(2), active area of polycrystalline VO(2) enables Si-VO(2) structures to achieve record values of absorption modulation, ~4 dB μm(-1), and intracavity phase modulation, ~π/5 rad μm(-1). This in turn yields large, tunable changes to resonant wavelength, |Δλ(SMT)| ~ 3 nm, approximately 60 times larger than Si-only control devices, and enables reconfigurable filtering and optical modulation in excess of 7 dB from modest Q-factor (~10(3)), high-bandwidth ring resonators (>100 GHz). All-optical integrated Si-VO(2) devices thus constitute platforms for reconfigurable photonics, bringing new opportunities to realize dynamic on-chip networks and ultrafast optical shutters and modulators.

  16. Photocurrent spectroscopy of exciton and free particle optical transitions in suspended carbon nanotube pn-junctions

    SciTech Connect

    Chang, Shun-Wen; Theiss, Jesse; Hazra, Jubin; Aykol, Mehmet; Kapadia, Rehan; Cronin, Stephen B.

    2015-08-03

    We study photocurrent generation in individual, suspended carbon nanotube pn-junction diodes formed by electrostatic doping using two gate electrodes. Photocurrent spectra collected under various electrostatic doping concentrations reveal distinctive behaviors for free particle optical transitions and excitonic transitions. In particular, the photocurrent generated by excitonic transitions exhibits a strong gate doping dependence, while that of the free particle transitions is gate independent. Here, the built-in potential of the pn-junction is required to separate the strongly bound electron-hole pairs of the excitons, while free particle excitations do not require this field-assisted charge separation. We observe a sharp, well defined E{sub 11} free particle interband transition in contrast with previous photocurrent studies. Several steps are taken to ensure that the active charge separating region of these pn-junctions is suspended off the substrate in a suspended region that is substantially longer than the exciton diffusion length and, therefore, the photocurrent does not originate from a Schottky junction. We present a detailed model of the built-in fields in these pn-junctions, which, together with phonon-assistant exciton dissociation, predicts photocurrents on the same order of those observed experimentally.

  17. Optically induced indirect photonic transitions in a slow light photonic crystal waveguide.

    PubMed

    Castellanos Muñoz, Michel; Petrov, Alexander Yu; O'Faolain, Liam; Li, Juntao; Krauss, Thomas F; Eich, Manfred

    2014-02-07

    We demonstrate indirect photonic transitions in a silicon slow light photonic crystal waveguide. The transitions are driven by an optically generated refractive index front that moves along the waveguide and interacts with a signal pulse copropagating in the structure. We experimentally confirm a theoretical model which indicates that the ratio of the frequency and wave vector shifts associated with the indirect photonic transition is identical to the propagation velocity of the refractive index front. The physical origin of the transitions achieved here is fundamentally different than in previously proposed refractive index modulation concepts with fixed temporal and spatial modulation frequencies; as here, the interaction with the refractive index front results in a Doppler-like signal frequency and wave vector shift. Consequently, the bandwidth over which perfect mode frequency and wave vector matching is achieved is not intrinsically limited by the shape of the photonic bands, and tuning of the indirect photonic transitions is possible without any need for geometrical modifications of the structure. Our device is genuinely nonreciprocal, as it provides different frequency shifts for co- and counterpropagating signal and index fronts.

  18. Bose–Einstein condensation versus Dicke–Hepp–Lieb transition in an optical cavity

    SciTech Connect

    Piazza, Francesco; Strack, Philipp; Zwerger, Wilhelm

    2013-12-15

    We provide an exact solution for the interplay between Bose–Einstein condensation and the Dicke–Hepp–Lieb self-organization transition of an ideal Bose gas trapped inside a single-mode optical cavity and subject to a transverse laser drive. Based on an effective action approach, we determine the full phase diagram at arbitrary temperature, which features a bi-critical point where the transitions cross. We calculate the dynamically generated band structure of the atoms and the associated suppression of the critical temperature for Bose–Einstein condensation in the phase with a spontaneous periodic density modulation. Moreover, we determine the evolution of the polariton spectrum due to the coupling of the cavity photons and the atomic field near the self-organization transition, which is quite different above or below the Bose–Einstein condensation temperature. At low temperatures, the critical value of the Dicke–Hepp–Lieb transition decreases with temperature and thus thermal fluctuations can enhance the tendency to a periodic arrangement of the atoms. -- Highlights: •Atoms inside a driven cavity can undergo two transitions: self-organization and BEC. •The phase diagram has four phases which coexist at a bi-critical point. •Atom–cavity coupling creates a dynamical lattice for the atoms. •Finite temperature can enhance the tendency towards self-organization. •We calculate the detailed spectrum of the polaritonic excitations.

  19. Observation of Spin Polarized Clock Transition in 87Sr Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Lin, Yi-Ge; Li, Ye; Lin, Bai-Ke; Meng, Fei; Zang, Er-Jun; Li, Tian-Chu; Fang, Zhan-Jun

    2014-12-01

    We report our observation of the spin polarized 1S0 → 3P0 clock transition spectrum in an optical lattice clock based on fermionic 87Sr. The atoms are trapped and pre-cooled to about 2 μK with two stages of laser cooling at 461 nm and 689 nm, respectively. Then the atoms are loaded into an optical lattice formed by the interference of counter-propagating laser beams at 813 nm. An external cavity diode laser at 698 nm, which is stabilized to a high finesse cavity with a linewidth of about 5 Hz and a drift rate of less than 0.2 Hz/s, is used to excite the atoms to the 3P0 state. The π-polarized clock transition spectrum of resolvable mF states is obtained by applying a small bias magnetic field along the polarization axis of the probe beam. A spin polarized clock transition spectrum as narrow as 10 Hz with an 80 ms probe pulse is obtained.

  20. Optical transitions from the lowest to higher exciton and biexciton Rydberg states in CuCl

    NASA Astrophysics Data System (ADS)

    Miyajima, K.; Sakaniwa, K.; Sugawara, M.

    2016-11-01

    We measured the optical transitions due to the internal energy levels of an exciton and biexciton in a CuCl single crystal using pump-probe spectroscopy. The transient absorption bands due to the transitions from the 1 s to 2 p and from the 1 s to 3 p exciton states were observed at 3 K, which is consistent with their reported energies. Simultaneously, the transient absorption peak due to the biexciton was observed, which corresponds to a transition from the lowest state (composed of two 1 s excitons) to higher states (composed of 1 s and 2 p excitons). The value of the observed biexciton peak energy was reasonable considering the hydrogen molecule orbitals and the electron-to-hole effective mass ratio. In addition, the transient absorption peaks were broadened at 77 K, because of the increase in the homogeneous width of the 2 p exciton state. The transient absorption spectrum was almost completely determined by this width. Our findings are of importance with regard to the optical phenomena in the infrared region related to the quantum coherence of excitons and biexcitons in semiconductors.

  1. Near-uv and optical observations of the transiting hot Jupiter WASP-1b

    NASA Astrophysics Data System (ADS)

    Pearson, K. A.; Zellem, R.; Biddle, L. I.; Amaya, H.; Watson, Z.; Griffith, C.; Small, L.; Hume, J.

    2014-03-01

    We present simultaneous near-UV (U-band) and optical (B-band) photometric observations of the primary transit of the highly irradiated, hot-Jupiter WASP-1b on the Kuiper 61" telescope. We use our results to search for timing transit variations, which would indicate additional planets, and provide new constraints on WASP-1b's physical parameters. Assuming the opacity at these two photometric bands is dominated by Rayleigh scattering by molecular hydrogen, we can place strong upper limits on its radius. Such constraints can limit the degeneracy between an exoplanet's physical radius and atmospheric composition in radiative transfer retrievals. Additionally its host star is chromospherically active and WASP-1b orbits within in the co-rotation radius of the star making it likely that WASP-1b has a bowshock. Therefore, we will search for a planetary magnetic field as indicated by an early ingress in the near-UV light curve compared to the optical due to the bowshock itself. Such measurements would confirm the observational methodology of detecting magnetic fields around transiting exoplanets, place an upper limit on WASP-1b's magnetic field strength, and confirm previous theoretical estimations of hot Jupiter magnetic fields.

  2. Electronic and Optical properties of Vacancy Defects in two dimensional monolayer Transition metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Khan, Mahtab; Erementchouk, Mikhail; Leuenberger, Michael

    Defects play an important role in tailoring electronic and optical properties of two-dimensional monolayer transition metal dichalcogenides (TMDCs). Recently it has been shown that the presence of vacancy defects (VDs) in two-dimensional monolayer MoS_2 induces localized states which give rise to extra resonance peaks in both in-plane χ∥ and out-of-plane χ⊥ susceptibilities.1 In-plane χ∥ and out-of-plane χ⊥ susceptibilities are related to the presence of even and odd states with respect to the Mo plane, respectively1. Moreover, monolayer TMDCs have a large spin orbit coupling (SOC), originating from d-orbitals of heavy transition metals and being of the order of a few 100 meV. We present a more general picture of the electronic and optical properties of defected monolayer TMDCs. In particular, we consider MoS2, MoSe2, WS2 and WSe2 with three types of VDs (i) Mo, W vacancy, (ii) S2, Se2 vacancy, and (iii) S, Se vacancy. In addition, we investigate the effects of SOC on the band structures and the optical susceptibilities of VDs in TMDCs. 1. Mikhail Erementchouk, M. A. Khan, and Michael N. Leuenberger, Phys. Rev. B 92, 121401(R) (2015).

  3. Observation of the 1S0-3P0 transition in atomic ytterbium for optical clocks and qubit arrays.

    PubMed

    Hong, Tao; Cramer, Claire; Cook, Eryn; Nagourney, Warren; Fortson, E N

    2005-10-01

    We report an observation of the weak 6 1S0-6 3P0 transition in (171,173)Yb as an important step to establishing Yb as a primary candidate for future optical frequency standards, and to open up a new approach for qubits using the 1S0 and 3P0 states of Yb atoms in an optical lattice.

  4. Acoustical and optical investigations of the size effect in nematic-isotropic phase transition in liquid crystal microemulsions

    NASA Astrophysics Data System (ADS)

    Maksimochkin, G. I.; Pasechnik, S. V.; Lukin, A. V.

    2015-07-01

    The absorption of ultrasound (at a frequency of 2.7 MHz) and the depolarized light transmission and scattering (at a wavelength of 630 nm) in liquid crystal (LC) emulsions have been studied during the nematic-isotropic (N-I) phase transition in LC droplets with radii ranging from 150 to 2300 nm. The obtained acoustical and optical data are used to determine the influence of the droplet size on characteristics of the N-I phase transition. It is shown that the acoustical and optical characteristics of LC emulsions have good prospects to be used for the investigation of phase transitions in submicron samples.

  5. Observation of optical transition radiation from electron beams generated by laser plasma accelerator

    NASA Astrophysics Data System (ADS)

    Lin, Chen; Nakamura, K.; Van, Tilborg J.; Gonsalves, A. J.; Sokollik, T.; Shiraishi, S.; Leemans, W. P.; Guo, Zhi-Yu

    2013-02-01

    Laser plasma accelerators (LPAs) have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation (OTR) from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils (located at 2.3 m and 3.8 m away from the exit of the LPA) were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.

  6. First Observation of the Point Spread Function of Optical Transition Radiation

    NASA Astrophysics Data System (ADS)

    Karataev, Pavel; Aryshev, Alexander; Boogert, Stewart; Howell, David; Terunuma, Nobuhiro; Urakawa, Junji

    2011-10-01

    We represent the first experimental observation of the point spread function (PSF) of optical transition radiation (OTR) performed at KEK-Accelerator Test Facility extraction line. We have demonstrated that the PSF vertical polarization component has a central minimum with a two lobe distribution. However, the distribution width varied significantly with wavelength. We assume that we observed a severe effect from spherical or chromatic aberrations which are not taken into account in any existing theoretical model. We believe that the result of this work will encourage theoreticians to continue developing the theory as it is important for various transition radiation applications. Nonuniform distribution of the OTR PSF creates an opportunity for developing a submicrometer transverse beam size monitor.

  7. Nonequilibrium phase transition of interacting bosons in an intra-cavity optical lattice.

    PubMed

    Bakhtiari, M Reza; Hemmerich, A; Ritsch, H; Thorwart, M

    2015-03-27

    We investigate the nonlinear light-matter interaction of a Bose-Einstein condensate trapped in an external periodic potential inside an optical cavity which is weakly coupled to vacuum radiation modes and driven by a transverse pump field. Based on a generalized Bose-Hubbard model which incorporates a single cavity mode, we include the collective backaction of the atoms on the cavity light field and determine the nonequilibrium quantum phases within the nonperturbative bosonic dynamical mean-field theory. With the system parameters adapted to recent experiments, we find a quantum phase transition from a normal phase to a self-organized superfluid phase, which is related to the Hepp-Lieb-Dicke superradiance phase transition. For even stronger pumping, a self-organized Mott insulator phase arises.

  8. First observation of the point spread function of optical transition radiation.

    PubMed

    Karataev, Pavel; Aryshev, Alexander; Boogert, Stewart; Howell, David; Terunuma, Nobuhiro; Urakawa, Junji

    2011-10-21

    We represent the first experimental observation of the point spread function (PSF) of optical transition radiation (OTR) performed at KEK-Accelerator Test Facility extraction line. We have demonstrated that the PSF vertical polarization component has a central minimum with a two lobe distribution. However, the distribution width varied significantly with wavelength. We assume that we observed a severe effect from spherical or chromatic aberrations which are not taken into account in any existing theoretical model. We believe that the result of this work will encourage theoreticians to continue developing the theory as it is important for various transition radiation applications. Nonuniform distribution of the OTR PSF creates an opportunity for developing a submicrometer transverse beam size monitor.

  9. High-accuracy optical clock based on the octupole transition in 171Yb+.

    PubMed

    Huntemann, N; Okhapkin, M; Lipphardt, B; Weyers, S; Tamm, Chr; Peik, E

    2012-03-02

    We experimentally investigate an optical frequency standard based on the 467 nm (642 THz) electric-octupole reference transition (2)S(1/2)(F=0)→(2)F(7/2)(F=3) in a single trapped (171)Yb(+) ion. The extraordinary features of this transition result from the long natural lifetime and from the 4f(13)6s(2) configuration of the upper state. The electric-quadrupole moment of the (2)F(7/2) state is measured as -0.041(5)ea(0)(2), where e is the elementary charge and a(0) the Bohr radius. We also obtain information on the differential scalar and tensorial components of the static polarizability and of the probe-light-induced ac Stark shift of the octupole transition. With a real-time extrapolation scheme that eliminates this shift, the unperturbed transition frequency is realized with a fractional uncertainty of 7.1×10(-17). The frequency is measured as 642 121 496 772 645.15(52) Hz.

  10. Magneto-optical activity at the structural phase transition in paramagnetic KMnF 3

    NASA Astrophysics Data System (ADS)

    Pezzoni, R.; Rigamonti, A.; Torre, S.

    1985-09-01

    The magneto-optical Verdet constant ø has been measured in the paramagnetic phase of KMnF 3 and particularly in the neighbourhood of the cubic-tetragonal phase transition driven by the softening of zone boundary modes. ø is positive and displays a sizeable decrease on cooling, thus indicating the presence of a temperature dependent paramagnetic contribution that, in view of the 6S ground state of the Mn 2+ ion, is attributed to the role of spin-orbit interaction. In a temperature range of about 20K around Tc = 186K, a cusp-shaped anomaly of ø is observed. From the dependence on the wavelength, and by taking into account also EPR linewidth and g measurements and optical absorption spectra, an analysis of the possible mechanisms for the cusp-shaped anomaly is given. It is argued that the enhancement of the critical rotational fluctuations of the MnF 6 octahedra can be responsible for this effect.

  11. Time-Resolved Emittance Characterization of an Induction Linac Beam using Optical Transition Radiation

    SciTech Connect

    Le Sage, G P

    2002-11-05

    An induction linac is used by Lawrence Livermore National Laboratory to perform radiographic testing at the Flash X-ray Radiography facility. Emittance characterization is important since x-ray spot size impacts the resolution of shadow-graphs. Due to the long pulse length, high current, and beam energy, emittance measurement using Optical Transition Radiation is an attractive alternative for reasons that will be described in the text. The utility of OTR-based emittance measurement has been well demonstrated for both RF and induction linacs. We describe the time-resolved emittance characterization of an induction linac electron beam. We have refined the optical collection system for the induction linac application, and have demonstrated a new technique for probing the divergence of a subset of the beam profile. The experimental apparatus, data reduction, and conclusions will be presented. Additionally, a new scheme for characterizing the correlation between beam divergence and spatial coordinates within the beam profile will be described.

  12. Identification of volume phase transition of a single microgel particle using optical tweezers

    NASA Astrophysics Data System (ADS)

    Karthickeyan, D.; Gupta, Deepak K.; Tata, B. V. R.

    2016-10-01

    Poly (N-isopropyl acrylamide-co-acrylic acid) (PNIPAM-co-Aac) microgel particles are pH responsive and exhibit volume phase transition (VPT) upon variation of pH. Dynamic light scattering (DLS) is used conventionally to identify VPT and requires a dilute suspension with particle concentration ˜107 particles cm-3 and if particles are polydisperse in nature, DLS data interpretation is relatively difficult. Here we show that optical tweezers allow one to measure the VPT of a single microgel particle by measuring the optical trap stiffness, κ of trapped particle as a function of pH. We report here a sudden change in κ at VPT, which is shown to arise from a sudden decrease in particle diameter with a concomitant increase in the refractive index of the particle at VPT.

  13. Bose-Einstein quantum phase transition in an optical lattice model

    SciTech Connect

    Aizenman, Michael; Lieb, Elliott H.; Seiringer, Robert; Solovej, Jan Philip; Yngvason, Jakob

    2004-08-01

    Bose-Einstein condensation (BEC) in cold gases can be turned on and off by an external potential, such as that presented by an optical lattice. We present a model of this phenomenon which we are able to analyze rigorously. The system is a hard core lattice gas at half of the maximum density and the optical lattice is modeled by a periodic potential of strength {lambda}. For small {lambda} and temperature, BEC is proved to occur, while at large {lambda} or temperature there is no BEC. At large {lambda} the low-temperature states are in a Mott insulator phase with a characteristic gap that is absent in the BEC phase. The interparticle interaction is essential for this transition, which occurs even in the ground state. Surprisingly, the condensation is always into the p=0 mode in this model, although the density itself has the periodicity of the imposed potential.

  14. Magneto-optical Phase Transition in a Nanostructured Co/Pd Thin Film

    NASA Astrophysics Data System (ADS)

    Nwokoye, Chidubem; Bennett, Lawrence; Della Torre, Edward; Siddique, Abid; Zhang, Ming; Wagner, Michael; Narducci, Frank

    Interest in the study of magnetism in nanostructures at low temperatures is growing. We report work that extends the magnetics experiments in that studied Bose-Einstein Condensation (BEC) of magnons in confined nanostructures. We report experimental investigation of the magneto-optical properties, influenced by photon-magnon interactions, of a Co/Pd thin film below and above the magnon BEC temperature. Comparison of results from SQUID and MOKE experiments revealed a phase transition temperature in both magnetic and magneto-optical properties of the material that is attributed to the magnon BEC. Recent research in magnonics has provided a realization scheme for developing magnon BEC qubit gates for a quantum computing processor. Future research work will explore this technology and find ways to apply quantum computing to address some computational challenges in communication systems. We recognize financial support from the Naval Air Systems Command Section 219 grant.

  15. Quantum phase transition of alkaline-earth fermionic atoms confined in an optical superlattice

    NASA Astrophysics Data System (ADS)

    Silva-Valencia, J.; Franco, R.; Figueira, M. S.

    2013-03-01

    Using the density matrix renormalization group method, we evaluate the spin and charge gaps of alkaline-earth fermionic atoms in a periodic one-dimensional optical superlattice. The number of delocalized atoms is equal to the lattice size and we consider an antiferromagnetic coupling between delocalized and localized atoms. We found a quantum phase transition from a Kondo insulator spin liquid state without confining potential to a charge-gapped antiferromagnetic state with nonzero potential. For each on-site coupling, there is a critical potential point for which the spin gap vanishes and its value increases linearly with the local interaction.

  16. Transverse Beam Shape Measurements of Intense Proton Beams Using Optical Transition Radiation

    NASA Astrophysics Data System (ADS)

    Scarpine, Victor E.

    A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

  17. Progress on the Flash X-Ray Optical Transition Radiation Diagnostic

    SciTech Connect

    Tang, V; Houck, T; Brown, C

    2008-03-30

    This document summarizes the Flash X-Ray accelerator (FXR) optical transition radiation (OTR) spot-size diagnostics efforts in FY07. During this year, new analysis, simulation, and experimental approaches were utilized to interpret OTR spot data from both dielectric foils such as Kapton (VN type) and metal coated foils. Significant new findings of the intricacies involved in the diagnostic and of FXR operational issues were achieved. Geometry and temperature based effects were found to affect the beam image profiles from the OTR foils. These effects must be taken into account in order to deduce accurately the beam current density profile.

  18. Synthesis and Characterization of Layered Double Hydroxides Containing Optically Active Transition Metal Ion

    NASA Astrophysics Data System (ADS)

    Tyagi, S. B.; Kharkwal, Aneeta; Nitu; Kharkwal, Mamta; Sharma, Raghunandan

    2017-01-01

    The acetate intercalated layered double hydroxides of Zn and Mn, have been synthesized by chimie douce method. The materials were characterized by XRD, TGA, CHN, IR, XPS, SEM-EDX and UV-visible spectroscopy. The photoluminescence properties was also studied. The optical properties of layered hydroxides are active transition metal ion dependent, particularly d1-10 system plays an important role. Simultaneously the role of host - guest orientation has been considered the basis of photoluminescence. Acetate ion can be exchanged with iodide and sulphate ions. The decomposed product resulted the pure phase Mn doped zinc oxide are also reported.

  19. Strain-induced fundamental optical transition in (In,Ga)As/GaP quantum dots

    SciTech Connect

    Robert, C. E-mail: cedric.robert@tyndall.ie; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O.; Nestoklon, M. O.; Pereira da Silva, K.; Alonso, M. I.; Goñi, A. R.; Turban, P.

    2014-01-06

    The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions.

  20. Transverse beam shape measurements of intense proton beams using optical transition radiation

    SciTech Connect

    Scarpine, Victor E.; /Fermilab

    2012-03-01

    A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

  1. Phase Transition of Bosons Driven by a Staggered Gauge Field in AN Optical Lattice

    NASA Astrophysics Data System (ADS)

    Cha, Min-Chul

    2013-06-01

    We have studied the ground state properties of hard-core bosons in a two-leg optical ladder in the presence of uniform and staggered frustrations due to an artificial gauge field. By calculating the ground state via the Lanczos method, we find first-order phase transitions tuned by the staggered gauge field between the Meissner and the vortex states. The momentum distributions show that the Meissner state has edge and staggered currents, while the vortex states have vortex-solid or vortex-glass phases in the presence of a staggered field.

  2. Ellipsometric method for the measurement of temperature and optical constants of incandescent transition metals

    NASA Technical Reports Server (NTRS)

    Hansen, George P.; Krishnan, Shankar; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    The development of a unique noncontact temperature measurement device utilizing rotating analyzer ellipsometry is described. The technique circumvents the necessity of spectral emissivity estimation by direct measurement concomitant with radiance brightness. Simultaneous determinations of dielectric constants and refractive indices allow changes in the physical and chemical state of a heated surface to be monitored. The results of optical property measurements at 633 nm as functions of temperature between 1000 and 2500 K for eight transition metals including Hf, Ir, Mo, Nb, Pd, Pt, Ta, and V are presented together with preliminary results of oxidation studies on iridium.

  3. One-way optical modal transition based on causality in momentum space.

    PubMed

    Yu, Sunkyu; Piao, Xianji; Yoo, KyungWan; Shin, Jonghwa; Park, Namkyoo

    2015-09-21

    The concept of parity-time (PT) symmetry has been used to identify a route toward unidirectional dynamics in optical k-space: imposing asymmetry on the flow of light. Although PT-symmetric potentials have been implemented under the requirement of V(x) = V*(-x), this precondition has only been interpreted within the mathematical framework for the symmetry of Hamiltonians and has not been directly linked to unidirectionality induced by PT symmetry. In this paper, within the context of light-matter interactions, we develop an alternative route toward unidirectionality in k-space by employing the concept of causality. We demonstrate that potentials with real and causal momentum spectra produce unidirectional transitions of optical modes inside the k-continuum, which corresponds to an exceptional point on the degree of PT symmetry. Our analysis reveals a critical link between non-Hermitian problems and spectral theory and also enables multi-dimensional designer manipulation of optical modes, in contrast to the one-dimensional approach that used a Schrödinger-like equation in previous PT-symmetric optics.

  4. Optical fingerprint of dark 2p-states in transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Berghäuser, Gunnar; Knorr, Andreas; Malic, Ermin

    2017-03-01

    Atomically thin transition metal dichalcogenides exhibit a remarkably strong Coulomb interaction. This results in a fascinating many-particle physics including a variety of bright and dark excitonic states that determine optical and electronic properties of these materials. So far, the impact of dark states has remained literally in the dark to a large extent, since a measurement of these optically forbidden states is very challenging. Here we demonstrate a strategy to measure a direct fingerprint of dark states even in standard linear absorption spectroscopy. We present a microscopic study on bright and dark higher excitonic states in the presence of disorder for the exemplary material of tungsten disulfide (WS2). We show that the geometric phase cancels the degeneration of 2s and 2p states and that a significant disorder-induced coupling of these bright and dark states offers a strategy to circumvent optical selection rules. As a proof, we show a clear fingerprint of dark 2p states in the absorption spectrum of WS2. The predicted softening of optical selection rules through exciton-disorder coupling is of general nature and therefore applicable to related two-dimensional semiconductors.

  5. Spectroscopy of the helium 2 3S 2 3P transition above 0.01 Tesla application to optical pumping studies

    NASA Astrophysics Data System (ADS)

    Courtade, E.; Marion, F.; Nacher, P. J.; Tastevin, G.; Dohnalik, T.; Kiersnowski, K.

    2000-08-01

    Optical pumping of helium makes use of the 2 3S-2 3P transition at 1083 nm. We report on a study of this transition in magnetic fields up to 1.5 T. Based on these results, an optical method to measure nuclear polarisation in arbitrary field has been developed. Preliminary results on optical pumping at 0.1 T are presented.

  6. ADAPTIVE OPTICS IMAGES. II. 12 KEPLER OBJECTS OF INTEREST AND 15 CONFIRMED TRANSITING PLANETS

    SciTech Connect

    Adams, E. R.; Dupree, A. K.; Kulesa, C.; McCarthy, D.

    2013-07-01

    All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or producing a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are an effective way of resolving most blends. Here we present visual companions and detection limits for 12 Kepler planet candidate host stars, of which 4 have companions within 4''. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.''1, while KOI 174 has a companion at 0.''5. In addition, observations were made of 15 transiting planets that were previously discovered by other surveys. The only companion found within 1'' of a known planet is the previously identified companion to WASP-2b. An additional four systems have companions between 1'' and 4'': HAT-P-30b (3.''7, {Delta}Ks = 2.9), HAT-P-32b (2.''9, {Delta}Ks = 3.4), TrES-1b (2.''3, {Delta}Ks = 7.7), and WASP-P-33b (1.''9, {Delta}Ks = 5.5), some of which have not been reported previously. Depending on the spatial resolution of the transit photometry for these systems, these companion stars may require a reassessment of the planetary parameters derived from transit light curves. For all systems observed, we report the limiting magnitudes beyond which additional fainter objects located 0.''1-4'' from the target may still exist.

  7. All-Optical Materials Design of Dissipationless Chiral Edge Modes in Transition-Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas

    Spurred by the recent progress in transient melting, enhancement and induction of electronic order, a particularly tantalizing prospect concerns the possibility to instead access dynamical steady states with distinct non-equilibrium phase transitions, to affect electronic transport. Here, we show that the interplay of crystal symmetry and optical pumping of monolayer transition-metal dichalcogenides (TMDCs) provides a novel avenue to engineer topologically-protected chiral edge modes, facilitating optically-switchable conduction channels that are insensitive to disorder. Intriguingly, while TMDCs are canonically described as condensed-matter realizations of massive relativistic fermions, here we predict from first principles that circularly-polarized pumping instead accesses the intrinsic three-band nature near the band edges to selectively photo-induce topological band inversions at low pump intensities, while simultaneously limiting absorption for sub-gap pump frequencies. The results presented provide a new strategy to predict and design topological materials out of equilibrium, and should be readily applicable to other classes of semiconductors.

  8. Energy band gap and optical transition of metal ion modified double crossover DNA lattices.

    PubMed

    Dugasani, Sreekantha Reddy; Ha, Taewoo; Gnapareddy, Bramaramba; Choi, Kyujin; Lee, Junwye; Kim, Byeonghoon; Kim, Jae Hoon; Park, Sung Ha

    2014-10-22

    We report on the energy band gap and optical transition of a series of divalent metal ion (Cu(2+), Ni(2+), Zn(2+), and Co(2+)) modified DNA (M-DNA) double crossover (DX) lattices fabricated on fused silica by the substrate-assisted growth (SAG) method. We demonstrate how the degree of coverage of the DX lattices is influenced by the DX monomer concentration and also analyze the band gaps of the M-DNA lattices. The energy band gap of the M-DNA, between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), ranges from 4.67 to 4.98 eV as judged by optical transitions. Relative to the band gap of a pristine DNA molecule (4.69 eV), the band gap of the M-DNA lattices increases with metal ion doping up to a critical concentration and then decreases with further doping. Interestingly, except for the case of Ni(2+), the onset of the second absorption band shifts to a lower energy until a critical concentration and then shifts to a higher energy with further increasing the metal ion concentration, which is consistent with the evolution of electrical transport characteristics. Our results show that controllable metal ion doping is an effective method to tune the band gap energy of DNA-based nanostructures.

  9. Optical transitions and point defects in F:SnO2 films: Effect of annealing

    NASA Astrophysics Data System (ADS)

    El Akkad, Fikry; Paulose, Tressia A. P.

    2014-03-01

    FTO films were deposited on borosilicate glass using chemical spray pyrolysis at 450 °C then subjected to post deposition annealing in air at 500, 550 and 600 °C. The films are characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical and electrical measurements. They are found to have the Rutile structure with strong orientation along the (1 1 0) and (2 0 0) planes and with grain size varying with annealing temperature in the range 20-100 nm. Electron concentration and oxygen vacancy concentration in the range (2.61-7.07) × 1020 cm-3 and (1.49-2.41) × 1022 cm-3 were determined using Hall and XPS measurements respectively. The analysis of optical absorption spectra revealed the presence of three direct optical transitions of energies E1 = 3.78 ± 0.07 eV, E2 = 4.39 ± 0.07 eV and E3 = 4.81 ± 0.08 eV. Taking into account the Moss-Burstein and the Urbach tailing effects, E2 was identified as being due to a direct optical transition across the Γ3v+-Γ1c+ gap. The mean value of the width of this gap is determined to be 3.86 ± 0.14 eV. The two other energies E1 and E3 are assigned to electronic transitions originating from the lower valence bands Γ5v- and Γ1v+ respectively to a defect level at Ec -0.61 ± 0.02 eV attributed to the second ionization state of the oxygen vacancy. On the other hand, the analysis of the Hall mobility results on the basis of current theories provides evidence that fluorine is at the origin of a double donor which, according to XPS measurements, must contain FSn bonds. This double donor, suggested to be the complex center [F-Sn-F]++, dominates the electrical properties of as-deposited films and creates isolated substitutional fluorine FO at higher annealing temperatures possibly by thermal dissociation.

  10. Hard-templating of chiral TiO2 nanofibres with electron transition-based optical activity

    PubMed Central

    Wang, Cui; Liu, Shaohua; Duan, Yingying; Huang, Zhehao; Che, Shunai

    2015-01-01

    The fabrication of optically active inorganic nanomaterials with chiral superstructures attracts attention because of their potential applications in chemical sensing and non-linear optics. Here, we present a facile way to prepare TiO2 nanofibres, in which the nanocrystals are helically arranged into a chiral superstructure. Notably, the chiral superstructure shows strong optical activity due to the difference of absorbing left- and right-handed circularly polarized light. This special optical activity resulted from electron transition from the valence band to the conduction band of TiO2 through a vicinal effect of helically arranged TiO2 nanocrystals. PMID:27877835

  11. Indirect interband transition induced by optical near fields with large wave numbers

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Maiku; Nobusada, Katsuyuki

    2016-05-01

    Optical near fields (ONFs) have Fourier components with large wave numbers that are two or three orders of magnitude larger than those of far-field propagating light owing to their nonuniformity in space. By utilizing these large wave numbers, the ONF is expected to induce an indirect interband transition between Bloch states having different wave numbers and directly generate an electron-hole pair without electron-phonon coupling. We perform time-dependent dynamics calculations of a one-dimensional periodic potential with an indirect band-gap structure and demonstrate that the ONF definitely induces an indirect interband transition. Instead of using the general Bloch boundary condition, which is usually imposed in conventional band structure calculations, we adopt an alternative boundary condition, the Born-von Kármán boundary condition, to appropriately treat indirect interband transitions. The calculated absorption spectra for the far-field and ONF excitations show different absorption edges and spectral patterns. We argue that this difference can be experimentally measured as evidence of the effects of the large wave numbers of the ONF.

  12. Potential of electric quadrupole transitions in radium isotopes for single-ion optical frequency standards

    SciTech Connect

    Versolato, O. O.; Wansbeek, L. W.; Jungmann, K.; Timmermans, R. G. E.; Willmann, L.; Wilschut, H. W.

    2011-04-15

    We explore the potential of the electric quadrupole transitions 7s {sup 2}S{sub 1/2}-6d {sup 2}D{sub 3/2}, 6d {sup 2}D{sub 5/2} in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive {sup A}Ra{sup +} candidates, with A= 223-229, are identified. In particular, we show that the transition 7s {sup 2}S{sub 1/2} (F=2,m{sub F}=0)-6d {sup 2}D{sub 3/2} (F=0,m{sub F}=0) at 828 nm in {sup 223}Ra{sup +}, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of 10{sup -17}. With more experimental effort, the {sup 223,225,226}Ra{sup +} clocks could be pushed to a projected performance reaching the 10{sup -18} level.

  13. Stochastic dynamic study of optical transition properties of single GFP-like molecules.

    PubMed

    Lin, Hanbing; Yuan, Jian-Min

    2016-03-01

    Due to high fluctuations and quantum uncertainty, the processes of single-molecules should be treated by stochastic methods. To study fluorescence time series and their statistical properties, we have applied two stochastic methods, one of which is an analytic method to study the off-time distributions of certain fluorescence transitions and the other is Gillespie's method of stochastic simulations. These methods have been applied to study the optical transition properties of two single-molecule systems, GFPmut2 and a Dronpa-like molecule, to yield results in approximate agreement with experimental observations on these systems. Rigorous oscillatory time series of GFPmut2 before it unfolds in the presence of denaturants have not been obtained based on the stochastic method used, but, on the other hand, the stochastic treatment puts constraints on the conditions under which such oscillatory behavior is possible. Furthermore, a sensitivity analysis is carried out on GFPmut2 to assess the effects of transition rates on the observables, such as fluorescence intensities.

  14. A Design Report for the Optical Transition Radiation Imager for the LCLS Undulator

    SciTech Connect

    Yang, Bingxin

    2010-12-13

    The Linac Coherent Light Source (LCLS), a free-electron x-ray laser, is under design and construction. Its high-intensity electron beam, 3400 A in peak current and 46 TW in peak power, is concentrated in a small area (37 micrometer in rms radius) inside its undulator. Ten optical transition radiation (OTR) imagers are planned between the undulator segments for characterizing the transverse profiles of the electron beam. In this note, we report on the optical and mechanical design of the OTR imager. Through a unique optical arrangement, using a near-normal-incidence screen and a multi-layer coated mirror, this imager will achieve a fine resolution (12 micrometer or better) over the entire field of view (8 mm x 5 mm), with a high efficiency for single-shot imaging. A digital camera will be used to read out the beam images in a programmable region (5 mm x 0.5 mm) at the full beam repetition rate (120 Hz), or over the entire field at a lower rate (10 Hz). Its built-in programmable amplifier will be used as an electronic intensity control.

  15. Prediction of direct band gap silicon superlattices with dipole-allowed optical transition

    NASA Astrophysics Data System (ADS)

    Kim, Sunghyun; Oh, Young Jun; Lee, In-Ho; Lee, Jooyoung; Chang, K. J.

    While cubic diamond silicon (c-Si) is an important element in electronic devices, it has poor optical properties owing to its indirect gap nature, thereby limiting its applications to optoelectronic devices. Here, we report Si superlattice structures which are computationally designed to possess direct band gaps and excellent optical properties. The computational approach adopts density functional calculations and conformational space annealing for global optimization. The Si superlattices, which consist of alternating stacks of Si(111) layers and a defective layer with Seiwatz chains, have either direct or quasi-direct band gaps depending on the details of attacking layers. The photovoltaic efficiencies are calculated by solving Bethe-Salpeter equation together with quasiparticle G0W0 calculations. The strong direct optical transition is attributed to the overlap of the valence and conduction band edge states in the interface region. Our Si superlattices exhibit high thermal stability, with the energies lower by an order of magnitude than those of the previously reported Si allotropes. We discuss a possible route to the synthesis of the superlattices through wafer bonding. This work is supported by Samsung Science and Technology Foundation under Grant No. SSTF-BA1401-08.

  16. Molecular-Based Optical Measurement Techniques for Transition and Turbulence in High-Speed Flow

    NASA Technical Reports Server (NTRS)

    Bathel, Brett F.; Danehy, Paul M.; Cutler, Andrew D.

    2013-01-01

    photogrammetry (for model attitude and deformation measurement) are excluded to limit the scope of this report. Other physical probes such as heat flux gauges, total temperature probes are also excluded. We further exclude measurement techniques that require particle seeding though particle based methods may still be useful in many high speed flow applications. This manuscript details some of the more widely used molecular-based measurement techniques for studying transition and turbulence: laser-induced fluorescence (LIF), Rayleigh and Raman Scattering and coherent anti-Stokes Raman scattering (CARS). These techniques are emphasized, in part, because of the prior experience of the authors. Additional molecular based techniques are described, albeit in less detail. Where possible, an effort is made to compare the relative advantages and disadvantages of the various measurement techniques, although these comparisons can be subjective views of the authors. Finally, the manuscript concludes by evaluating the different measurement techniques in view of the precision requirements described in this chapter. Additional requirements and considerations are discussed to assist with choosing an optical measurement technique for a given application.

  17. Transition.

    ERIC Educational Resources Information Center

    Thompson, Sandy, Ed.; And Others

    1990-01-01

    This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…

  18. Multicomponent measurements of the Jefferson Lab energy recovery linac electron beam using optical transition and diffraction radiation

    NASA Astrophysics Data System (ADS)

    Holloway, M. A.; Fiorito, R. B.; Shkvarunets, A. G.; O'Shea, P. G.; Benson, S. V.; Douglas, D.; Evtushenko, P.; Jordan, K.

    2008-08-01

    High brightness electron accelerators, such as energy recovery linacs (ERL), often have complex particle distributions that can create difficulties in beam transport as well as matching to devices such as wigglers used to generate radiation from the beam. Optical transition radiation (OTR), OTR interferometry (OTRI), and optical diffraction-transition radiation interferometry (ODTRI) have proven to be effective tools for diagnosing both the spatial and angular distributions of charged particle beams. OTRI and ODTRI have been used to measure rms divergences, and optical transverse phase space mapping has been demonstrated using OTRI. In this work we present the results of diagnostic experiments using OTR and optical diffraction radiation conducted at the Jefferson Laboratory’s 115 MeV ERL which show the presence of two separate components within the beam’s spatial and angular distributions. By assuming a correlation between the spatial and angular features, we estimate an rms emittance value for each of the two components.

  19. Interplay of Cu and oxygen vacancy in optical transitions and screening of excitons in ZnO:Cu films

    SciTech Connect

    Darma, Yudi; Rusydi, Andrivo; Seng Herng, Tun; Marlina, Resti; Fauziah, Resti; Ding, Jun

    2014-02-24

    We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films.

  20. Optical transitions in highly charged californium ions with high sensitivity to variation of the fine-structure constant.

    PubMed

    Berengut, J C; Dzuba, V A; Flambaum, V V; Ong, A

    2012-08-17

    We study electronic transitions in highly charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, α. The transitions are in the optical range despite the large ionization energies because they lie on the level crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf(16+) is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf(16+) has very large nuclear charge and large ionization energy, resulting in the largest α sensitivity seen in atomic systems. The lines include positive and negative shifters.

  1. Optical Transitions in Highly Charged Californium Ions with High Sensitivity to Variation of the Fine-Structure Constant

    NASA Astrophysics Data System (ADS)

    Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V.; Ong, A.

    2012-08-01

    We study electronic transitions in highly charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, α. The transitions are in the optical range despite the large ionization energies because they lie on the level crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf16+ is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf16+ has very large nuclear charge and large ionization energy, resulting in the largest α sensitivity seen in atomic systems. The lines include positive and negative shifters.

  2. Distinct Length Scales in the VO{sub 2} Metal–Insulator Transition Revealed by Bi-chromatic Optical Probing

    SciTech Connect

    Wang, Lei; Novikova, Irina B.; Klopf, John M.; Madaras, Scott E.; Williams, Gwyn P.; Madaras, Eric; Lu, Liwei; Wolf, Stuart A.; Lukaszew, Rosa A.

    2014-01-01

    Upon a heating-induced metal–instulator transition (MIT) in VO{sub 2}, microscopic metallic VO{sub 2} puddles nucleate and coarsen within the insulating matrix. This coexistence of the two phases across the transition spans distinct length scales as their relative domain sizes change. Far-field optical probing is applied to follow the dynamic evolution of the highly correlated metallic domains as the MIT progresses.

  3. Evaluation of the Laser Ablation of Transition Metals/Metal Compounds by Time-of-Flight and Optical Spectroscopy

    DTIC Science & Technology

    1993-01-01

    METAL COMPOUNDS BY TIME- OF -FLIGHT AND OPTICAL SPECTROSCOPY Terry L. Thiem, Lyn R. Watson, James A. Gardner, Rainer A. Dressier, Richard H. Salter and...AD-A267 275 77:.>- June 30, 1993 Reprint Evaluation of tie Laser Ablation of Transition Metals/ Metal Compounds by Time- of -Flight and Optical ...are generated as measured using time- of -flight spectroscopy . The energy range can be controlled with the laser power, similar to studies conducted on

  4. Low-frequency optical dielectric response and rigidity transitions in network glasses

    SciTech Connect

    Gonzalez-Leal, J. M.; Angel, J. A.; Marquez, E.; Jimenez-Garay, R.; Krecmer, P.

    2006-11-15

    Self-organization occurring in As{sub x}S{sub 1-x} and As{sub x}Se{sub 1-x} glass alloy films reflects in their low-frequency optical dielectric response, and valuable information about the building blocks conforming their structure, can be derived from the analysis of the refractive-index dispersion data. The experimental results are discussed in the framework of the single-oscillator approach proposed by Wemple and DiDomenico, which provides a meaningful parametrization of the phenomena ruling the coupling between the photon-probe and the electron plasma in the near-infrared spectral region. Rigidity transitions occurring in both binary glassy systems are discussed in terms of the differences observed in the oscillator parameters, and these electronic evidences are linked to those arguments found in the literature, based on calorimetric and Raman measurements, that point to a segregated-phase view of glass materials.

  5. Extended Coherence Time on the Clock Transition of Optically Trapped Rubidium

    NASA Astrophysics Data System (ADS)

    Kleine Büning, G.; Will, J.; Ertmer, W.; Rasel, E.; Arlt, J.; Klempt, C.; Ramirez-Martinez, F.; Piéchon, F.; Rosenbusch, P.

    2011-06-01

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of Rb87 by applying the recently discovered spin self-rephasing [C. Deutsch , Phys. Rev. Lett. 105, 020401 (2010)PRLTAO0031-900710.1103/PhysRevLett.105.020401]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10-11τ-1/2, where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  6. Optical study of the multiple charge-density-wave transitions in ErTe3

    NASA Astrophysics Data System (ADS)

    Hu, B. F.; Cheng, B.; Yuan, R. H.; Dong, T.; Fang, A. F.; Guo, W. T.; Chen, Z. G.; Zheng, P.; Shi, Y. G.; Wang, N. L.

    2011-10-01

    We present an optical spectroscopy study on singe crystalline ErTe3, a rare-earth-element tritelluride, which experiences two successive charge-density wave (CDW) transitions at Tc1=267 K and Tc2=150 K. Two corresponding gap features, centered at 2770 cm-1 (˜343 meV) and 890 cm-1 (˜110 meV), respectively, are clearly seen in ordered state. A pronounced Drude component, which exists at all measurement temperatures, demonstrates the partial gap character of both CDW orders. About half of the unmodulated Fermi surface (FS) remains in the CDW state at the lowest measurement temperature. The study also indicates that fluctuation effect may be still prominent in this two-dimensional material.

  7. Bound-Free Transitions to GeV Energy via Optical Tunneling

    NASA Astrophysics Data System (ADS)

    Gordon, Daniel

    2015-11-01

    Many laser plasmas are created through the mechanism of tunneling ionization. For weakly to moderately relativistic laser amplitudes (a = eA / mc ~ 1), the photoelectron spectrum can extend to the MeV range, with the electron gaining approximately the ponderomotive potential at the position where the bound-free transition occurred. When a ~ 100 , a new regime of acceleration appears, in which ultrarelativistic energy is obtained in a fraction of an optical cycle. We compute photoelectron characteristics based on relativistic tunneling ionization rates, and advanced particle tracking simulations, utilizing state-of-the art computer hardware. It is found that using near-term multi-petawatt lasers, free space acceleration from rest to GeV energy is possible. The effect of radiation reaction is also examined.

  8. Synthetic Dimensions and Spin-Orbit Coupling with an Optical Clock Transition

    NASA Astrophysics Data System (ADS)

    Livi, L. F.; Cappellini, G.; Diem, M.; Franchi, L.; Clivati, C.; Frittelli, M.; Levi, F.; Calonico, D.; Catani, J.; Inguscio, M.; Fallani, L.

    2016-11-01

    We demonstrate a novel way of synthesizing spin-orbit interactions in ultracold quantum gases, based on a single-photon optical clock transition coupling two long-lived electronic states of two-electron 173Yb atoms. By mapping the electronic states onto effective sites along a synthetic "electronic" dimension, we have engineered fermionic ladders with synthetic magnetic flux in an experimental configuration that has allowed us to achieve uniform fluxes on a lattice with minimal requirements and unprecedented tunability. We have detected the spin-orbit coupling with fiber-link-enhanced clock spectroscopy and directly measured the emergence of chiral edge currents, probing them as a function of the flux. These results open new directions for the investigation of topological states of matter with ultracold atomic gases.

  9. Emittance and Energy Measurements of Low-Energy Electron Beam Using Optical Transition Radiation Techniques

    NASA Astrophysics Data System (ADS)

    Sakamoto, Fumito; Iijima, Hokuto; Dobashi, Katsuhiro; Imai, Takayuki; Ueda, Toru; Watanabe, Takahiro; Uesaka, Mitsuru

    2005-03-01

    Emittance and energy of an electron beam in the range of 8 to 22 MeV were measured via optical transition radiation (OTR) techniques. The beam divergence effect on observations of the far-field OTR image at low energies was studied by means of numerical analysis. The numerical analysis indicates that if the beam divergence is under 1.5 mrad, a simultaneous single-shot measurement of emittance and energy is possible. The results of the single-shot experiment agree with independent measurements conducted using the quadrupole scan method and an electron spectrometer. The experiments were performed with an S-band linac at the Nuclear Engineering Research Laboratory, The University of Tokyo (UTNL).

  10. Evidence for anomalous optical transition radiation linear polarization effects in beam-profile monitors

    NASA Astrophysics Data System (ADS)

    Lumpkin, A. H.; Johnson, A. S.; Ruan, J.; Thurman-Keup, R. M.; Yao, C.-Y.; Evtushenko, P.

    2013-10-01

    Investigations of the effects of optical transition radiation (OTR) polarization components on beam profiles are presented. The transverse profiles are examined using the OTR perpendicular and parallel polarization components with respect to the dimension of interest. We observed ˜15% projected profile size reductions with the perpendicularly polarized components on a 65-μm beam image size case at 14 MeV, a 150-μm beam image size at 4.5 GeV, and a 1100-μm beam image size at 7 GeV. These effects are all several times larger than expected (and anomalous in this sense) when compared to the standard OTR point-spread function calculations. We propose the time-averaged induced-current distribution which generates the OTR represents the actual beam size more faithfully with the perpendicular polarization component and recommend its routine use and subsequent deconvolution.

  11. Further time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H. . Advanced Photon Source Accelerator Systems Div.); Wilke, M.D. )

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 [mu]s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  12. Time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H. ); Wilke, M.D. )

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  13. Time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H.; Wilke, M.D.

    1992-09-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  14. Further time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H.; Wilke, M.D.

    1992-12-31

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  15. Extended coherence time on the clock transition of optically trapped rubidium.

    PubMed

    Büning, G Kleine; Will, J; Ertmer, W; Rasel, E; Arlt, J; Klempt, C; Ramirez-Martinez, F; Piéchon, F; Rosenbusch, P

    2011-06-17

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of (87)Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10(-11)τ(-1/2), where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  16. Extended Coherence Time on the Clock Transition of Optically Trapped Rubidium

    SciTech Connect

    Kleine Buening, G.; Will, J.; Ertmer, W.; Rasel, E.; Klempt, C.; Arlt, J.; Ramirez-Martinez, F.; Rosenbusch, P.; Piechon, F.

    2011-06-17

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of {sup 87}Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4x10{sup -11{tau}-1/2}, where {tau} is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  17. Optically excited structural transition in atomic wires on surfaces at the quantum limit.

    PubMed

    Frigge, T; Hafke, B; Witte, T; Krenzer, B; Streubühr, C; Samad Syed, A; Mikšić Trontl, V; Avigo, I; Zhou, P; Ligges, M; von der Linde, D; Bovensiepen, U; Horn-von Hoegen, M; Wippermann, S; Lücke, A; Sanna, S; Gerstmann, U; Schmidt, W G

    2017-03-29

    Transient control over the atomic potential-energy landscapes of solids could lead to new states of matter and to quantum control of nuclear motion on the timescale of lattice vibrations. Recently developed ultrafast time-resolved diffraction techniques combine ultrafast temporal manipulation with atomic-scale spatial resolution and femtosecond temporal resolution. These advances have enabled investigations of photo-induced structural changes in bulk solids that often occur on timescales as short as a few hundred femtoseconds. In contrast, experiments at surfaces and on single atomic layers such as graphene report timescales of structural changes that are orders of magnitude longer. This raises the question of whether the structural response of low-dimensional materials to femtosecond laser excitation is, in general, limited. Here we show that a photo-induced transition from the low- to high-symmetry state of a charge density wave in atomic indium (In) wires supported by a silicon (Si) surface takes place within 350 femtoseconds. The optical excitation breaks and creates In-In bonds, leading to the non-thermal excitation of soft phonon modes, and drives the structural transition in the limit of critically damped nuclear motion through coupling of these soft phonon modes to a manifold of surface and interface phonons that arise from the symmetry breaking at the silicon surface. This finding demonstrates that carefully tuned electronic excitations can create non-equilibrium potential energy surfaces that drive structural dynamics at interfaces in the quantum limit (that is, in a regime in which the nuclear motion is directed and deterministic). This technique could potentially be used to tune the dynamic response of a solid to optical excitation, and has widespread potential application, for example in ultrafast detectors.

  18. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Phase Transition and Optical Properties of Solid Oxygen under High Pressure: A Density Functional Theory Study

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Hui; Tian, Fu-Bo; Ma, Yan-Ming; He, Zhi; Cui, Tian; Liu, Bing-Bing; Zou, Guang-Tian

    2008-07-01

    Crystal structures and optical properties of the δ-O2 phase and the ∈-O8 phase have been investigated by using the ab initio pseudopotential plane-wave method. It is found that the phase transition is of the first order with a discontinuous volumetric change from the antiferromagnetic δ-O2 phase to the nonmagnetic ∈-O8 phase, consistent with the experimental findings. The energy band calculations show that the direct band gap changes into an indirect band gap after the phase transition. The apparent change in the optical properties can be used for identifying the phase transition from δ-O2 to ∈-O8.

  19. Intrinsic evolutions of optical functions, band gap, and higher-energy electronic transitions in VO2 film near the metal-insulator transition region

    NASA Astrophysics Data System (ADS)

    Li, W. W.; Yu, Q.; Liang, J. R.; Jiang, K.; Hu, Z. G.; Liu, J.; Chen, H. D.; Chu, J. H.

    2011-12-01

    Transmittance spectra of (011) vanadium dioxide (VO2) film have been studied in the temperature range of 45-80 °C. Owing to increasing carrier concentration, the near-infrared extinction coefficient and optical conductivity around metal-insulator transition (MIT) rapidly increase with the temperature. Moreover, three electronic transitions can be uniquely assigned and show the hysteresis behavior near the MIT region. It was found that the optical band gap decreases from 0.457 to 0.042 eV before the MIT, then reduces to zero for the metal state. This confirms the fact that the a1g and egπ bands are moved close and finally overlap with the temperature.

  20. Theoretical calculations of phase transitions and optical properties of solid iodine under high pressures

    NASA Astrophysics Data System (ADS)

    San, Xiaojiao; Wang, Liancheng; Ma, Yanming; Liu, Zhiming; Cui, Tian; Liu, Bingbing; Zou, Guangtian

    2008-04-01

    The structural stability and optical properties of solid iodine under pressure have been studied using the ab initio pseudopotential plane-wave method. The dependence of lattice parameters on pressure indicates that the first structural phase transition from phase I to phase V occurs at about 20 GPa. From the pressure dependence of our elastic constants for solid iodine in phase I, it is found that the first structural transformation from molecular phase I to the intermediate phase V occurs at about 20 GPa due to the softening of the elastic constant C44, which is very close to the transition pressure of 20 GPa obtained by geometry optimizations and 23.2 GPa obtained by experimental measurements. The optimized structure for phase V is a face-centered orthorhombic (fco) phase with equal interatomic distances d1 = d2 = d3, but this fco structure is mechanically unstable, with shear elastic stiffness coefficient C44<0. To understand the modulated phase V, we use a periodic crystal structure to mimic the incommensurate phase V and obtain some quantitative information. In our calculation, the modulated phase is thermodynamically and mechanically stable. It is believed that phase V is not a monatomic phase but an intermediate state between a molecular and a monatomic state.

  1. Characterization and mitigation of coherent-optical-transition-radiation signals from a compressed electron beam

    NASA Astrophysics Data System (ADS)

    Lumpkin, A. H.; Sereno, N. S.; Berg, W. J.; Borland, M.; Li, Y.; Pasky, S. J.

    2009-08-01

    The Advanced Photon Source (APS) injector complex includes an option for rf photocathode (PC) gun beam injection into the 450-MeV S-band linac. At the 150-MeV point, a four-dipole chicane was used to compress the micropulse bunch length from a few ps to sub-0.5 ps (FWHM). Noticeable enhancements of the optical transition radiation (OTR) signal sampled after the APS chicane were then observed as has been reported in the Linac Coherent Light Source (LCLS) injector commissioning. A far-infrared (FIR) coherent transition radiation detector and interferometer were used to monitor the bunch compression process and correlate the appearance of localized spikes of OTR signal (5 to 10 times brighter than adjacent areas) within the beam-image footprint. We have performed spectral-dependency measurements at 375 MeV with a series of bandpass filters centered in 50-nm increments from 400 to 700 nm and with an imaging spectrometer and observed a broadband enhancement in these spikes. Mitigation concepts of the observed coherent OTR, which exhibits an intensity enhancement in the red part of the visible spectrum as compared to incoherent OTR, are described.

  2. Symmetry of electron states and optical transitions in GaN/AlN hexagonal quantum dots

    NASA Astrophysics Data System (ADS)

    Tronc, P.; Smirnov, V. P.; Zhuravlev, K. S.

    2004-11-01

    The exact symmetry of hexagonal quantum dots (QDs) made of materials with the wurtzite structure such as GaN/AlN QDs for example, is described by the C3v point group and does not depend on the existence of a wetting layer. We have determined the possible exact symmetries of electron states and vibration modes in the dots and derived the optical selection rules. The vibration modes involved in the Frölich interaction are totally symmetric with respect to the C3v group and can induce transitions only between states with the same symmetry. The not totally symmetric modes provide other channels for lowering the energy of excited carriers and excitons by connecting states with symmetries different one from another. The rapid decay of created polarons, due to the short lifetime of vibration modes, releases the carriers and excitons into ground levels. In the envelope function approximation (EFA), the symmetry of the dots is represented by the C6v point group. Interband transitions are allowed only between states whose envelope functions have the same symmetry. EFA artificially increases the number of dark exciton symmetries.

  3. Band gap energy and optical transitions in polyenes formed by thermal decomposition of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Kulak, A. I.; Bondarava, G. V.; Shchurevich, O. A.

    2013-07-01

    The band gap of the ensemble of oligoene clusters formed by thermocatalytic decomposition of polyvinyl alcohol is parametrized using optical absorption spectra. A band gap energy of E gm =1.53 ± 0.02 eV at the end of an infinite polyene chain is found by extrapolating the energies of π → π* transitions in clusters with a number of double bonds varying from 4 to 12. This value is close to the band gap of trans-polyacetylene and the lower bound for the Tauc energy E gT =1.50 eV, which characterizes the minimum interband transition energy. E gT is essentially independent of the concentration of oligoene clusters, which is determined by the concentration of the AlCl3 thermal decomposition catalyst. The Urbach energy determined from the long wavelength edge of the spectrum falls from 2.21 to 0.66 eV as the AlCl3 concentration is raised from 11.1 to 41.7 mmol per mol of polyvinyl alcohol structural units.

  4. Dephasing mechanisms of optical transitions in rare-earth-doped transparent ceramics

    NASA Astrophysics Data System (ADS)

    Kunkel, Nathalie; Bartholomew, John; Welinski, Sacha; Ferrier, Alban; Ikesue, Akio; Goldner, Philippe

    2016-11-01

    We identify and analyze dephasing mechanisms that broaden the optical transitions of rare-earth ions in randomly oriented transparent ceramics. The study examines the narrow F70↔D50 transition of Eu3 + dopants in a series of Y2O3 ceramic samples prepared under varying conditions. We characterize the temperature and magnetic field dependence of the homogeneous linewidth, as well as long-term spectral diffusion on time scales up to 1 s. The results highlight significant differences between samples with differing thermal treatments and Zr4 + additive concentrations. In particular, several distinct magnetic interactions from defect centers are observed, which are clearly distinguished from the broadening due to interactions with two-level systems and phonons. By minimizing the broadening due to the different defect centers, linewidths of the order of 4 kHz are achieved for all samples. The linewidths are limited by temperature-dependent interactions and by an interaction that is yet to be identified. Although the homogeneous linewidth can be narrowed further in these ceramic samples, the broadening is now comparable to the linewidths achieved in rare-earth-ion-doped single crystals. Thus, this work emphasizes the usefulness of studying ceramics to gain insights into dephasing mechanisms relevant to single crystals and suggests that ceramics may be an interesting alternative for applications in classical and quantum information processing.

  5. Observation of the 5 p3 /2→6 p3 /2 electric-dipole-forbidden transition in atomic rubidium using optical-optical double-resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ponciano-Ojeda, F.; Hernández-Gómez, S.; López-Hernández, O.; Mojica-Casique, C.; Colín-Rodríguez, R.; Ramírez-Martínez, F.; Flores-Mijangos, J.; Sahagún, D.; Jáuregui, R.; Jiménez-Mier, J.

    2015-10-01

    Direct evidence of excitation of the 5 p3 /2→6 p3 /2 electric-dipole-forbidden transition in atomic rubidium is presented. The experiments were performed in a room-temperature rubidium cell with continuous-wave external cavity diode lasers. Optical-optical double-resonance spectroscopy with counterpropagating beams allows the detection of the nondipole transition free of Doppler broadening. The 5 p3 /2 state is prepared by excitation with a laser locked to the maximum F cyclic transition of the D2 line, and the forbidden transition is produced by excitation with a 911 nm laser. Production of the forbidden transition is monitored by detection of the 420 nm fluorescence that results from decay of the 6 p3 /2 state. Spectra with three narrow lines (≈13 MHz FWHM) with the characteristic F -1 , F , and F +1 splitting of the 6 p3 /2 hyperfine structure in both rubidium isotopes were obtained. The results are in very good agreement with a direct calculation that takes into account the 5 s →5 p3 /2 preparation dynamics, the 5 p3 /2→6 p3 /2 nondipole excitation geometry, and the 6 p3 /2→5 s1 /2 decay. The comparison also shows that the electric-dipole-forbidden transition is a very sensitive probe of the preparation dynamics.

  6. Exciton formation assisted by longitudinal optical phonons in monolayer transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Thilagam, A.

    2016-09-01

    We examine a mechanism by which excitons are generated via the longitudinal optical (LO) phonon-assisted scattering process after optical excitation of monolayer transition metal dichalcogenides. The exciton formation time is computed as a function of the exciton center-of-mass wavevector, electron and hole temperatures, and carrier densities for known values of the Fröhlich coupling constant, LO phonon energy, lattice temperature, and the exciton binding energy in layered structures. For the monolayer MoS2, we obtain ultrafast exciton formation times on the sub-picosecond time scale at charge densities of 5 × 1011 cm-2 and carrier temperatures less than 300 K, in good agreement with recent experimental findings ( ≈0.3 ps). While excitons are dominantly created at zero center-of-mass wavevectors at low charge carrier temperatures ( ≈30 K), the exciton formation time is most rapid at non-zero wavevectors at higher temperatures ( ≥120 K) of charge carriers. The results show the inverse square-law dependence of the exciton formation times on the carrier density, consistent with a square-law dependence of photoluminescence on the excitation density. Our results show that excitons are formed more rapidly in exemplary monolayer selenide-based dichalcogenides (MoSe2 and WSe2) than sulphide-based dichalcogenides (MoS2 and WS2).

  7. Tolerancing, alignment and test of the Transiting Exoplanet Survey Satellite (TESS) optical assembly

    NASA Astrophysics Data System (ADS)

    Primeau, Brian; Balonek, Gregory; MacDonald, Robert; Chrisp, Michael; Chesbrough, Christian; Andre, James; Clark, Kristin

    2016-09-01

    The Transiting Exoplanet Survey Satellite (TESS) will carry four visible waveband seven-element refractive f/1.4 lenses, each with a 34 degree diagonal field of view. This paper describes the tolerancing, assembly and alignment methods developed during the build of the TESS Risk Reduction Unit optical system. Lens assembly tolerances were derived from a sensitivity analysis using an image quality metric customized for mission performance. The optomechanical design consists of a two-stage lens housing that provides access for active alignment of each lens using a Trioptics OptiCentric measurement system. Thermal stresses and alignment shifts are mitigated by mounting the optics with cast RTV silicone spacers into individually aligned bezels, and custom fixtures were developed to aid in RTV bonding with reduced alignment error. The lens assembly was tested interferometrically over the field of view at room temperature and results were used to successfully predict lens performance and compensator adjustments and detector shim thickness for the -75C operational temperature and pressure.

  8. Robotic Transit Follow-up: Adaptive Optics Imaging of Thousands of Stars

    NASA Astrophysics Data System (ADS)

    Law, Nicholas M.; Morton, T.; Baranec, C.; Riddle, R. L.; Tendulkar, S. P.; Johnson, J. A.; Bui, K.; Burse, M.; Chordia, P.; Das, H.; Dekany, R.; Kulkarni, S. R.; Punnadi, S.; Ramaprakash, A. N.; Robo-AO Collaboration

    2013-01-01

    Stars that host transiting exoplanet candidates may have close companions. If undetected, these companions can produce false-positive planets or affect the measured exoplanet characteristics. High-angular-resolution imaging is required to resolve these systems. Up to now, it has been impossible to obtain adaptive optics images of all the thousands of candidates generated by large surveys like Kepler because of the faintness of the targets and the excessive observing time required. The Robo-AO robotic laser adaptive optics system, newly-commissioned on the Palomar 60-inch telescope, is the first system capable of rapidly observing thousands of targets at high resolution. Robo-AO routinely images 200+ targets per night and produces 0.1" FWHM images in visible wavelengths similar to the Kepler passband. We are using Robo-AO to perform a stellar companion search of unprecedented size, including every Kepler planet candidate and 3,000 nearby planet-search stars. In our first observing season we have imaged over 1,000 Kepler objects of interest and 75% of the Northern stars within 25pc. We will describe the system and discuss its use for future exoplanet surveys such as TESS. We will also present the first results from the survey: a comprehensive assessment of stellar multiplicity among Kepler exoplanet hosts and the discovery of new close stellar companions around Kepler objects of interest.

  9. Rapid, all-optical crystal orientation imaging of two-dimensional transition metal dichalcogenide monolayers

    SciTech Connect

    David, Sabrina N.; Zhai, Yao; Zande, Arend M. van der; O'Brien, Kevin; Huang, Pinshane Y.; Chenet, Daniel A.; Hone, James C.; Zhang, Xiang; Yin, Xiaobo

    2015-09-14

    Two-dimensional (2D) atomic materials such as graphene and transition metal dichalcogenides (TMDCs) have attracted significant research and industrial interest for their electronic, optical, mechanical, and thermal properties. While large-area crystal growth techniques such as chemical vapor deposition have been demonstrated, the presence of grain boundaries and orientation of grains arising in such growths substantially affect the physical properties of the materials. There is currently no scalable characterization method for determining these boundaries and orientations over a large sample area. We here present a second-harmonic generation based microscopy technique for rapidly mapping grain orientations and boundaries of 2D TMDCs. We experimentally demonstrate the capability to map large samples to an angular resolution of ±1° with minimal sample preparation and without involved analysis. A direct comparison of the all-optical grain orientation maps against results obtained by diffraction-filtered dark-field transmission electron microscopy plus selected-area electron diffraction on identical TMDC samples is provided. This rapid and accurate tool should enable large-area characterization of TMDC samples for expedited studies of grain boundary effects and the efficient characterization of industrial-scale production techniques.

  10. Instantaneous electron beam emittance measurement system based on the optical transition radiation principle

    NASA Astrophysics Data System (ADS)

    Jiang, Xiao-Guo; Wang, Yuan; Zhang, Kai-Zhi; Yang, Guo-Jun; Shi, Jin-Shui; Deng, Jian-Jun; Li, Jin

    2014-01-01

    One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns (FWHM) electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm (FWHM) in diameter and the corresponding beam divergence is about 10.5 mrad.

  11. Optically trapped atom interferometry using the clock transition of large 87Rb Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Altin, P. A.; McDonald, G.; Döring, D.; Debs, J. E.; Barter, T. H.; Close, J. D.; Robins, N. P.; Haine, S. A.; Hanna, T. M.; Anderson, R. P.

    2011-06-01

    We present a Ramsey-type atom interferometer operating with an optically trapped sample of 106 Bose-condensed 87Rb atoms. We investigate this interferometer experimentally and theoretically with an eye to the construction of future high precision atomic sensors. Our results indicate that, with further experimental refinements, it will be possible to produce and measure the output of a sub-shot-noise-limited, large atom number BEC-based interferometer. The optical trap allows us to couple the |F=1, mF=0rang→|F=2, mF=0rang clock states using a single photon 6.8 GHz microwave transition, while state selective readout is achieved with absorption imaging. We analyse the process of absorption imaging and show that it is possible to observe atom number variance directly, with a signal-to-noise ratio ten times better than the atomic projection noise limit on 106 condensate atoms. We discuss the technical and fundamental noise sources that limit our current system, and present theoretical and experimental results on interferometer contrast, de-phasing and miscibility.

  12. Multisectional linear ion trap and novel loading method for optical spectroscopy of electron and nuclear transitions.

    PubMed

    Sysoev, Alexey A; Troyan, Victor I; Borisyuk, Peter V; Krasavin, Andrey V; Vasiliev, Oleg S; Palchikov, Vitaly G; Avdeev, Ivan A; Chernyshev, Denis M; Poteshin, Sergey S

    2015-01-01

    There is a growing need for the development of atomic and nuclear frequency standards because of the important contribution of methods for precision time and frequency measurements to the development of fundamental science, technology, and the economy. It is also conditioned by their potential use in optical clocks and quantum logic applications. It is especially important to develop a universal method that could allow one to use ions of most elements effectively (including ones that are not easily evaporated) proposed for the above-mentioned applications. A linear quadrupole ion trap for the optical spectroscopy of electron and nuclear transitions has been developed and evaluated experimentally. An ion source construction is based on an ultra-high vacuum evaporator in which a metal sample is subjected to an electron beam of energy up to 1 keV, resulting in the appearance of gaseous atoms and ions of various charge state. The linear ion trap consists of five successive quadrupole sections including an entrance quadrupole section, quadrupole mass filter, quadrupole ion guide, ion-trap section, and exit quadrupole section. The same radiofrequency but a different direct current voltage feeds the quadrupole sections. The instrument allows the mass and energy selected trapping of ions from ion beams of various intensities and their localization in the area of laser irradiation. The preliminary results presented show that the proposed instrument and methods allow one to produce effectively up to triply charged thorium ions as well as to trap ions for future spectroscopic study. The instrument is proposed for future use in optical clocks and quantum logic application development.

  13. Dependence of energy levels and optical transitions on layer thicknesses in InSe/GaSe superlattices

    NASA Astrophysics Data System (ADS)

    Erkoç, Şakir; Katırcıoğlu, Şenay

    1998-01-01

    We have investigated the dependence of energy levels and optical transition matrix elements in InSe/GaSe superlattices on well and/or barrier widths. Self-consistent-field calculations have been performed within the effective-mass theory approximation.

  14. Measurement of the Yb I S10-P11 transition frequency at 399 nm using an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Kleinert, Michaela; Gold Dahl, M. E.; Bergeson, Scott

    2016-11-01

    We determine the frequency of the Yb I S10-P11 transition at 399 nm using an optical frequency comb. Although this transition was measured previously using an optical transfer cavity [D. Das et al., Phys. Rev. A 72, 032506 (2005), 10.1103/PhysRevA.72.032506], recent work has uncovered significant errors in that method. We compare our result of 751 526 533.49 ± 0.33 MHz for the 174Yb isotope with those from the literature and discuss observed differences. We verify the correctness of our method by measuring the frequencies of well-known transitions in Rb and Cs, and by demonstrating proper control of systematic errors in both laser metrology and atomic spectroscopy. We also demonstrate the effect of quantum interference due to hyperfine structure in a divalent atomic system and present isotope shift measurements for all stable isotopes.

  15. Laminar microvascular transit time distribution in the mouse somatosensory cortex revealed by Dynamic Contrast Optical Coherence Tomography.

    PubMed

    Merkle, Conrad W; Srinivasan, Vivek J

    2016-01-15

    The transit time distribution of blood through the cerebral microvasculature both constrains oxygen delivery and governs the kinetics of neuroimaging signals such as blood-oxygen-level-dependent functional Magnetic Resonance Imaging (BOLD fMRI). However, in spite of its importance, capillary transit time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of an intravascular tracer as it passes through the field-of-view. Quantitative transit time metrics are derived from temporal analysis of the dynamic scattering signal, closely related to tracer concentration. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against dilution curves measured using a fluorescent plasma label in surface pial vessels, we used DyC-OCT to investigate the transit time distribution in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with earlier transit times and less heterogeneity in the middle cortical layers. The early transit times in the middle cortical layers may explain, at least in part, the early BOLD fMRI onset times observed in these layers. The layer-dependencies in heterogeneity may help explain how a single vascular supply manages to deliver oxygen to individual cortical layers with diverse metabolic needs.

  16. Modelling for Transient Optically Induced Metal - Transitions in Narrow-Gap Semiconductors and Semimetals.

    NASA Astrophysics Data System (ADS)

    Vidal, Jordina

    1994-01-01

    The theoretical work presented in this thesis is based on models developed to interpret a series of optical experiments with short-pulse lasers, which allow a time -domain study of phenomena on a sub-picosecond timescale. By means of a pump-probe technique, we observe large amplitude oscillations in the time domain reflectivity response of a series of narrow-gap semiconductors and semimetals. The oscillations have the frequency of the fully-symmetric optical phonon mode of the system, and are maximally displaced from their midpoint value at zero time delay between pump and probe. These features indicate that a coherent phonon vibration is generated in these materials via an electronic excitation at different points of the Brillouin zone, which displaces instantaneously the equilibrium positions of the atoms. It is precisely this generation of coherent phonons that makes the time-domain technique distinct from conventional frequency domain techniques, such as Raman and neutron scattering. Using a range of theoretical techniques, from nearly free electron models to state-of-the art ab initio calculations, I have made quantitative microscopic evaluations of the coherent phonon phenomenon. The studies focus on two unique aspects of having such coherent atomic vibrations in a narrow gap material, with special emphasis on the group V semimetals Sb and Bi. First of all, I have performed dynamical band structure calculations, as a function of the coherent atomic motion, in order to inspect the possibility of a transient metal-insulator transition at a terahertz frequency. Secondly, I have calculated the evolution of the displaced atoms in quasi-equilibrium with the laser -excited carriers, as the electron-ion coupled system returns to its ground state equilibrium. These calculations are fundamental, insofar they provide a quantitative microscopic description of the coherent phonon phenomenon. Moreover, the predicted magnitude of the atomic displacements, and the resulting

  17. Dynamic contrast optical coherence tomography: quantitative measurement of microvascular transit-time distributions in vivo (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Merkle, Conrad W.; Srinivasan, Vivek J.

    2016-03-01

    Transit time is a fundamental microcirculatory parameter that is critical in determining oxygen delivery from capillaries to surrounding tissue. Recently, it was demonstrated theoretically that capillary transit-time heterogeneity potentially leads to non-uniform oxygen extraction in micro-domains. However, in spite of its importance, capillary transit-time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of the kinetics of an intravascular tracer during its passage through the field-of-view. DyC-OCT is used to quantitatively measure the transit-time distribution in microvascular networks in cross-section at the single-capillary level. Transit-time metrics are derived from analysis of the temporal characteristics of the dynamic scattering signal, related to tracer concentration, using indicator-dilution theory. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against the dilution curves measured using a fluorescent plasma label in the surface pial vessels of a mouse brain, imaged through a thinned-skull, glass coverslip-reinforced cranial window, the laminar transit-time distribution was investigated in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with the earliest transit times in the middle cortical layers, and the lowest heterogeneity in cortical layer 4. The new DyC-OCT technique affords a novel perspective of microvascular networks, with the unique capability of performing simultaneous measurements of transit-time distributions across cortical laminae.

  18. Effect of MWCNTs on the electro-optic properties of 5CB LC cells during the Freedericksz Transition

    NASA Astrophysics Data System (ADS)

    Eakle, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    2014-03-01

    Multi-walled carbon nanotubes (MWCNTs) affect the electro-optic properties of liquid crystals, but the mechanisms of interaction between the two remain not well understood. To address this, we are investigating the effect of alternating electric fields on the optical properties and Freedericksz Transition of 5CB liquid crystal with different concentrations of MWCNTs. 5CB cells with ITO electrodes were made using spin-coated PVA for sample alignment and MylarTM spacer films to control the thickness, which ranged from 12 to 23 microns. Transmission optical ellipsometry was used to measure the optical retardance (phase delay) and uniaxial director angle of 5CB liquid crystals as the peak voltage of a high-frequency (1 kHz - 1 MHz) AC electric field was varied from 0 to 10 V. For constant frequency, the Freedericksz Transition was noted by a sharp decrease in retardance from an initial plateau, which gradually decreased toward zero as the voltage increased. With increasing frequency, the decay broadened and the Freedericksz Transition occurred at higher voltage. Numerical simulations of CNT-facilitated switching are also presented. Research was funded by the National Science Foundation, Polymers Program of the Division of Materials Research, through DMR-12061010.

  19. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    SciTech Connect

    Gong, W.; Peng, X. Li, W.; Guo, H.

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  20. Frequency stabilization of a 1083 nm fiber laser to 4He transition lines with optical heterodyne saturation spectroscopies

    NASA Astrophysics Data System (ADS)

    Gong, W.; Peng, X.; Li, W.; Guo, H.

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  1. Theoretical considerations on imaging of micron size electron beam with optical transition radiation

    NASA Astrophysics Data System (ADS)

    Xiang, Dao; Huang, Wen-Hui

    2007-01-01

    Optical transition radiation (OTR) has been widely used to image electron beam profile. In this paper, we systematically investigated the issues related to imaging of electron beam with OTR. It is found that the point-spread function (PSF) largely depends on the acceptance angle of the lens and is only very weakly dependent on beam energy and the distance from the OTR target to the lens. This excludes the potential obstacles to imaging of high-energy electron beam for which, the photons are emitted in a relatively small cone and the far field condition is hard to fulfill. The image of a whole beam is found by convoluting the real beam distribution with the PSF. It is shown that for micron size beam, the image formed with OTR largely deviates from the real beam distribution. And the real beam distribution could be restored from deconvoluting the image with the PSF. The effectiveness of the restoration is demonstrated, which opens up the possibility of measuring micron size beam profile with OTR.

  2. Characterization of Fast-Electron Beam Propagation Through Solid-Density Matter by Optical Transition Radiation

    NASA Astrophysics Data System (ADS)

    Storm, M.; Myatt, J.; Stoeckl, C.

    2006-10-01

    A diagnostic has been developed to measure the emission of optical transition radiation (OTR) produced by relativistic electrons emerging at the rear side of laser-illuminated targets. The device will be deployed in the newly completed multiterawatt (MTW) experimental facility at the University of Rochester's Laboratory for Laser Energetics. The MTW laser is capable of producing 10-J, 600-fs pulses of 1053-nm-wavelength radiation, which are focused using an f/2 off-axis parabolic mirror to intensities in excess of 10^19 Wcm-2. A 20x microscope objective with a resolution of better than 1 μm will image the OTR signal onto a CCD camera. A postprocessor to the particle-in-cell code LSP will be used to generate a simulated OTR signal from the calculated fast-electron distributions at the rear side of the target for comparison with experimental data. This talk will present the characteristics and capabilities of the OTR device along with the most recently acquired data. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460.

  3. Optical signatures of electric-field-driven magnetic phase transitions in graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Basak, Tista; Shukla, Alok

    2016-06-01

    Experimental challenges in identifying various types of magnetic ordering in graphene quantum dots (QDs) pose a major hurdle in the application of these nanostructures for spintronic devices. Based upon phase diagrams obtained by employing the π -electron Pariser-Parr-Pople (PPP) model Hamiltonian, we demonstrate that the magnetic states undergo phase transition under the influence of an external electric field. Our calculations of the electroabsorption spectra of these QDs indicate that the spectrum in question carries strong signatures of their magnetic state (FM vs AFM), thus suggesting the possibility of an all-optical characterization of their magnetic nature. Further, the gaps for the up and the down spins are the same in the absence of an external electric field, both for the antiferromagnetic (AFM) and the ferromagnetic (FM) states of QDs. But, once the QDs are exposed to a suitably directed external electric field, gaps for different spins split and exhibit distinct variations with respect to the strength of the field. The nature of variation exhibited by the energy gaps corresponding to the up and down spins is different for the AFM and FM configurations of QDs. This selective manipulation of the spin-polarized gap splitting by an electric field in finite graphene nanostructures can open up new frontiers in the design of graphene-based spintronic devices.

  4. Optical spectroscopy in turbid media utilizing an integrating sphere: mitochondrial chromophore analysis during metabolic transitions

    PubMed Central

    Chess, David J.; Billings, Eric; Covian, Raúl; Glancy, Brian; French, Stephanie; Taylor, Joni; de Bari, Heather; Murphy, Elizabeth; Balaban, Robert S.

    2013-01-01

    Recent evidence suggests that the activity of mitochondrial oxidative phosphorylation Complexes (MOPC) is modulated at multiple sites. Herein, a method of optically monitoring electron distribution within and between MOPC is described using a center-mounted sample in an integrating sphere (to minimize scattering effects) with a rapid-scanning spectrometer. The redox-sensitive MOPC absorbances (~465 to 630 nm) were modeled using linear least squares analysis with individual chromophore spectra. Classical mitochondrial activity transitions (e.g., ADP-induced increase in oxygen consumption) were used to characterize this approach. Most notable in these studies was the observation that intermediates of the catalytic cycle of cytochrome oxidase are dynamically modulated with metabolic state. The MOPC redox state, along with measurements of oxygen consumption and mitochondrial membrane potential, was used to evaluate the conductances of different sections of the electron transport chain. This analysis then was applied to mitochondria isolated from rabbit hearts subjected to ischemia-reperfusion (I/R). Surprisingly, I/R resulted in an inhibition of all measured MOPC conductances, suggesting a coordinated down-regulation of mitochondrial activity with this well-established cardiac perturbation. PMID:23665273

  5. Laser driven intraband optical transitions in two-dimensional quantum dots and quantum rings

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.; Kirakosyan, A. A.; Laroze, D.

    2017-01-01

    The intraband optical absorption have been investigated in the presence of hydrogenic donor impurity in GaAs/GaAlAs quantum dot and quantum ring in the intense laser field. The single electron energy spectrum and wave functions have been found using the effective mass approximation and exact diagonalization technique. Different selection rules are obtained for intraband transitions depending on the direction of incident light polarization. Due to the accidental degeneracy of the laser dressed impurity states the crossings of the curves of the threshold energies and the dipole matrix elements on laser field parameter have been observed. The intraband absorption coefficient is calculated for different locations of hydrogenic donor impurity and different values of intense laser field parameter. The obtained results show that the absorption spectrum can exhibit either a blue- or redshift depending on the impurity location, values of the laser field parameter and direction of incident light polarization. The obtained theoretical results indicate a novel opportunity to tune the performance of new devices, based on the quantum dots and quantum rings and to control their specific properties by means of intense laser and hydrogenic donor impurity.

  6. Ionic and Optical Properties of Methylammonium Lead Iodide Perovskite across the Tetragonal-Cubic Structural Phase Transition

    SciTech Connect

    Hoque, Md Nadim Ferdous; Islam, Nazifah; Li, Zhen; Ren, Guofeng; Zhu, Kai; Fan, Zhaoyang

    2016-09-01

    Practical hybrid perovskite solar cells (PSCs) must endure temperatures above the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI3). However, the ionic and optical properties of MAPbI3 in such a temperature range, and particularly, dramatic changes in these properties resulting from a structural phase transition, are not well studied. Herein, we report a striking contrast at approximately 45 degrees C in the ionic/electrical properties of MAPbl3 owing to a change of the ion activation energy from 0.7 to 0.5 eV, whereas the optical properties exhibit no particular transition except for the steady increase of the bandgap with temperature. These observations can be explained by the 'continuous' nature of perovskite phase transition. We speculate that the critical temperature at which the ionic/electrical properties change, although related to crystal symmetry variation, is not necessarily the same temperature as when tetragonal-cubic structural phase transition occurs.

  7. Interband optical transition energy and oscillator strength in a lead based CdSe quantum dot quantum well heterostructure

    SciTech Connect

    Saravanamoorthy, S. N.; Peter, A. John

    2015-06-24

    Binding energies of the exciton and the interband optical transition energies are studied in a CdSe/Pb{sub 1-x}Cd{sub x}Se/CdSe spherical quantum dot-quantum well nanostructure taking into account the geometrical confinement effect. The core and shell are taken as the same material. The initial and final states of energy and the overlap integrals of electron and hole wave functions are determined by the oscillator strength. The oscillator strength and the radiative transition life time with the dot radius are investigated for various Cd alloy content in the core and shell materials.

  8. Dynamical quantum phase transition of a two-component Bose-Einstein condensate in an optical lattice

    SciTech Connect

    Collin, Anssi; Martikainen, Jani-Petri; Larson, Jonas

    2010-01-15

    We study the dynamics of a two-component Bose-Einstein condensate where the two components are coupled via an optical lattice. In particular, we focus on the dynamics as one drives the system through a critical point of a first-order phase transition characterized by a jump in the internal populations. Solving the time-dependent Gross-Pitaevskii equation, we analyze the breakdown of adiabaticity, impact of nonlinear atom-atom scattering, and role of a harmonic trapping potential. Our findings demonstrate that the phase transition is resilient to both contact interaction between atoms and external trapping confinement.

  9. Sub-Doppler spectroscopy based on optical pumping and transit relaxation of atoms in a thin gas cell

    NASA Astrophysics Data System (ADS)

    Izmailov, Azad Ch.

    2007-06-01

    The paper is the review of methods, achievements, and possibilities of the recently elaborated and well tested high-resolution laser spectroscopy based on sub-Doppler absorption and polarization resonances (on centers of quantum transitions), which arise because of the optical pumping and specific transit relaxation of atoms (molecules) in a thin cell with a rarefied gas. Theoretical basis of this spectroscopy is presented. Experimental technique and results on the record of the sub-Doppler spectral structure of Cs and Rb atoms and on the frequency stabilization of diode lasers by given spectroscopy methods are discussed.

  10. Multiphonon scattering of light with direct transitions between optical modes in uniaxial single crystals and its application to an all-optical computing

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Tepichin Rodriguez, Eduardo; Aguirre Lopez, Arturo

    2004-11-01

    A specific case of a multi-phonon non-collinear light scattering in optically uniaxial media is presented. Compared to our previous studies, an innovation lies in the fact that now we consider passing just the quartet of incident light beams through a single crystal that is perturbed by the triplet of coherent acoustic waves. The exact and closed analytical model for describing this strongly nonlinear phenomenon is developed. In fact, specially designed regime of a four-order light scattering whit direct coupling of all the light modes, when transitions of four input light beams into four output light modes are allowed and electronically controlled, is examined. The feasibility of applying such an effect to an all-optical computing and performing an all-optical adder is analyzed.

  11. Identifying and discriminating phase transitions along decaying shocks with line imaging Doppler interferometric velocimetry and streaked optical pyrometry

    SciTech Connect

    Millot, Marius

    2016-01-15

    Ultrafast line-imaging velocity interferometer system for any reflector and streaked optical pyrometry are now commonly used to obtain high precision equation of state and electronic transport data under dynamic compression at major high energy density science facilities. We describe a simple way to improve distinguishing phase transformation signatures from other signals when monitoring decaying shock waves. The line-imaging capability of these optical diagnostics offers additional supporting evidence to the assignment of particular anomalies—such as plateaus or reversals—to the occurrence of a phase transition along the Hugoniot. We illustrate the discussion with two example datasets collected during laser driven shock compression of quartz and stishovite.

  12. Dynamic contrast optical coherence tomography images transit time and quantifies microvascular plasma volume and flow in the retina and choriocapillaris

    PubMed Central

    Merkle, Conrad W.; Leahy, Conor; Srinivasan, Vivek J.

    2016-01-01

    Despite the prevalence of optical imaging techniques to measure hemodynamics in large retinal vessels, quantitative measurements of retinal capillary and choroidal hemodynamics have traditionally been challenging. Here, a new imaging technique called dynamic contrast optical coherence tomography (DyC-OCT) is applied in the rat eye to study microvascular blood flow in individual retinal and choroidal layers in vivo. DyC-OCT is based on imaging the transit of an intravascular tracer dynamically as it passes through the field-of-view. Hemodynamic parameters can be determined through quantitative analysis of tracer kinetics. In addition to enabling depth-resolved transit time, volume, and flow measurements, the injected tracer also enhances OCT angiograms and enables clear visualization of the choriocapillaris, particularly when combined with a post-processing method for vessel enhancement. DyC-OCT complements conventional OCT angiography through quantification of tracer dynamics, similar to fluorescence angiography, but with the important added benefit of laminar resolution. PMID:27867732

  13. Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

    NASA Astrophysics Data System (ADS)

    Mlyuka, N. R.; Niklasson, G. A.; Granqvist, C. G.

    2009-10-01

    Thermochromic films of MgxV1-xO2 were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by ˜3 K/at. %Mg, while the optical transmittance increased concomitantly. Specifically, the transmittance of visible light and of solar radiation was enhanced by ˜10% when the Mg content was ˜7 at. %. Our results point at the usefulness of these films for energy efficient fenestration.

  14. Bio-optical profile data report coastal transition zone program, R/V Thomas Washington, June 24 - July 21, 1988

    NASA Technical Reports Server (NTRS)

    Davis, Curtiss O.; Rhea, W. Joseph

    1990-01-01

    Twenty-three vertical profiles of the bio-optical properties of the ocean were made during a research cruise on the R/V Thomas Washington, June 24 to July 21, 1988, as part of the Coastal Transition Zone Program off Point Arena, California. A summary is given, to provide investigators with an overview of the data collected. The entire data set is available in digital form for interested researchers.

  15. Bio-optical profile data report coastal transition zone program, R/V Point Sur, June 15-28, 1987

    NASA Technical Reports Server (NTRS)

    Davis, Curtiss O.; Rhea, W. Joseph

    1990-01-01

    Twenty vertical profiles of the bio-optical properties of the ocean were made during a research cruise on the R/V Point Sur, June 15 to 28, 1987, as part of the Coastal Transition Zone Program off Point Arena, California. Extracted chlorophyll values were also measured at some stations to provide calibration data for the in situ fluorometer. This summary provides investigators with an overview of the data collected. The entire data set is available in digital form.

  16. On the size-dependent magnetism and all-optical magnetization switching of transition-metal silicide nanostructures

    SciTech Connect

    Glushkov, G. I.; Tuchin, A. V.; Popov, S. V.; Bityutskaya, L. A.

    2015-12-15

    Theoretical investigations of the electronic structure, synthesis, and all-optical magnetization switching of transition-metal silicide nanostructures are reported. The magnetic moment of the nanostructures is studied as a function of the silicide cluster size and configuration. The experimentally demonstrated magnetization switching of nanostructured nickel silicide by circularly polarized light makes it possible to create high-speed storage devices with high density data recording.

  17. Thermophysical, Electrical, and Optical Properties of Selected Metal-Nonmetal Transition Materials: Comprehensive Bibliography with Typical Data.

    DTIC Science & Technology

    1978-02-01

    ELECTRICAL, AND OPTICAL PROPERTIES OF SELECTED METAL-NONMETAL TRANSITION MATERIALS Comprehensive Bibliography with Typical Data Y. S. TOULOUKIAN , C. Y. HO, and...volume entitled "Thermo-Iphysical Properties of Selected Aerospace Materials. Part II: Thermophysical Properties of Seven Materials." Y. S. TOULOUKIAN ...Kolomoets, N.V., and Ovechkina, V.N., "Preparation and Study of the Properties of Samarium(II) Sulfide-Based Alloys ," Izv. Akad. Nauk SSSR, Neorg

  18. Changes in adsorption and optical properties of liquid crystal langmuir films at structural phase transition

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. B.; Levshin, N. L.; Khlybov, S. V.; Yudin, S. G.

    2012-12-01

    The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

  19. Optical transitions in semiconductor nanospherical core/shell/shell heterostructure in the presence of radial electrostatic field

    NASA Astrophysics Data System (ADS)

    Baghdasaryan, D. A.; Hayrapetyan, D. B.; Harutyunyan, V. A.

    2017-04-01

    The electronic states and optical properties of spherical nanolayer in the presence of the electrostatic radial field in the strong size quantization regime have been considered. Both analytical and numerical methods have been applied to the problem of one-electron states in the system. According to the intensity of the external electrostatic field, three regimes have been distinguished: week, intermediate and strong. Perturbative approach have been applied to the case of week, WKB to the case of intermediate and variation approach to the case of strong field intensities. The analytical dependencies of the one electron energy and wave function on the electric field value and geometrical parameters of the nanolayer have been achieved. The comparison of the results obtained by the analytical method with the results of the numerical method have been made. The interband and intraband optical transitions caused by incident optical light polarized in z direction have been considered in this system. The selection rules for this transitions have been obtained. The dependence of the absorption coefficient on the energy of incident light for both cases of interband and intraband transitions for every regime of the electrostatic field value have been received.

  20. Structural phase transition in IrTe2: A combined study of optical spectroscopy and band structure calculations

    PubMed Central

    Fang, A. F.; Xu, G.; Dong, T.; Zheng, P.; Wang, N. L.

    2013-01-01

    Ir1−xPtxTe2 is an interesting system showing competing phenomenon between structural instability and superconductivity. Due to the large atomic numbers of Ir and Te, the spin-orbital coupling is expected to be strong in the system which may lead to nonconventional superconductivity. We grew single crystal samples of this system and investigated their electronic properties. In particular, we performed optical spectroscopic measurements, in combination with density function calculations, on the undoped compound IrTe2 in an effort to elucidate the origin of the structural phase transition at 280 K. The measurement revealed a dramatic reconstruction of band structure and a significant reduction of conducting carriers below the phase transition. We elaborate that the transition is not driven by the density wave type instability but caused by the crystal field effect which further splits/separates the energy levels of Te (px, py) and Te pz bands. PMID:23362455

  1. Optical-lattice-assisted magnetic phase transition in a spin-orbit-coupled Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Martone, Giovanni I.; Ozawa, Tomoki; Qu, Chunlei; Stringari, Sandro

    2016-10-01

    We investigate the effect of a periodic potential generated by a one-dimensional optical lattice on the magnetic properties of an S =1 /2 spin-orbit-coupled Bose gas. By increasing the lattice strength one can achieve a magnetic phase transition between a polarized and an unpolarized Bloch wave phase, characterized by a significant enhancement of the contrast of the density fringes. If the wave vector of the periodic potential is chosen close to the roton momentum, the transition could take place at very small lattice intensities, revealing the strong enhancement of the response of the system to a weak density perturbation. By solving the Gross-Pitaevskii equation in the presence of a three-dimensional trapping potential, we shed light on the possibility of observing the magnetic phase transition in currently available experimental conditions.

  2. Optical conductivity of visons in Z2 spin liquids close to a valence bond solid transition on the kagome lattice

    NASA Astrophysics Data System (ADS)

    Huh, Yejin; Punk, Matthias; Sachdev, Subir

    2013-06-01

    We consider Z2 spin liquids on the kagome lattice on the verge of a valence bond solid (VBS) transition, where vortex excitations carrying Z2 magnetic flux—so-called visons—condense. We show that these vison excitations can couple directly to the external electromagnetic field, even though they carry neither spin nor charge. This is possible via a magnetoelastic coupling mechanism recently identified. [Potter, Senthil, and Lee, arXiv:1301.3495; Hao, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.174432 85, 174432 (2012)] For the case of transitions to a 36-site unit cell VBS state, the corresponding finite ac conductivity has a specific power-law frequency dependence, which is related to the crossover exponent of the quantum critical point. The visons’ contribution to the optical conductivity at transitions to VBS states with a 12-site unit cell vanishes, however.

  3. Performance of horn-coupled transition edge sensors for L- and S-band optical detection on the SAFARI instrument

    NASA Astrophysics Data System (ADS)

    Goldie, D. J.; Glowacka, D. M.; Withington, S.; Chen, Jiajun; Ade, P. A. R.; Morozov, D.; Sudiwala, R.; Trappe, N. A.; Quaranta, O.

    2016-07-01

    We describe the geometry, architecture, dark- and optical performance of ultra-low-noise transition edge sensors as THz detectors for the SAFARI instrument. The TESs are fabricated from superconducting Mo/Au bilayers coupled to impedance-matched superconducting β-phase Ta thin-film absorbers. The detectors have phonon-limited dark noise equivalent powers of order 0.5 - 1.0 aW/ √ Hz and saturation powers of order 20 - 40 fW. The low temperature test configuration incorporating micro-machined backshorts is also described, and construction and typical performance characteristics for the optical load are shown. We report preliminary measurements of the optical performance of these TESs for two SAFARI bands; L-band at 110 - 210 μm and S-band 34 - 60 μm .

  4. Variation of optical conductivity spectra in the course of bandwidth-controlled metal-insulator transitions in pyrochlore iridates

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Fujioka, J.; Tokura, Y.

    2016-06-01

    We spectroscopically investigate a series of pyrochlore iridates R2Ir2O7 (R : rare-earth and Y ions) where the metal-insulator transitions are induced by systematic bandwidth control via chemical substitutions of R ions. We establish the phase diagram of R2Ir2O7 , as endorsed by the variation of the optical conductivity spectra, in which the competing phases including paramagnetic insulator (PI), paramagnetic metal (PM), and antiferromagnetic insulator (AFI) show up as a function of bandwidth and temperature. For small R -ionic radius (R = Y-Sm), i.e., strongly correlated region, pronounced peaks on the edge of the optical gap are discerned below the magnetic transition temperature TN, which is attributable to exciton and magnon sideband absorptions. It turns out that the estimated nearest-neighbor exchange interaction increases as R -ionic radius increases, whereas TN monotonically decreases, indicating that the all-in all-out magnetic order arises from the interplay among several exchange interactions inherent to extended 5 d orbitals on the frustrated lattice. For larger R -ionic radius (R = Sm-Pr), i.e., relatively weakly correlated region, the optical conductivity spectra markedly change below 0.3 eV in the course of PM-AFI transition, implying that the magnetic order induces the insulating state. In particular, we have found distinct electrodynamics in the composition of R =Nd0.5Pr0.5 which is located on the boundary of the quantum PM-AFI transition, pointing to the possible emergence of unconventional topological electronic phases related possibly to the correlated Weyl electrons.

  5. Steady-state linear optical properties and Kerr nonlinear optical response of a four-level quantum dot with phonon-assisted transition

    NASA Astrophysics Data System (ADS)

    Yan-Chao, She; Ting-Ting, Luo; Wei-Xi, Zhang; Mao-Wu, Ran; Deng-Long, Wang

    2016-01-01

    The linear optical properties and Kerr nonlinear optical response in a four-level loop configuration GaAs/AlGaAs semiconductor quantum dot are analytically studied with the phonon-assisted transition (PAT). It is shown that the changes among a single electromagnetically induced transparency (EIT) window, a double EIT window and the amplification of the probe field in the absorption curves can be controlled by varying the strength of PAT κ. Meanwhile, double switching from the anomalous dispersion regime to the normal dispersion regime can likely be achieved by increasing the Rabi energy of the external optical control field. Furthermore, we demonstrate that the group velocity of the probe field can be practically regulated by varying the PAT and the intensity of the optical control field. In the nonlinear case, it is shown that the large SPM and XPM can be achieved as linear absorption vanishes simultaneously, and the PAT can suppress both third-order self-Kerr and the cross-Kerr nonlinear effect of the QD. Our study is much more practical than its atomic counterpart due to its flexible design and the controllable interference strength, and may provide some new possibilities for technological applications. Project supported by the National Natural Science Foundation of China (Grant No. 61367003), the Scientific Research Fund of Hunan Provincial Education Department, China (Grant No. 12A140), and the Scientific Research Fund of Guizhou Provincial Education Department, China (Grant Nos. KY[2015]384 and KY[2015]446).

  6. Ultra-narrow linewidth optical filter based on Faraday effect at isotope 87Rb 420 nm transitions

    NASA Astrophysics Data System (ADS)

    Bi, Gang; Kang, Jia; Fu, Jun; Ling, Li; Chen, Jingbiao

    2016-12-01

    An ultra-narrow linewidth optical filter with isotope 87Rb vapor at 420 nm, within the best waveband 400-500 nm for deep sea communication is achieved for the first time. The Faraday effect, circular dichroism, and nonlinear saturation techniques are utilized to narrow the bandwidth from previous 2.5 GHz to about 15 MHz level on the energy transition 5S1/2 → 6P3/2. By changing the temperature and magnetic field, the maximum transmission is obtained when the temperature and the magnetic field of the 87Rb cell are at 100 °C and 12 G. We discuss the varying influences of temperature, magnetic field, and pump power on the transmission of the atomic filter. The maximum single peak transmission at 5S1/2, F = 2 → 6P3/2, F‧ = 3 transition is 2.1% with a bandwidth of 17.8 MHz, and 1.9% at the 5S1/2, F = 2 → 6P3/2, F‧ = 2 , 3 (cross-over) transition with that of 14.2 MHz. The calculated equivalent noise bandwidth of this system is 32.5 MHz. Compared with the conventional Faraday anomalous dispersion optical filter, the bandwidth of our system is narrowed at least two orders of magnitude and is closer to the natural linewidth. This ultra-narrow linewidth filter has the potential to be applied to submarine communication or the pump laser in a four-level Rb-based active optical clock.

  7. Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

    PubMed Central

    Torriss, B.; Margot, J.; Chaker, M.

    2017-01-01

    Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing. PMID:28098240

  8. Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

    NASA Astrophysics Data System (ADS)

    Torriss, B.; Margot, J.; Chaker, M.

    2017-01-01

    Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing.

  9. Multicriticality and interaction-induced first-order phase transitions in mixtures of ultracold bosons in an optical lattice

    NASA Astrophysics Data System (ADS)

    Anufriiev, S.; Zaleski, T. A.

    2016-10-01

    We study a critical behavior of mixtures of two species of ultracold bosons trapped in an optical lattice. Using mean-field approximation, we determine the ground-state phase diagram of the system for a wide range of parameters. The introduction of interactions between different species of atoms strongly renormalizes the phase diagram. It can alter the critical behavior modifying multicriticality of crossing points and order of phase transitions in their vicinity between mixed and superfluid states. For selected values of model parameters, the behavior of the system falls out of the X Y model universality class, which usually is a hallmark of superfluid phase transition. We supplement our analysis with analytical calculations to explain the observed scenario.

  10. Molecular Dynamics at Electrical- and Optical-Driven Phase Transitions: Time-Resolved Infrared Studies Using Fourier-Transform Spectrometers

    NASA Astrophysics Data System (ADS)

    Peterseim, Tobias; Dressel, Martin

    2017-01-01

    The time-dependent optical properties of molecular systems are investigated by step-scan Fourier-transform spectroscopy in order to explore the dynamics at phase transitions and molecular orientation in the milli- and microsecond range. The electrical switching of liquid crystals traced by vibrational spectroscopy reveals a rotation of the molecules with a relaxation time of 2 ms. The photo-induced neutral-ionic transition in TTF-CA takes place by a suppression of the dimerization in the ionic phase and creation of neutral domains. The time-dependent infrared spectra, employed to investigate the domain-wall dynamics, depend on temperature and laser pulse intensity; the relaxation of the spectra follows a stretched-exponential decay with relaxation times in the microsecond range strongly dependent on temperature and laser intensity. We present all details of the experimental setups and thoroughly discuss the technical challenges.

  11. Anisotropy of optical transitions in ordered ensemble of CdSe quantum rods.

    PubMed

    Mukhina, Maria V; Maslov, Vladimir G; Baranov, Alexander V; Artemyev, Mikhail V; Orlova, Anna O; Fedorov, Anatoly V

    2013-09-01

    We report on the observation of spectral dependence of absorption anisotropy in a CdSe quantum rod (QR) ensemble, which is aligned in a polymer film with a nanocrystal concentration of 2×10(-5) M. The experimental data on the polarization direction and anisotropy factor were obtained for the lowest excitonic transition and the second group of transitions in the QR. The nonzero constant value of anisotropy was investigated for the high-energy transitions, and is evidence of the one-dimensional confinement in the QR.

  12. Transition from two-dimensional photonic crystals to dielectric metasurfaces in the optical diffraction with a fine structure

    PubMed Central

    Rybin, Mikhail V.; Samusev, Kirill B.; Lukashenko, Stanislav Yu.; Kivshar, Yuri S.; Limonov, Mikhail F.

    2016-01-01

    We study experimentally a fine structure of the optical Laue diffraction from two-dimensional periodic photonic lattices. The periodic photonic lattices with the C4v square symmetry, orthogonal C2v symmetry, and hexagonal C6v symmetry are composed of submicron dielectric elements fabricated by the direct laser writing technique. We observe surprisingly strong optical diffraction from a finite number of elements that provides an excellent tool to determine not only the symmetry but also exact number of particles in the finite-length structure and the sample shape. Using different samples with orthogonal C2v symmetry and varying the lattice spacing, we observe experimentally a transition between the regime of multi-order diffraction, being typical for photonic crystals to the regime where only the zero-order diffraction can be observed, being is a clear fingerprint of dielectric metasurfaces characterized by effective parameters. PMID:27491952

  13. Investigation of optical transitions in InAs/GaAs(Sb)/AlAsSb quantum dots using modulation spectroscopy

    SciTech Connect

    Bittner, Zachary S. Hellstroem, Staffan; Polly, Stephen J.; Hubbard, Seth M.; Laghumavarapu, Ramesh B.; Liang, Baolai; Huffaker, Diana L.

    2014-12-22

    InAs quantum dots (QDs) were grown in an AlAs{sub 0.56}Sb{sub 0.44}/GaAs matrix in the unintentionally doped (uid) region of an In{sub 0.52}Al{sub 0.48}As solar cell, establishing a variety of optical transitions both into and out of the QDs. The ultimate goal is to demonstrate sequential absorption, where one photon is absorbed, promoting an electron from the valence band into the QD, and a second photon is absorbed in order to promote the trapped electron from a QD state into the host conduction band. In this study, we directly investigate the optical properties of the solar cell using photoreflectance and evaluate the possibility of sequential absorption by measuring spectral responsivity with broadband infrared illumination.

  14. Transition from two-dimensional photonic crystals to dielectric metasurfaces in the optical diffraction with a fine structure

    NASA Astrophysics Data System (ADS)

    Rybin, Mikhail V.; Samusev, Kirill B.; Lukashenko, Stanislav Yu.; Kivshar, Yuri S.; Limonov, Mikhail F.

    2016-08-01

    We study experimentally a fine structure of the optical Laue diffraction from two-dimensional periodic photonic lattices. The periodic photonic lattices with the C4v square symmetry, orthogonal C2v symmetry, and hexagonal C6v symmetry are composed of submicron dielectric elements fabricated by the direct laser writing technique. We observe surprisingly strong optical diffraction from a finite number of elements that provides an excellent tool to determine not only the symmetry but also exact number of particles in the finite-length structure and the sample shape. Using different samples with orthogonal C2v symmetry and varying the lattice spacing, we observe experimentally a transition between the regime of multi-order diffraction, being typical for photonic crystals to the regime where only the zero-order diffraction can be observed, being is a clear fingerprint of dielectric metasurfaces characterized by effective parameters.

  15. Electron and lattice dynamics of transition metal thin films observed by ultrafast electron diffraction and transient optical measurements

    PubMed Central

    Nakamura, A.; Shimojima, T.; Nakano, M.; Iwasa, Y.; Ishizaka, K.

    2016-01-01

    We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant (g) and the electron and lattice temperatures (Te, Tl) are evaluated from UED, with which we simulate the transient optical transmittance. The simulation well agrees with the experimentally obtained transmittance data, except for the slight deviations at the initial photoexcitation and the relaxed quasi-equilibrium state. We also present the results similarly obtained for polycrystalline Au, Cu, and Mo thin films and demonstrate the electron and lattice dynamics occurring in metals with different electron-phonon coupling strengths. PMID:28004010

  16. Ultra-thin and flexible endoscopy probe for optical coherence tomography based on stepwise transitional core fiber.

    PubMed

    Lee, Jangbeom; Chae, Yugyeong; Ahn, Yeh-Chan; Moon, Sucbei

    2015-05-01

    We present an ultra-thin fiber-body endoscopy probe for optical coherence tomography (OCT) which is based on a stepwise transitional core (STC) fiber. In a minimalistic design, our probe was made of spliced specialty fibers that could be directly used for beam probing optics without using a lens. In our probe, the OCT light delivered through a single-mode fiber was efficiently expanded to a large mode field of 24 μm diameter for a low beam divergence. The size of our probe was 85 μm in the probe's diameter while operated in a 160-μm thick protective tubing. Through theoretical and experimental analyses, our probe was found to exhibit various attractive features in terms of compactness, flexibility and reliability along with its excellent fabrication simplicity.

  17. Absolute frequency measurement of the 674-nm {sup 88}Sr{sup +} clock transition using a femtosecond optical frequency comb

    SciTech Connect

    Margolis, H.S.; Huang, G.; Barwood, G.P.; Lea, S.N.; Klein, H.A.; Rowley, W.R.C.; Gill, P.; Windeler, R.S.

    2003-03-01

    The frequency of the 5s {sup 2}S{sub 1/2}-4d {sup 2}D{sub 5/2} electric quadrupole transition at 674 nm in a single, trapped, laser-cooled {sup 88}Sr{sup +} ion has been measured with respect to the Systeme International (SI) second using a femtosecond laser optical frequency comb. The measured frequency of 444 779 044 095.52 kHz, with an estimated standard uncertainty of 0.10 kHz, is more accurate than, and in agreement with, the value previously measured using a conventional frequency chain.

  18. Multimode mean-field model for the quantum phase transition of a Bose-Einstein condensate in an optical resonator

    NASA Astrophysics Data System (ADS)

    Kónya, G.; Szirmai, G.; Domokos, P.

    2011-11-01

    We develop a mean-field model describing the Hamiltonian interaction of ultracold atoms and the optical field in a cavity. The Bose-Einstein condensate is properly defined by means of a grand-canonical approach. The model is efficient because only the relevant excitation modes are taken into account. However, the model goes beyond the two-mode subspace necessary to describe the self-organization quantum phase transition observed recently. We calculate all the second-order correlations of the coupled atom field and radiation field hybrid bosonic system, including the entanglement between the two types of fields.

  19. Time-domain separation of optical properties from structural transitions in resonantly bonded materials.

    PubMed

    Waldecker, Lutz; Miller, Timothy A; Rudé, Miquel; Bertoni, Roman; Osmond, Johann; Pruneri, Valerio; Simpson, Robert E; Ernstorfer, Ralph; Wall, Simon

    2015-10-01

    The extreme electro-optical contrast between crystalline and amorphous states in phase-change materials is routinely exploited in optical data storage and future applications include universal memories, flexible displays, reconfigurable optical circuits, and logic devices. Optical contrast is believed to arise owing to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase-change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 fs owing to a rapid depletion of electrons from resonantly bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2-ps time constant. The optical changes are an order of magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes.

  20. Correcting artifacts in transition to a wound optic fiber: Example from high-resolution temperature profiling in the Dead Sea

    NASA Astrophysics Data System (ADS)

    Arnon, Ali; Selker, John; Lensky, Nadav

    2014-06-01

    Spatial resolution fiber-optic cables allow for detailed observation of thermally complex heterogeneous hydrologic systems. A commercially produced high spatial resolution helically wound optic fiber sensing cable is employed in the Dead Sea, in order to study the dynamics of thermal stratification of the hypersaline lake. Structured spatial artifacts were found in the data from the first 10 m of cable (110 m of fiber length) following the transition from straight fiber optic. The Stokes and Anti-Stokes signals indicate that this is the result of differential attenuation, thought to be due to cladding losses. Though the overall spatial form of the loss was consistent, the fine structure of the loss changed significantly in time, and was strongly asymmetrical, and thus was not amenable to standard calibration methods. Employing the fact that the cable was built with a duplex construction, and using high-precision sensors mounted along the cable, it was possible to correct the artifact in space and time, while retaining the high-quality of data obtained in the early part of the cable (prior to significant optical attenuation). The defect could easily be overlooked; however, reanalyzing earlier experiments, we have observed the same issue with installations employing similar cables in Oregon and France, so with this note we both alert the community to this persistent concern and provide an approach to correct the data in case of similar problems.

  1. Quantum and thermal phase transitions in a bosonic atom-molecule mixture in a two-dimensional optical lattice

    NASA Astrophysics Data System (ADS)

    de Forges de Parny, L.; Rousseau, V. G.

    2017-01-01

    We study the ground state and the thermal phase diagram of a two-species Bose-Hubbard model, with U(1 ) ×Z2 symmetry, describing atoms and molecules on a two-dimensional optical lattice interacting via a Feshbach resonance. Using quantum Monte Carlo simulations and mean-field theory, we show that the conversion between the two species, coherently coupling the atomic and molecular states, has a crucial impact on the Mott-superfluid transition and stabilizes an insulating phase with a gap controlled by the conversion term—the Feshbach insulator—instead of a standard Mott-insulating phase. Depending on the detuning between atoms and molecules, this model exhibits three phases: the Feshbach insulator, a molecular condensate coexisting with noncondensed atoms, and a mixed atomic-molecular condensate. Employing finite-size scaling analysis, we observe three-dimensional (3D) X Y (3D Ising) transition when U(1 ) (Z2) symmetry is broken, whereas the transition is first order when both U(1 ) and Z2 symmetries are spontaneously broken. The finite-temperature phase diagram is also discussed. The thermal disappearance of the molecular superfluid leads to a Berezinskii-Kosterlitz-Thouless transition with unusual universal jump in the superfluid density. The loss of the quasi-long-range coherence of the mixed atomic and molecular superfluid is more subtle since only atoms exhibit conventional Berezinskii-Kosterlitz-Thouless criticality. We also observe a signal compatible with a classical first-order transition between the mixed superfluid and the normal Bose liquid at low temperature.

  2. Optical transitions and frequency upconversion emission of Er 3+ions in novel lead-bismuthate glass

    NASA Astrophysics Data System (ADS)

    Sun, Hongtao; Dai, Shixun; Zhang, Debao; Xu, Shiqing; Zhang, Junjie; Hu, Lili; Jiang, Zhonghong

    2004-12-01

    Er 3+-doped strontiam lead bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd-Ofelt analysis was performed on the absorption spectrum and the transition probabilities, excited state lifetimes, and the fluorescence branching ratios were calculated and discussed. Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H→4I, 4S→4I, and 4F→4I, respectively, were observed. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for the green and red emissions.

  3. Optical properties of TiN thin films close to the superconductor-insulator transition.

    SciTech Connect

    Pfuner, F.; Degiorgi, L.; Baturina, T. I.; Vinokur, V. M.; Baklanov, M. R.; Materials Science Division; ETH Zurich; Inst. Semiconductor Physics; IMEC Kapeldreef

    2009-11-10

    We present the intrinsic optical properties over a broad spectral range of TiN thin films deposited on an Si/SiO{sub 2} substrate. We analyze the measured reflectivity spectra of the film-substrate multilayer structure within a well-establish procedure based on the Fresnel equation and extract the real part of the optical conductivity of TiN. We identify the metallic contribution as well as the finite energy excitations and disentangle the spectral weight distribution among them. The absorption spectrum of TiN bears some similarities with the electrodynamic response observed in the normal state of the high-temperature superconductors. Particularly, a mid-infrared feature in the optical conductivity is quite reminiscent of a pseudogap-like excitation.

  4. Giant magneto-optical Raman effect in a layered transition metal compound

    PubMed Central

    Ji, Jianting; Zhang, Anmin; Fan, Jiahe; Li, Yuesheng; Wang, Xiaoqun; Zhang, Jiandi; Plummer, E. W.; Zhang, Qingming

    2016-01-01

    We report a dramatic change in the intensity of a Raman mode with applied magnetic field, displaying a gigantic magneto-optical effect. Using the nonmagnetic layered material MoS2 as a prototype system, we demonstrate that the application of a magnetic field perpendicular to the layers produces a dramatic change in intensity for the out-of-plane vibrations of S atoms, but no change for the in-plane breathing mode. The distinct intensity variation between these two modes results from the effect of field-induced broken symmetry on Raman scattering cross-section. A quantitative analysis on the field-dependent integrated Raman intensity provides a unique method to precisely determine optical mobility. Our analysis is symmetry-based and material-independent, and thus the observations should be general and inspire a new branch of inelastic light scattering and magneto-optical applications. PMID:26884198

  5. ZnO:Mo:In nanofilms on SiO2 substrate under investigation framework of the second optical transition

    NASA Astrophysics Data System (ADS)

    Souissi, A.; Amlouk, M.; Guermazi, S.

    2017-02-01

    ZnO and ZnO:Mo:In nanofilms were deposited on SiO2 substrate at 460 °C by the spray pyrolysis method with the molar ratio (Mo/Zn) set at 1% and (In/Zn) dosed at 1%, 2%, 3% and 10%. The optical, dielectric and photonic characteristics of these samples were analyzed from the optical spectra of transmission and reflection, which revealed the presence of two absorption edges. The first one was related to the ZnO:Mo:In typical transition and the second edge originated from the ZnO:Mo:In/SiO2 interface transition by the probable formation of an ultrafine layer identified as SiOx and/or ZnO(1-x)SiO2(x). The optical gap and Urbach energies of ZnO:Mo:In nanofilms varied almost uniformly and in a complementary manner depending on the co-doping of ∼3.28-3.24 eV and ∼82-136 meV. These energies associated with the interface varied randomly from 3.93 to 4.18 eV and ∼263 to 408 meV, and showed strong dependencies with the structural, crystalline and vibrational properties previously studied. They also displayed possible correlations with electron scattering time and the dc photoconductivity which reaches high value for film prepared using In = 2%. AFM study showed variable morphologies of the surfaces that are responsive to codoping elements, therefore at the interface, wherein the film growth began. All these factors influenced the results described above. The study also showed good agreement between rms roughness and TC texture coefficient of the studied films, of high transparency ∼89-92%. The films prepared with In = 2% revealed a high photoconductivity and could be used in photocatalytic and photonic applications.

  6. LINKING Lyα AND LOW-IONIZATION TRANSITIONS AT LOW OPTICAL DEPTH

    SciTech Connect

    Jaskot, A. E.; Oey, M. S.

    2014-08-20

    We suggest that low optical depth in the Lyman continuum (LyC) may relate the Lyα emission, C II and Si II absorption, and C II* and Si II* emission seen in high-redshift galaxies. We base this analysis on Hubble Space Telescope Cosmic Origins Spectrograph spectra of four Green Pea (GP) galaxies, which may be analogs of z > 2 Lyα emitters (LAEs). In the two GPs with the strongest Lyα emission, the Lyα line profiles show reduced signs of resonant scattering. Instead, the Lyα profiles resemble the Hα line profiles of evolved star ejecta, suggesting that the Lyα emission originates from a low column density and similar outflow geometry. The weak C II absorption and presence of non-resonant C II* emission in these GPs support this interpretation and imply a low LyC optical depth along the line of sight. In two additional GPs, weak Lyα emission and strong C II absorption suggest a higher optical depth. These two GPs differ in their Lyα profile shapes and C II* emission strengths, however, indicating different inclinations of the outflows to our line of sight. With these four GPs as examples, we explain the observed trends linking Lyα, C II, and C II* in stacked LAE spectra, in the context of optical depth and geometric effects. Specifically, in some galaxies with strong Lyα emission, a low LyC optical depth may allow Lyα to escape with reduced scattering. Furthermore, C II absorption, C II* emission, and Lyα profile shape can reveal the optical depth, constrain the orientation of neutral outflows in LAEs, and identify candidate LyC emitters.

  7. Optically allowed transitions among Fe IV levels belonging to lowest three configurations

    NASA Astrophysics Data System (ADS)

    Deb, Narayan C.; Hibbert, Alan

    2008-05-01

    Oscillator strengths and transition rates for the dipole allowed transitions among 3d^5, 3d^44s and 3d^44p levels of Fe IV are calculated with the CIV3 program of Hibbert [1]. Using Hartree-Fock functions up to 3d orbitals we have optimised 4s, 4p, 4d, 4f, 5s, 5p and 5d orbitals of which 4s and 4p are taken to be the spectroscopic and the remaining orbitals representing corrections to the spectroscopic orbitals or the correlation effects. The J-dependent levels of all 108 LS states are included in the calculation and relativistic effects are accounted for via the Breit-Pauli operator. Configurations are chosen in two steps: (a) two promotions were allowed from the 3p, 3d and 4l subshells, using all the above orbitals; (b) selective promotions from the 3s subshell are included, but only to the 3d, 4s and 4p orbitals. The ab initio fine-structure levels were then fine-tuned to reproduce the observed energy levels as closely as possible, and the wavefunctions used to calculate oscillator strengths for all possible E1 transitions. For many of these transitions, the present results show agreement between length and velocity forms to within 5%.[1] A.Hibbert, Comput. Phys. Commun. 9 (1975) 141

  8. Atomic loss and gain as a resource for nonequilibrium phase transitions in optical lattices

    NASA Astrophysics Data System (ADS)

    Everest, B.; Marcuzzi, M.; Lesanovsky, I.

    2016-02-01

    Recent breakthroughs in the experimental manipulation of strongly interacting atomic Rydberg gases in lattice potentials have opened an avenue for the study of many-body phenomena. Considerable efforts are currently being undertaken to achieve clean experimental settings that show a minimal amount of noise and disorder and are close to zero temperature. A complementary direction investigates the interplay between coherent and dissipative processes. Recent experiments have revealed a glimpse into the emergence of a rich nonequilibrium behavior stemming from the competition of laser excitation, strong interactions, and radiative decay of Rydberg atoms. The aim of the present theoretical work is to show that local incoherent loss and gain of atoms can in fact be the source of interesting out-of-equilibrium dynamics. This perspective opens up paths for the exploration of nonequilibrium critical phenomena and, more generally, phase transitions, some of which so far have been rather difficult to study. To demonstrate the richness of the encountered dynamical behavior we consider here three examples. The first two feature local atom loss and gain together with an incoherent excitation of Rydberg states. In this setting either a continuous or a discontinuous phase transition emerges with the former being reminiscent of genuine nonequilibrium transitions of stochastic processes with multiple absorbing states. The third example considers the regime of coherent laser excitation. Here the many-body dynamics is dominated by an equilibrium transition of the "model A" universality class.

  9. The second- and third- order nonlinear optical properties and electronic transition of a NLO chromophore: A DFT study

    NASA Astrophysics Data System (ADS)

    Altürk, Sümeyye; Avci, Davut; Tamer, Ömer; Atalay, Yusuf

    2016-03-01

    It is well known that the practical applications of second-order and third-order nonlinear optical (NLO) materials have been reported in modern technology, such as optical data processing, transmission and storage, etc. In this respect, the linear and nonlinear optical parameters (the molecular static polarizability (α), and the first-order static hyperpolarizability (β0), the second-order static hyperpolarizability (γ)), UV-vis spectra and HOMO and LUMO energies of 2-(1'-(4'''-Methoxyphenyl)-5'-(thien-2″-yl)pyrrol-2'-yl)-1,3-benzothiazole were investigated by using the HSEh1PBE/6-311G(d,p) level of density functional theory. The UV-vis spectra were simulated using TD/HSEh1PBE/6- 311G(d,p) level, and the major contributions to the electronic transitions were obtained. The molecular hardness (η) and electronegativity (χ) parameters were also obtained by using molecular frontier orbital energies. The NLO parameters of the title compound were calculated, and obtained data were compared with that of para-Nitroaniline (pNA) which is a typical NLO material and the corresponding experimental data. Obtained data of the chromosphere display significant molecular second-and third-nonlinearity.

  10. Probe spectroscopy in an operating magneto-optical trap: The role of Raman transitions between discrete and continuum atomic states

    SciTech Connect

    Brzozowski, Tomasz M.; Brzozowska, Maria; Zachorowski, Jerzy; Zawada, Michal; Gawlik, Wojciech

    2005-01-01

    We report on cw measurements of probe beam absorption and four-wave-mixing spectra in a {sup 85}Rb magneto-optical trap taken while the trap is in operation. The trapping beams are used as pump light. We concentrate on the central feature of the spectra at small pump-probe detuning and attribute its narrow resonant structures to the superposition of Raman transitions between light-shifted sublevels of the ground atomic state and to atomic recoil processes. These two contributions have different dependencies on trap parameters and we show that the former is inhomogeneously broadened. The strong dependence of the spectra on the probe-beam polarization indicates the existence of large optical anisotropy of the cold-atom sample, which is attributed to the recoil effects. We point out that the recoil-induced resonances can be isolated from other contributions, making pump-probe spectroscopy a highly sensitive diagnostic tool for atoms in a working magneto-optical trap.

  11. Optical absorption and heating rate dependent glass transition in vanadyl doped calcium oxy-chloride borate glasses

    NASA Astrophysics Data System (ADS)

    Dahiya, M. S.; Khasa, S.; Agarwal, A.

    2015-04-01

    Some important results pertaining to optical and thermal properties of vanadyl doped oxy-halide glasses in the chemical composition CaCl2-CaO-B2O3 are discussed. These glasses have been prepared by conventional melt quench technique. From X-ray diffraction (XRD) profiles the amorphous nature of the doped glasses has been confirmed. The electronic polarizability is calculated and found to increase with increase in chloride content. The optical absorption spectra have been recorded in the frequency range of 200-3200 nm. Recorded spectra are analyzed to evaluate cut-off wavelength (λcut-off), optical band gap (Eg), band tailing (B), Urbach energy (ΔE) and refractive index (n). Thermal analysis has been carried out for the prepared glasses at three different heating rates viz. 5, 10 and 20 °C/min. The glass transition temperature (Tg) along with thermal activation energy (Ea) corresponding to each heating rate are evaluated from differential scanning calorimetry (DSC) thermographs. It is found that Ea decrease and Tg increase with increase in heating rate. The variation in Tg is also observed with the substitution of calcium chloride in place of calcium oxide. The increasing and higher values of Ea suggest that prepared glasses have good thermal stability. Variation in Tg and Eg suggests that Cl- anions enter into the voids of borate network at low concentrations (<5.0%) and contribute to the network formation at high concentration (>5.0%).

  12. Anisotropic optical properties of few-layer transition metal dichalcogenide ReS2

    NASA Astrophysics Data System (ADS)

    Li, Zhenglu; Cao, Ting; da Jornada, Felipe H.; Wu, Meng; Louie, Steven G.

    We present first-principles (DFT, GW and GW-BSE) calculations of the electronic and optical properties of few-layer rhenium disulfide (ReS2). Monolayer ReS2 shows strong many-electron effects with a fundamental quasiparticle band gap of 2.38 eV based on G0W0 calculation and a large exciton binding energy of 690 meV based on solving the Bethe-Salpeter equation. Highly anisotropic linear-polarized optical absorptions are revealed for few-layer and bulk ReS2. The band gap shows a decreasing trend with the optical polarization direction near the absorption edge gradually rotating from around 67 degree in the monolayer to 85 degree in the bulk, referencing to the Re-chain. Our calculations are consistent with recent experimental data and theoretical studies, and provide a systematic understanding of the electronic and optical properties in few-layer ReS2. This work was supported by National Science Foundation Grant No. DMR15-1508412 and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at Lawrence Berkeley National Laboratory's NERSC facility.

  13. Mean-field analysis of quantum phase transitions in a periodic optical superlattice

    SciTech Connect

    Dhar, Arya; Singh, Manpreet; Pai, Ramesh V.; Das, B. P.

    2011-09-15

    We analyze the various phases exhibited by a system of ultracold bosons in a periodic optical superlattice using the mean-field decoupling approximation. We investigate for a wide range of commensurate and incommensurate densities. We find the gapless superfluid phase, the gapped Mott insulator phase, and gapped insulator phases with distinct density wave orders.

  14. Charge-transfer states and optical transitions at the pentacene-TiO2 interface

    NASA Astrophysics Data System (ADS)

    Ljungberg, M. P.; Vänskä, O.; Koval, P.; Koch, S. W.; Kira, M.; Sánchez-Portal, D.

    2017-03-01

    Pentacene molecules have recently been observed to form a well-ordered monolayer on the (110) surface of rutile TiO2, with the molecules adsorbed lying flat, head to tail. With the geometry favorable for direct optical excitation and given its ordered character, this interface seems to provide an intriguing model to study charge-transfer excitations where the optically excited electrons and holes reside on different sides of the organic–inorganic interface. In this work, we theoretically investigate the structural and electronic properties of this system by means of ab initio calculations and compute its excitonic absorption spectrum. Molecular states appear in the band gap of the clean TiO2 surface, which enables charge-transfer excitations directly from the molecular HOMO to the TiO2 conduction band. The calculated optical spectrum shows a strong polarization dependence and displays excitonic resonances corresponding to the charge-transfer states, which could stimulate new experimental work on the optical response of this interface.

  15. Pressure coefficients for direct optical transitions in MoS2, MoSe2, WS2, and WSe2 crystals and semiconductor to metal transitions

    PubMed Central

    Dybała, F.; Polak, M. P.; Kopaczek, J.; Scharoch, P.; Wu, K.; Tongay, S.; Kudrawiec, R.

    2016-01-01

    The electronic band structure of MoS2, MoSe2, WS2, and WSe2, crystals has been studied at various hydrostatic pressures experimentally by photoreflectance (PR) spectroscopy and theoretically within the density functional theory (DFT). In the PR spectra direct optical transitions (A and B) have been clearly observed and pressure coefficients have been determined for these transitions to be: αA = 2.0 ± 0.1 and αB = 3.6 ± 0.1 meV/kbar for MoS2, αA = 2.3 ± 0.1 and αB = 4.0 ± 0.1 meV/kbar for MoSe2, αA = 2.6 ± 0.1 and αB = 4.1 ± 0.1 meV/kbar for WS2, αA = 3.4 ± 0.1 and αB = 5.0 ± 0.5 meV/kbar for WSe2. It has been found that these coefficients are in an excellent agreement with theoretical predictions. In addition, a comparative study of different computational DFT approaches has been performed and analyzed. For indirect gap the pressure coefficient have been determined theoretically to be −7.9, −5.51, −6.11, and −3.79, meV/kbar for MoS2, MoSe2, WS2, and WSe2, respectively. The negative values of this coefficients imply a narrowing of the fundamental band gap with the increase in hydrostatic pressure and a semiconductor to metal transition for MoS2, MoSe2, WS2, and WSe2, crystals at around 140, 180, 190, and 240 kbar, respectively. PMID:27215469

  16. Electron-impact Excitation of Ni II: Effective Collision Strengths for Optically Allowed Fine-structure Transitions

    NASA Astrophysics Data System (ADS)

    Cassidy, C. M.; Ramsbottom, C. A.; Scott, M. P.

    2011-09-01

    In this paper, we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of Ni II. Attention is expressly concentrated on the optically allowed fine-structure transitions between the 3d 9, 3d 84s, and 3d 74s 2 even parity levels and the 3d 84p and 3d 74s 4p odd parity levels. The parallel RMATRXII R-matrix package has been recently extended to allow for the inclusion of relativistic fine-structure effects. This suite of codes has been utilized in conjunction with the parallel PSTGF and PSTGICF programs in order to compute converged total collision strengths for the allowed transitions with which this study is concerned. All 113 LS terms identified with the 3d 9, 3d 84s, 3d 74s 2, 3d 84p, and 3d 74s 4p basis configurations were included in the target wavefunction representation, giving rise to a sophisticated 295 jj-level, 1930 coupled channel scattering complex. Maxwellian averaged effective collision strengths have been computed at 30 individual electron temperatures ranging from 30 to 1,000,000 K. This range comfortably encompasses all temperatures significant to astrophysical and plasma applications. The convergence of the collision strengths is exhaustively investigated and comparisons are made with previous theoretical works, where significant discrepancies exist for the majority of transitions. We conclude that intrinsic in achieving converged collision strengths and thus effective collision strengths for the allowed transitions is the combined inclusion of contributions from the (N + 1) partial waves extending to a total angular momentum value of L = 50 and further contributions from even higher partial waves accomplished by employing a "top-up" procedure.

  17. Exploring the optical contrast effect in strong atomic lines for exoplanets transiting active stars

    NASA Astrophysics Data System (ADS)

    Cauley, Paul W.; Redfield, Seth

    2017-01-01

    Transmission spectroscopy is a powerful tool for detecting and characterizing planetary atmospheres. Non-photospheric features on the stellar disk, however, can contaminate the planetary signal: during transit the observed spectrum is weighted towards the features not currently being occulted by the planet. This contrast effect can mimic absorption in the planetary atmosphere for strong atomic lines such as Na I, Ca II, and the hydrogen Balmer lines. While the contrast effect is negligible for quiet stars, contributions to the transmission signal from active stellar surfaces can produce ~1% changes in the line core. It is therefore critical that these contrast signals be differentiated from true absorption features in the planetary atmosphere. Here we present our work on simulating the contrast effect for an active stellar surface. We discuss the particular case of HD 189733 b, a well-studied hot Jupiter orbiting an active K-dwarf, due to the plethora of atomic absorption signals reported in its atmosphere.Specifically, we focus on Hα to address recent suggestions that the measured in-transit signals are a result of stellar activity. In the contrast model we include center-to-limb variations and calculate limb darkening parameters as a function of wavelength across the line of interest. The model includes contributions to the spectrum from spots, faculae and plages, filaments, and the bare stellar photosphere. Stellar rotation is also included. We find that it is very difficult to reproduce the measured in-transit Hα signals for reasonable active region parameters. In addition, it is difficult to create an in-transit contrast signature that lasts for the duration of the transit unless the planet is crossing an active latitudinal belt and is always obscuring active regions. This suggests that the Hα measurements arise predominantly in the planetary atmosphere. However, the contrast effect likely contributes to these signals. Furthermore, our results could be

  18. Forbidden optical transition in Ti-like Xe, Ba, and Ir

    SciTech Connect

    Bekker, H.; Windberger, A.; Binder, M.; López-Urrutia, J. R. Crespo; Versolato, O. O.; Klawitter, R.

    2015-01-09

    We present measurements of the (3d{sup 4}){sup 5}D{sub 2}−{sup 5}D{sub 3} transitions in the Ti-like ions Xe{sup 32+}, Ba{sup 34+}, and Ir{sup 55+} produced and trapped in the Heidelberg electron beam ion trap. The obtained wavelengths have a precision at the few ppm-level and are thereby the most precise measurements of these transitions up to date. For Z=60−75 semi-empirical calculations have shown excellent agreement, however our measurements combined with data from other works shows that outside this range predictions quickly deviate. The value obtained for Ir{sup 55+} 357.434(2) nm confirms the linear mismatch to ab initio calculations for Z > 70, as hypothesized in Utter et al., Phys. Rev. A 67, 012508 (2003)

  19. Population inversion on vibrational transitions of molecules under nonresonant optical excitation

    SciTech Connect

    Parkhomenko, A. I. Shalagin, A. M.

    2010-09-15

    The possibility of obtaining a population inversion on vibrational transitions of molecules through nonlinear effects when the pump radiation is absorbed in the wings of spectral lines is investigated theoretically. We show that a population inversion can be produced in molecules on vibrational transitions when intense pump radiation is absorbed in the blue wing of the R branch of the vibrational-rotational molecular spectrum. This effect is related to inequality of the probabilities of the absorption and stimulated emission of radiation and is attributable to collisional transitions between rotational levels. We have ascertained that the larger the rotational constant of the molecule and the higher the pump radiation intensity, the higher the effective frequency of the collisions that give rise to a population inversion. Using the carbon monoxide (CO) molecule as an example, we show that when intense ({approx}1010 W cm{sup -2}) pump radiation is absorbed in the blue wing of the R branch, a noticeable population inversion can be produced and the gain at the center of the R and P branches of the molecular spectrum can reach 0.011 and 0.250 cm{sup -1} at temperatures T = 300 and 100 K, respectively.

  20. Optical stability of 3d transition metal ions doped-cadmium borate glasses towards γ-rays interaction

    NASA Astrophysics Data System (ADS)

    Marzouk, M.; ElBatal, H.; Eisa, W.

    2016-07-01

    This work reports the preparation of glasses of binary cadmium borate with the basic composition (mol% 45 CdO 55 B2O3) and samples of the same composition containing 0.2 wt% dopants of 3d transition metal (TM) oxides (TiO2 → CuO). The glasses have been investigated by combined optical and Fourier Transform infrared spectroscopic measurements before and after being subjected to gamma irradiation with a dose of 8 Mrad (8 × 104 Gy). Optical absorption of the undoped glass before irradiation reveals strong charge transfer UV absorption which is related to the presence of unavoidable contaminated trace iron impurities (mainly Fe3+) within the raw materials used for the preparation of the base cadmium borate glass. The optical spectra of the 3d TM ions exhibit characteristic bands which are related the stable oxidation state of the 3d TM ions within the host glass. Gamma irradiation produces some limited variations in the optical spectra due to the stability of the host glass containing high percent 45 mol% of heavy metal oxide (CdO) which causes some shielding effects towards irradiation. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (∆E) have been calculated. The values of the optical energy gap are found to be dependent on the glass composition. Infrared absorption spectral measurements reveal characteristic absorption bands due to both triangular and tetrahedral borate groups with the BO3 units vibrations more intense than BO4 units due to the known limit value for the change of BO3 to BO4 groups. The introduction of 3d TM ions with the doping level (0.2 wt%) causes no changes in the number or position of the IR bands because of the presence of TM ions in modifying sites in the glass network. It is observed that gamma irradiation causes some limited changes in the FT-IR spectral bands due to the stability of the host heavy cadmium borate glass.

  1. Optical Design of the Camera for Transiting Exoplanet Survey Satellite (TESS)

    NASA Technical Reports Server (NTRS)

    Chrisp, Michael; Clark, Kristin; Primeau, Brian; Dalpiaz, Michael; Lennon, Joseph

    2015-01-01

    The optical design of the wide field of view refractive camera, 34 degrees diagonal field, for the TESS payload is described. This fast f/1.4 cryogenic camera, operating at -75 C, has no vignetting for maximum light gathering within the size and weight constraints. Four of these cameras capture full frames of star images for photometric searches of planet crossings. The optical design evolution, from the initial Petzval design, took advantage of Forbes aspheres to develop a hybrid design form. This maximized the correction from the two aspherics resulting in a reduction of average spot size by sixty percent in the final design. An external long wavelength pass filter was replaced by an internal filter coating on a lens to save weight, and has been fabricated to meet the specifications. The stray light requirements were met by an extended lens hood baffle design, giving the necessary off-axis attenuation.

  2. Report on the Radiation Effects Testing of the Infrared and Optical Transition Radiation Camera Systems

    SciTech Connect

    Holloway, Michael Andrew

    2016-04-20

    Presented in this report are the results tests performed at Argonne National Lab in collaboration with Los Alamos National Lab to assess the reliability of the critical 99Mo production facility beam monitoring diagnostics. The main components of the beam monitoring systems are two cameras that will be exposed to radiation during accelerator operation. The purpose of this test is to assess the reliability of the cameras and related optical components when exposed to operational radiation levels. Both X-ray and neutron radiation could potentially damage camera electronics as well as the optical components such as lenses and windows. This report covers results of the testing of component reliability when exposed to X-ray radiation. With the information from this study we provide recommendations for implementing protective measures for the camera systems in order to minimize the occurrence of radiation-induced failure within a ten month production run cycle.

  3. Single-Slit Diffraction: Transitioning from Geometric Optics to the Fraunhofer Regime

    ERIC Educational Resources Information Center

    Panuski, Christopher L.; Mungan, Carl E.

    2016-01-01

    Suppose a red laser beam (of wavelength ? equal to 0.660 µm) is expanded using an optical telescope into a collimated, approximately plane wave that is 5.68 mm in diameter. Pass that beam through a tall rectangular slit whose width "a" is gradually reduced from 3.30 to 0.100 mm. Look at its image on a screen located at a distance…

  4. Optical thickness identification of transition metal dichalcogenide nanosheets on transparent substrates.

    PubMed

    Zhang, Hao; Ran, Feirong; Shi, Xiaotong; Fang, Xiangru; Wu, Shiyu; Liu, Yue; Zheng, Xianqiang; Yang, Peng; Liu, Yang; Wang, Lin; Huang, Xiao; Li, Hai; Huang, Wei

    2017-04-21

    Transparent and flexible devices based on two-dimensional (2D) materials hold great potential for many electronic/optoelectronic applications. The direct and fast thickness identification of 2D materials on transparent substrates is therefore an essential step in such applications, but remains challenging. Here, we present a simple, rapid and reliable optical method to identify the thickness of 2D nanosheets on transparent substrates, such as polydimethylsiloxane, glass, and coverslip. Under reflection and transmission light, 1-20L MoS2 and 1-14L WSe2 nanosheets can be reliably identified by measuring the optical contrast difference between the 2D nanosheets and substrates in color, red, green or blue channels. Meanwhile, the values of all the measured contrast differences as a function of layer number can be well fitted with the Boltzmann function, indicating the generalizability and reliability of our optical method. Our method will not only facilitate the fundamental study of the thickness-dependent properties of 2D nanosheets, but will also expand their potential applications in the field of flexible/transparent electronics and optoelectronics.

  5. Adsorption-induced changes of intramolecular optical transitions: PTCDA/NaCl and PTCDA/KCl.

    PubMed

    Hochheim, Manuel; Bredow, Thomas

    2015-09-15

    Structural and optical properties of isolated perylene-3,4,9,10-tetracarboxylic acid dianhydride molecules adsorbed on (100) oriented NaCl and KCl surfaces were studied theoretically to analyze the recently observed red-shift of the optical excitation spectrum after adsorption (Müller et al., Phys. Rev. B, 2011, 83, 241203; Paulheim et al. Phys. Chem. Chem. Phys., 2013, 15, 4906). The ground-state structures were obtained by periodic dispersion-corrected density functional theory (DFT) calculations. For the excited-state calculations, nonperiodic time-dependent DFT methods were applied for a cluster model embedded in point charges. The range-separated hybrid functional CAM-B3LYP was used. Correlation-consistent basis sets were used and the calculated excitation energies were extrapolated to the complete basis set limit. The shift of the first optical excitation energy was analyzed in terms of electronic and geometric contributions. It was found that both the distortion of the molecule due to the interaction with the surface and the electrostatic potential of the surface play an important role.

  6. Optical thickness identification of transition metal dichalcogenide nanosheets on transparent substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Ran, Feirong; Shi, Xiaotong; Fang, Xiangru; Wu, Shiyu; Liu, Yue; Zheng, Xianqiang; Yang, Peng; Liu, Yang; Wang, Lin; Huang, Xiao; Li, Hai; Huang, Wei

    2017-04-01

    Transparent and flexible devices based on two-dimensional (2D) materials hold great potential for many electronic/optoelectronic applications. The direct and fast thickness identification of 2D materials on transparent substrates is therefore an essential step in such applications, but remains challenging. Here, we present a simple, rapid and reliable optical method to identify the thickness of 2D nanosheets on transparent substrates, such as polydimethylsiloxane, glass, and coverslip. Under reflection and transmission light, 1-20L MoS2 and 1-14L WSe2 nanosheets can be reliably identified by measuring the optical contrast difference between the 2D nanosheets and substrates in color, red, green or blue channels. Meanwhile, the values of all the measured contrast differences as a function of layer number can be well fitted with the Boltzmann function, indicating the generalizability and reliability of our optical method. Our method will not only facilitate the fundamental study of the thickness-dependent properties of 2D nanosheets, but will also expand their potential applications in the field of flexible/transparent electronics and optoelectronics.

  7. Optical transitions of Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 glass.

    PubMed

    Shen, Xiang; Nie, Qiuhua; Xu, Tiefeng; Gao, Yuan

    2005-10-01

    Optical absorption and emission properties of the Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 (TWB) glass has been investigated. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 microm fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 77 nm. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 1.03 x 10(-21) cm2 at 1.531 microm. This value is much larger than those of the silicate and phosphate glasses. Efficient green and weak red upconversion luminescence from Er3+ centers in the glass sample was observed at room temperature, and the upconversion excitation processes have been analyzed.

  8. Observations of a mode transition in a hydrogen hollow cathode discharge using phase resolved optical emission spectroscopy

    SciTech Connect

    Dixon, Sam Charles, Christine; Dedrick, James; Boswell, Rod; Gans, Timo; O'Connell, Deborah

    2014-07-07

    Two distinct operational modes are observed in a radio frequency (rf) low pressure hydrogen hollow cathode discharge. The mode transition is characterised by a change in total light emission and differing expansion structures. An intensified CCD camera is used to make phase resolved images of Balmer α emission from the discharge. The low emission mode is consistent with a typical γ discharge, and appears to be driven by secondary electrons ejected from the cathode surface. The bright mode displays characteristics common to an inductive discharge, including increased optical emission, power factor, and temperature of the H{sub 2} gas. The bright mode precipitates the formation of a stationary shock in the expansion, observed as a dark region adjacent to the source-chamber interface.

  9. Plasmonic phase transition and phase retardation: essential optical characteristics of localized surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Yu; Lin, Chun-Hung; Chen, Wei-Ting

    2013-09-01

    Phase transition that occurs around the spectral position of localized surface plasmon resonance (LSPR) has various applications for light manipulation and refractive index sensing. Previous studies focused on phase responses of specific plasmonic structures, whereas the general theoretical analysis remains inadequate. In this study, we analytically modeled the phase spectra and the intensity spectra of silver nanodots with temporal coupled-mode theory. The phase transition occurs at the transmission dip, whereas the phase of reflection varies much more gradually. We further derived the equation for the slope of the phase at the transmission dip, which is a function of the rates of Ohmic dissipation and emission. The theoretical analysis is also applicable for wide varieties of LSPR systems and provides an intuitive physical mechanism for phase properties. Then, based on the fundamental discussion, we further investigated plasmonic phase retardation in anisotropic nanodots for the application of boosting the figure of merit (FOM) of refractive index sensing. The anisotropic nanodots induce plasmonic phase transitions, which spectrally split, for transmission waves polarized along the symmetric axes. Thus, anisotropy induces relative phase retardation in the narrow spectral region between the wavelengths of the LSPRs. We numerically manipulated the full width at half maximum of the ellipsometric spectra by adjusting the aspect ratio of the nanodots and observed an FOM of 24.3. In addition, experiments were performed to demonstrate the feasibility of this arrangement.Phase transition that occurs around the spectral position of localized surface plasmon resonance (LSPR) has various applications for light manipulation and refractive index sensing. Previous studies focused on phase responses of specific plasmonic structures, whereas the general theoretical analysis remains inadequate. In this study, we analytically modeled the phase spectra and the intensity spectra of

  10. Singlet biradical{yields}singlet zwitterion optical transition in a twisted olefin

    SciTech Connect

    Piotrowiak, P.; Strati, G.; Smirnov, S.N.; Warman, J.M.; Schuddeboom, W.

    1996-09-18

    We report the first direct observation of the singlet biradical $YLD singlet zwitterion transition in a twisted olefin, biphenanthrenylidene. Biphenanthrenylidene (full name, bi-4H-cyclopenta[def]phenanthren-4-ylidene, abbreviated as BPH) is an analogue of tetraphenylethylene (TPE) and stilbene, both of which are the favorite models of photoisomerization reactions. The investigations have been focusing on the dynamics of the twisting motion of the double bond which leads to decoupling of the two halves of the olefin and results in the formation of the D{sub 2d} 90{degree}-twisted zwitterionic or biradical excited state. 13 refs., 2 figs., 1 tab.

  11. Transition from unidirectional to delayed bidirectional coupling in optically coupled semiconductor lasers.

    PubMed

    Bonatto, Cristian; Kelleher, Bryan; Huyet, Guillaume; Hegarty, Stephen P

    2012-02-01

    We investigate the transition from unidirectional to delayed bidirectional coupling of semiconductor lasers. By tuning the coupling strength in one direction we show how the locking region evolves as a function of the detuning and coupling strength. We consider two representative values of the relaxation oscillation damping: one where the relaxation oscillations are very underdamped and one where they are very overdamped. Qualitatively different dynamical scenarios are shown to emerge for each case. Several features of the delayed bidirectional system can be seen as remaining from the unidirectional system while others clearly arise due to the delayed coupling and are similar to effects seen in delayed feedback configurations.

  12. Surface plasmon optical study of the interfacial phase transition of elastinlike polypeptide grafted on gold.

    PubMed

    Xu, Fei; Joon, Huang Min; Trabbic-Carlson, Kimberly; Chilkoti, Ashutosh; Knoll, Wolfgang

    2008-09-01

    The conformational changes in elastinlike polypeptides (ELPs) grafted to a solid/solution interface via different architectures were studied using surface plasmon resonance spectroscopy and surface plasmon field-enhanced fluorescence spectroscopy (SPFS). SPFS provides a simple and convenient optical method to study the influence of the grafting method and the graft density on the conformational changes in ELPs at the solid-solution interface as a function of environmental variables. A typical response of the ELP, consistent with its stimuli responsiveness, was a gradual collapse upon increasing the ionic strength; this effect was inversely correlated with the surface graft density of the ELP.

  13. Single-Slit Diffraction: Transitioning from Geometric Optics to the Fraunhofer Regime

    NASA Astrophysics Data System (ADS)

    Panuski, Christopher L.; Mungan, Carl E.

    2016-09-01

    Suppose a red laser beam (of wavelength λ equal to 0.660 μm) is expanded using an optical telescope into a collimated, approximately plane wave that is 5.68 mm in diameter. Pass that beam through a tall rectangular slit whose width a is gradually reduced from 3.30 to 0.100 mm. Look at its image on a screen located at a distance L from the slit equal to 0.656 m. As the slit is narrowed, you predict that the width of the pattern will: (A) smoothly increase, (B) smoothly decrease, (C)increase and then decrease, or (D) decrease and then increase.

  14. Optical transitions of Er3+ ions in RbMgF3 and RbMgF3: Mn

    NASA Astrophysics Data System (ADS)

    Shinn, M. D.; Windscheif, J. C.; Sardar, D. K.; Sibley, W. A.

    1982-09-01

    Optical absorption, emission, and excitation spectra, as well as lifetime values, are presented for Er3+ ions in RbMgF3. Previous workers have demonstrated that Er3+ ions can reside in a number of different site symmetries in crystalline hosts such as CaF2 and CdF2. The numerous sites in this type lattice are most likely due to compensating fluorine interstitials which are necessarily present for charge compensation. In a unit cell of RbMgF3 there are two nonequivalent Mg2+ sites with C3v symmetry. Evidence is presented in this paper that Er3+ ions in RbMgF3 substitute for Mg2+ ions in both types of sites. The charge compensation is not local, which leaves the symmetry of the Er3+ sites unchanged. Absorption data for Er3+-ion transitions in both sites are shown. Emission from Er3+ ions is observed from one type of site in RbMgF3 and from both types of sites in RbMgF3: Mn. Lifetime values for the 4S32 and 4F92 transitions are shorter than those normally measured in fluoride host lattices, and the emissions are quenched above 200 K. Energy migration among Er3+ ions and subsequent energy transfer to Mn2+-ion impurities are responsible for the steady-state and transient-emission behavior.

  15. Synthetic Mimics of Bacterial Lipid A Trigger Optical Transitions in Liquid Crystal Microdroplets at Ultralow Picogram-per-Milliliter Concentrations

    PubMed Central

    2016-01-01

    We report synthetic six-tailed mimics of the bacterial glycolipid Lipid A that trigger changes in the internal ordering of water-dispersed liquid crystal (LC) microdroplets at ultralow (picogram-per-milliliter) concentrations. These molecules represent the first class of synthetic amphiphiles to mimic the ability of Lipid A and bacterial endotoxins to trigger optical responses in LC droplets at these ultralow concentrations. This behavior stands in contrast to all previously reported synthetic surfactants and lipids, which require near-complete monolayer coverage at the LC droplet surface to trigger ordering transitions. Surface-pressure measurements and SAXS experiments reveal these six-tailed synthetic amphiphiles to mimic key aspects of the self-assembly of Lipid A at aqueous interfaces and in solution. These and other results suggest that these amphiphiles trigger orientational transitions at ultralow concentrations through a unique mechanism that is similar to that of Lipid A and involves formation of inverted self-associated nanostructures at topological defects in the LC droplets. PMID:26562069

  16. Direct Excitation of the Forbidden Clock Transition in Neutral {sup 174}Yb Atoms Confined to an Optical Lattice

    SciTech Connect

    Barber, Z.W.; Hoyt, C.W.; Oates, C.W.; Hollberg, L.; Taichenachev, A.V.; Yudin, V.I.

    2006-03-03

    We report direct single-laser excitation of the strictly forbidden (6s{sup 2}){sup 1}S{sub 0}{r_reversible}(6s6p){sup 3}P{sub 0} clock transition in {sup 174}Yb atoms confined to a 1D optical lattice. A small ({approx}1.2 mT) static magnetic field was used to induce a nonzero electric dipole transition probability between the clock states at 578.42 nm. Narrow resonance linewidths of 20 Hz (FWHM) with high contrast were observed, demonstrating a resonance quality factor of 2.6x10{sup 13}. The previously unknown ac Stark shift-canceling (magic) wavelength was determined to be 759.35{+-}0.02 nm. This method for using the metrologically superior even isotope can be easily implemented in current Yb and Sr lattice clocks and can create new clock possibilities in other alkaline-earth-like atoms such as Mg and Ca.

  17. Optical properties, lattice dynamics, and structural phase transition in hexagonal 2 H -BaMn O3 single crystals

    NASA Astrophysics Data System (ADS)

    Stanislavchuk, T. N.; Litvinchuk, A. P.; Hu, Rongwei; Jeon, Young Hun; Ji, Sung Dae; Cheong, S.-W.; Sirenko, A. A.

    2015-10-01

    Optical properties and lattice dynamics of hexagonal 2 H -BaMn O3 single crystals are studied experimentally in a wide temperature range by means of rotating analyzer ellipsometry and Raman scattering. The magnitude of the direct electronic band gap is found to be Eg=3.2 eV . At room temperature the far-infrared (IR) ellipsometry spectra reveal six IR-active phonons; two of them are polarized along the c axis and four are polarized within the a-b plane. Seven phonon modes are identified in the Raman scattering experiments. Group theoretical mode analysis and complementary density functional theory lattice dynamics calculations are consistent with the 2 H -BaMn O3 structure belonging to the polar P 63m c space group at room temperature. All observed vibrational modes are assigned to specific eigenmodes of the lattice. The neutron diffraction measurements reveal a structural phase transition upon cooling below TC=130 ±5 K , which is accompanied by a lattice symmetry change from P 63m c to P 63c m . Simultaneously, at temperatures below TC several additional IR- and Raman-active modes are detected in experimental spectra. This confirms the occurrence of a structural transition, which is possibly associated with the appearance of electrical polarization along the c axis and a previously known tripling of the primitive cell volume at low temperatures.

  18. Experimental study for the detection of the laminar/turbulent aerodynamic transition on a wing aircraft, using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Molin, S.; Dolfi, D.; Doisy, M.; Seraudie, A.; Arnal, D.; Coustols, E.; Mandle, J.

    2010-09-01

    We demonstrate the feasibility of detection of the nature (laminar/turbulent/transitional) of the aerodynamic boundary layer of a profile of a wing aircraft model, using a Distributed FeedBack (DFB) Fiber Laser as optical fiber sensor. Signals to be measured are pressure variations : ΔP~1Pa at few 100Hz in the laminar region and ΔP~10Pa at few kHz in the turbulent region. Intermittent regime occurring in-between these two regions (transition) is characterized by turbulent bursts in laminar flow. Relevant pressure variations have been obtained in a low-speed research-type wind tunnel of ONERA Centre of Toulouse. In order to validate the measurements, a "classical" hot film sensor, the application and use of which have been formerly developed and validated by ONERA, has been placed at the neighborhood of the fiber sensor. The hot film allows measurement of the boundary layer wall shear stress whose characteristics are a well known signature of the boundary layer nature (laminar, intermittent or turbulent) [1]. In the three regimes, signals from the fiber sensor and the hot film sensor are strongly correlated, which allows us to conclude that a DFB fiber laser sensor is a good candidate for detecting the boundary layer nature, and thus for future integration in an aircraft wing. The work presented here has been realized within the framework of "Clean Sky", a Joint Technology Initiative of the European Union.

  19. Fractional Mott insulator-to-superfluid transition of Bose-Hubbard model in a trimerized Kagomé optical lattice.

    PubMed

    Chen, Qi-Hui; Li, Peng; Su, Haibin

    2016-06-29

    By generalizing the traditional single-site strong coupling expansion approach to a cluster one, we study the zero-temperature phase diagram of bosonic atoms in a trimerized Kagomé optical lattice. Some new features are present in this system. Due to the strong intra-trimer hopping interaction, there will be a new Mott insulator (MI), which is by definition incompressible but with a fractional filling per trimer. This is different from the traditional MI, which has an integral filling and originates only from the repulsive interaction between particles. We investigate the MI-to-superfluid transition and the nature of the fractional MI by calculating the critical exponents of phase transitions and the low-lying energy excitation spectra of quasiparticles (quasihole). We will show how the low-energy properties of this system can be understood qualitatively as a Bose-Hubbard model in triangular lattice from the point of view of the cluster strong coupling expansion. We also discuss how our results are related to experiment by studying the Bragg spectroscopy.

  20. Fractional Mott insulator-to-superfluid transition of Bose-Hubbard model in a trimerized Kagomé optical lattice

    NASA Astrophysics Data System (ADS)

    Chen, Qi-Hui; Li, Peng; Su, Haibin

    2016-06-01

    By generalizing the traditional single-site strong coupling expansion approach to a cluster one, we study the zero-temperature phase diagram of bosonic atoms in a trimerized Kagomé optical lattice. Some new features are present in this system. Due to the strong intra-trimer hopping interaction, there will be a new Mott insulator (MI), which is by definition incompressible but with a fractional filling per trimer. This is different from the traditional MI, which has an integral filling and originates only from the repulsive interaction between particles. We investigate the MI-to-superfluid transition and the nature of the fractional MI by calculating the critical exponents of phase transitions and the low-lying energy excitation spectra of quasiparticles (quasihole). We will show how the low-energy properties of this system can be understood qualitatively as a Bose-Hubbard model in triangular lattice from the point of view of the cluster strong coupling expansion. We also discuss how our results are related to experiment by studying the Bragg spectroscopy.

  1. Effect of the order-disorder transition on the optical properties of Cu2ZnSnS4

    NASA Astrophysics Data System (ADS)

    Valentini, M.; Malerba, C.; Menchini, F.; Tedeschi, D.; Polimeni, A.; Capizzi, M.; Mittiga, A.

    2016-05-01

    The effect of the order-disorder transition on the band gap of kesterite Cu2ZnSnS4, an interesting material for solar cells, has been investigated by optical spectroscopy. The band gap energy (Eg) decreases continuously with increasing annealing temperature, Ta, and reaches its minimum at Ta ˜ 273 °C. Eg is about 200 meV higher in the most ordered state, than in the fully disordered state. Its value and the transition kinetic depend on the sample stoichiometry. A simplified model able to explain the order degree and stoichiometry effects on the Eg value is developed. Ordering results in narrower Raman peaks without affecting the shape of the photoluminescence spectrum—except for the change in Eg—or the characteristic energy of the exponential tail below the fundamental absorption edge. Although a prolonged annealing increases the order degree, the material properties are still influenced by residual disorder as well as by defects related to the off-stoichiometry composition.

  2. Phase transition from BCT to spinel structure in CdAl2Se4 and its optical properties

    NASA Astrophysics Data System (ADS)

    Singh, Poonam; Verma, U. P.; Jensen, Per

    2013-10-01

    We present a detailed first principle investigation on CdAl2Se4 both at ambient and the high pressure conditions. At ambient condition CdAl2Se4 exists in body centered tetragonal (BCT) phase and at high pressure in spinel phase. Corresponding to different volume the total energy has been optimized using three functional, viz., the local density approximation (LDA), the generalized gradient approximation (GGA) and the Engel-Vosko generalised gradient approximation (EV-GGA). In all the cases phase transition from the BCT to the spinel phase has been observed. The equilibrium lattice constants, energy band gaps, bulk modulus have been reported at ambient conditions in both the phases. According to our prediction CdAl2Se4 is a direct band gap material in both the studied phases, contrary to the earlier results reported by Funetes-cabrea and Sankey for spinel phase. Among optical constants index of refraction, absorption coefficient and optical conductivity are calculated and compared with the existing results in both the phases within the energy range of 0-25 eV.

  3. Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures

    PubMed Central

    Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

    2016-01-01

    As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices. PMID:27553787

  4. Magnetic and natural optical activity of f- f transitions in multiferroic Nd0.5Gd0.5Fe3(BO3)4

    NASA Astrophysics Data System (ADS)

    Malakhovskii, A. V.; Sukhachev, A. L.; Leont'ev, A. A.; Temerov, V. L.

    2016-05-01

    Spectra of absorption, magnetic circular dichroism, and natural circular dichroism of the f-f transitions 4 I 9/2 → 4 F 3/2, 2 H 9/2 + 4 F 5/2, 4 S 3/2 + 4 F 7/2, 2 G 7/2 + 4 G 5/2, 2 K 13/2 + 4 G 7/2, and 4 G 9/2 in the Nd3+ ions in the Nd0.5Gd0.5Fe3(BO3)4 crystal have been measured as a function of the temperature in the interval of 90-300 K. Temperature dependences of the magneto-optical activity (MOA) and natural optical activity (NOA) of the transitions have been obtained. It has been found that, in contrast to allowed transitions, the temperature dependence of the MOA of the f-f transitions does not obey the Curie-Weiss law and the NOA depends on temperature. The NOA of some transitions changes the sign with variation in temperature. These phenomena have been explained by the presence of three contributions to the allowance of the f-f transitions, which lead to three contributions of different signs to the MOA and NOA. The range of the MOA of the f-f transitions in the Nd3+ ion has been predicted theoretically and confirmed experimentally.

  5. Optical conductivity of Weyl semimetals and signatures of the gapped semimetal phase transition

    NASA Astrophysics Data System (ADS)

    Tabert, C. J.; Carbotte, J. P.

    2016-02-01

    The interband optical response of a three-dimensional Dirac cone is linear in photon energy (Ω ) . Here, we study the evolution of the interband response within a model Hamiltonian which contains Dirac, Weyl, and gapped semimetal phases. In the pure Dirac case, a single linear dependence is observed, while in the Weyl phase, we find two quasilinear regions with different slopes. These regions are also distinct from the large-Ω dependence. As the boundary between the Weyl (WSM) and gapped phases is approached, the slope of the low-Ω response increases, while the photon-energy range over which it applies decreases. At the phase boundary, a square root behavior is obtained which is followed by a gapped response in the gapped semimetal phase. The density of states parallels these behaviors with the linear law replaced by quadratic behavior in the WSM phase and the square root dependence at the phase boundary changed to |ω| 3 /2. The optical spectral weight under the intraband (Drude) response at low temperature (T ) and/or small chemical potential (μ ) is found to change from T2 (μ2) in the WSM phase to T3 /2 (|μ |3/2) at the phase boundary.

  6. Exploring the quantum-classical transition in an optical Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Zhang, Keye; Meystre, Pierre; Zhang, Weiping

    2014-05-01

    Recent experiments have demonstrated the Bose-Einstein condensation of photons in a dye microcavity. A remarkable feature is that it behaves as a condensate of massive particles essentially at room temperature and is coupled to the heat reservoir that realizes grand-canonical conditions. We analyze theoretically the control of that system by a secondary coherent cavity field that produces an optomechanical-like coupling between the probe and the condensate. We find that the controllable quantum statistics associated with the size of the reservoir allow one to prepare the photon condensate in a variety of nonclassical states, carry out quantum nondemolition measurements of its number fluctuations, and provide an effective tool to explore the physics of the quantum-classical transition regime.

  7. Band structure and optical transitions in the Hg3Se2Cl2 crystals

    NASA Astrophysics Data System (ADS)

    Bokotey, O. V.; Vakulchak, V. V.; Nebola, I. I.; Bokotey, A. A.

    2016-12-01

    First-principles calculations of the band structure for Hg3Se2Cl2 crystal were performed by means of density functional theory (DFT). The exchange and correlation potential was described within a framework of the local density approximation based on exchange-correlation energy optimization to calculate the total energy. DOS/PDOS and valence charge distribution were studied in details. Absorption near the fundamental edge was found to be due to indirect and direct allowed transitions. For device applications based on Hg3Se2Cl2 crystal, understanding these fundamental issues is highly important and essential. It should be noted that optoelectronic applications of Hg3Se2Cl2 are caused by coexistence of the large polarized Hg cations and a huge contribution of an harmonic phonon subsystem caused by anions.

  8. Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy.

    PubMed

    Wang, Zefang; Zhao, Liang; Mak, Kin Fai; Shan, Jie

    2017-02-08

    We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe2 and MoSe2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe2 and parallel spins in monolayer MoSe2. The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first-principles calculations. These values also suggest that both n- and p-type WSe2 and MoSe2 can be relevant for spin- and valley-based applications.

  9. Pressure Sensor via Optical Detection Based on a 1D Spin Transition Coordination Polymer

    PubMed Central

    Jureschi, Cătălin M.; Linares, Jorge; Rotaru, Aurelian; Ritti, Marie Hélène; Parlier, Michel; Dîrtu, Marinela M.; Wolff, Mariusz; Garcia, Yann

    2015-01-01

    We have investigated the suitability of using the 1D spin crossover coordination polymer [Fe(4-(2′-hydroxyethyl)-1,2,4-triazole)3]I2·H2O, known to crossover around room temperature, as a pressure sensor via optical detection using various contact pressures up to 250 MPa. A dramatic persistent colour change is observed. The experimental data, obtained by calorimetric and Mössbauer measurements, have been used for a theoretical analysis, in the framework of the Ising-like model, of the thermal and pressure induced spin state switching. The pressure (P)-temperature (T) phase diagram calculated for this compound has been used to obtain the P-T bistability region. PMID:25621610

  10. Theoretical study of intraband optical transitions in conduction band of dot-in-a-well system

    SciTech Connect

    Chaganti, Venkata R.; Apalkov, Vadym

    2014-02-15

    We study numerically absorption optical spectra of n-doped InAs/In{sub 015}Ga{sub 085}As/GaAs quantum dot-in-a-well systems. The absorption spectra are mainly determined by the size of a quantum dot and have weak dependence on the thickness of quantum well and position of the dot in a well. The dot-in-a-well system is sensitive to both in-plane and out-of-plane polarizations of the incident light with much stronger absorption intensities for the in-plane-polarized light. The absorption spectrum of in-plane-polarized light has also a multi-peak structure with two or three peaks of comparable intensities, while the absorption spectrum of out-of-plane polarized light has a single well-pronounced peak.

  11. Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Zefang; Zhao, Liang; Mak, Kin Fai; Shan, Jie

    2017-02-01

    We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe2 and MoSe2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe2, and parallel spins in monolayer MoSe2. The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first principles calculations. These values also suggest that both n- and p-type WSe2 and MoSe2 can be relevant for spin- and valley-based applications

  12. Optically trapped atom interferometry using the clock transition of large 87Rb Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Altin, P. A.; McDonald, G.; Döring, D.; Debs, J. E.; Barter, T. H.; Robins, N. P.; Close, J. D.; Haine, S. A.; Hanna, T. M.; Anderson, R. P.

    2011-11-01

    In our original paper (Altin et al 2011 New J. Phys. 13 065020), we presented the results from a Ramsey atom interferometer operating with an optically trapped sample of up to 106 Bose-condensed 87Rb atoms in the mF = 0 clock states. We were unable to observe projection noise fluctuations on the interferometer output, which we attribute to the stability of our microwave oscillator and background magnetic field. Numerical simulations of the Gross-Pitaevskii equations for our system show that dephasing due to spatial dynamics driven by interparticle interactions accounts for much of the observed decay in fringe visibility at long interrogation times. The simulations show good agreement with the experimental data when additional technical decoherence is accounted for, and suggest that the clock states are indeed immiscible. With smaller samples of 5 × 104 atoms, we observe a coherence time of τ = 1.0+0.5-0.3 s.

  13. Optical Transients Powered by Magnetars: Dynamics, Light Curves, and Transition to the Nebular Phase

    NASA Astrophysics Data System (ADS)

    Wang, Ling-Jun; Wang, S. Q.; Dai, Z. G.; Xu, Dong; Han, Yan-Hui; Wu, X. F.; Wei, Jian-Yan

    2016-04-01

    Millisecond magnetars can be formed via several channels: core collapse of massive stars, accretion-induced collapse of white dwarfs (WDs), double WD mergers, double neutron star (NS) mergers, and WD-NS mergers. Because the mass of ejecta from these channels could be quite different, their light curves are also expected to be diverse. We evaluate the dynamic evolution of optical transients powered by millisecond magnetars. We find that the magnetar with a short spin-down timescale converts its rotational energy mostly into the kinetic energy of the transient, while the energy of a magnetar with a long spin-down timescale goes into radiation of the transient. This leads us to speculate that hypernovae could be powered by magnetars with short spin-down timescales. At late times the optical transients will gradually evolve into a nebular phase because of the photospheric recession. We treat the photosphere and nebula separately because their radiation mechanisms are different. In some cases the ejecta could be light enough that the magnetar can accelerate it to a relativistic speed. It is well known that the peak luminosity of a supernova (SN) occurs when the luminosity is equal to the instantaneous energy input rate, as shown by Arnett. We show that photospheric recession and relativistic motion can modify this law. The photospheric recession always leads to a delay of the peak time {t}{pk} relative to the time {t}× at which the SN luminosity equals the instantaneous energy input rate. Relativistic motion, however, may change this result significantly.

  14. SEEDS ADAPTIVE OPTICS IMAGING OF THE ASYMMETRIC TRANSITION DISK OPH IRS 48 IN SCATTERED LIGHT

    SciTech Connect

    Follette, Katherine B.; Close, Laird M.; Grady, Carol A.; Swearingen, Jeremy R.; Sitko, Michael L.; Champney, Elizabeth H.; Van der Marel, Nienke; Maaskant, Koen; Min, Michiel; Takami, Michihiro; Kuchner, Marc J; McElwain, Michael W.; Muto, Takayuki; Mayama, Satoshi; Fukagawa, Misato; Russell, Ray W.; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Abe, Lyu; and others

    2015-01-10

    We present the first resolved near-infrared imagery of the transition disk Oph IRS 48 (WLY 2-48), which was recently observed with ALMA to have a strongly asymmetric submillimeter flux distribution. H-band polarized intensity images show a ∼60 AU radius scattered light cavity with two pronounced arcs of emission, one from northeast to southeast and one smaller, fainter, and more distant arc in the northwest. K-band scattered light imagery reveals a similar morphology, but with a clear third arc along the southwestern rim of the disk cavity. This arc meets the northwestern arc at nearly a right angle, revealing the presence of a spiral arm or local surface brightness deficit in the disk, and explaining the east-west brightness asymmetry in the H-band data. We also present 0.8-5.4 μm IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0 ± 1 and measure a low mass accretion rate of 10{sup –8.5} M {sub ☉} yr{sup –1}, both consistent with previous estimates. We investigate a variety of reddening laws in order to fit the multiwavelength spectral energy distribution of Oph IRS 48 and find a best fit consistent with a younger, higher luminosity star than previous estimates.

  15. Independent Control of Optical and Explosive Properties: Pyrazole-Tetrazine Complexes of First Row Transition Metals.

    PubMed

    Myers, Thomas W; Chavez, David E; Hanson, Susan K; Scharff, R Jason; Scott, Brian L; Veauthier, Jacqueline M; Wu, Ruilian

    2015-08-17

    Complexes of 3-amino-6-(3,5-dimethylpyrazole)tetrazine) (NH2TzDMP, 1) and 3-(3,3'-dinitroazetidine)-6-(3,5-dimethylpyrazole)tetrazine) (DNAZTzDMP, 2) with first row transition metal centers were synthesized. Reactions of Fe(II)(H2O)6(BF4)2 and Fe(NO3)3·9H2O with 1 and 2 both led to complexes of the form [(RTzDMP)3Fe]X2 (X = BF4, R = NH2 (3), DNAZ (4); X = NO3, R = NH2 (5), DNAZ (6)), which showed intense MLCT bands in the visible region of the spectrum. Ligands 1 and 2 also reacted with Cu(II)(NO3)2·5/2H2O to form [(RTzDMP)2Cu(NO3)][NO3] (R = NH2 (7), DNAZ (8)) in addition to reacting with Cu(I)(CH3CN)4(PF6) to form [(RTzDMP)2Cu][PF6] (R = NH2 (9), DNAZ (10)). Lastly reactions of 1 and 2 with Co(NO3)2·6H2O and Ni(NO3)2·6H2O led to [(NH2TzDMP)2Co(H2O) (NO3)][NO3] (11), [(DNAZTzDMP)2Co(H2O)2][NO3]2 (12), [(NH2TzDMP)3Ni][NO3]2 (13), and [(DNAZTzDMP)2Ni(H2O)2][NO3]2 (14). The complexes display rich electrochemical and photophysical properties that are unaffected by derivation with explosive groups.

  16. Renormalization of optical transition strengths in semiconductor nanoparticles due to band mixing

    DOE PAGES

    Velizhanin, Kirill A.

    2016-05-25

    We report that unique optical properties of semiconductor nanoparticles (SN) make them very promising in the multitude of applications including lasing, light emission and photovoltaics. In many of these applications it is imperative to understand the physics of interaction of electrons in a SN with external electromagnetic fields on the quantitative level. In particular, the strength of electron–photon coupling determines such important SN parameters as the radiative lifetime and absorption cross section. This strength is often assumed to be fully encoded by the so called Kane momentum matrix element. This parameter, however, pertains to a bulk semiconductor material and, asmore » such, is not sensitive to the quantum confinement effects in SNs. In this work we demonstrate that the quantum confinement, via the so called band mixing, can result in a significant suppression of the strength of electron interaction with electromagnetic field. Within the envelope function formalism we show how this suppression can be described by introducing an effective energy-dependent Kane momentum. Then, the effect of band mixing on the efficiencies of various photoinduced processes can be fully captured by the conventional formulae (e.g., spontaneous emission rate), once the conventional Kane momentum is substituted with the renormalized energy-dependent Kane momentum introduced in here. Lastly, as an example, we evaluate the energy-dependent Kane momentum for spherical PbSe and PbS SNs (i.e., quantum dots) and show that neglecting band mixing in these systems can result in the overestimation of absorption cross sections and emission rates by a factor of ~2.« less

  17. Renormalization of optical transition strengths in semiconductor nanoparticles due to band mixing

    SciTech Connect

    Velizhanin, Kirill A.

    2016-05-25

    We report that unique optical properties of semiconductor nanoparticles (SN) make them very promising in the multitude of applications including lasing, light emission and photovoltaics. In many of these applications it is imperative to understand the physics of interaction of electrons in a SN with external electromagnetic fields on the quantitative level. In particular, the strength of electron–photon coupling determines such important SN parameters as the radiative lifetime and absorption cross section. This strength is often assumed to be fully encoded by the so called Kane momentum matrix element. This parameter, however, pertains to a bulk semiconductor material and, as such, is not sensitive to the quantum confinement effects in SNs. In this work we demonstrate that the quantum confinement, via the so called band mixing, can result in a significant suppression of the strength of electron interaction with electromagnetic field. Within the envelope function formalism we show how this suppression can be described by introducing an effective energy-dependent Kane momentum. Then, the effect of band mixing on the efficiencies of various photoinduced processes can be fully captured by the conventional formulae (e.g., spontaneous emission rate), once the conventional Kane momentum is substituted with the renormalized energy-dependent Kane momentum introduced in here. Lastly, as an example, we evaluate the energy-dependent Kane momentum for spherical PbSe and PbS SNs (i.e., quantum dots) and show that neglecting band mixing in these systems can result in the overestimation of absorption cross sections and emission rates by a factor of ~2.

  18. Renormalization of optical transition strengths in semiconductor nanoparticles due to band mixing

    NASA Astrophysics Data System (ADS)

    Velizhanin, Kirill A.

    2016-12-01

    Unique optical properties of semiconductor nanoparticles (SN) make them very promising in the multitude of applications including lasing, light emission and photovoltaics. In many of these applications it is imperative to understand the physics of interaction of electrons in a SN with external electromagnetic fields on the quantitative level. In particular, the strength of electron-photon coupling determines such important SN parameters as the radiative lifetime and absorption cross section. This strength is often assumed to be fully encoded by the so called Kane momentum matrix element. This parameter, however, pertains to a bulk semiconductor material and, as such, is not sensitive to the quantum confinement effects in SNs. In this work we demonstrate that the quantum confinement, via the so called band mixing, can result in a significant suppression of the strength of electron interaction with electromagnetic field. Within the envelope function formalism we show how this suppression can be described by introducing an effective energy-dependent Kane momentum. Then, the effect of band mixing on the efficiencies of various photoinduced processes can be fully captured by the conventional formulae (e.g., spontaneous emission rate), once the conventional Kane momentum is substituted with the renormalized energy-dependent Kane momentum introduced in here. As an example, we evaluate the energy-dependent Kane momentum for spherical PbSe and PbS SNs (i.e., quantum dots) and show that neglecting band mixing in these systems can result in the overestimation of absorption cross sections and emission rates by a factor of ∼ 2.

  19. Growth evolution and phase transition from chalcocite to digenite in nanocrystalline copper sulfide: Morphological, optical and electrical properties

    PubMed Central

    Quintana-Ramirez, Priscilla Vasthi; Santos-Cruz, José; Vega-González, Marina; Martínez-Alvarez, Omar; Castaño-Meneses, Víctor Manuel; Acosta-Torres, Laura Susana; de la Fuente-Hernández, Javier

    2014-01-01

    Summary Copper sulfide is a promising p-type inorganic semiconductor for optoelectronic devices such as solar cells, due its small band gap energy and its electrical properties. In this work nanocrystalline copper sulfide (CuxS), with two stoichiometric ratios (x = 2, 1.8) was obtained by one-pot synthesis at 220, 230, 240 and 260 °C in an organic solvent and amorphous CuxS was obtained in aqueous solution. Nanoparticle-like nucleation centers are formed at lower temperatures (220 °C), mixtures of morphologies (nanorods, nanodisks and nanoprisms) are seen at 230 and 240 °C, in which the nanodisks are predominant, while big hexagonal/prismatic crystals are obtained at 260 °C according to TEM results. A mixture of chalcocite and digenite phases was found at 230 and 240 °C, while a clear transition to a pure digenite phase was seen at 260 °C. The evolution of morphology and transition of phases is consistent to the electrical, optical, and morphological properties of the copper sulfide. In fact, digenite Cu1.8S is less resistive (346 Ω/sq) and has a lower energy band gap (1.6 eV) than chalcocite Cu2S (5.72 × 105 Ω/sq, 1.87 eV). Low resistivity was also obtained in CuxS synthesized in aqueous solution, despite its amorphous structure. All CuxS products could be promising for optoelectronic applications. PMID:25247136

  20. Growth evolution and phase transition from chalcocite to digenite in nanocrystalline copper sulfide: Morphological, optical and electrical properties.

    PubMed

    Quintana-Ramirez, Priscilla Vasthi; Arenas-Arrocena, Ma Concepción; Santos-Cruz, José; Vega-González, Marina; Martínez-Alvarez, Omar; Castaño-Meneses, Víctor Manuel; Acosta-Torres, Laura Susana; de la Fuente-Hernández, Javier

    2014-01-01

    Copper sulfide is a promising p-type inorganic semiconductor for optoelectronic devices such as solar cells, due its small band gap energy and its electrical properties. In this work nanocrystalline copper sulfide (Cu x S), with two stoichiometric ratios (x = 2, 1.8) was obtained by one-pot synthesis at 220, 230, 240 and 260 °C in an organic solvent and amorphous Cu x S was obtained in aqueous solution. Nanoparticle-like nucleation centers are formed at lower temperatures (220 °C), mixtures of morphologies (nanorods, nanodisks and nanoprisms) are seen at 230 and 240 °C, in which the nanodisks are predominant, while big hexagonal/prismatic crystals are obtained at 260 °C according to TEM results. A mixture of chalcocite and digenite phases was found at 230 and 240 °C, while a clear transition to a pure digenite phase was seen at 260 °C. The evolution of morphology and transition of phases is consistent to the electrical, optical, and morphological properties of the copper sulfide. In fact, digenite Cu1.8S is less resistive (346 Ω/sq) and has a lower energy band gap (1.6 eV) than chalcocite Cu2S (5.72 × 10(5) Ω/sq, 1.87 eV). Low resistivity was also obtained in Cu x S synthesized in aqueous solution, despite its amorphous structure. All Cu x S products could be promising for optoelectronic applications.

  1. Ultracold fermions in a one-dimensional bipartite optical lattice: Metal-insulator transitions driven by shaking

    NASA Astrophysics Data System (ADS)

    Di Liberto, M.; Malpetti, D.; Japaridze, G. I.; Morais Smith, C.

    2014-08-01

    We theoretically investigate the behavior of a system of fermionic atoms loaded in a bipartite one-dimensional optical lattice that is under the action of an external time-periodic driving force. By using Floquet theory, an effective model is derived. The bare hopping coefficients are renormalized by zeroth-order Bessel functions of the first kind with different arguments for the nearest-neighbor and next-nearest-neighbor hopping. The insulating behavior characterizing the system at half filling in the absence of driving is dynamically suppressed, and for particular values of the driving parameter the system becomes either a standard metal or an unconventional metal with four Fermi points. The existence of the four-Fermi-point metal relies on the fact that, as a consequence of the shaking procedure, the next-nearest-neighbor hopping coefficients become significant compared to the nearest-neighbor ones. We use the bosonization technique to investigate the effect of on-site Hubbard interactions on the four-Fermi-point metal-insulator phase transition. Attractive interactions are expected to enlarge the regime of parameters where the unconventional metallic phase arises, whereas repulsive interactions reduce it. This metallic phase is known to be a Luther-Emery liquid (spin-gapped metal) for both repulsive and attractive interactions, contrary to the usual Hubbard model, which exhibits a Mott-insulator phase for repulsive interactions. Ultracold fermions in driven one-dimensional bipartite optical lattices provide an interesting platform for the realization of this long-studied four-Fermi-point unconventional metal.

  2. Band edge modulation and interband optical transition in AlN:Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Pu; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Zhong, Hong-xia; Ding, Yi-min; Lu, Jing; Wang, Xihua

    2014-04-01

    AlN nanotubes (NTs) have many novel characteristics and great potential applications in electronic and optoelectronic nanodevices. However, little is known about the influence of Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} co-doping effects on their optical properties. Here, we focus on investigating the electronic structures, clarify the interband optical transition mechanism and give a clear atomic picture for the important electron/hole localization centre in AlN:Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} NTs using the GGA-1/2 method. We find that the Mg_{{\\rm{Al}}} doping efficiency can be improved effectively due to O_{{\\rm{N}}} doping in AlN NTs. The Mg_{{\\rm{Al}}} and O_{{\\rm{N}}} form Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex easily along the AlN NT axis (C-axis). The Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex can result in a remarkable charge transfer around it and modify the valence band maximum and conduction band minimum significantly. Meanwhile, the Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex also forms the important exciton localization centre and effectively enhances the interband radiative recombination rate. Moreover, the light emission/absorption sensitively depends on its polarization. The parallel polarized light ({\\mathbf{E}}\\shortparallel {\\rm{C}}) is much stronger than the perpendicular one ({\\mathbf{E}}\\bot {\\rm{C}}). The Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} co-doping thus paves a new way for improving the performance of electronic and optoelectronic nanodevices based on AlN NTs.

  3. Contribution of the transition moments, form of the absorption band, exciton, and the correlation effects in the linear and nonlinear optical properties of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Díaz-Ponce, Javier Alejandro

    2017-04-01

    This work compares the linear and nonlinear optical properties of polyenes and polyenynes. The simulation was made for finite and infinite conjugation of conjugated polymers, such as polyacetylene, β-carotene, bis (p-toluene sulfonate) (PTS) polyenyne, and a short conjugated polyenyne poly-2,6-decadyin-1,6-ylene azelate (PHDAz). The resonance energy and degree of conjugation are determined by fitting the linear absorption spectra. These parameters are then used for calculating the two photon and third-order nonlinear optical properties. The contribution of the transition moment, the form of the absorption band, the exciton, and phonons in the optical properties are determined. The difference of the experimental values is assigned to correlation effects. We found that the exciton, the correlation effects, and the conduction band are more important in the optical properties of polyenynes than of polyenes. In this way, the dependence of the optical properties of polyenynes on the conduction band makes it possible to increase their nonlinear optical properties by interaction with photons (θ ≈ 0). The dependence of the optical properties on the conduction band also produces that the finiteness of the conjugation strongly decreases the optical properties of polyenynes in relation to polyenes with similar conjugation. On the other hand, the phonons are more important in the optical properties of polyenes than of polyenynes. Consequently, the band is indirect for the studied polyenes and direct for the polyenynes. Therefore, the nonlinear optical properties in the resonance frequency of polyenyne PTS are higher than those for polyacetylene. We also found that asymmetric oscillations of χ(3) in the Brillouin zone increases the χ(3) final value in polyenynes. In addition, we found a change of sign of the wave function coefficients by the Peierls distortion of polyenes to become polyenynes, but this change of sign does not affect the optical properties. As a corollary

  4. Coherent optical transition radiation and self-amplified spontaneous emission generated by chicane-compressed electron beams

    SciTech Connect

    Lumpkin, A.H.; Dejus, R.J.; Sereno, N.S.; /Argonne

    2009-02-01

    Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression of photoinjector beams by a chicane have been reported during the commissioning of the Linac Coherent Light Source (LCLS) accelerator and recently at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of 10 and 100 in the APS case at the 150-MeV and 375-MeV OTR stations, respectively. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal space charge (LSC) microbunching instability which leads to coherent OTR (COTR) emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible-UV regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and inducing the SASE startup at those structures. Separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength were reported. The details of these observations and operational parameters will be presented.

  5. Coherent optical transition radiation and self-amplified spontaneous emission generated by chicane-compressed electron beams

    NASA Astrophysics Data System (ADS)

    Lumpkin, A. H.; Dejus, R. J.; Sereno, N. S.

    2009-04-01

    Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression of photoinjector beams by a chicane have been reported during the commissioning of the Linac Coherent Light Source accelerator and recently at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of 10 and 100 in the APS case at the 150-MeV and 375-MeV OTR stations, respectively. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal space charge microbunching instability which leads to coherent OTR emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and inducing the SASE startup at those “prebunched” structures. Separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength were reported. The details of these observations and operational parameters will be presented.

  6. Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators

    NASA Astrophysics Data System (ADS)

    Silva, T. F.; Bonini, A. L.; Lima, R. R.; Maidana, N. L.; Malafronte, A. A.; Pascholati, P. R.; Vanin, V. R.; Martins, M. N.

    2012-09-01

    Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed.

  7. Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators.

    PubMed

    Silva, T F; Bonini, A L; Lima, R R; Maidana, N L; Malafronte, A A; Pascholati, P R; Vanin, V R; Martins, M N

    2012-09-01

    Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed.

  8. Energy Spread Monitoring for the JLAB Experimental Program: Synchrotron Light Interferometers, Optical Transition Radiation Monitors and Wire Scanners

    SciTech Connect

    Arne Freyberger; Yu-Chiu Chao; Pavel Chevtsov; Anthony Day; William Hicks; Michele Joyce; Jean-Claude Denard

    2004-05-01

    The hypernuclear physics program at JLAB requires an electron beam with small transverse size (sigma {approx} 100 {micro}m) and an upper limit on the RMS energy spread of delta E / E < 3 x 10{sup -}5. To measure and monitor these parameters, a beam size and energy spread measurement system has been created. The system consists of a set of wire scanners, Optical Transition Radiation (OTR) detectors, and Synchrotron Light Interferometers (SLI). The energy spread is measured via a set of wire scans performed at specific locations in the transport line, which is an invasive process. During physics operation the energy spread is monitored continuously with the OTR and/or the SLI. These devices are noninvasive [or nearly non-invasive in the case of OTR] and operate over a very wide range of beam energies (1.6 GeV) and currents ({approx}100 {micro}A down to few {micro}A). All components of this system are automated in an EPICS accelerator control environment. The paper presents our operational experience with the beam size and energy spread measurement system and its maintenance.

  9. Development of an optical transition radiation detector for profile monitoring of antiproton and proton beams at FNAL

    SciTech Connect

    Scarpine, V.E.; Lindenmeyer, C.W.; Tassotto, G.R.; Lumpkin, A.H.; /Argonne

    2005-05-01

    Optical transition radiation (OTR) detectors are being developed at Fermi National Accelerator Laboratory (FNAL) as part of the collider Run II upgrade program and as part of the NuMI primary beam line. These detectors are designed to measure 150 GeV antiprotons as well as 120 GeV proton beams over a large range of intensities. Design and development of an OTR detector capable of measuring beam in both directions down to beam intensities of {approx}5e9 particles for nominal beam sizes are presented. Applications of these OTR detectors as an on-line emittance monitor for both antiproton transfers and reverse-injected protons, as a Tevatron injection profile monitor, and as a high-intensity beam profile monitor for NuMI are discussed. In addition, different types of OTR foils are being evaluated for operation over the intensity range of {approx}5e9 to 5e13 particles per pulse, and these are described.

  10. Optical trapping of ultracold dysprosium atoms: transition probabilities, dynamic dipole polarizabilities and van der Waals C 6 coefficients

    NASA Astrophysics Data System (ADS)

    Li, H.; Wyart, J.-F.; Dulieu, O.; Nascimbène, S.; Lepers, M.

    2017-01-01

    The efficiency of the optical trapping of ultracold atoms depends on the atomic dynamic dipole polarizability governing the atom-field interaction. In this article, we have calculated the real and imaginary parts of the dynamic dipole polarizability of dysprosium in the ground and first excited levels. Due to the high electronic angular momentum of those two states, the polarizabilities possess scalar, vector and tensor contributions that we have computed, on a wide range of trapping wavelengths, using the sum-over-state formula. Using the same formalism, we have also calculated the C 6 coefficients characterizing the van der Waals interaction between two dysprosium atoms in the two lowest levels. We have computed the energies of excited states and the transition probabilities appearing in the sums, using a combination of ab initio and least-square-fitting techniques provided by the Cowan codes and extended in our group. Regarding the real part of the polarizability, for field frequencies far from atomic resonances, the vector and tensor contributions are two-orders-of-magnitude smaller than the scalar contribution, whereas for the imaginary part, the vector and tensor contributions represent a noticeable fraction of the scalar contribution. Finally, our anisotropic C 6 coefficients are much smaller than those published in the literature.

  11. Laser-induced phase transitions of Ge2Sb2Te5 thin films used in optical and electronic data storage and in thermal lithography.

    PubMed

    Chu, Cheng Hung; Shiue, Chiun Da; Cheng, Hsuen Wei; Tseng, Ming Lun; Chiang, Hai-Pang; Mansuripur, Masud; Tsai, Din Ping

    2010-08-16

    Amorphous thin films of Ge(2)Sb(2)Te(5), sputter-deposited on a ZnS-SiO(2) dielectric layer, are investigated for the purpose of understanding the structural phase-transitions that occur under the influence of tightly-focused laser beams. Selective chemical etching of recorded marks in conjunction with optical, atomic force, and electron microscopy as well as local electron diffraction analysis are used to discern the complex structural features created under a broad range of laser powers and pulse durations. Clarifying the nature of phase transitions associated with laser-recorded marks in chalcogenide Ge(2)Sb(2)Te(5) thin films provides useful information for reversible optical and electronic data storage, as well as for phase-change (thermal) lithography.

  12. Optical Imaging of Mesenchymal Epithelial Transition Factor (MET) for Enhanced Detection and Characterization of Primary and Metastatic Hepatic Tumors

    PubMed Central

    Esfahani, Shadi A.; Heidari, Pedram; Kim, Sun A.; Ogino, Shuji; Mahmood, Umar

    2016-01-01

    Purpose: To assess optical imaging of Mesenchymal-Epithelial Transition factor (MET) for delineation and characterization of intrahepatic models of human hepatocellular carcinoma (HCC) and metastatic colorectal cancer (CRC), and thereby demonstrate its potential use in precision oncology. Materials and Methods: MET expression in human CRC and HCC was assessed in tissue microarrays. We used GE-137, a modified cyanine 5-tagged peptide for MET targeting. HepG2 and Huh-7 (HCC) and HT-29 (CRC) cells with MET overexpression, and LNCaP cells (negative control) with minimal MET expression were incubated with the probe. Correlation between the relative fluorescence signal intensity and cellular MET expression level was assessed. Flow cytometry was used to assess probe specific binding and dissociation constant (Kd). Orthotopic xenograft models of human HCC and metastatic CRC were generated in nu/nu mice by subcapsular implantation of cells. Epifluorescence imaging was performed to capture the changes in deferential probe accumulation at different time points after injection. Target-to-liver background ratio (TBR) was calculated and the probe biodistribution within different organs was assessed. Histopathologic analysis of extracted xenografts was performed to correlate the tumors MET expression with probe uptake by cancer cells. Results: Approximately 91.5% of HCC and 81% of CRC microarray cores showed MET expression. HCC and CRC cells incubated with the probe showed substantial fluorescence compared to control LNCaP, with strong correlation between fluorescence signal and MET expression (R2 = 0.99, p < 0.001). Probe binding affinity to MET (Kd) was measured to be 2.9 ± 0.36 nM. Epifluorescence imaging showed intense uptake in subcapsular tumors with peak TBR of 5.46 ± 0.46 in Huh-7, 3.55 ± 0.38 in HepG2, and 15.93 ± 0.61 in HT-29 orthotopic xenografts at 4 hours post-injection (mean ± standard deviation). We demonstrated that in vivo probe uptake in xenografts is

  13. An optical transmission spectrum of the transiting hot Jupiter in the metal-poor WASP-98 planetary system

    NASA Astrophysics Data System (ADS)

    Mancini, L.; Giordano, M.; Mollière, P.; Southworth, J.; Brahm, R.; Ciceri, S.; Henning, Th.

    2016-09-01

    The WASP-98 planetary system represents a rare case of a hot Jupiter hosted by a metal-poor main-sequence star. We present a follow-up study of this system based on multiband photometry and high-resolution spectroscopy. Two new transit events of WASP-98 b were simultaneously observed in four passbands (g', r', i', z'), using the telescope-defocusing technique, yielding eight high-precision light curves with point-to-point scatters of less than 1 mmag. We also collected three spectra of the parent star with a high-resolution spectrograph, which we used to remeasure its spectral characteristics, in particular its metallicity. We found this to be very low, [Fe/H] = -0.49 ± 0.10, but larger than was previously reported, [Fe/H] = -0.60 ± 0.19. We used these new photometric and spectroscopic data to refine the orbital and physical properties of this planetary system, finding that the stellar and planetary mass measurements are significantly larger than those in the discovery paper. In addition, the multiband light curves were used to construct an optical transmission spectrum of WASP-98 b and probe the characteristics of its atmosphere at the terminator. We measured a lower radius at z' compared with the other three passbands. The maximum variation is between the r' and z' bands, has a confidence level of roughly 6σ and equates to 5.5 pressure scale heights. We compared this spectrum to theoretical models, investigating several possible types of atmospheres, including hazy, cloudy, cloud-free, and clear atmospheres with titanium and vanadium oxide opacities. We could not find a good fit to the observations, except in the extreme case of a clear atmosphere with TiO and VO opacities, in which the condensation of Ti and V was suppressed. As this case is unrealistic, our results suggest the presence of an additional optical-absorbing species in the atmosphere of WASP-98 b, of unknown chemical nature.

  14. Mg doping of thermochromic VO{sub 2} films enhances the optical transmittance and decreases the metal-insulator transition temperature

    SciTech Connect

    Mlyuka, N. R.; Niklasson, G. A.; Granqvist, C. G.

    2009-10-26

    Thermochromic films of Mg{sub x}V{sub 1-x}O{sub 2} were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by {approx}3 K/at. %Mg, while the optical transmittance increased concomitantly. Specifically, the transmittance of visible light and of solar radiation was enhanced by {approx}10% when the Mg content was {approx}7 at. %. Our results point at the usefulness of these films for energy efficient fenestration.

  15. Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

    NASA Astrophysics Data System (ADS)

    Su, Z. C.; Ning, J. Q.; Deng, Z.; Wang, X. H.; Xu, S. J.; Wang, R. X.; Lu, S. L.; Dong, J. R.; Yang, H.

    2016-03-01

    Anderson localization is a predominant phenomenon in condensed matter and materials physics. In fact, localized and delocalized states often co-exist in one material. They are separated by a boundary called the mobility edge. Mott transition may take place between these two regimes. However, it is widely recognized that an apparent demonstration of Anderson localization or Mott transition is a challenging task. In this article, we present a direct optical observation of a transition of radiative recombination dominant channels from delocalized (i.e., local extended) states to Anderson localized states in the GaInP base layer of a GaInP/GaAs single junction solar cell by the means of the variable-temperature electroluminescence (EL) technique. It is found that by increasing temperature, we can boost a remarkable transition of radiative recombination dominant channels from the delocalized states to the localized states. The delocalized states are induced by the local atomic ordering domains (InP/GaP monolayer superlattices) while the localized states are caused by random distribution of indium (gallium) content. The efficient transfer and thermal redistribution of carriers between the two kinds of electronic states was revealed to result in both a distinct EL mechanism transition and an electrical resistance evolution with temperature. Our study gives rise to a self-consistent precise picture for carrier localization and transfer in a GaInP alloy, which is an extremely technologically important energy material for fabricating high-efficiency photovoltaic devices.

  16. Influence of structure-selective fluorene-based polymer wrapping on optical transitions of single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tange, Masayoshi; Okazaki, Toshiya; Iijima, Sumio

    2013-12-01

    To understand how fluorene-based polymers selectively extract specific semiconducting single-wall carbon nanotubes (SWCNTs), we compared the optical transitions of SWCNTs wrapped with poly(9,9-dioctylfluorene-alt-pyridine) (PFOPy), i.e., structure-selective polymers, with those wrapped with poly(9,9-di-n-dodecylfluorene) (PFD), i.e., non-selective polymers, in organic solvents by using photoluminescence (PL) excitation spectroscopy. Two (n,m) species of PFOPy-wrapped SWCNTs with intermediate chiral angles exhibited blue-shifted emissions compared with the PFD-wrapped SWCNTs. The shifts in the peaks of PL signals cannot be explained in terms of the dielectric screening effect, but can plausibly be explained in terms of the strains of specific SWCNTs due to the PFOPy wrapping. Moreover, the emissions of specific SWCNTs wrapped with PFOPy were not blue-shifted as much when the solvent was changed from toluene to p-xylene, and this result could be accounted for by a change in the rigidity of the fluorene backbone. Moreover, using p-xylene instead of toluene lowered the selectivity of the SWCNT extraction, thereby suggesting the importance of having a rigid fluorene backbone for selective extraction of SWCNTs.To understand how fluorene-based polymers selectively extract specific semiconducting single-wall carbon nanotubes (SWCNTs), we compared the optical transitions of SWCNTs wrapped with poly(9,9-dioctylfluorene-alt-pyridine) (PFOPy), i.e., structure-selective polymers, with those wrapped with poly(9,9-di-n-dodecylfluorene) (PFD), i.e., non-selective polymers, in organic solvents by using photoluminescence (PL) excitation spectroscopy. Two (n,m) species of PFOPy-wrapped SWCNTs with intermediate chiral angles exhibited blue-shifted emissions compared with the PFD-wrapped SWCNTs. The shifts in the peaks of PL signals cannot be explained in terms of the dielectric screening effect, but can plausibly be explained in terms of the strains of specific SWCNTs due to the PFOPy

  17. Composition-dependent behavior of Co(d7) optical transitions in Cd1-x Cox Ga2S4 mixed crystals

    NASA Astrophysics Data System (ADS)

    Kim, Young-San; Park, Hyun; Hyun, Seung-Cheol; Jin, Moon-Seog; Park, Gye-Choon; Kim, Chang-Dae; Jang, Kiwan; Choi, In-Hwan; Kim, Wha-Tek

    2006-09-01

    The optical transitions due to the cobalt transition metal impurity centers with composition x in Cd1-k Cox Ga2S4 mixed crystals were investigated by optical absorption spectroscopy. The optical absorption spectra showed three crystal-field transitions between the ground state 4A2(4F) and the excited states 4T2(4F), 4T1(4F), and 4T1(4P) of substitutional Co2+ ions that were similar for all the investigated compositions. The crystal-field parameter (Dq ) and the Racah parameter (B ) obtained from the observed absorption bands showed a composition dependence such that the Dq parameter increases; on the other hand, the B parameter decreases with increasing composition x, which implies that the Racah parameter (B ) depends strongly on the host crystal. Also, the total splitting between the highest and the lowest states of the 4T1(4P) state split due to spin-orbit coupling showed a composition dependence varying from 1576 cm-1 to 1232 cm-1 with increasing x . The spin-orbit coupling parameter γ varied from 394 cm-1 to 308 cm-1 with composition x .

  18. Observation and Absolute Frequency Measurements of the {sup 1}S{sub 0}-{sup 3}P{sub 0} Optical Clock Transition in Neutral Ytterbium

    SciTech Connect

    Hoyt, C.W.; Barber, Z.W.; Oates, C.W.; Fortier, T.M.; Diddams, S.A.; Hollberg, L.

    2005-08-19

    We report the direct excitation of the highly forbidden (6s{sup 2}){sup 1}S{sub 0}{r_reversible}(6s6p){sup 3}P{sub 0} optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at {approx}70 {mu}K in a magneto-optical trap. The measured frequency in {sup 171}Yb (F=1/2) is 518 295 836 591.6{+-}4.4 kHz. The measured frequency in {sup 173}Yb (F=5/2) is 518 294 576 847.6{+-}4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10{sup 6}-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be {approx}10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.

  19. The Effect of Annealing Above Glass Transition Temperature on the Optical Properties of Se85Te10Bi5 Thin Films

    NASA Astrophysics Data System (ADS)

    Atyia, H. E.; Farid, A. S.

    2016-01-01

    Se85Te10Bi5 films have been deposited using the thermal evaporation technique. Films with different thicknesses in the thickness range 590.2-273.9 nm were annealed at different annealing temperatures above the glass transition temperature for 120 min. The structure of the annealed films was checked by x-ray diffraction analysis, which indicated a polycrystalline nature for all annealed films, and that the degree of crystallinity increased with increasing annealing temperature. From the reflectance ( R) and transmittance ( T) measurements, the values of the optical absorption coefficient ( α) for the annealed films were estimated to be in the wavelength range of 500-2500 nm. Analysis of the absorption coefficient data reveals allowed indirect transitions and the values of optical band gap ( E g). The values of ( E g) were found to be obeying the Tauc's relation and decreasing with increasing annealing temperature. This behavior is discussed as due to thermal disordering with the structural changes upon annealing. Optical parameters such as lattice and the infinite frequency dielectric constant as ( ɛ L and ɛ ∞), plasma frequency ( ω p), carrier concentration to the effective mass ratio ( N/m*), single- oscillator and dispersion energies ( E o and E d) were found. The dependence of the optical parameters on the annealing temperature was studied and discussed.

  20. Differential electron scattering cross sections for the first optically forbidden and resonance transitions in Mg II, Zn II and Cd II

    NASA Technical Reports Server (NTRS)

    Williams, I. D.; Chutjian, A.; Mawhorter, R. J.

    1986-01-01

    Differential electron scattering cross sections have been measured for dipole-forbidden and resonance transitions in Mg II, Zn II and Cd II in the angular range theta = 4-17 deg at 50 eV. These provide the first recorded angular distributions for an optically forbidden transition. It is found that while the cross section for excitation of the 4s (2)S-3d(9)4s(2) (2)D transition in Zn II is small, those for the 3s (2)S-3d (2)D, 4s (2)S (unresolved lines) in Mg II, and the 5s (2)S-4d(9)5s(2) D in Cd II are comparable in magnitude with the cross sections for resonance excitation. In addition, for Cd II it is found that the allowed and forbidden transitions have very similar angular distributions, and it is proposed that excitation to the 2D state may be dominated by a virtual 'double-dipole' transition via the 2P state. Also, the total excitation cross section of the resonance 2P state in Cd II is a factor of four higher than that predicted by the Gaunt factor approximation, suggesting that the accepted value for the oscillator strength may be too low.

  1. Infrared spectrum involving forbidden transitions & coriolis interaction and identification of optically pumped far infrared laser lines in asymmetrically mono-deuterated methanol (Methanol-D1)

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Indra

    2016-05-01

    In this paper new type of ΔK = 2 and 0 transitions have been identified in the Fourier Transform spectrum of Methanol-D1 (CH2DOH). These transitions are normally forbidden but a "Coriolis" type interaction with nearby states is believed to be contributing sufficient transition strength through intensity borrowing effect. This is the first time such forbidden transitions are reported to be identified in the excited states, in this molecule. The present conjecture is supported by observation of a many strong allowed transitions to upper terminating levels which are seen to be highly perturbed. This conclusion has been reached by comparing calculated energy levels using known molecular parameters (Pearson et al., 2012; Coudert et al., 2014; El Hilali et al., 2011; Quade et al., 1998; Richard Quade, 1998, 1999; Mukhopadhyay, 1997) and the actually observed FIR lines. The upper levels are seen to be upshifted from expected position. A closer look at the calculated energy values seems to indicate a possible interaction between the above states and other proximate torsional-rotational states could occur. The possible candidates for the interacting level manifolds are narrowed down through the presence of the forbidden transition. We also take the opportunity to propose alternate rotational quantum numbers for some of the assignments recently reported in the literature (El Hilali et al., 2011). Some ambiguities are pointed out on the data and the reported analysis. There remain too many such irregularities and we propose to gather a large body assigned transitions in a future catalog. Assignments and relevant comments on optically pumped FIR laser radiation are also made.

  2. Parity- and spin-forbidden optical transitions of Cr{sup +3} in GdAlO{sub 3}

    SciTech Connect

    Basso, H.C.

    1997-10-01

    In this paper, the electric-dipole transition induced by exchange is used to explain the strong dependence of spin- and parity-forbidden transitions of Cr{sup +3} on the sublattice magnetization of an antiferromagnet host. {copyright} {ital 1997} {ital The American Physical Society}

  3. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E.; Bruckbauer, J.; Edwards, P. R.; Martin, R. W.

    2014-11-07

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280 nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  4. In-situ investigation of the order-disorder transition in Cu2ZnSnSe4 by optical transmission spectroscopy

    NASA Astrophysics Data System (ADS)

    Stroth, Christiane; Sayed, Mohamed H.; Neerken, Janet; Mikolajczak, Ulf; Rey, Germain; Parisi, Jürgen; Gütay, Levent

    2017-02-01

    The existence of disorder is one possible reason for the limited performance of kesterite solar cells. Therefore further knowledge of the order-disorder phase transition, of factors which influence the degree of order and of methods to determine this material property is still required. In this study we investigated the order-disorder transition in the kesterite material Cu2ZnSnSe4 by in-situ optical transmission spectroscopy during heat treatments. We show in-situ results for the temperature dependence of the band gap and its tailing properties. The influence of cooling rates on the phase transition was analyzed as well as the ordering kinetics during annealing at a constant temperature. The critical temperature of the phase transition was determined and the existence of a control temperature range is shown, which allows for controlling the degree of order by the cooling rate within this range. Additionally we performed Raman analysis to link Raman spectra to the degree of order in Cu2ZnSnSe4. A correlation between the intensity ratio of A-modes as well as B-/ E- Raman modes and the degree of order was found.

  5. Laser-Induced Optical Pumping Measurements of Cross Section for Fine- and Hyperfine-Structure Transitions in Sodium Induced by Collisions with Helium and Argon Atoms

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Sung, C. C.

    1999-01-01

    Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections lor DELTA.F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), DELTA.F cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates m(sub F) measured previously using polarization sensitive absorption. Also, fine-structure transition cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

  6. Laser Induced Optical Pumping Measurements of Cross Sections for Fine and Hyperfine Structure Transitions in Sodium Induced by Collisions with Helium Argon Atoms

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Sung, C. C.

    1998-01-01

    Optical pumping of the ground states of sodium can radically alter the shape of the laser induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for (Delta)F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), (Delta)F cross sections. The hyperfine cross sections measured using this method, which is thought to be novel, are compared with cross sections for transitions involving polarized magnetic substates, m(sub F), measured previously using polarization sensitive absorption. Also, fine structure transition ((Delta)J) cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

  7. Effect of magnetic ordering of Dy2BaNiO5 on the crystal-field levels of dysprosium: optical spectroscopy of f-f transitions

    NASA Astrophysics Data System (ADS)

    Galkin, A. S.; Klimin, S. A.

    2016-12-01

    Optical transmission spectroscopy study of the Haldane magnet Dy2BaNiO5 was performed in the region of f-f transitions of the Dy3+ ion in a wide range of temperatures (5-300 K). At temperatures lower than TN (59 K), Kramers doublets of the rare-earth ion split. Spectroscopic data obtained were used to calculate the Schottky-type anomaly in the temperature dependence of the magnetic susceptibility of Dy2BaNiO5 and to model the experimental data available in literature. Anomalous behavior of crystal-field energies of the Dy3+ ion was attributed to the magnetoelectric interactions.

  8. Phase Transitions and Domain Structure in Mixed Tetragonal-Rhombohedral BiFeO3 thin films using Raman Spectroscopy and Nonlinear Optics

    NASA Astrophysics Data System (ADS)

    Vlahos, E.; Kumar, A.; Denev, S.; Melville, A.; Adamo, C.; Ihlefeld, J. F.; Sheng, G.; Zeches, R. J.; Zhang, J. X.; He, Q.; Yang, C. H.; Erni, R.; Rossell, M. D.; J, A.; Hatt; Chu, Y.-H.; Wang, C. H.; Ederer, C.; Gopalan, V.; Chen, L. Q.; Schlom, D. G.; Spaldin, N. A.; Martin, L. W.; Ramesh, R.; Tenne, Dmitri

    2010-03-01

    We have shown that biaxially strained BiFeO3 thin films can undergo an isosymmetric phase transition from a rhombohedral-like to a tetragonal-like phase. This talk discusses the evolution of the tetragonal and the mixed phases in BiFeO3/YAlO3 thin films with varying film thickness using optical second harmonic generation (SHG) and Raman spectroscopy. 25nm, 75nm, and 225 nm thick films were studied; thinner films are dominated by the tetragonal phase, whereas thicker films exhibit both tetragonal and rhombohedral phases. The evolution of these phases as function of film thickness and temperature was experimentally determined.

  9. Observation and Analysis of Optical Transitions Radiation at the NPS linac and its Use for Diagnostics of Electron Beams

    DTIC Science & Technology

    1990-06-01

    is the radiation caused by a charged particle moving in a medium at a speed faster than the speed of light in that same medium, had been known since... particle which experiences a change in the dielectric properties of the medium through which it travels produces electromagnetic radiation. This...energy of the charged particle causing the radiation. The radiation of photons which have frequencies in the optical region is known as optical

  10. The Optical Gravitational Lensing Experiment. Planetary and Low-Luminosity Object Transits in the Carina Fields of the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Udalski, A.; Szewczyk, O.; Zebrun, K.; Pietrzynski, G.; Szymanski, M.; Kubiak, M.; Soszynski, I.; Wyrzykowski, L.

    2002-12-01

    We present results of the second "planetary and low-luminosity object transit" campaign conducted by the OGLE-III survey. Three fields (35' X 35' each) located in the Carina regions of the Galactic disk (l ≈ 290°) were monitored continuously in February-May 2002. About 1150 epochs were collected for each field. The search for low depth transits was conducted on about 103 000 stars with photometry better than 15 mmag. In total, we discovered 62 objects with shallow depth (≤ 0.08 mag) flat-bottomed transits. For each of these objects several individual transits were detected and photometric elements were determined. Also lower limits on radii of the primary and companion were calculated. The 2002 OGLE sample of stars with transiting companions contains considerably more objects that may be Jupiter-sized (R < 1.6 R_Jup) compared to our 2001 sample. There is a group of planetary candidates with the orbital periods close to or shorter than one day. If confirmed as planets, they would be the shortest period extrasolar planetary systems. In general, the transiting objects may be extrasolar planets, brown dwarfs, or M-type dwarfs. One should be, however, aware that in some cases unresolved blends of regular eclipsing stars can mimic transits. Future spectral analysis and eventual determination of the amplitude of radial velocity should allow final classification. High resolution spectroscopic follow-up observations are, therefore, strongly encouraged. All photometric data are available to the astronomical community from the OGLE INTERNET archive.

  11. Optical Constants and Band Gap Evolution with Phase Transition in Sub-20-nm-Thick TiO2 Films Prepared by ALD.

    PubMed

    Shi, Yue-Jie; Zhang, Rong-Jun; Zheng, Hua; Li, Da-Hai; Wei, Wei; Chen, Xin; Sun, Yan; Wei, Yan-Feng; Lu, Hong-Liang; Dai, Ning; Chen, Liang-Yao

    2017-12-01

    Titanium dioxide (TiO2) ultrathin films with different thicknesses below 20 nm were grown by atomic layer deposition (ALD) on silicon substrates at 300 °C. Spectroscopic ellipsometry (SE) measurements were operated to investigate the effect of thickness on the optical properties of ultrathin films in the spectra range from 200 to 1000 nm with Forouhi-Bloomer (F-B) dispersion relation. It has been found that the refractive index and extinction coefficient of the investigated TiO2 ultrathin film increase while the band gap of TiO2 ultrathin film decreases monotonically with an increase in film thickness. Furthermore, with the purpose of studying the temperature dependence of optical properties of TiO2 ultrathin film, the samples were annealed at temperature from 400 to 900 °C in N2 atmosphere. The crystalline structure of deposited and annealed films was deduced by SE and supported by X-ray diffraction (XRD). It was revealed that the anatase TiO2 film started to transform into rutile phase when the annealing temperature was up to 800 °C. In this paper, a constructive and effective method of monitoring the phase transition in ultrathin films by SE has been proposed when the phase transition is not so obvious analyzed by XRD.

  12. Optical Imaging of Phase Transition and Li-Ion Diffusion Kinetics of Single LiCoO2 Nanoparticles During Electrochemical Cycling.

    PubMed

    Jiang, Dan; Jiang, Yingyan; Li, Zhimin; Liu, Tao; Wo, Xiang; Fang, Yimin; Tao, Nongjian; Wang, Wei; Chen, Hong-Yuan

    2017-01-11

    Understanding the phase transition and Li-ion diffusion kinetics of Li-ion storage nanomaterials holds promising keys to further improve the cycle life and charge rate of the Li-ion battery. Traditional electrochemical studies were often based on a bulk electrode consisting of billions of electroactive nanoparticles, which washed out the intrinsic heterogeneity among individuals. Here, we employ optical microscopy, termed surface plasmon resonance microscopy (SPRM), to image electrochemical current of single LiCoO2 nanoparticles down to 50 fA during electrochemical cycling, from which the phase transition and Li-ion diffusion kinetics can be quantitatively resolved in a single nanoparticle, in operando and high throughput manner. SPRM maps the refractive index (RI) of single LiCoO2 nanoparticles, which significantly decreases with the gradual extraction of Li-ions, enabling the optical read-out of single nanoparticle electrochemistry. Further scanning electron microscopy characterization of the same batch of nanoparticles led to a bottom-up strategy for studying the structure-activity relationship. As RI is an intrinsic property of any material, the present approach is anticipated to be applicable for versatile kinds of anode and cathode materials, and to facilitate the rational design and optimization toward durable and fast-charging electrode materials.

  13. Observations of CEF-split intermultiplet transitions in optically opaque EuBa{sub 2}Cu{sub 3}O{sub 7} using inelastic neutron scattering

    SciTech Connect

    Staub, U.; Soderholm, L.; Osborn, R.; Balcar, E.; Trunov, V.

    1995-02-01

    Inelastic neutron scattering (INS) results on the intermultiplet transitions J=0 {yields} 1 and J=l {yields} 2 in optically opaque EuBa{sub 2}Cu{sub 3}O{sub 7} are reported. Whereas these multiplets are split by the crystalline electric field (CEF), their low J values are influenced to first order only by the 2 second-order (J=l) and additional fourth-order (J=2) CEF parameters. B{sub 0}{sup 2}, B{sub 2}{sup 2} and the spin-orbit coupling parameter were obtained by fitting the splitting of the J=1 multiplet and the energy separation between the J=0 and 1 multiplets. The J=0 to 1 splitting observed here is smaller than previously seen by optical spectroscopic studies on a variety of transparent, ionic compounds, necessitating fitting of the free-ion parameter. Additional spectroscopic information on the J=2 multiplet indicates that additional fitting of free ion parameters must be included to adequately model the observed low energy separation between the two lowest J-multiplets. Preliminary calculation on the Q-dependence of the CEF split J=0 to 1 transitions and the comparison with observations are presented.

  14. Understanding ferromagnetism and optical absorption in 3d transition metal-doped cubic ZrO{sub 2} with the modified Becke-Johnson exchange-correlation functional

    SciTech Connect

    Boujnah, M.; Zaari, H.; El Kenz, A.; Labrim, H.; Benyoussef, A.; Mounkachi, O.

    2014-03-28

    The electronic structure, magnetic, and optical properties in cubic crystalline phase of Zr{sub 1−x}TM{sub x}O{sub 2} (TM = V, Mn, Fe, and Co) at x = 6.25% are studied using density functional theory with the Generalized Gradient Approximation and the modified Becke-Johnson of the exchange-correlation energy and potential. In our calculations, the zirconia is a p-type semiconductor and has a large band gap. We evaluated the possibility of long-range magnetic order for transition metal ions substituting Zr. Our results show that ferromagnetism is the ground state in V, Mn, and Fe-doped ZrO{sub 2} and have a high value of energy in Mn-doped ZrO{sub 2}. However, in Co-doped ZrO{sub 2}, antiferromagnetic ordering is more stable than the ferromagnetic one. The exchange interaction mechanism has been discussed to explain the responsible of this stability. Moreover, it has been found that the V, Mn, and Fe transition metals provide half-metallic properties considered to be the leading cause, responsible for ferromagnetism. Furthermore, the optical absorption spectra in the TM -doped cubic ZrO{sub 2} are investigated.

  15. Influence of thin AlAs layer insertion on intersubband optical transitions in GaAs/AlGaAs quantum- well structures

    NASA Astrophysics Data System (ADS)

    Liu, Dongfeng; Wang, Everett X.; Guo, Kangxian

    2017-02-01

    In this work, we demonstrate the thin AlAs layer insertion into GaAs/AlGaAs quantum well (QW) structures and its influence in energy transition in the frequency range of mid-infrared. To realize the more accurate calculation, the graded interface model of QW structures is integrated into our self-consistent solving of Schrodinger and Poisson equations to obtain the energy level and envelope wave functions of QW. We find the thin AlAs layer inserted at various positions in the well can obviously tune intersubband optical transitions. The corresponding tuning range can be 50 meV. We find that the thicker AlAs layer (2 monolayers) can provide wider tuning range and larger oscillator strength between subbands 1 and 3, compared with the thinner one (1 monolayer). Our results suggest that thin semiconductor layer may be an idea optimization design for the quantum well terahertz lasers which are based on optical pumping with mid-infrared lasers.

  16. Optical properties of light-sensitive liquid-crystal elastomers in the vicinity of the nematic-paranematic phase transition

    NASA Astrophysics Data System (ADS)

    Gregorc, Marko; Li, Hui; Domenici, Valentina; Ambrožič, Gabriela; Čopič, Martin; Drevenšek-Olenik, Irena

    2013-02-01

    We investigate light-induced patterning of a monodomain side-chain liquid crystal elastomer (SC-LCE) doped with light-sensitive azobenzene moiety in the temperature region close to the nematic-paranematic phase transition. We show that a strongly nonlinear relationship between the concentration of the cis isomers of the azomesogens and the refractive index modification of the material, which is characteristic for the phase transition region, results in nonmonotonous time dependence of the diffraction efficiency of a probe beam. From this effect we determine the sensitivity of the nematic transition temperature on the molar fraction of the cis isomers. The relation between the cis isomer molar fraction and nematic order also provides a possibility for recording hidden holograms, which can be made visible by cooling the sample from the paranematic to the nematic phase.

  17. Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

    PubMed Central

    Morzyński, Piotr; Bober, Marcin; Bartoszek-Bober, Dobrosława; Nawrocki, Jerzy; Krehlik, Przemysław; Śliwczyński, Łukasz; Lipiński, Marcin; Masłowski, Piotr; Cygan, Agata; Dunst, Piotr; Garus, Michał; Lisak, Daniel; Zachorowski, Jerzy; Gawlik, Wojciech; Radzewicz, Czesław; Ciuryło, Roman; Zawada, Michał

    2015-01-01

    We report a stability below 7 × 10−17 of two independent optical lattice clocks operating with bosonic 88Sr isotope. The value (429 228 066 418 008.3(1.9)syst (0.9)stat Hz) of the absolute frequency of the 1S0 – 3P0 transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures. PMID:26639347

  18. Absolute measurement of the 1S0 - 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link.

    PubMed

    Morzyński, Piotr; Bober, Marcin; Bartoszek-Bober, Dobrosława; Nawrocki, Jerzy; Krehlik, Przemysław; Śliwczyński, Łukasz; Lipiński, Marcin; Masłowski, Piotr; Cygan, Agata; Dunst, Piotr; Garus, Michał; Lisak, Daniel; Zachorowski, Jerzy; Gawlik, Wojciech; Radzewicz, Czesław; Ciuryło, Roman; Zawada, Michał

    2015-12-07

    We report a stability below 7 × 10(-17) of two independent optical lattice clocks operating with bosonic (88)Sr isotope. The value (429 228 066 418 008.3(1.9)(syst) (0.9)(stat) Hz) of the absolute frequency of the (1)S(0) - (3)P(0) transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures.

  19. Spatially direct and indirect optical transitions observed for AlInAs/AlGaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Neffati, R.; Saïdi, I.; Ben Radhia, S.; Ben Daly, A.; Maaref, M. A.; Boujdaria, K.; Lemaître, A.; Bernardot, F.; Testelin, C.

    2016-09-01

    The effects of the Aluminium concentration on the emission of Al0.45In0.55As/AlyGa1-y As quantum dots (QDs) are investigated by photoluminescence (PL), with the excitation power density as a variable parameter. The influence of a varying barrier composition on the QD emission is investigated theoretically and discussed with respect to PL measurements. For the highest barrier composition value (y = 0.77), we interpret the QD emission as originating from indirect type-II transitions involving electrons in the barrier X valley and heavy holes (HH), with S and P symmetry, in Al0.45In0.55As QDs. The PL spectra of the y = 0.38 sample exhibits three lines: two of them are related to indirect type-II transitions, in which the electron ground state belongs to the indirect gap (L and X) minima in the barrier conduction band, whereas the third transition is attributed to a direct type-I transitions.

  20. Microstructural and Optical properties of transition metal (Cu) doped ZnO diluted magnetic semiconductor nano thin films fabricated by sol gel method

    NASA Astrophysics Data System (ADS)

    Ozturk, Ozgur; Asikuzun, Elif; Tasci, A. Tolga; Arda, Lutfi; Demirozu Senol, Sevim; Celik, Sukru; Terzioglu, Cabir

    Undoped and Cu (Copper) doped ZnO (Zn1-xCuxO) semiconductor thin films were produced by using sol-gel method. Cu was doped 1%, 2%, 3%, 4% and 5% ratio. Methanol and monoethanolamine (MEA) were used as solvent and stabilizer. In this study, the effect of Cu doping was investigated on microstructural and optical properties of ZnO DMS thin films. XRD, SEM, AFM and UV-VIS spectrometer measurements were performed for the microstructural and optical characterization. XRD, SEM and AFM results were showed that all of Cu doped ZnO based thin films have a hexagonal structure. The grain size of Cu doped ZnO thin films and morphology of surface were changed with increasing Cu doping. The optical transmittance of transition metal (Cu) doped ZnO thin films were decreased with doping. Keywords:Diluted Magnetic Semiconductor (DMS), Thin Film, Cu-doping, Bandgap Energy, ZnO. This research has been supported by the Kastamonu University Scientific Research Projects Coordination Department under the Grant No. KU-BAP-05/2015-12 and the Scientific and Technological Research Council of Turkey (TUBITAK) Project No. 114F259.

  1. Metal mono-chalcogenides ZnX and CdX (X = S, Se and Te) monolayers: Chemical bond and optical interband transitions by first principles calculations

    NASA Astrophysics Data System (ADS)

    Safari, Mandana; Izadi, Zohreh; Jalilian, Jaafar; Ahmad, Iftikhar; Jalali-Asadabadi, Saeid

    2017-02-01

    In this paper, we explore the structural, electronic and optical properties of ZnX and CdX (X = S, Se and Te) compounds in the two-dimensional (2D) graphene-like structure using the full potential augmented plane waves plus local orbitals (FP-APW + lo) method. Unlike their bulk phase, they are optically inactive because of their indirect band gap nature except CdS and ZnS. These two compounds maintain their direct band gap nature and hence are optically active. The static dielectric constants for these monolayers illustrate increasing trend with decrease in the band gap values. Furthermore, an acceptable description of electron transitions in these monolayers is accomplished according to the imaginary parts of the dielectric functions and absorption spectra in ZnS and CdS as examples of each group of CdX and ZnX. The results presented in this article revealed that ZnS and CdS in the 2D structure can be effectively used in optoelectronic devices such as solar cell materials and so forth.

  2. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Study of Phase Transition Properties in Epitaxial Ferroelectric Film

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Dong; Teng, Bao-Hua; Ju, Yong-Feng; Cheng, Deng-Mu; Zhang, Chun-Lai

    2010-10-01

    Based on the transverse Ising model and using decoupling approximation to the Fermi-type Green's function, we study the phase transition properties of the epitaxial ferroelectric film with one substrate. A general recursive equation of the ferroelectric thin film with two n-layer materials is obtained, which enables us to study the phase transition properties for any number layers for epitaxial ferroelectric thin film. With the help of this equation, we analyze the effect of the exchange interaction and the transverse field in the phase diagram, the influence to the polarizations and Curie temperature numerically. The results show that epitaxial ferroelectric film are able to induce a strong increase or decrease of Curie temperature to different exchange interactions and transverse fields within the epitaxial film layers. The theoretical results are in reasonable accordance with experimental data of different ferroelectric thin film.

  3. Microstructure processes induced by phase transitions in a CuAu alloy as studied by acoustic emission and optical cinematography

    SciTech Connect

    Masek, P.; Chmelik, F.; Sima, V.; Brinck, A.; Neuhaeuser, H.

    1999-01-15

    Combined acoustic emission measurements and surface cinematography observations have been applied to determine the structure evolution during thermal loading of the CuAu alloy. Thermal history and the fashion of thermal loading have been shown to affect considerably the structure response of the CuAu alloy on temperature changes. On thermal loading, intense plastic deformation occurs in certain temperature intervals due to the relaxation of internal stresses induced by phase transitions and structure anisotropy. The main mechanism is twinning taking place most probably in (110) planes. Dislocation glide and grain-boundary sliding have also been observed as minor mechanisms. A shape-restoration effect associated with the order-disorder transition is revealed. Thermal cycling with upper temperatures over 500 C may also result in structural damage.

  4. Free-Surface Optical Scattering as an Indicator of the Shock-Induced Solid-Liquid Phase Transition in Tin

    SciTech Connect

    Stevens, G. D.; Lutz, S. S.; Marshall, B. R.; Turley, W. D.; Veeser, L. R.; Furlanetto, M. R.; Hixson, R. S.; Holtkamp, D. B.; Jensen, B. J.; Rigg, P. A.; Wilke, M. D.

    2008-07-01

    When highly polished metal surfaces melt upon release after shock loading, they exhibit features that suggest significant surface changes accompany the phase transition. The reflection of light from such surfaces changes from specular (pre-shock) to diffuse upon melting. A familiar manifestation of this phenomenon is the loss of signal light in VISAR measurements, which occurs at pressures high enough to melt the free surface. Unlike many other potential material phase-sensitive diagnostics (e.g., reflectometry, conductivity) that show relatively small (1%–10%) changes, the specularity of reflection provides a more sensitive and definitive indication of the solid-liquid phase transition. Data will be presented that support the hypothesis that specularity changes indicate melt in a way that can be measured easily and unambiguously.

  5. Warm ice giant GJ 3470b - II. Revised planetary and stellar parameters from optical to near-infrared transit photometry

    NASA Astrophysics Data System (ADS)

    Biddle, Lauren I.; Pearson, Kyle A.; Crossfield, Ian J. M.; Fulton, Benjamin J.; Ciceri, Simona; Eastman, Jason; Barman, Travis; Mann, Andrew W.; Henry, Gregory W.; Howard, Andrew W.; Williamson, Michael H.; Sinukoff, Evan; Dragomir, Diana; Vican, Laura; Mancini, Luigi; Southworth, John; Greenberg, Adam; Turner, Jake D.; Thompson, Robert; Taylor, Brian W.; Levine, Stephen E.; Webber, Matthew W.

    2014-09-01

    It is important to explore the diversity of characteristics of low-mass, low-density planets to understand the nature and evolution of this class of planets. We present a homogeneous analysis of 12 new and 9 previously published broad-band photometric observations of the Uranus-sized extrasolar planet GJ 3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M dwarfs. The consistency of our analysis explains some of the discrepancies between previously published results and provides updated constraints on the planetary parameters. Our data are also consistent with previous transit observations of this system. The physical properties of the transiting system can only be constrained as well as the host star is characterized, so we provide new spectroscopic measurements of GJ 3470 from 0.33 to 2.42 μm to aid our analysis. We find R* = 0.48 ± 0.04 R⊙, M* = 0.51 ± 0.06 M⊙, and Teff = 3652 ± 50K for GJ 3470, along with a rotation period of 20.70 ± 0.15 d and an R-band amplitude of 0.01 mag, which is small enough that current transit measurements should not be strongly affected by stellar variability. However, to report definitively whether stellar activity has a significant effect on the light curves, this requires future multiwavelength, multi-epoch studies of GJ 3470. We also present the most precise orbital ephemeris for this system: To = 2455983.70472 ± 0.00021BJDTDB, P = 3.336 6487^{+0.000 0043}_{-0.000 0033} d, and we see no evidence for transit timing variations greater than 1 min. Our reported planet to star radius ratio is 0.076 42 ± 0.000 37. The physical parameters of this planet are Rp = 3.88 ± 0.32 R⊕ and Mp = 13.73 ± 1.61 M⊕. Because of our revised stellar parameters, the planetary radius we present is smaller than previously reported values. We also perform a second analysis of the transmission spectrum of the entire ensemble of transit observations to date, supporting the existence of an H2-dominated atmosphere

  6. Measurement of Electron Beam Emittance Using Optical Transition Radiation and Development of a Diffuse Screen Electron Beam Monitor

    DTIC Science & Technology

    1990-12-01

    Zerodur ,irror, 2" relfects light. 1OZ20BD.1; 20th wave zerodur mirror , 1" reflects light. LS-35; 3’ x 5’ optical breadboard; for mounting components...profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen. The 20 DISTRIBUTION...Beam current and profile measurements using the diffuse screen were compared with measurements using a front surface mirror and a fluorescent screen

  7. Optical transition probabilities in Er3+- and Tm3+-doped LiLa9(SiO4)6O2 crystals.

    PubMed

    Cantelar, E; Quintanilla, M; Cussó, F; Cavalli, E; Bettinelli, M

    2010-06-02

    In this work, Er(3+) and Tm(3+)-doped LiLa(9)(SiO(4))(6)O(2) crystals have been grown from an Li(2)MoO(4) flux in the 1360-940 °C temperature range. Optical absorption spectra have been measured to obtain the experimental oscillator strengths of the transitions from the ground state to the excited levels. Judd-Ofelt calculations have been performed to estimate the Ω(2), Ω(4) and Ω(6) intensity parameters. The dynamics of selected Er(3+) and Tm(3+) manifolds have been investigated under selective pulsed excitation in order to determine the energy gap law by comparing the observed decay rates with the Judd-Ofelt predictions.

  8. Bound internal conversion versus nuclear excitation by electron transition: Revision of the theory of optical pumping of the Thm229 isomer

    NASA Astrophysics Data System (ADS)

    Karpeshin, F. F.; Trzhaskovskaya, M. B.

    2017-03-01

    Two-photon optical pumping of the 7.6-eV nuclear isomer in the singly ionized atoms of 229Th is considered. Differences between two mechanisms of the pumping, nuclear excitation in the electronic transition (NEET) and bound internal conversion (BIC), are derived and analyzed numerically. The BIC mechanism turns out to be more effective, by orders of magnitude, in accordance with previous calculations. Moreover, a numerical smallness in the NEET scheme is explicitly pointed out concerning singly and doubly charged ions. That is related to the smallness of the final vertex, responsible for conservation of energy. In the case of BIC, the calculated pumping rate of the isomer for the most effective scheme may be as high as 0.03 s-1.

  9. Effects of γ-irradiation on optical, electrical, and laser characteristics of pure and transition metal doped II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Konak, Tetyana; Tekavec, Michael; Fedorov, Vladimir V.; Mirov, Sergey B.

    2011-02-01

    We report a comprehensive study of gamma-irradiation on optical, electrical, and laser characteristics of pure and transition-metal doped single and polycrystalline ZnS and ZnSe. Polished pure, Cr-doped, and Ag, Au, Cu, Al, In, and Mn co-doped ZnS and ZnSe crystals after absorption and electro-conductivity characterization were gamma-irradiated at doses of 1.37x108, and 1.28x108 rad at +10 and -3°C, respectively. Dynamic RT absorption studies, electro-conductivity measurements and mid-IR lasing were performed for different exposition times of crystals at RT. Cr:ZnSe and Cr:ZnS lasers based on identical gamma-irradiated and non-irradiated crystals featured a very similar pump thresholds, slope efficiencies, and output powers.

  10. L-lysine-L-tartaric acid: New molecular complex with nonlinear optical properties. Structure, vibrational spectra and phase transitions

    SciTech Connect

    Debrus, S.; Marchewka, M.K. . E-mail: mkm@int.pan.wroc.pl; Baran, J.; Drozd, M.; Czopnik, R.; Pietraszko, A.; Ratajczak, H.

    2005-09-15

    The first X-ray diffraction and vibrational spectroscopic analysis of a novel complex between L-lysine and L-tartaric acid is reported. The structure was solved in two temperatures (320 and 260 K) showing incommensurate phase between them. Room-temperature powder infrared and Raman measurements for the L-lysine-L-tartaric acid molecular complex (1:1) were carried out. DSC measurements on powder samples indicate two phase transitions points at about 295, 300 and 293, 300 K, for heating and cooling, respectively, with noticeable temperature interval between them. Second harmonic generation efficiency d {sub eff}=0.35 d {sub eff} (KDP)

  11. Pressure dependence of the metal-insulator transition in κ-(BEDT-TTF)2Hg(SCN)2Cl: optical and transport studies.

    PubMed

    Löhle, A; Rose, E; Singh, S; Beyer, R; Tafra, E; Ivek, T; Zhilyaeva, E I; Lyubovskaya, R N; Dressel, M

    2017-02-08

    The two-dimensional organic conductor κ-(BEDT-TTF)2-Hg(SCN)2Cl exhibits a pronounced metal-insulator transition at [Formula: see text] K. From the splitting of the molecular vibrations, the phase transition can be unambiguously assigned to charge-ordering with [Formula: see text]. We have investigated the pressure evolution of this behavior by temperature-dependent electrical transport measurements and optical investigations applying hydrostatic pressure up to 12 kbar. The data reveal a mean-field like down-shift of [Formula: see text] with a critical pressure of [Formula: see text] kbar and a metallic state above the suppression of the charge-ordered state; no traces of superconductivity could be identified down to T  =  1.5 K. As the charge order [Formula: see text] sets in abruptly with decreasing temperature, its size remains unaffected by pressure. However, the fraction of charge imbalanced molecules decreases until it is completely absent above 1.6 kbar.

  12. Pressure dependence of the metal-insulator transition in κ-(BEDT-TTF)2Hg(SCN)2Cl: optical and transport studies

    NASA Astrophysics Data System (ADS)

    Löhle, A.; Rose, E.; Singh, S.; Beyer, R.; Tafra, E.; Ivek, T.; Zhilyaeva, E. I.; Lyubovskaya, R. N.; Dressel, M.

    2017-02-01

    The two-dimensional organic conductor κ-(BEDT-TTF)2-Hg(SCN)2Cl exhibits a pronounced metal-insulator transition at {{T}\\text{CO}}=30 K. From the splitting of the molecular vibrations, the phase transition can be unambiguously assigned to charge-ordering with 2{δρ}=0.2e . We have investigated the pressure evolution of this behavior by temperature-dependent electrical transport measurements and optical investigations applying hydrostatic pressure up to 12 kbar. The data reveal a mean-field like down-shift of {{T}\\text{CO}}≤ft( p\\right) with a critical pressure of {{p}c}=0.7+/- 0.1 kbar and a metallic state above the suppression of the charge-ordered state; no traces of superconductivity could be identified down to T  =  1.5 K. As the charge order {δρ} sets in abruptly with decreasing temperature, its size remains unaffected by pressure. However, the fraction of charge imbalanced molecules decreases until it is completely absent above 1.6 kbar.

  13. Measurement of the optical properties of lunar rocks in the transition zone, resulting from observations made by Lunokhod 2

    NASA Technical Reports Server (NTRS)

    Lipskiy, Y. N.; Shevchenko, V. V.

    1977-01-01

    Photometric measurements were carried out directly on the lunar surface with the aid of a calibration device, a plate with fields of different brightness, placed in the field of view of the panoramic telephotometers. The brightness of the fields of the calibration plate were measured in preliminary studies, relative to the brightness of a magnesia screen. This permitted determination of the reflectance features of the surficial lunar material relative to the standard most widely used in brightness studies of natural substances. The total brightness of sections a few centimeters across was recorded in direct proximity to the apparatus. The total area investigated in one panorama was about one square meter. Several areas in the mare and highland regions were studied. The albedos of various surface objects were obtained. A comparison of the brightness measurements with data from the RIFMA-M instrument discloses a correlation of the albedo change with change in chemical composition of the surface rock. Direct photometric studies of the lunar surface in the "mare-highland" transition zone assist in tracing the transition from one type of rock to another, and in obtaining information on the processes of material exchange between these two types of lunar landscape.

  14. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO{sub 2} doped with transition metal cations

    SciTech Connect

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-15

    The effect of nanocrystalline TiO{sub 2} doping with transition metal cations (Cu{sup 2+}, Fe{sup 3+}, Co{sup 2+}, Cr{sup 3+}) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO{sub 2} samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV. - Graphical abstract: A red shift of the absorption edge of nanocrystalline single-phase anatase after doping with transition metal cations. Highlights: Black-Right-Pointing-Pointer Single-phase anatase and rutile powders surface-doped with transition metal cations. Black-Right-Pointing-Pointer Absorption edge and band gap of rutile do not change with surface doping. Black-Right-Pointing-Pointer Band gap of surface-doped anatase reduces being the lowest for A/Fe. Black-Right-Pointing-Pointer The surface-doping improves photocatalytic activity of anatase. Black-Right-Pointing-Pointer The surface-doping inhibits photocatalytic activity of rutile.

  15. Substrate-induced renormalization of the quasiparticle and optical gaps in monolayer transition metal dichalcogenides from GW and GW-BSE calculations

    NASA Astrophysics Data System (ADS)

    da Jornada, Felipe H.; Ong, Chin Shen; Qiu, Diana Y.; Louie, Steven G.

    There has been a considerable effort to experimentally characterize the electronic and optical properties of novel atomically thin 2D semiconductors, such as mono- and few-layer transition metal dichalcogenides (TMDs). However, the role that different substrates play in these experiments still remains unclear. From a theoretical perspective, it is hard to include the substrate in an ab initio framework, while in experiments, it is often difficult to suspend these samples. Here, we present a new method to compute the substrate effect on the quasiparticle and optical properties of quasi-2D materials based on state-of-the-art ab initio GW and GW plus Bethe-Salpeter equation (GW-BSE) methods. We compute the effects of different metallic and semiconducting substrates, and show that the quasiparticle gap and exciton binding energy can be dramatically reduced even with semiconducting substrates. This work was supported by the National Science Foundation under Grant No. DMR15-1508412 and the DOE under Contract No. DE-AC02-05CH11231.

  16. Surface alignment, anchoring transitions, optical properties, and topological defects in the nematic phase of thermotropic bent-core liquid crystal A131

    NASA Astrophysics Data System (ADS)

    Senyuk, B.; Wonderly, H.; Mathews, M.; Li, Q.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2010-10-01

    We study optical, structural, and surface anchoring properties of thermotropic nematic bent-core material A131. The focus is on the features associated with orientational order as the material has been reported to exhibit not only the usual uniaxial nematic but also the biaxial nematic phase. We demonstrate that A131 experiences a surface anchoring transition from a perpendicular to tilted alignment when the temperature decreases. The features of the tilted state are consistent with surface-induced birefringence associated with smectic layering near the surface and a molecular tilt that changes along the normal to the substrates. The surface-induced birefringence is reduced to zero by a modest electric field that establishes a uniform uniaxial nematic state. Both refractive and absorptive optical properties of A131 are consistent with the uniaxial order. We found no evidence of the “polycrystalline” biaxial behavior in the cells placed in crossed electric and magnetic fields. We observe stable topological point defects (boojums and hedgehogs) and nonsingular “escaped” disclinations pertinent only to the uniaxial order. Finally, freely suspended films of A131 show uniaxial nematic and smectic textures; a decrease in the film thickness expands the temperature range of stability of smectic textures, supporting the idea of surface-induced smectic layering. Our conclusion is that A131 features only a uniaxial nematic phase and that the apparent biaxiality is caused by subtle surface effects rather than by the bulk biaxial phase.

  17. Influence of transition metal doping on the structural, optical, and magnetic properties of TiO2 films deposited on Si substrates by a sol–gel process

    PubMed Central

    2013-01-01

    Transition metal (TM)-doped TiO2 films (TM = Co, Ni, and Fe) were deposited on Si(100) substrates by a sol–gel method. With the same dopant content, Co dopants catalyze the anatase-to-rutile transformation (ART) more obviously than Ni and Fe doping. This is attributed to the different strain energy induced by the different dopants. The optical properties of TM-doped TiO2 films were studied with spectroscopic ellipsometry data. With increasing dopant content, the optical band gap (EOBG) shifts to lower energy. With the same dopant content, the EOBG of Co-doped TiO2 film is the smallest and that of Fe-doped TiO2 film is the largest. The results are related to electric disorder due to the ART. Ferromagnetic behaviors were clearly observed for TM-doped TiO2 films except the undoped TiO2 film which is weakly magnetic. Additionally, it is found that the magnetizations of the TM-doped TiO2 films decrease with increasing dopant content. PMID:24350904

  18. Transition metal (Fe, Co and Ni) oxide nanoparticles grafted graphitic carbon nitrides as efficient optical limiters and recyclable photocatalysts

    NASA Astrophysics Data System (ADS)

    Sridharan, Kishore; Kuriakose, Tintu; Philip, Reji; Park, Tae Joo

    2014-07-01

    A single-step pyrolysis assisted route towards the large scale fabrication of metal oxide nanoparticles (Fe2O3, Co3O4 and NiO) ingrained in graphitic carbon nitride (GCN) is demonstrated. Urea, an abundantly available precursor, plays a dual role during the synthesis: while it acts as a reducing agent, it also gets converted to GCN. The formation of GCN and the in-situ growth and embedment of oxide nanoparticles are discussed on the basis of the experimental results. The wide absorption of the samples in the visible light region makes them suitable for nonlinear transmission and photocatalytic activity studies. Visible light photocatalytic activities of the samples are studied by monitoring the degradation of Rhodamine B dye. Optical limiting properties of the prepared samples are studied through the open aperture z-scan technique using 5 ns laser pulses at a wavelength of 532 nm. The cost-efficient and time saving synthetic approach is complemented by the magnetic behaviour of the samples, which enables their use as recyclable photocatalyst and magnetically controllable optical limiters.

  19. Characterization by combined optical and FT infrared spectra of 3d-transition metal ions doped-bismuth silicate glasses and effects of gamma irradiation.

    PubMed

    ElBatal, F H; Abdelghany, A M; ElBatal, H A

    2014-03-25

    Optical and infrared absorption spectral measurements were carried out for binary bismuth silicate glass and other derived prepared samples with the same composition and containing additional 0.2% of one of 3d transition metal oxides. The same combined spectroscopic properties were also measured after subjecting the prepared glasses to a gamma dose of 8 Mrad. The experimental optical spectra reveal strong UV-near visible absorption bands from the base and extended to all TMs-doped samples and these specific extended and strong UV-near visible absorption bands are related to the contributions of absorption from both trace iron (Fe(3+)) ions present as contaminated impurities within the raw materials and from absorption of main constituent trivalent bismuth (Bi(3+)) ions. The strong UV-near visible absorption bands are observed to suppress any further UV bands from TM ions. The studied glasses show obvious resistant to gamma irradiation and only small changes are observed upon gamma irradiation. This observed shielding behavior is related to the presence of high Bi(3+) ions with heavy mass causing the observed stability of the optical absorption. Infrared absorption spectra of the studied glasses reveal characteristic vibrational bands due to both modes from silicate network and the sharing of Bi-O linkages and the presence of TMs in the doping level (0.2%) causes no distinct changes within the number or position of the vibrational modes. The presence of high Bi2O3 content (70 mol%) appears to cause stability of the structural building units towards gamma irradiation as revealed by FTIR measurements.

  20. Properties of bosons in a one-dimensional bichromatic optical lattice in the regime of the pinning transition: A worm-algorithm Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Sakhel, Asaad R.

    2016-09-01

    The sensitivity of the pinning transition (PT) as described by the sine-Gordon model of strongly interacting bosons confined in a shallow, one-dimensional, periodic optical lattice (OL), is examined against perturbations of the OL. The PT has been recently realized experimentally by Haller et al. [Nature (London) 466, 597 (2010), 10.1038/nature09259] and is the exact opposite of the superfluid-to-Mott-insulator transition in a deep OL with weakly interacting bosons. The continuous-space worm-algorithm (WA) Monte Carlo method [Boninsegni et al., Phys. Rev. E 74, 036701 (2006), 10.1103/PhysRevE.74.036701] is applied for the present examination. It is found that the WA is able to reproduce the PT, which is another manifestation of the power of continuous-space WA methods in capturing the physics of phase transitions. In order to examine the sensitivity of the PT, it is tweaked by the addition of the secondary OL. The resulting bichromatic optical lattice (BCOL) is considered with a rational ratio of the constituting wavelengths λ1 and λ2 in contrast to the commonly used irrational ratio. For a weak BCOL, it is chiefly demonstrated that this PT is robust against the introduction of a weaker, secondary OL. The system is explored numerically by scanning its properties in a range of the Lieb-Liniger interaction parameter γ in the regime of the PT. It is argued that there should not be much difference in the results between those due to an irrational ratio λ1/λ2 and those due to a rational approximation of the latter, bringing this in line with a recent statement by Boers et al. [Phys. Rev. A 75, 063404 (2007), 10.1103/PhysRevA.75.063404]. The correlation function, Matsubara Green's function (MGF), and the single-particle density matrix do not respond to changes in the depth of the secondary OL V1. For a stronger BCOL, however, a response is observed because of changes in V1. In the regime where the bosons are fermionized, the MGF reveals that hole excitations are

  1. Phase transitions and optical properties of the semiconducting and metallic phases of single-layer MoS₂.

    PubMed

    Fair, K M; Ford, M J

    2015-10-30

    We report density functional theory calculations for single layer MoS2 in its 2H, semiconducting and 1T metallic phases in order to understand the relative stability of these two phases and transition between them in the presence of adsorbed lithium atoms and under compressive strain. We have determined the diffusion barriers between the two phases and demonstrate how the presence of Li adatoms or strain can significantly reduce these barriers. We show that the 2H and 1T structures have the same energy under 15% biaxial, compressive strain. This is the same strain value posited by Lin et al (2014 Nat. Nanotechnology 9 391-396) for their intermediate α phase. Calculations of the 1T and 2H permittivity and electron energy loss spectrum are also performed and characterized.

  2. Definition of Shifts of Optical Transitions Frequencies due to Pulse Perturbation Action by the Photon Echo Signal Form

    NASA Astrophysics Data System (ADS)

    Lisin, V. N.; Shegeda, A. M.; Samartsev, V. V.

    2015-09-01

    A relative phase shift between the different groups of excited dipoles, which appears as result of its frequency splitting due to action of a pulse of electric or magnetic fields, depends on a time, if the pulse overlaps in time with echo-pulse. As а consequence, the echo waveform is changed. The echo time form is modulated. The inverse modulation period well enough approximates Zeeman and pseudo-Stark splitting in the cases of magnetic and, therefore, electrical fields. Thus the g-factors of ground 4I15/2 and excited 4F9/2 optical states of Er3+ ion in LuLiF4 and YLiF4 have been measured and pseudo-Stark shift of R1 line in ruby has been determined.

  3. Superfluid to Normal Fluid Phase Transition in the Bose Gas Trapped in Two-Dimensional Optical Lattices at Finite Temperature

    NASA Astrophysics Data System (ADS)

    Pires, M. O. C.; de Passos, E. J. V.

    2017-02-01

    We develop the Hartree-Fock-Bogoliubov theory at finite temperature for Bose gas trapped in the two-dimensional optical lattice with the on-site energy low enough that the gas presents superfluid properties. We obtain the condensate density as function of the temperature neglecting the anomalous density in the thermodynamics equation. The condensate fraction provides two critical temperature. Below the temperature T_{C1}, there is one condensate fraction. Above two condensate fractions merger up to the critical temperature T_{C2}. At temperatures larger than T_{C2}, the condensate fraction is null and, therefore, the gas is normal fluid. We resume by a finite-temperature phase diagram where three domains can be identified: the normal fluid, the superfluid with one stable condensate fraction and the superfluid with two condensate fractions being unstable one of them.

  4. A Real-Time Orbit Determination Method for Smooth Transition from Optical Tracking to Laser Ranging of Debris

    PubMed Central

    Li, Bin; Sang, Jizhang; Zhang, Zhongping

    2016-01-01

    A critical requirement to achieve high efficiency of debris laser tracking is to have sufficiently accurate orbit predictions (OP) in both the pointing direction (better than 20 arc seconds) and distance from the tracking station to the debris objects, with the former more important than the latter because of the narrow laser beam. When the two line element (TLE) is used to provide the orbit predictions, the resultant pointing errors are usually on the order of tens to hundreds of arc seconds. In practice, therefore, angular observations of debris objects are first collected using an optical tracking sensor, and then used to guide the laser beam pointing to the objects. The manual guidance may cause interrupts to the laser tracking, and consequently loss of valuable laser tracking data. This paper presents a real-time orbit determination (OD) and prediction method to realize smooth and efficient debris laser tracking. The method uses TLE-computed positions and angles over a short-arc of less than 2 min as observations in an OD process where simplified force models are considered. After the OD convergence, the OP is performed from the last observation epoch to the end of the tracking pass. Simulation and real tracking data processing results show that the pointing prediction errors are usually less than 10″, and the distance errors less than 100 m, therefore, the prediction accuracy is sufficient for the blind laser tracking. PMID:27347958

  5. The effect of temperature and pressure on optical absorption spectra of transition zone minerals - Implications for the radiative conductivity of the Earth's interior

    NASA Astrophysics Data System (ADS)

    Thomas, S.; Jacobsen, S. D.; Bina, C. R.; Goncharov, A. F.; Frost, D. J.; McCammon, C. A.

    2010-12-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivities of the Earth’s interior [e.g., 1]. Recent high-pressure studies imply that e.g. ringwoodite, γ-(Mg,Fe)2SiO4, does not become opaque in the near infrared and visible region, as previously assumed, but remains transparent to 21.5 GPa [2]. Therefore, it has been concluded that radiative heat transfer does not necessarily become blocked at high pressures of the mantle and ferromagnesian minerals actually might contribute to the heat flow in the Earth’s interior [2]. However, experimental results on temperature effects on radiative heat transfer are not available. We studied the effect of both, pressure and temperature, on the optical absorption of hydrous Fe-bearing ringwoodite, γ-(Mg,Fe)2SiO4, and hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, which are the main components of the Earth’s transition zone. Gem-quality single-crystals were synthesized at 18 GPa and 1400 °C in a 5000t multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For optical absorption measurements in the IR - VIS - UV spectral range (400 - 50000 cm-1) 50 µm sized single-crystals of ringwoodite and wadsleyite were double polished to thicknesses of 13 µm and 18 µm, respectively, and loaded in resistively heated diamond-anvil cells with argon as pressure medium. After taking measurements at high pressure and room temperature, ringwoodite was studied at 26 GPa up to 650 °C and wadsleyite spectra were recorded at 16 GPa up to 450 °C. At ambient pressure the absorption spectrum of ringwoodite reveals a crystal field band (Fe2+) at 12075 cm-1, an intervalence charge transfer band (Fe2+ to Fe3+) at 16491 cm-1, and an absorption edge due to ligand-metal charge transfer close to 30000 cm-1. The wadsleyite spectrum is characterized by a similar absorption edge in the VIS-UV range

  6. Temperature-Triggered Dielectric-Optical Duple Switch Based on an Organic-Inorganic Hybrid Phase Transition Crystal: [C5N2H16]2SbBr5.

    PubMed

    Mao, Chen-Yu; Liao, Wei-Qiang; Wang, Zhong-Xia; Zafar, Zainab; Li, Peng-Fei; Lv, Xing-Hui; Fu, Da-Wei

    2016-08-01

    Molecular optical-electrical duple switches (switch "ON" and "OFF" bistable states) represent a class of highly desirable intelligent materials because of their sensitive switchable physical and/or chemical responses, simple and environmentally friendly processing, light weights, and mechanical flexibility. In the current work, the phase transition of 1 (general formula R2MX5, [C5N2H16]2[SbBr5]) can be triggered by the order-disorder transition of the organic cations at 278.3 K. The temperature-induced phase transition causes novel bistable optical-electrical duple characteristics, which indicates that 1 might be an excellent candidate for a potential switchable optical-electrical (fluorescence/dielectric) material. In the dielectric measurements, remarkable bistable dielectric responses were detected, accompanied by striking anisotropy along various crystallographic axes. For the intriguing fluorescence emission spectra, the intensity and position changed significantly with the occurrence of the structural phase transition. We believe that these findings might further promote the application of halogenoantimonates(III) and halogenobismuthates(III) in the field of optoelectronic multifunctional devices.

  7. Method of optical self-mixing for pulse wave transit time in comparison with other methods and correlation with blood pressure

    NASA Astrophysics Data System (ADS)

    Meigas, Kalju; Lass, Jaanus; Kattai, Rain; Karai, Deniss; Kaik, Juri

    2004-07-01

    This paper is a part of research to develop convenient method for continuous monitoring of arterial blood pressure by non-invasive and non-oscillometric way. A simple optical method, using self-mixing in a diode laser, is used for detection of skin surface vibrations near the artery. These vibrations, which can reveal the pulsate propagation of blood pressure waves along the vasculature, are used for pulse wave registration. The registration of the Pulse Wave Transit Time (PWTT) is based on computing the time delay in different regions of the human body using an ECG as a reference signal. In this study, the comparison of method of optical self-mixing with other methods as photoplethysmographic (PPG) and bioimpedance (BI) for PWTT is done. Also correlation of PWTT, obtained with different methods, with arterial blood pressure is calculated. In our study, we used a group of volunteers (34 persons) who made the bicycle exercise test. The test consisted of cycling sessions of increasing workloads during which the HR changed from 60 to 180 beats per minute. In addition, a blood pressure (NIBP) was registered with standard sphygmomanometer once per minute during the test and all NIBP measurement values were synchronized to other signals to find exact time moments where the systolic blood pressure was detected (Korotkoff sounds starting point). Computer later interpolated the blood pressure signal in order to get individual value for every heart cycle. The other signals were measured continuously during all tests. At the end of every session, a recovery period was included until person's NIBP and heart rate (HR) normalized. As a result of our study it turned out that time intervals that were calculated from plethysmographic (PPG) waveforms were in the best correlation with systolic blood pressure. The diastolic pressure does not correlate with any of the parameters representing PWTT. The pulse wave signals measured by laser and piezoelectric transducer are very similar

  8. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO2 doped with transition metal cations

    NASA Astrophysics Data System (ADS)

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-01

    The effect of nanocrystalline TiO2 doping with transition metal cations (Cu2+, Fe3+, Co2+, Cr3+) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO2 samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV.

  9. Fischer carbene mediated covalent grafting of a peptide nucleic acid on gold surfaces and IR optical detection of DNA hybridization with a transition metalcarbonyl label

    NASA Astrophysics Data System (ADS)

    Srivastava, Pratima; Ghasemi, Mahsa; Ray, Namrata; Sarkar, Amitabha; Kocabova, Jana; Lachmanova, Stepanka; Hromadova, Magdalena; Boujday, Souhir; Cauteruccio, Silvia; Thakare, Pramod; Licandro, Emanuela; Fosse, Céline; Salmain, Michèle

    2016-11-01

    Amine-reactive surfaces comprising N-hydroxysuccinimide ester groups as well as much more unusual Fischer alkoxymetallocarbene groups were generated on gold-coated surfaces via self-assembled monolayers of carboxy- and azido-terminated thiolates, respectively. These functions were further used to immobilize homothymine peptide nucleic acid (PNA) decamer in a covalent fashion involving the primary amine located at its N-terminus. These stepwise processes were monitored by polarization modulation reflection - absorption infrared spectroscopy (PM-RAIRS) that gave useful information on the molecular composition of the organic layers. PNA grafting and hybridization with complementary DNA strand were successfully transduced by quartz crystal microbalance (QCM) measurements. Unfortunately, attempts to transduce the hybridization optically by IR in a label-free fashion were inconclusive. Therefore we undertook to introduce an IR reporter group, namely a transition metalcarbonyl (TMC) entity at the 5‧ terminus of complementary DNA. Evidence for the formation of PNA-DNA heteroduplex was brought by the presence of ν(Ctbnd O) bands in the 2000 cm-1 region of the IR spectrum of the gold surface owing to the metalcarbonyl label.

  10. Geometric, electronic and optical properties of zinc/tin codoped In2O3 modulated by the bixbyite/corundum phase transition

    NASA Astrophysics Data System (ADS)

    Lu, Ying-Bo; Li, Y. H.; Ling, Z. C.; Cong, Wei-Yan; Zhang, Peng; Xin, Y. Q.; Yang, T. L.

    2016-02-01

    As transparent conducting oxides (TCOs), In2O3 in the high pressure phase attracts extensive research interests. Because physical properties are determined by the geometric structures, we investigate the electronic and optical properties of Zn/Sn codoped In2O3 materials (IZTO) being modulated by the bixbyite/corundum phase transition via Density Functional Theory calculations. For IZTO in high pressure phase, i.e. corundum phase, Sn/Zn dopant pair tends to form face-sharing ZnO6 and SnO6 octahedrons. The radius differences between Zn2+/Sn4+ dopants and In3+ host cations make Jahn-Teller effect occur and IZTO transform from bixbyite to corundum phase under a slight higher pressure than that of pure In2O3. Although Zn/Sn cosubstitution of In ions may increase the free carrier effective mass m * near the band edge, when IZTO crystal transforms to corundum phase, the more dense packing structure results in stronger cation s-orbital overlaps than in bixbyite phase, which makes m * recover to a smaller value. In addition, corundum IZTO has a larger indirect band gap and a high dopant solubility. So these investigations may open a new way to search for TCOs materials with low indium content.

  11. Structural, optical and transport properties of transition metals doped (A: Co, Ni and Cu) BiFe{sub 0.9}A{sub 0.1}O{sub 3}

    SciTech Connect

    Parveen, Azra Agrawal, Shraddha; Naqvi, A. H.

    2015-06-24

    Nanoparticles of pure and Transition metals doped (Co, Ni and Cu) BiFeO{sub 3} of the composition BiFe{sub 0.9}A{sub 0.1}O{sub 3} (A = Co, Ni and Cu) have been successfully synthesized by sol gel auto combustion method using citric acid as a chelating agent and calcinated at 300°C. Microstructural analyses were done by XRD, TEM and SEM techniques. The crystallite size was resolute by powder X-ray diffraction technique whereas, UV-VIS technique was used to study the optical properties and band gap (Eg) of all samples. The variation of a. c. conductivity has been studied as function of frequency. It was observed that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. It was also observed that doping of Transition Metals affects the optical properties effectively and band gaps were also increased.

  12. Electronic band gaps and exciton binding energies in monolayer M oxW1 -xS2 transition metal dichalcogenide alloys probed by scanning tunneling and optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Rigosi, Albert F.; Hill, Heather M.; Rim, Kwang Taeg; Flynn, George W.; Heinz, Tony F.

    2016-08-01

    Using scanning tunneling spectroscopy (STS) and optical reflectance contrast measurements, we examine band-gap properties of single layers of transition metal dichalcogenide (TMDC) alloys: Mo S2 , M o0.5W0.5S2 , M o0.25W0.75S2 , M o0.1W0.9S2 , and W S2 . The quasiparticle band gap, spin-orbit separation of the excitonic transitions at the K /K' point in the Brillouin zone, and binding energies of the A exciton are extracted from STS and optical data. The exciton binding energies change roughly linearly with tungsten concentration. For our samples on an insulating substrate, we report quasiparticle band gaps from 2.17 ± 0.04 eV (Mo S2) to 2.38 ± 0.06 eV (W S2) , with A exciton binding energies ranging from 310 to 420 meV.

  13. Spectroscopic properties of long-lifetime Tm3+ optical centers in Ca-Sr-Ba fluorides in the form of single crystals and ceramics at the 1G4-3H5 magnetic dipole allowed transition

    NASA Astrophysics Data System (ADS)

    Doroshenko, M. E.; Papashvili, A. G.; Martynova, K. A.; Konyushkin, V. A.; Nakladov, A. N.; Osiko, V. V.

    2017-02-01

    The spectroscopic properties of new long-lifetime Tm3+ tetragonal optical centers at low (77 K) temperature were investigated using a site-selective time-resolved technique. The absorption and excitation spectra at the 3H6-1G4 transition and the fluorescence spectra at the 1G4-3H5 transition were measured in CaF2, SrF2, and BaF2 single crystals. The appearance of additional weak lines in the excitation and fluorescence spectra in hot-formed ceramics produced from the same crystals was observed. These lines were attributed to the recently observed long-lifetime tetragonal optical centers with a modified local environment formed in fluoride ceramics.

  14. Optical evaluation of multichannel radiative transitions originating from {sup 4}G{sub 5/2} level of Sm{sup 3+} in heavy-metal-gallate glasses

    SciTech Connect

    Zhang, J.; Yang, D. L.; Gong, H.; Lin, H.; Pun, E. Y. B.

    2010-06-15

    Conventional visible and novel infrared (IR) emissions of Sm{sup 3+} in heavy-metal-gallate glasses (Li{sub 2}O-K{sub 2}O-BaO-PbO-Bi{sub 2}O{sub 3}-Ga{sub 2}O{sub 3}, LKBPBG for short) with low phonon energy have been observed. Judd-Ofelt parameters {Omega}{sub 2} (3.00x10{sup -20} cm{sup 2}), {Omega}{sub 4} (5.19x10{sup -20} cm{sup 2}), and {Omega}{sub 6} (1.69x10{sup -20} cm{sup 2}) indicate a higher asymmetry and stronger covalent environment in the optical glasses. For the visible fluorescence bands peaked at 564, 601, 648, and 710 nm, the maximum stimulated emission cross-sections ({sigma}{sub e}) were derived to be 1.35x10{sup -22}, 9.21x10{sup -22}, 9.58x10{sup -22}, and 3.91x10{sup -22} cm{sup 2}, respectively, the values are larger than those in phosphate, oxyfluoroborate, tellurite, and calibo glasses obviously. The observed 1185 nm IR emission lies in the low-loss window of telecommunication system, and the maximum value of {sigma}{sub e} for this band was obtained to be 6.09x10{sup -23} cm{sup 2}. The characterization of multichannel radiative transitions of Sm{sup 3+} in LKBPBG glasses is beneficial in exposing its potential applications in visible and IR optoelectronic devices.

  15. Transition Planning

    ERIC Educational Resources Information Center

    Statfeld, Jenna L.

    2011-01-01

    Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…

  16. Optical performance of an ultra-sensitive horn-coupled transition-edge-sensor bolometer with hemispherical backshort in the far infrared.

    PubMed

    Audley, Michael D; de Lange, Gert; Gao, Jian-Rong; Khosropanah, Pourya; Hijmering, Richard; Ridder, Marcel; Mauskopf, Philip D; Morozov, Dmitry; Trappe, Neil A; Doherty, Stephen

    2016-04-01

    The next generation of far infrared space observatories will require extremely sensitive detectors that can be realized only by combining extremely low intrinsic noise with high optical efficiency. We have measured the broad-band optical response of ultra-sensitive transtion edge sensor (TES) bolometers (NEP≈2aW/Hz) in the 30-60-μm band where radiation is coupled to the detectors with a few-moded conical feedhorn and a hemispherical backshort. We show that these detectors have an optical efficiency of 60% (the ratio of the power detected by the TES bolometer to the total power propagating through the feedhorn). We find that the measured optical efficiency can be understood in terms of the modes propagating through the feedhorn with the aid of a spatial mode-filtering technique.

  17. Optical absorption and NMR spectroscopic studies on paramagnetic neodymium(III) complexes with beta-diketone and heterocyclic amines. The environment effect on 4f-4f hypersensitive transitions.

    PubMed

    Ansari, A A; Irfanullah, M; Iftikhar, K

    2007-08-01

    The optical absorption spectra of [Nd(acac)3(H2O)2].H2O, [Nd(acac)3bpy] and [Nd(acac)3phen(H2O)2] (where acac=acetylacetone, bpy=2,2'-bipyridyl and phen=1,10-phenanthroline) complexes in the visible region, in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile, pyridine, nitrobenzene and dimethylsulphoxide) have been analyzed. The transition 4G(5/2)<--4I(9/2) (Nd-VI) located near the middle of the visible region (17,500 cm(-1)) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. The oscillator strength of this transition for the chelate as well as its adducts with phen and bpy in any of the solvent employed is larger than the oscillator strength of Nd3+ aqua-ion. It is most intense in pyridine for all the complexes studied and, therefore, pyridine is the most effective in promoting f-f spectral intensity. The band shape and oscillator strength of the hypersensitive transitions display pronounced changes as compared to Nd3+ aqua-ion. The band shapes of the hypersensitive transitions show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of change in the environment about the Nd(III) ion in the various solutions and suggests change in the environment about the Nd(III) ion in the various solutions and suggests coordination of solvent molecule(s), in some cases. A comparative account of hypersensitivity in the present complexes with those of other adducts of Nd(beta-diketoenolate)3 with heterocyclic amines is discussed. The NMR signals of heterocyclic amines have been shifted to high fields while the resonances due to acetylacetone moiety have moved to low fields. The paramagnetic shift in the complexes is dipolar in nature.

  18. Latching micro optical switch

    DOEpatents

    Garcia, Ernest J; Polosky, Marc A

    2013-05-21

    An optical switch reliably maintains its on or off state even when subjected to environments where the switch is bumped or otherwise moved. In addition, the optical switch maintains its on or off state indefinitely without requiring external power. External power is used only to transition the switch from one state to the other. The optical switch is configured with a fixed optical fiber and a movable optical fiber. The movable optical fiber is guided by various actuators in conjunction with a latching mechanism that configure the switch in one position that corresponds to the on state and in another position that corresponds to the off state.

  19. Magneto-Optical Measurements of a Cascade of Transitions in Superconducting La1.875Ba0.125CuO4 Single Crystals

    NASA Astrophysics Data System (ADS)

    Karapetyan, Hovnatan; Hücker, M.; Gu, G. D.; Tranquada, J. M.; Fejer, M. M.; Xia, Jing; Kapitulnik, A.

    2012-10-01

    Recent experiments on the original cuprate high-temperature superconductor, La2-xBaxCuO4, revealed a remarkable sequence of phase transitions. Here we investigate such crystals with the polar Kerr effect, which is sensitive to time-reversal-symmetry breaking. Concurrent birefringence measurements accurately locate the structural phase transitions from high-temperature tetragonal to low-temperature orthorhombic, and then to lower-temperature tetragonal, at which temperature strong Kerr signal onsets. Hysteretic behavior of the Kerr signal suggests that time-reversal symmetry is already broken well above room temperature, an effect that was previously observed in high quality YBa2Cu3O6+x crystals.

  20. Electromagnetically induced absorption and electromagnetically induced transparency for optical transitions F{sub g} → F{sub e} in the field of elliptically polarized waves

    SciTech Connect

    Lazebnyi, D. B. Brazhnikov, D. V.; Taichenachev, A. V.; Basalaev, M. Yu. Yudin, V. I.

    2015-12-15

    Nonlinear laser spectroscopy is considered in the scheme of two collinear waves with arbitrary elliptical polarizations. Emphasis is placed on investigating the nonlinear corrections in the absorption spectrum of one of the waves. The spontaneous transfer of low-frequency Zeeman coherence is shown to affect the sign of the subnatural-width resonance. For a closed transition, the direction of the resonance profile has been found to depend only on the angular momenta F{sub e} and F{sub g}. On this basis, a classification has been developed for various transitions by the direction of the subnatural-width resonance profile.

  1. An ultra-stable optical frequency standard for telecommunication purposes based upon the 5S1/2 → 5D5/2 two-photon transition in rubidium

    NASA Astrophysics Data System (ADS)

    Terra, Osama; Hussein, Hatem

    2016-02-01

    In this study, we report the development of a frequency standard for optical fiber communication applications based on a two-photon transition in rubidium at 385.2 THz. This standard kills two birds with one stone in the sense it is capable of providing us with two highly stable serviceable wavelengths at 778.1 and 1556.2 nm. In this system, we exploit the narrow line-width of a fiber laser emitting at 1556.2 nm in conjunction with an erbium-doped fiber amplifier to generate a sufficient second harmonic laser beam at 778.1 nm in a periodically polled lithium niobate waveguide mixer in order to probe and frequency-lock the laser to the 5S1/2 ( F g = 3)-5D5/2 ( F e = 5) hyperfine two-photon transition component in 85Rb. The metrological performance of the standard is evaluated with the aid of an optical frequency comb synthesizer. Allan variance measurement shows a stability of 4 × 10-12 at 1 s (limited by the comb stability), reaching a floor of 6.8 × 10-13 at 1000 s. After correction of all the major systematic frequency shifts including the light shift, the absolute frequency is found to be 385 285 142 374.0 (5.0) kHz. Moreover, the absolute frequencies of most of the hyperfine components of the 5S1/2-5D5/2 transition of the two naturally existing rubidium isotopes are measured using a femtosecond frequency comb synthesizer after stabilizing a laser on each component.

  2. Indirect optical absorption and origin of the emission from β-FeSi2 nanoparticles: Bound exciton (0.809 eV) and band to acceptor impurity (0.795 eV) transitions

    NASA Astrophysics Data System (ADS)

    Lang, R.; Amaral, L.; Meneses, E. A.

    2010-05-01

    We investigated the optical absorption of the fundamental band edge and the origin of the emission from β-FeSi2 nanoparticles synthesized by ion-beam-induced epitaxial crystallization of Fe+ implanted SiO2/Si(100) followed by thermal annealing. From micro-Raman scattering and transmission electron microscopy measurements it was possible to attest the formation of strained β-FeSi2 nanoparticles and its structural quality. The optical absorption near the fundamental gap edge of β-FeSi2 nanoparticles evaluated by spectroscopic ellipsometry showed a step structure characteristic of an indirect fundamental gap material. Photoluminescence spectroscopy measurements at each synthesis stage revealed complex emissions in the 0.7-0.9 eV spectral region, with different intensities and morphologies strongly dependent on thermal treatment temperature. Spectral deconvolution into four transition lines at 0.795, 0.809, 0.851, and 0.873 eV was performed. We concluded that the emission at 0.795 eV may be related to a radiative direct transition from the direct conduction band to an acceptor level and that the emission at 0.809 eV derives from a recombination of an indirect bound exciton to this acceptor level of β-FeSi2. Emissions 0.851 and 0.873 eV were confirmed to be typical dislocation-related photoluminescence centers in Si. From the energy balance we determined the fundamental indirect and direct band gap energies to be 0.856 and 0.867 eV, respectively. An illustrative energy band diagram derived from a proposed model to explain the possible transition processes involved is presented.

  3. Measurement of Isotope Shifts, Hyperfine Splittings and Stark Shift for the Ytterbium (6S)2 SINGLET-S(0) to (6S6P) TRIPLET-P(1) Transition Using AN Acousto-Optically Modulated Laser Beam.

    NASA Astrophysics Data System (ADS)

    Li, Jian

    1995-11-01

    Accurate measurements of isotope shifts, hyperfine splittings and Stark shifts are of interest for studying atomic structure. This thesis reports a new method to precisely measure small frequency intervals. This was done using an acousto-optic modulator to frequency shift part of a laser beam. The frequency shifted and unshifted laser beams were then superimposed and excited an atomic beam. The laser frequency was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier. Each transition generated two peaks in the spectrum separated by the acousto-optic modulation frequency, which permitted the frequency to be calibrated. This method was tested by measuring the isotope shifts and hyperfine splittings of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition at 555.6 nm. The shifts (MHz) relative to ^{176} Yb are: ^{173}Yb {it F}=7/2,-1432.1+/-1.2; ^{171}Yb {it F}=1/2, -1176.9+/-1.1; ^{174}Yb, 953.8+/-1.0; ^{172}Yb 1953.9+/-1.6; ^{170}Yb 3240.4+/-2.8; ^{173}Yb {it F}=5/2,3265.8+/-2.8; ^ {168}Yb, 4611.9+/-4.4; ^ {171,173}Yb {it F}=3/2,4760.1 +/-3.7 where the negative sign indicates that the transition occurs at a lower frequency than in ^{176}Yb. The magnetic dipole (a) and electric quadrupole (b) hyperfine coupling constants (MHz) of the (6s6p) ^3P_1 state for ^{171,173}Yb were determined to be a_{171}=3959.1 +/-3.0, a_{173}=-1094.44+/-0.84 and b_{173}=-827.89+/-0.85. These results were in agreement with the most accurate data found in the literature that were obtained by measuring frequency shifts using a Fabry Perot etalon whose length was stabilized with a helium neon laser locked to an iodine line. In contrast, our method uses cheaper and simpler apparatus. Next, the Stark shift of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition was measured by passing the atomic beam through a uniform electric field. The Stark shift rate was found to be -15.419+/-0.048 kHz/(kV/cm)^2. No

  4. Relativistic distorted-wave collision strengths for the 16 Δn=0 optically allowed transitions with n=2 in the 67 O-like ions with 26≤Z≤92

    SciTech Connect

    Fontes, Christopher J. Zhang, Hong Lin

    2015-01-15

    Relativistic distorted-wave collision strengths have been calculated for the 16 Δn=0 optically allowed transitions with n=2 in the 67 O-like ions with nuclear charge number Z in the range 26≤Z≤92. The calculations were made for the four final, or scattered, electron energies E{sup ′}=0.20,0.42,0.80, and 1.40, where E{sup ′} is in units of Z{sub eff}{sup 2} Ry with Z{sub eff}=Z−5.83. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous work by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 82 (2002) 357]. In that earlier work, collision strengths were also provided for O-like ions, but for a more comprehensive data set consisting of all possible 45 Δn=0 transitions, six scattered energies, and the 79 ions with Z in the range 14≤Z≤92. The collision strengths covered in the present work should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang, D.H. Sampson, At. Data Nucl. Data Tables 82 (2002) 357] and are presented here to replace those earlier results.

  5. A DFT study of the structural, electronic and optical properties of transition metal doped fluorite oxides: Ce0.75M0.25O2 (M=Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Tian, Dong; Zeng, Chunhua; Fu, Yunchang; Wang, Hua; Luo, Hongchun; Xiang, Chao; Wei, Yonggang; Li, Kongzhai; Zhu, Xing

    2016-04-01

    The structural, electronic and optical properties of Ce1-xMxO2 (M=Fe, Co, Ni; x=0, 0.25) fluorite type oxides are studied by using the method of density functional theory (DFT) + U method. The calculated equilibrium lattice parameter, cell volume, bulk modulus and optical properties for CeO2 are in good agreement with the available experimental data and other theoretical results. The lattice parameter, cell volume, bulk modulus and bond length of Ce-O decreased after substituting Ce atom with Fe (or Co, Ni). Meanwhile, the band-gap (Eg) reduction is observed. It is interesting to find that doping of Fe (or Co, Ni) in CeO2 obviously decreases the O 2p-Ce 4f transition intensity and the covalent character of the Ce-O bond. On the contrary, the static dielectric constant ε0 and refractive index n0 for the doped system increased. Compared with the undoped CeO2, the doped system has steep absorption peaks ranging from 1.0 eV to 2.0 eV at lower energy, and it can be used for visible light absorption applications. The Ce0.75Co0.25O2 has a high refractive index and reflectivity, therefore it is suitable as a high-refractive index film material in single and multilayered optical coatings.

  6. Transition circumnstellar disks in Lupus

    NASA Astrophysics Data System (ADS)

    Romero, G. A.; Schreiber, M. R.; Cieza, L. A.; Rebassa-Manssergas, A.; Williams, J. P.; Merin, B.; Smith-Castelli, A.; Orellana, M.

    2011-10-01

    Based on Spitzer selected YSOs, we present a study of transition disks located in Lupus. Several mechanisms have been proposed to explain their defining characteristic: an inner opacity hole and an optically thick outer disk. These processes are: planet formation, grain growth, photoevaporation, tidal truncation in close binaries. We have carried out Adaptive Optics (AO) imaging, submillimeter photometry, and echelle spectroscopy in order to observationally characterize our transition disk sample. With the analyzed data we can distinguish the four scenarios and identify candidate transition disk systems that are currently forming planets. Such objects are excellent targets to be followed-up with Herschel and ALMA.

  7. First pure frequency measurement of an optical transition in helium: Lamb shift on the 2[sup 3][ital S][sub 1] metastable level

    SciTech Connect

    Pavone, F.S.; Marin, F.; De Natale, P.; Inguscio, M. , University of Florence, Largo E. Fermi, 2 I-50125 Firenze ); Biraben, F. )

    1994-07-04

    The 2[sup 3][ital S][sub 1-]3[sup 3][ital P][sub 0][sup 4]He transition at [lambda][sub 0]=389 nm is measured with respect to a previously frequency calibrated [sup 87]Rb two-photon transition at 2[lambda][sub 0]=778 nm. The [sup 4]He absolute frequency is 770 732 839 058 (190) kHz, with an accuracy of 2.4 parts in 10[sup 10]. A Lamb shift value of +4057.61 (79) MHz, with 600 kHz uncertainty arising from the theoretical position of the 3[sup 3][ital P][sub 0] energy level, is extracted for the 2[sup 3][ital S][sub 1] level. This value is more than 2 orders of magnitude more accurate than the current best theoretical predictions.

  8. Magneto-optical Signatures of a Cascade of Transitions in La 1.875Ba 0.125CuO 4

    SciTech Connect

    Karapetyan, Hovnatan; Hucker, M.; Gu, G.D.; Tranquada, J.M.; Fejer, M.M.; Xia, Jing; Kapitulnik, A.

    2012-09-14

    Recent experiments on the original cuprate high temperature superconductor, La{sub 2-x}Ba{sub x}CuO{sub 4}, revealed a remarkable sequence of phase transitions. Here we investigate such crystals with polar Kerr effect which is sensitive to time-reversal-symmetry breaking. Concurrent birefringence measurements accurately locate the structural phase transitions from high-temperature tetragonal to low temperature orthorhombic, and then to lower temperature tetragonal, at which temperature a strong Kerr signal onsets. Hysteretic behavior of the Kerr signal suggests that time-reversal symmetry is already broken well above room temperature, an effect that was previously observed in high quality YBa{sub 2}Cu{sub 3}O{sub 6+x} crystals.

  9. Predictions of Optical Excitations in Transition-Metal Complexes with Time Dependent-Density Functional Theory:  Influence of Basis Sets.

    PubMed

    Petit, Laurence; Maldivi, Pascale; Adamo, Carlo

    2005-09-01

    The calculation of the absorption spectra of four families of transition-metal complexes (Ni(CO)4, MnO4(-), MF6 (M = Cr, Mo, W) and CpM(CO)2 (M = Rh, Ir)) has been undertaken to unravel the influence of basis sets onto excitation energies, oscillator strengths, and assignments. Three among the most common pseudopotentials, with the corresponding valence basis sets, and two all-electron basis sets have been used for the metal center description in the framework of the time dependent Density Functional Theory (TD-DFT). Our results show that this approach does not particularly depend on the basis set used on the metal atoms. Furthermore, the chosen functional PBE0 provides transitions in good agreement with experiments, and it provides an accuracy of about 0.3 eV, comparable to that of refined post-Hartree-Fock methods.

  10. Magneto-optical measurements of a cascade of transitions in superconducting La1.875Ba0.125CuO4 single crystals.

    PubMed

    Karapetyan, Hovnatan; Hücker, M; Gu, G D; Tranquada, J M; Fejer, M M; Xia, Jing; Kapitulnik, A

    2012-10-05

    Recent experiments on the original cuprate high-temperature superconductor, La(2-x)Ba(x)CuO4, revealed a remarkable sequence of phase transitions. Here we investigate such crystals with the polar Kerr effect, which is sensitive to time-reversal-symmetry breaking. Concurrent birefringence measurements accurately locate the structural phase transitions from high-temperature tetragonal to low-temperature orthorhombic, and then to lower-temperature tetragonal, at which temperature strong Kerr signal onsets. Hysteretic behavior of the Kerr signal suggests that time-reversal symmetry is already broken well above room temperature, an effect that was previously observed in high quality YBa2Cu3O(6+x) crystals.

  11. Effective medium based optical analysis with finite element method simulations to study photochromic transitions in Ag-TiO2 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Abhilash, T.; Balasubrahmaniyam, M.; Kasiviswanathan, S.

    2016-03-01

    Photochromic transitions in silver nanoparticles (AgNPs) embedded titanium dioxide (TiO2) films under green light illumination are marked by reduction in strength and blue shift in the position of the localized surface plasmon resonance (LSPR) associated with AgNPs. These transitions, which happen in the sub-nanometer length scale, have been analysed using the variations observed in the effective dielectric properties of the Ag-TiO2 nanocomposite films in response to the size reduction of AgNPs and subsequent changes in the surrounding medium due to photo-oxidation. Bergman-Milton formulation based on spectral density approach is used to extract dielectric properties and information about the geometrical distribution of the effective medium. Combined with finite element method simulations, we isolate the effects due to the change in average size of the nanoparticles and those due to the change in the dielectric function of the surrounding medium. By analysing the dynamics of photochromic transitions in the effective medium, we conclude that the observed blue shift in LSPR is mainly because of the change in the dielectric function of surrounding medium, while a shape-preserving effective size reduction of the AgNPs causes decrease in the strength of LSPR.

  12. Work transitions.

    PubMed

    Fouad, Nadya A; Bynner, John

    2008-01-01

    Individuals make choices in, and adjust to, a world of work that is often a moving target. Because work is so central to human functioning, and transitions in and out of work can have major mental health repercussions, the authors argue that applied psychologists in health services need to understand those transitions. This article focuses on the different types of transition throughout a person's working life and the resources needed at different stages to ensure the success of these transitions. The authors start by examining the roles of capability and adaptability in supporting and facilitating adjustment to work transitions and their relation to identity development. They then examine the role of social and institutional contexts in shaping work transitions and their outcomes. The authors focus on voluntary versus involuntary transitions and then broaden the lens in discussing the policy implications of research on work transitions.

  13. Detailed optical spectroscopy of hybridization gap and hidden-order transition in high-quality URu2Si2 single crystals

    NASA Astrophysics Data System (ADS)

    Bachar, N.; Stricker, D.; Muleady, S.; Wang, K.; Mydosh, J. A.; Huang, Y. K.; van der Marel, D.

    2016-12-01

    We present a detailed temperature and frequency dependence of the optical conductivity measured on clean high-quality single crystals of URu2Si2 of a c - and a b -plane surfaces. Our data demonstrate the itinerant character of the narrow 5 f bands, becoming progressively coherent as the temperature is lowered below a crossover temperature T*˜75 K. T* is higher than in previous reports as a result of a different sample preparation, which minimizes residual strain. We furthermore present the density-response (energy-loss) function of this compound, and determine the energies of the heavy-fermion plasmons with a - and c -axis polarization. Our observation of a suppression of optical conductivity below 50 meV along both the a and c axes, along with a heavy-fermion plasmon at 18 meV, points toward the emergence of a band of coherent charge carriers crossing the Fermi energy and the emergence of a hybridization gap on part of the Fermi surface. The evolution towards coherent itinerant states is accelerated below the hidden order temperature THO=17.5 K. In the hidden order phase the low-frequency optical conductivity shows a single gap at ˜6.5 meV, which closes at THO.

  14. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Hofstadter's Butterfly and Phase Transition of Checkerboard Superconducting Network in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Hou, Jing-Min; Tian, Li-Jim

    2010-03-01

    We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes-Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum.

  15. A unified derivation of Hamiltonian and optical transition matrix elements for open shell diatomic and polyatomic molecules using transformation tools of modern quantum mechanics

    SciTech Connect

    Schwenke, David W.

    2015-04-14

    In this work, we systematically derive the matrix elements of the nuclear rotation operators for open shell diatomic and polyatomic molecules in a parity adapted Hund’s case (a) basis. Our expressions are valid for an arbitrary number of electrons and arbitrary electronic configurations. The common ad hoc sign changes of angular momentum operators are shown to be equivalent to a change in phase of basis functions. We show how to relate this basis to that required for scattering calculations. We also give the expressions for Einstein A coefficients for electric dipole, electric quadrupole, and magnetic dipole transitions.

  16. Doping-Induced Type-II to Type-I Transition and Interband Optical Gain in InAs/AlSb Quantum Wells

    NASA Technical Reports Server (NTRS)

    Kolokolov, K. I.; Ning, C. Z.

    2003-01-01

    We show that proper doping of the barrier regions can convert the well-known type-II InAs/AlSb QWs to type I, producing strong interband transitions comparable to regular type-I QWs. The interband gain for TM mode is as high as 4000 l/cm, thus providing an important alternative material system in the mid-infrared wavelength range. We also study the TE and TM gain as functions of doping level and intrinsic electron-hole density.

  17. Electronic structure, optical properties and the mechanism of the B3-B8 phase transition of BeSe: insights from hybrid functionals, lattice dynamics and NPH molecular dynamics

    NASA Astrophysics Data System (ADS)

    Dutta, Rajkrishna; Alptekin, Sebahaddin; Mandal, Nibir

    2013-03-01

    We have investigated the electronic structure and the mechanism of the pressure induced phase transition of beryllium selenide (BeSe) by employing a first-principles pseudopotential method within the framework of density functional theory. Our study demonstrates that use of the hybrid PBE0 functional (PBE stands for Perdew, Burke and Ernzerhof) leads to significant improvement in the band gap calculations, compared to those using either of the common density functionals (local density approximation (LDA) and generalized gradient approximation (GGA)), which severely underestimate the band gap of BeSe. The band gap obtained from the hybrid PBE0 functional shows excellent agreement with available experimental data. A constant-pressure (NPH) first-principles molecular dynamics (FPMD) approach has been adopted to characterize the first-order pressure induced phase transition from the zinc blende (ZB) to the nickel arsenide (NiAs) structure. We have shown that the FPMD simulation overestimates the transition pressure PT (compared to static enthalpy and experimental data) due to overpressure in the simulation box. The MD simulation reveals the structural pathway (cubic → orthorhombic → monoclinic → hexagonal), leading from the ZB phase to the NiAs phase. To find an explanation for the phase transition we calculated the vibrational and elastic properties under pressure. Negative Grüneisen parameters were obtained for the transverse acoustic phonon modes at the X and L high symmetry points. However, no mechanical instability or imaginary frequencies were found at pressures near PT. Thus the transition results from a thermodynamic instability rather than an elastic/dynamical one. We have also calculated the optical properties of both the B3 and B8 phases, such as the real and imaginary parts of the dielectric constant, reflectivity, loss function and refractive index, and compared them with the existing experimental and theoretical data. An abrupt decrease is obtained

  18. Relating C-band Microwave and Optical Satellite Observations as A Function of Snow Thickness on First-Year Sea Ice during the Winter to Summer Transition

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Yackel, J.

    2015-12-01

    The Arctic sea ice and its snow cover have a direct impact on both the Arctic and global climate system through their ability to moderate heat exchange across the ocean-sea ice-atmosphere (OSA) interface. Snow cover plays a key role in the OSA interface radiation and energy exchange, as it controls the growth and decay of first-year sea ice (FYI). However, meteoric accumulation and redistribution of snow on FYI is highly stochastic over space and time, which makes it poorly understood. Previous studies have estimated local-scale snow thickness distributions using in-situ technique and modelling but it is spatially limited and challenging due to logistic difficulties. Moreover, snow albedo is also critical for determining the surface energy balance of the OSA during the critical summer ablation season. Even then, due to persistent and widespread cloud cover in the Arctic at various spatio-temporal scales, it is difficult and unreliable to remotely measure albedo of snow cover on FYI in the optical spectrum. Previous studies demonstrate that only large-scale sea ice albedo was successfully estimated using optical-satellite sensors. However, space-borne microwave sensors, with their capability of all-weather and 24-hour imaging, can provide enhanced information about snow cover on FYI. Daily spaceborne C-band scatterometer data (ASCAT) and MODIS data are used to investigate the the seasonal co-evolution of the microwave backscatter coefficient and optical albedo as a function of snow thickness on smooth FYI. The research focuses on snow-covered FYI near Cambridge Bay, Nunavut (Fig.1) during the winter to advanced-melt period (April-June, 2014). The ACSAT time series (Fig.2) show distinct increase in scattering at melt onset indicating the first occurrence of melt water in the snow cover. The corresponding albedo exhibits no decrease at this stage. We show how the standard deviation of ASCAT backscatter on FYI during winter can be used as a proxy for surface roughness

  19. Interfacial interaction in monolayer transition metal dichalcogenide/metal oxide heterostructures and its effects on electronic and optical properties: The case of MX2/CeO2

    NASA Astrophysics Data System (ADS)

    Yang, Ke; Huang, Wei-Qing; Hu, Wangyu; Huang, Gui-Fang; Wen, Shuangchun

    2017-01-01

    Using the density functional theory (DFT), we systematically study the interfacial interaction in monolayer MX2 (M = Mo, W; X = S, Se)/CeO2 heterostructures and its effects on electronic and optical properties. The interfacial interaction in the MX2/CeO2 heterostructures depends largely on chalcogens, and its strength determines the band gap variation and important electronic states at the band edges of the heterostructures. The MX2/CeO2 heterostructures with the same chalcogen have similar absorption spectra, from ultraviolet to near-infrared regions. These results suggest that chalcogens importantly determine the properties of MX2/metal oxide heterostructures.

  20. Dynamics of the magneto structural phase transition in La(Fe{sub 0.9}Co{sub 0.015}Si{sub 0.085}){sub 13} observed by magneto-optical imaging

    SciTech Connect

    Kuepferling, M. Basso, V.; Bennati, C.; Laviano, F.; Ghigo, G.

    2014-05-07

    We investigate the temperature induced ferromagnetic to paramagnetic phase transition in Co substituted La(Fe{sub x}Co{sub y}Si{sub 1−x−y}){sub 13} with x = 0.9 and low Co content of y = 0.015 (T{sub c}≃200 K) by means of magneto-optical imaging with indicator film and by calorimetry at very low temperature rates. We were able to visualize the motion of the ferromagnetic (FM)/paramagnetic (PM) front which is forming reproducible patterns independently of the temperature rate. The average velocity of the FM/PM front was calculated to be 10{sup −4} m/s during the continuous propagation and 4×10{sup −3} m/s during an avalanche. The heat flux was measured at low temperature rates by a differential scanning calorimeter and shows a reproducible sequence of individual and separated avalanches which occurs independently of the rate. We interpret the observed effects as the result of the athermal character of the phase transition.

  1. Kinetics of an oxygen - iodine active medium with iodine atoms optically pumped on the 2P1/2 - 2P3/2 transition

    NASA Astrophysics Data System (ADS)

    Zagidullin, M. V.; Malyshev, M. S.; Azyazov, V. N.

    2015-08-01

    The kinetics of the processes occurring in an O2 - I2 - He - H2O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the 2P1/2 - 2P3/2 transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen - iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O2(a1Δ) exceeding 10%. Having formed a supersonic gas flow with a temperature ~100 K from this medium, one can reach a small-signal gain of about 10-2 cm-1 on the 2P1/2 - 2P3/2 transition in iodine atoms. The specific power per unit flow cross section in the oxygen - iodine laser with this active medium may reach ~100 W cm-2.

  2. Relativistic distorted-wave collision strengths for the 49 Δn=0 optically allowed transitions with n=2 in the 67 B-like ions with 26≤Z≤92

    SciTech Connect

    Fontes, Christopher J. Zhang, Hong Lin

    2014-05-15

    Relativistic distorted-wave collision strengths have been calculated for the 49 Δn=0 optically allowed transitions with n=2 in the 67 B-like ions with nuclear charge number Z in the range 26≤Z≤92. The calculations were made for the four final, or scattered, electron energies E{sup ′}=0.20, 0.42, 0.80, and 1.40, where E{sup ′} is in units of Z{sub eff}{sup 2} Ry with Z{sub eff}=Z−3.33. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous work by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 56 (1994) 41]. In that earlier work, collision strengths were also provided for B-like ions, but for a more comprehensive data set consisting of all 105 Δn=0 transitions, six scattered energies and the 85 ions with Z in the range 8≤Z≤92. The collision strengths covered in the present work should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 56 (1994) 41] and are presented here to replace those earlier results.

  3. Relativistic distorted-wave collision strengths for the 49 Δn=0 optically allowed transitions with n=2 in the 67 N-like ions with 26≤Z≤92

    SciTech Connect

    Fontes, Christopher J. Zhang, Hong Lin

    2014-09-15

    Relativistic distorted-wave collision strengths have been calculated for the 49 Δn=0 optically allowed transitions with n=2 in the 67 N-like ions with nuclear charge number Z in the range 26≤Z≤92. The calculations were made for the four final, or scattered, electron energies E{sup ′}=0.20, 0.42, 0.80, and 1.40, where E{sup ′} is in units of Z{sub eff}{sup 2} Ry with Z{sub eff}=Z−5. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in the previous work by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 72 (1999) 153]. In that earlier work, collision strengths were also provided for N-like ions, but for a more comprehensive data set consisting of all possible 105 Δn=0 transitions, six scattered energies and the 81 ions with Z in the range 12≤Z≤92. The collision strengths covered in the present work should be more accurate than the corresponding data given by Zhang and Sampson [H.L. Zhang and D.H. Sampson, At. Data Nucl. Data Tables 72 (1999) 153] and are presented here to replace those earlier results.

  4. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    PubMed Central

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-01-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state. PMID:28205643

  5. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers.

    PubMed

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-02-16

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state.

  6. Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

    NASA Astrophysics Data System (ADS)

    Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Karabiyik, Mustafa; Pala, Nezih

    2017-02-01

    Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (λ~1.55 μm), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (λ~1.85 μm) far from the telecommunication wavelength, which constitutes the ON state.

  7. Tailoring transition metal complexes for nonlinear optics applications. 2. A theoretical investigation of the second-order nonlinear optical properties of M(CO)(5)L complexes (M = Cr, W; L = Py, PyCHO, Pyz, PyzBF(3), BPE, BPEBF(3)).

    PubMed

    Bruschi, Maurizio; Fantucci, Piercarlo; Pizzotti, Maddalena

    2005-10-27

    In this work, we report an ab initio investigation of second-order nonlinear optical (NLO) properties and absorption electronic spectra of push-pull transition metal chromophores of the formula [M(CO)(5)L] (M = Cr, W; L = pyridine (Py), 4-formyl-pyridine (PyCHO), pyrazine (Pyz), trans-1,2-bis(4-pyridyl)ethylene (BPE)). Pyz and BPE are considered either with one nitrogen atom free or interacting with the strong acceptor BF(3). All of the molecular properties have been calculated using two different and methodologically independent approaches: the time dependent and coupled perturbed density functional theories (TDDFT and CPDFT) and the sum-over-states (SOS) approach, where the excited states are obtained via the single configuration interaction (SCI) ab initio method. DFT results are in acceptable agreement with the experimental energy values of electronic transitions (with the exception of chromophores with the large pi-delocalization, like BPE); SCI calculations overestimate excitation energies and produce an inversion in the order of d(M) --> pi(L) and d(M) --> pi(CO) transitions. The SCI-SOS approach gives first-order hyperpolarizabilities, basically in agreement as trend and values with the experiments and seems to be a tool generally suitable for the evaluation of these properties also for transition metal complexes. On the other hand, the first-order hyperpolarizabilities computed using the CPDFT approach are consistently overestimated in comparison with the experimental results, especially in the case of a ligand with large pi-delocalization. We also show that the "two-level" approximation taking into account only the lowest energy charge transfer excitation (e.g., d(M) --> pi(L)) is not applicable to chromophores with the extended pi-delocalized ligand (BPE) coordinated to a transition metal, due to significant contributions originating from intraligand pi(L) --> pi(L) transitions. This study reports a detailed analysis and comparison of electronic NLO

  8. Dependence of the ground-state transition energy versus optical pumping in GaAsSb/InGaAs/GaAs heterostructures

    SciTech Connect

    Morozov, S. V.; Kryzhkov, D. I. Aleshkin, V. Ya.; Yablonsky, A. N.; Krasilnik, Z. F.; Zvonkov, B. N.; Vikhrova, O. V.

    2014-01-13

    In this work, we report on the time-resolved photoluminescence studies of a double quantum well In{sub 0.2}Ga{sub 0.8}As/GaAs{sub 0.8}Sb{sub 0.2}/GaAs heterostructure which, in contrast to the GaAsSb/GaAs structures, is expected to provide effective confinement of electrons due to additional InGaAs layer. The studies at 4.2 K have revealed a complicated nonmonotonic dependence of the ground-state transition energy on the concentration of nonequilibrium charge carriers in the quantum well. The effect observed in this work is important in terms of creating sources of radiation, including stimulated emission, on the basis of InGaAs/GaAsSb/GaAs structures.

  9. Transition from a nanocrystalline phase to an amorphous phase in In-Si-O thin films: The correlation between the microstructure and the optical properties

    SciTech Connect

    Park, Jun-Woo; So, Hyeon Seob; Lee, Hosun; Lee, Hye-Min; Kim, Hyo-Joong; Kim, Han-Ki

    2015-04-21

    We investigated the structural and optical properties of In-Si-O thin films as the phase abruptly changes from nanocrystalline (nc) to amorphous (a) with increasing Si content. In-Si-O thin films were deposited on Si substrate using a co-sputtering deposition method. The RF power of the In{sub 2}O{sub 3} target was fixed at 100 W, while the power applied to the SiO{sub 2} target was varied between 0 W and 60 W. At the Si = 2.8 at. %, i.e., at the onset of amorphous phase, the optical properties, including the dielectric functions, optical gap energies, and phonon modes, changed abruptly which were triggered by changes in the crystallinity and surface morphology. X-ray diffraction (XRD) spectra showed crystalline (c-) In{sub 2}O{sub 3}-like peaks below Si = 2.2%. Additionally, a broad peak associated with an amorphous (a-) In{sub 2}O{sub 3} phase appeared above 2.8%. However, the Raman spectra of In-Si-O showed very weak peaks associated with c-In{sub 2}O{sub 3} below 2.2%, and then showed a strong Raman peak associated with a-In-Si-O above 2.8%. X-ray photoelectron spectroscopy measurements showed that oxygen vacancy-related peak intensities increased abruptly above Si = 2.8%. The contrasting results of XRD and Raman measurements can be explained as follows: first, the large enhancement in Drude tails in the a-In-Si-O phase was caused by Si-induced amorphization and a large increase in the density of oxygen vacancies in the In-Si-O thin films. Second, the apparently drastic increase of the Raman peak intensity near 364 cm{sup −1} (for amorphous phase, i.e., above Si = 2.8%) is attributed to a disorder-activated infrared mode caused by both the amorphization and the increase in the oxygen vacancy density in In-Si-O thin films.

  10. Optic glioma

    MedlinePlus

    Glioma - optic; Optic nerve glioma; Juvenile pilocytic astrocytoma; Brain cancer - optic glioma ... Optic gliomas are rare. The cause of optic gliomas is unknown. Most optic gliomas are slow-growing ...

  11. H- - H Collision Induced Radiative Transitions

    NASA Astrophysics Data System (ADS)

    Dadonova, A. V.; Devdariani, A. Z.

    2012-12-01

    Exchange interaction leads to the formation of gerade and ungerade states of temporary molecules (quasimolecules) formed during the H- +H slow collisions. The work deals with the radiation produced by optical transitions between those states. The main characteristics involved in the description of optical transitions in quasimolecules, i.e., energy terms, an optical dipole transition moments, have been calculated in the frame of zero-range potentials model. The main feature of calculations is that the results can be expressed analytically in closed forms via the Lambert W function.

  12. Optical clock networks

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz

    2017-01-01

    Within the last decade, optical atomic clocks have surpassed the best cesium clocks, which are used to realize the unit of time and frequency, in terms of accuracy and stability by about two orders of magnitude. When remote optical atomic clocks are connected by links without degradation in the clock signals, an optical clock network is formed, with distinct advantages for the dissemination of time, geodesy, astronomy and basic and applied research. Different approaches for time and frequency transfer in the microwave and optical regime, via satellites and free-space links, optical fibre links, or transportable optical atomic clocks, can be used to form a hybrid clock network that may allow a future redefinition of the unit of time based on an optical reference transition.

  13. Acoustic phonon assisted free-carrier optical absorption in an n-type monolayer MoS{sub 2} and other transition-metal dichalcogenides

    SciTech Connect

    Bhargavi, K. S.; Patil, Sukanya; Kubakaddi, S. S.

    2015-07-28

    The theory of free-carrier absorption (FCA) is given for monolayers of transition-metal dichalcogenides, particularly for molybdenum disulphide (MoS{sub 2}), when carriers are scattered by phonons. Explicit expressions for the absorption coefficient α are obtained and discussed for acoustic phonon scattering via screened deformation potential and piezoelectric coupling taking polarization of the radiation in the plane of the layer. It is found that α monotonously decreases with the increasing photon frequency Ω, increases with the increasing temperature T, and linearly depends on two-dimensional electron concentration n{sub s}. Effect of screening, which is ignored in all the earlier FCA studies, is found to reduce α significantly, attributing to the larger effective mass of the electrons. Results are also obtained in the classical and quantum limit giving the power laws α ∼ Ω{sup −2} and T. Comparison of the results is made with those in bulk semiconductors and semiconductor quantum wells.

  14. Cross Sections for Electron-impact Excitation of Electronic States in Atoms and Molecules -Application Examples of the BEf-scaling model in Optically-allowed Transitions

    NASA Astrophysics Data System (ADS)

    Kato, Hidetoshi

    2012-10-01

    The differential cross section (DCS) and integral cross section (ICS) measurements of electron-impact electronic excitation for noble gases were reported by many groups. Unfortunately, despite all these endeavours, if we were to characterize the level of agreement between these studies, then we could only conclude that it remains ``patchy'' at best. Hence, we report measurements of DCS and ICS for electron-impact excitation of the lowest electronic states in noble gases (Ne, Ar, Kr and Xe), and compare with results from a scaled Born cross section (BEf-scaling). We have previously found for the He atom and a number of molecules, including H2, O2, CO, H2O, CO2, N2O and C6H6 that the BEf-scaling approach, for calculating ICSs for dipole-allowed electronic-state transitions, can lead to a very accurate description of the various scattering processes from threshold to 2000 eV [1]. Exceptions to this general statement have only been found in those cases where resonance effects due to the temporary capture of the incident electron by the target and contamination from an accidentally degenerate or near-degenerate triplet state have arisen. Our results for noble gases will be presented in detail at the conference.[4pt] [1] H. Kato et al., NIFS Research Report, NIFS-DATA-108, 1 (2009).

  15. Condensed Matter: Electronic Structure, Electrical, Magnetic, and Optical Properties Entanglement Entropy Signature of Quantum Phase Transitions in a Multiple Spin Interactions Model

    NASA Astrophysics Data System (ADS)

    Huang, Hai-Lin

    2011-02-01

    Through the Jordan—Wigner transformation, the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Green's function theory. In the absence of four-spin interactions, the ground state presents plentiful quantum phases due to the multiple spin interactions and magnetic fields. It is shown that the two-site entanglement entropy is a good indicator of quantum phase transition (QPT). In addition, the alternating interactions can destroy the magnetization plateau and wash out the spin-gap of low-lying excitations. However, in the presence of four-spin interactions, apart from the second order QPTs, the system manifests the first order QPT at the tricritical point and an additional new phase called “spin waves”, which is due to the collapse of the continuous tower-like low-lying excitations modulated by the four-spin interactions for large three-spin couplings.

  16. Transitional Care

    ERIC Educational Resources Information Center

    Naylor, Mary; Keating, Stacen A.

    2008-01-01

    Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…

  17. Trapped Ion Optical Clocks at NPL

    SciTech Connect

    Margolis, H. S.; Barwood, G. P.; Hosaka, K.; Klein, H. A.; Lea, S. N.; Walton, B. R.; Webster, S. A.; Gill, P.; Huang, G.; Stannard, A.

    2006-11-07

    Forbidden transitions in single laser-cooled trapped ions provide highly stable and accurate references for optical frequency standards. This paper describes recent progress on strontium and ytterbium ion optical frequency standards under development at NPL.

  18. Effect of low temperature vacuum annealing on microstructural, optical, electronic, electrical, nanomechanical properties and phase transition behavior of sputtered vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Porwal, Deeksha; Esther, A. Carmel Mary; Dey, Arjun; Gupta, A. K.; Raghavendra Kumar, D.; Bera, Parthasarathi; Barshilia, Harish C.; Bhattacharya, Manjima; Mukhopadhyay, Anoop Kumar; Khan, Kallol; Sharma, Anand Kumar

    2016-10-01

    Vanadium oxide thin films were deposited on quartz substrate by pulsed RF magnetron sputtering technique at 400-600 W and subsequently annealed at 100 °C in vacuum (1.5 × 10-5 mbar). Phase analysis, surface morphology and topology of the films e.g., both as-deposited and annealed were investigated by x-ray diffraction, field emission scanning electron microscopy and atomic force microscopy techniques. X-ray photoelectron spectroscopy (XPS) was employed to understand the elemental oxidation of the films. Transmittance of the films was evaluated by UV-vis-NIR spectrophotometer in the wavelength range of 200-1600 nm. Sheet resistance of the films was measured by two-probe method both for as-deposited and annealed conditions. XPS study showed the existence of V5+ and V4+ species. Metal to insulator transition temperature of the as-deposited film decreased from 339 °C to 326 °C after annealing as evaluated by differential scanning calorimetric technique. A significant change in transmittance was observed in particular at near infrared region due to alteration of surface roughness and grain size of the film after annealing. Sheet resistance values of the annealed films decreased as compared to the as-deposited films due to the lower in oxidation state of vanadium which led to increase in carrier density. Combined nanoindentation and finite element modeling were applied to evaluate nanohardness (H), Young’s modulus (E), von Mises stress and strain distribution. Both H and E were improved after annealing due to increase in crystallinity of the film.

  19. Ultrasound assisted optical tomography: estimation of phase shift experienced by photon on transit through US insonified region for detection of breast tumor

    NASA Astrophysics Data System (ADS)

    Singh, Suheshkumar; Kanhirodan, Rajan; Vasu, R. M.

    2012-03-01

    A Monte Carlo model of ultrasound modulation of multiply scattered coherent light in a highly scattering media has been carried out for estimating the phase shift experienced by a photon beam on its transit through US insonified region. The phase shift is related to the tissue stiffness, thereby opening an avenue for possible breast tumor detection. When the scattering centers in the tissue medium is exposed to a deterministic forcing with the help of a focused ultrasound (US) beam, due to the fact that US-induced oscillation is almost along particular direction, the direction defined by the transducer axis, the scattering events increase, thereby increasing the phase shift experienced by light that traverses through the medium. The phase shift is found to increase with increase in anisotropy g of the medium. However, as the size of the focused region which is the region of interest (ROI) increases, a large number of scattering events take place within the ROI, the ensemble average of the phase shift (Δφ) becomes very close to zero. The phase of the individual photon is randomly distributed over 2π when the scattered photon path crosses a large number of ultrasound wavelengths in the focused region. This is true at high ultrasound frequency (1 MHz) when mean free path length of photon ls is comparable to wavelength of US beam. However, at much lower US frequencies (100 Hz), the wavelength of sound is orders of magnitude larger than ls, and with a high value of g (g 0.9), there is a distinct measurable phase difference for the photon that traverses through the insonified region. Experiments are carried out for validation of simulation results.

  20. Transition metals

    PubMed Central

    Rodrigo-Moreno, Ana; Poschenrieder, Charlotte; Shabala, Sergey

    2013-01-01

    Transition metals such as Iron (Fe) and Copper (Cu) are essential for plant cell development. At the same time, due their capability to generate hydroxyl radicals they can be potentially toxic to plant metabolism. Recent works on hydroxyl-radical activation of ion transporters suggest that hydroxyl radicals generated by transition metals could play an important role in plant growth and adaptation to imbalanced environments. In this mini-review, the relation between transition metals uptake and utilization and oxidative stress-activated ion transport in plant cells is analyzed, and a new model depicting both apoplastic and cytosolic mode of ROS signaling to plasma membrane transporters is suggested. PMID:23333964

  1. Optical Coherence Tomographic and Visual Results at Six Months after Transitioning to Aflibercept for Patients on Prior Ranibizumab or Bevacizumab Treatment for Exudative Age-Related Macular Degeneration (An American Ophthalmological Society Thesis)

    PubMed Central

    Chan, Clement K.; Jain, Atul; Sadda, Srinivas; Varshney, Neeta

    2014-01-01

    Purpose: To study optical coherence tomographic (OCT) results and vision at 6 months after transition (post-Tx) from intravitreal bevacizumab and/or ranibizumab to aflibercept for treatment of neovascular age-related macular degeneration (nAMD). The null hypothesis was the lack of improvements in OCT metrics and vision outcome in study eyes at 6 months after transitioning from bevacizumab or ranibizumab to aflibercept. Methods: This retrospective study assessed 6 monthly OCT (Cirrus) data after transitioning to aflibercept for eyes on prior Legacy-ranibizumab, Legacy-bevacizumab, or mixed treatment for nAMD. Outcome measures were subretinal fluid (SRF), cystoid macular edema (CME), pigment epithelial detachment (PED) heights and volumes, central 1- and 3-mm subfield, Macular Volume, and best spectacle and pinhole visual acuity (VA). A single masked investigator performed all OCT measurements. Results: One hundred eighty-nine eyes in 172 patients in Legacy-bevacizumab (95 eyes), Legacy-ranibizumab (84 eyes), or Mixed Group(10 eyes) were switched to aflibercept and followed for 6 months. Significant post-Tx reductions were noted in SRF/CME heights and volumes (all P<.001). Similar findings were noted for PED heights (122.8 μm vs 79.4 μm) and PED volumes (all P<.001). Post-Tx VA was better (20/43 vs 20/51, P<.001). There were no differences between Legacy-bevacizumab and Legacy-ranibizumab groups in OCT and VA changes. Post-Tx VA, SRF/CME, and PED heights and volumes were improved for Nonresponders (suboptimal response to bevacizumab/ranibizumab) (P=.001 to <.001), but not Responders (good responses to same). The only adverse event was a retinal pigment epithelial tear in one eye. Conclusions: Significant improvements in vision and OCT metrics developed in Nonresponders but not in Responders. Post-Tx VA and OCT measures were similar for eyes on prior bevacizumab or ranibizumab. Post-Tx adverse events were uncommon. PMID:25646034

  2. α- to β-[C 6H 4(NH 3) 2] 2Bi 2I 10 reversible solid-state transition, thermochromic and optical studies in the p-phenylenediamine-based iodobismuthate(III) material

    NASA Astrophysics Data System (ADS)

    Hrizi, Chakib; Trigui, Ameni; Abid, Younes; Chniba-Boudjada, Nassira; Bordet, Pierre; Chaabouni, Slaheddine

    2011-12-01

    α-[C 6H 4(NH 3) 2] 2Bi 2I 10, which is a new material containing low-dimensional iodobismuthate anions, was synthesized and through its single crystal X-ray diffraction measurements, was proven to crystallize at room temperature in the centrosymmetric space group P2 1/c. It consists of a p-phenylenediammonium dication and a discrete (0-D) anion built up of edge-sharing bioctahedron. Due to the hydrogen bonds and the interatomic distances (Bi-I, I⋯I and π-π) changes, α-phase was transformed into the corresponding centrosymmetric β-phase, β-[C 6H 4(NH 3) 2] 2Bi 2I 10, through a single-crystal to single-crystal transformation occurring upon cooling to -28/-26 °C. Below the transition temperature, β-[C 6H 4(NH 3) 2] 2Bi 2I 10 crystallizes in the monoclinic system, centrosymmetric space group P2 1/n. Besides, the optical transmission measurements on α-[C 6H 4(NH 3) 2] 2Bi 2I 10 thin films have revealed two absorption bands at 2.47 and 3.01 eV. Finally, two room temperature photoluminescence emissions attributed to excitons radiative recombinations confined within the bioctahedra Bi 2I 104-, were observed in the red spectral range at 1.9 and 2.05 eV energy.

  3. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  4. Optical profile determining apparatus and associated methods including the use of a plurality of wavelengths in the reference beam and a plurality of wavelengths in a reflective transit beam

    NASA Technical Reports Server (NTRS)

    Montgomery, Robert M. (Inventor)

    2006-01-01

    An optical profile determining apparatus includes an optical detector and an optical source. The optical source generates a transmit beam including a plurality of wavelengths, and generates a reference beam including the plurality of wavelengths. Optical elements direct the transmit beam to a target, direct a resulting reflected transmit beam back from the target to the optical detector, and combine the reference beam with the reflected transmit beam so that a profile of the target is based upon fringe contrast produced by the plurality of wavelengths in the reference beam and the plurality of wavelengths in the reflected transmit beam.

  5. Presidential Transitions

    DTIC Science & Technology

    2006-06-09

    Podesta for the Heads of Executive Departments and Agencies, “Presidential Transition Guidance,” Nov. 13, 2000. 89 U.S. General Services Administration...2000, presidential election, White House Chief of Staff John Podesta issued a November 13, 2000, memorandum to executive branch agencies stating that

  6. Tessellations & Transitions.

    ERIC Educational Resources Information Center

    Cassidy, Joan

    1998-01-01

    Describes two sixth-grade lessons on the work of M. C. Escher: (1) the first lesson instructs students on tessellations, or tiles that interlock in a repeated pattern; (2) the second lesson explores Escher's drawings of transitions from two- to three-dimensional space. (DSK)

  7. Profound Understanding of Effect of Transition Metal Dopant, Sintering Temperature, and pO2 on the Electrical and Optical Properties of Proton Conducting BaCe0.9Sm0.1O3-δ.

    PubMed

    Handal, Hala T; Hassan, Azfar; Leeson, Ryan; Eloui, Sherif M; Fitzpatrick, Martin; Thangadurai, Venkataraman

    2016-01-19

    This study reports the effect of transition metal (TM) substitution on the electrical and optical properties of BaCe0.9Sm0.1O3-δ (BCS). Concentrations of 5-10 mol % of each of Fe and Co have been doped for the B-site of BCS by citric acid autocombustion method. Powder X-ray diffraction has revealed the formation of an orthorhombic perovskite-type structure. FTIR confirmed a distortion in the lattice upon TM-doping in BCS. Scanning electron microscopy (SEM) images of 1400 °C sintered samples have manifested a higher densification in BaCe0.8Sm0.1Co0.1O3-δ (BCSC10) with a grain size ∼11 μm compared to the parent compound BCS (∼2 μm). Thermogravimetric (TG) analysis showed a water uptake in case of BaCe0.85Sm0.1Co0.05O3-δ (BCSC5), while BaCe0.85Sm0.1Fe0.05O3-δ (BCSF5) did not show a noteworthy uptake of water. TG has also proved that the incorporation of Fe and Co in BCS did not improve the chemical stability in CO2 at elevated temperature. The band gap estimated using Kubelka-Munk model based on the diffuse reflectance data was found to be the lowest for BCSC5 (2.47 eV). However, it increases upon lowering oxygen partial pressure (pO2), which was interpreted by a band structure modifications. Among the samples investigated, BCSC10 sintered at 1400 °C showed the highest electrical conductivity of 0.02 S cm(-1) in air at 600 °C, while its proton mobility appears to be negligible under the investigated humidity atmosphere.

  8. Bi-stable optical actuator

    DOEpatents

    Holdener, Fred R.; Boyd, Robert D.

    2000-01-01

    The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

  9. Optical atomic clocks

    NASA Astrophysics Data System (ADS)

    Poli, N.; Oates, C. W.; Gill, P.; Tino, G. M.

    2013-12-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  10. Superlattice optical device

    DOEpatents

    Biefeld, R.M.; Fritz, I.J.; Gourley, P.L.; Osbourn, G.C.

    A semiconductor optical device which includes a superlattice having direct transitions between conduction band and valence band states with the same wave vector, the superlattice being formed from a plurality of alternating layers of two or more different materials, at least the material with the smallest bandgap being an indirect bandgap material.

  11. Optical and infrared lasers

    NASA Technical Reports Server (NTRS)

    Javan, A.

    1978-01-01

    Quantum mechanical predictions for the gain of an optically pumped CW FIR laser are presented for cases in which one or both of the pump and FIR transitions are pressure or Doppler broadened. The results are compared to those based on the rate equation model. Some of the quantum mechanical predictions are verified in CH3OH.

  12. Superlattice optical device

    DOEpatents

    Biefeld, Robert M.; Fritz, Ian J.; Gourley, Paul L.; Osbourn, Gordon C.

    1986-01-01

    A semiconductor optical device which includes a superlattice having direct transitions between conduction band and valence band states with the same wave vector, the superlattice being formed from a plurality of alternating layers of two or more different materials, at least the material with the smallest bandgap being an indirect bandgap material.

  13. Eliminating Transitions

    ERIC Educational Resources Information Center

    Gallick, Barb; Lee, Lisa

    2010-01-01

    Adults often find themselves transitioning from one activity to another in a short time span. Most of the time, they do not feel they have a lot of control over their schedules, but wish that they could carve out extended time to relax and focus on one project. Picture a group of children in the block area who have spent 15 or 20 minutes building…

  14. Stimulated coherent transition radiation

    SciTech Connect

    Hung-chi Lihn

    1996-03-01

    Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.

  15. Electronic Transitions of Yttrium Monoxide

    NASA Astrophysics Data System (ADS)

    Ng, Y. W.; Wang, Na; Clark, Andrew B.; Cheung, A. S.-C.

    2013-06-01

    The electronic transition spectrum of yttrium monoxide (YO) in the spectral region between 284nm and 307nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence (LIF) spectroscopy. The YO molecule was produced by reacting laser-ablated yttrium atoms with O_{2} seeded in argon. Twenty transition bands were observed in that region and a few bands were selected for further study using optical-optical double resonance (OODR) spectroscopy. The excited C^{2} Π state has been reached via the intermediate B^{2} Σ^{+} state from the ground X^{2} Σ^{+} state. The excited sub-states observed so far have Ω = 0.5 and 1.5. A least squares fit of the measured rotational lines yielded molecular constants for the newly observed excited states.

  16. Active Faraday optical frequency standard.

    PubMed

    Zhuang, Wei; Chen, Jingbiao

    2014-11-01

    We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.

  17. Optic neuritis

    MedlinePlus

    ... optic neuritis is unknown. The optic nerve carries visual information from your eye to the brain. The ... brain , including special images of the optic nerve Visual acuity testing Visual field testing Examination of the ...

  18. Arbitrary unitary transformations on optical states using a quantum memory

    SciTech Connect

    Campbell, Geoff T.; Pinel, Olivier; Hosseini, Mahdi; Buchler, Ben C.; Lam, Ping Koy

    2014-12-04

    We show that optical memories arranged along an optical path can perform arbitrary unitary transformations on frequency domain optical states. The protocol offers favourable scaling and can be used with any quantum memory that uses an off-resonant Raman transition to reversibly transfer optical information to an atomic spin coherence.

  19. Optically switchable photonic metasurfaces

    SciTech Connect

    Waters, R. F.; MacDonald, K. F.; Hobson, P. A.; Zheludev, N. I.

    2015-08-24

    We experimentally demonstrate an optically switchable gallium-based metasurface, in which a reversible light-induced transition between solid and liquid phases occurring in a confined nanoscale surface layer of the metal drives significant changes in reflectivity and absorption. The metasurface architecture resonantly enhances the metal's “active plasmonic” phase-change nonlinearity by an order of magnitude, offering high contrast all-optical switching in the near-infrared range at low, μW μm{sup −2}, excitation intensities.

  20. Plasmon-assisted optical vias for photonic ASICS

    DOEpatents

    Skogen, Erik J.; Vawter, Gregory A.; Tauke-Pedretti, Anna

    2017-03-21

    The present invention relates to optical vias to optically connect multilevel optical circuits. In one example, the optical via includes a surface plasmon polariton waveguide, and a first optical waveguide formed on a first substrate is coupled to a second optical waveguide formed on a second substrate by the surface plasmon polariton waveguide. In some embodiments, the first optical waveguide includes a transition region configured to convert light from an optical mode to a surface plasmon polariton mode or from a surface plasmon polariton mode to an optical mode.

  1. Gallium arsenide deep-level optical emitter for fibre optics.

    PubMed

    Pan, Janet L; McManis, Joseph E; Osadchy, Thomas; Grober, Louise; Woodall, Jerry M; Kindlmann, Peter J

    2003-06-01

    Fibre-optic components fabricated on the same substrate as integrated circuits are important for future high-speed communications. One industry response has been the costly push to develop indium phosphide (InP) electronics. However, for fabrication simplicity, reliability and cost, gallium arsenide (GaAs) remains the established technology for integrated optoelectronics. Unfortunately, the GaAs bandgap wavelength (0.85 microm) is far too short for fibre optics at 1.3-1.5 microm. This has led to work on materials that have a large lattice mismatch on GaAs. Here we demonstrate the first light-emitting diode (LED) that emits at 1.5 microm fibre-optic wavelengths in GaAs using optical transitions from arsenic antisite (As(Ga)) deep levels. This is an enabling technology for fibre-optic components that are lattice-matched to GaAs integrated circuits. We present experimental results showing significant internal optical power (24 mW) and speed (in terahertz) from GaAs optical emitters using deep-level transitions. Finally, we present theory showing the ultimate limit to the efficiency-bandwidth product of semiconductor deep-level optical emitters.

  2. Optical microspectrometer

    DOEpatents

    Sweatt, William C.; Christenson, Todd R.

    2004-05-25

    An optical microspectrometer comprises a grism to disperse the spectra in a line object. A single optical microspectrometer can be used to sequentially scan a planar object, such as a dye-tagged microchip. Because the optical microspectrometer is very compact, multiple optical microspectrometers can be arrayed to provide simultaneous readout across the width of the planar object The optical microspectrometer can be fabricated with lithographic process, such as deep X-ray lithography (DXRL), with as few as two perpendicular exposures.

  3. Optically tunable optical filter

    NASA Astrophysics Data System (ADS)

    James, Robert T. B.; Wah, Christopher; Iizuka, Keigo; Shimotahira, Hiroshi

    1995-12-01

    We experimentally demonstrate an optically tunable optical filter that uses photorefractive barium titanate. With our filter we implement a spectrum analyzer at 632.8 nm with a resolution of 1.2 nm. We simulate a wavelength-division multiplexing system by separating two semiconductor laser diodes, at 1560 nm and 1578 nm, with the same filter. The filter has a bandwidth of 6.9 nm. We also use the same filter to take 2.5-nm-wide slices out of a 20-nm-wide superluminescent diode centered at 840 nm. As a result, we experimentally demonstrate a phenomenal tuning range from 632.8 to 1578 nm with a single filtering device.

  4. Topological Lifshitz transitions

    NASA Astrophysics Data System (ADS)

    Volovik, G. E.

    2017-01-01

    Different types of Lifshitz transitions are governed by topology in momentum space. They involve the topological transitions with the change of topology of Fermi surfaces, Weyl and Dirac points, nodal lines, and also the transitions between the fully gapped states.

  5. Transitions: A Personal Perspective.

    ERIC Educational Resources Information Center

    Wood, Ann Stace

    1995-01-01

    Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)

  6. Different ways to active optical frequency standards

    NASA Astrophysics Data System (ADS)

    Pan, Duo; Xue, Xiaobo; Zhang, Xiaogang; Chen, Jingbiao

    2016-06-01

    Active optical frequency standard, or active optical clock, is a new concept of optical frequency standard, where a weak feedback with phase coherence information in optical bad-cavity limitation is formed, and the continuous self-sustained coherent stimulated emission between two atomic transition levels with population inversion is realized. Through ten years of both theoretical and experimental exploration, the narrow linewidth and suppression of cavity pulling effect of active optical frequency standard have been initially proved. In this paper, after a simple review, we will mainly present the most recent experimental progresses of active optical frequency standards in Peking University, including 4-level cesium active optical frequency standards and active Faraday optical frequency standards. The future development of active optical frequency standards is also discussed.

  7. Method and apparatus for bistable optical information storage for erasable optical disks

    DOEpatents

    Land, Cecil E.; McKinney, Ira D.

    1990-01-01

    A method and an optical device for bistable storage of optical information, together with reading and erasure of the optical information, using a photoactivated shift in a field dependent phase transition between a metastable or a bias-stabilized ferroelectric (FE) phase and a stable antiferroelectric (AFE) phase in an lead lanthanum zirconate titanate (PLZT). An optical disk contains the PLZT. Writing and erasing of optical information can be accomplished by a light beam normal to the disk. Reading of optical information can be accomplished by a light beam at an incidence angle of 15 to 60 degrees to the normal of the disk.

  8. Method and apparatus for bistable optical information storage for erasable optical disks

    DOEpatents

    Land, C.E.; McKinney, I.D.

    1988-05-31

    A method and an optical device for bistable storage of optical information, together with reading and erasure of the optical information, using a photoactivated shift in a field dependent phase transition between a metastable or a bias-stabilized ferroelectric (FE) phase and a stable antiferroelectric (AFE) phase in a lead lanthanum zirconate titanate (PLZT). An optical disk contains the PLZT. Writing and erasing of optical information can be accomplished by a light beam normal to the disk. Reading of optical information can be accomplished by a light beam at an incidence angle of 15 to 60 degrees to the normal of the disk. 10 figs.

  9. The nature of transition blazars

    SciTech Connect

    Ruan, J. J.; Anderson, S. F.; Plotkin, R. M.; Brandt, W. N.; Schneider, D. P.; Burnett, T. H.; Myers, A. D.

    2014-12-10

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

  10. Optical Solitons

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    2005-08-01

    1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

  11. Optical Solitons

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    1992-04-01

    1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

  12. Optical probe

    DOEpatents

    Hencken, Kenneth; Flower, William L.

    1999-01-01

    A compact optical probe is disclosed particularly useful for analysis of emissions in industrial environments. The instant invention provides a geometry for optically-based measurements that allows all optical components (source, detector, rely optics, etc.) to be located in proximity to one another. The geometry of the probe disclosed herein provides a means for making optical measurements in environments where it is difficult and/or expensive to gain access to the vicinity of a flow stream to be measured. Significantly, the lens geometry of the optical probe allows the analysis location within a flow stream being monitored to be moved while maintaining optical alignment of all components even when the optical probe is focused on a plurality of different analysis points within the flow stream.

  13. Toward high throughput optical metamaterial assemblies.

    PubMed

    Fontana, Jake; Ratna, Banahalli R

    2015-11-01

    Optical metamaterials have unique engineered optical properties. These properties arise from the careful organization of plasmonic elements. Transitioning these properties from laboratory experiments to functional materials may lead to disruptive technologies for controlling light. A significant issue impeding the realization of optical metamaterial devices is the need for robust and efficient assembly strategies to govern the order of the nanometer-sized elements while enabling macroscopic throughput. This mini-review critically highlights recent approaches and challenges in creating these artificial materials. As the ability to assemble optical metamaterials improves, new unforeseen opportunities may arise for revolutionary optical devices.

  14. Optical keyboard

    DOEpatents

    Veligdan, James T.; Feichtner, John D.; Phillips, Thomas E.

    2001-01-01

    An optical keyboard includes an optical panel having optical waveguides stacked together. First ends of the waveguides define an inlet face, and opposite ends thereof define a screen. A projector transmits a light beam outbound through the waveguides for display on the screen as a keyboard image. A light sensor is optically aligned with the inlet face for sensing an inbound light beam channeled through the waveguides from the screen upon covering one key of the keyboard image.

  15. Autoresonant Dynamics of Optical Guided Waves

    SciTech Connect

    Barak, Assaf; Lamhot, Yuval; Segev, Mordechai; Friedland, Lazar

    2009-09-18

    We study, theoretically and experimentally, autoresonant dynamics of optical waves in a spatially chirped nonlinear directional coupler. We show that adiabatic passage through a linear resonance in a weakly coupled light-wave system yields a sharp threshold transition to nonlinear phase locking and amplification to predetermined amplitudes. This constitutes the first observation of autoresonance phenomena in optics.

  16. Tips for Transition

    ERIC Educational Resources Information Center

    Kellems, Ryan, Comp.; Morningstar, Mary E., Comp.

    2009-01-01

    The Tips for Transition contains 134 Transition Tips submitted from all over the country by practitioners. The purpose of the Tips was to identify grassroots transition practices being used by practitioners. Tips are categorized into the following domains: (1) Transition Planning; (2) Student Involvement; (3) Family Involvement; (4) Curriculum and…

  17. System for testing optical fibers

    DOEpatents

    Davies, Terence J.; Franks, Larry A.; Nelson, Melvin A.

    1981-01-01

    A system for nondestructively determining the attenuation coefficient, .alpha.(.lambda.), of low-loss optical fiber wave guides. Cerenkov light pulses are generated at a plurality of locations in the fiber by a beam of charged particles. The transit times of selected spectral components and their intensities are utilized to unfold the .alpha.(.lambda.) values over the measured spectrum.

  18. TRANSVERSE MODE ELECTRO-OPTIC MATERIALS.

    DTIC Science & Technology

    electro - optic modulators presently used are crystals such as KDP which exhibit a longitudinal electro - optic effect. It has been demonstrated that a more efficient modulator can be produced when a crystal having a transverse electro - optic effect is employed. Generally these crystals are produced either from the melt or from fluxes. Since melt grown crystals must be cooled through several hundred degrees and often must undergo phase transitions, these crystals are generally highly strained. Flux grown crystals are also

  19. Optical Micromachining

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Under an SBIR (Small Business Innovative Research) with Marshall Space Flight Center, Potomac Photonics, Inc., constructed and demonstrated a unique tool that fills a need in the area of diffractive and refractive micro-optics. It is an integrated computer-aided design and computer-aided micro-machining workstation that will extend the benefits of diffractive and micro-optic technology to optical designers. Applications of diffractive optics include sensors and monitoring equipment, analytical instruments, and fiber optic distribution and communication. The company has been making diffractive elements with the system as a commercial service for the last year.

  20. Fluidic optics

    NASA Astrophysics Data System (ADS)

    Whitesides, George M.; Tang, Sindy K. Y.

    2006-09-01

    Fluidic optics is a new class of optical system with real-time tunability and reconfigurability enabled by the introduction of fluidic components into the optical path. We describe the design, fabrication, operation of a number of fluidic optical systems, and focus on three devices, liquid-core/liquid-cladding (L2) waveguides, microfluidic dye lasers, and diffraction gratings based on flowing, crystalline lattices of bubbles, to demonstrate the integration of microfluidics and optics. We fabricate these devices in poly(dimethylsiloxane) (PDMS) with soft-lithographic techniques. They are simple to construct, and readily integrable with microanalytical or lab-on-a-chip systems.

  1. Optic Nerve.

    PubMed

    Gordon, Lynn K

    2016-10-28

    Optic nerve diseases arise from many different etiologies including inflammatory, neoplastic, genetic, infectious, ischemic, and idiopathic. Understanding some of the characteristics of the most common optic neuropathies along with therapeutic approaches to these diseases is helpful in designing recommendations for individual patients. Although many optic neuropathies have no specific treatment, some do, and it is those potentially treatable or preventable conditions which need to be recognized in order to help patients regain their sight or develop a better understanding of their own prognosis. In this chapter several diseases are discussed including idiopathic intracranial hypertension, optic neuritis, ischemic optic neuropathies, hereditary optic neuropathies, trauma, and primary tumors of the optic nerve. For each condition there is a presentation of the signs and symptoms of the disease, in some conditions the evaluation and diagnostic criteria are highlighted, and where possible, current therapy or past trials are discussed.

  2. A potassium Faraday anomalous dispersion optical filter

    NASA Technical Reports Server (NTRS)

    Yin, B.; Shay, T. M.

    1992-01-01

    The characteristics of a potassium Faraday anomalous dispersion optical filter operating on the blue and near infrared transitions are calculated. The results show that the filter can be designed to provide high transmission, very narrow pass bandwidth, and low equivalent noise bandwidth. The Faraday anomalous dispersion optical filter (FADOF) provides a narrow pass bandwidth (about GHz) optical filter for laser communications, remote sensing, and lidar. The general theoretical model for the FADOF has been established in our previous paper. In this paper, we have identified the optimum operational conditions for a potassium FADOF operating on the blue and infrared transitions. The signal transmission, bandwidth, and equivalent noise bandwidth (ENBW) are also calculated.

  3. Hydrothermal synthesis, structure and optical properties of two novel nanosized Ln26 @CO3 (Ln=Dy and Tb) cluster-based lanthanide-transition-metal organic frameworks (Ln MOFs).

    PubMed

    Zhang, Yu; Huang, Lian; Miao, Hao; Wan, Hong Xiang; Mei, Hua; Liu, Ying; Xu, Yan

    2015-02-16

    Invited for the cover of this issue is the group of Hua Mei and Yan Xu at Nanjing Tech University, China. The image depicts star-like {Tb26 } clusters, which are simplified as blue balls, and Ag atoms, which are distributed in the MOF structure uniformly to give a lanthanide-MOF structure with good optical properties. Read the full text of the article at 10.1002/chem.201405178.

  4. Electro-Optic Generation and Detection of Femtosecond Electromagnetic Pulses

    DTIC Science & Technology

    1991-11-20

    electromagnetic pulses from an electro - optic crystal following their generation by electro - optic Cherenkov radiation, and their subsequent propagation and detection...in free space; (4) The measurement of subpicosecond electrical response of a new organic electrooptic material (polymer); (5) The observation of terahertz transition radiation from the surfaces of electro - optic crystals.

  5. The ACCESS Transiting Exoplanets Spectroscopy Survey and the Impact of Heterogeneous Stellar Atmospheres on Transit Spectroscopy

    NASA Astrophysics Data System (ADS)

    Apai, Daniel; Rackham, Benjamin V.; Lopez-Morales, Mercedes; Espinoza, Nestor; Jordan, Andres; Osip, David; Lewis, Nikole K.; Rodler, Florian; Fraine, Jonathan; Morley, Caroline; Fortney, Jonathan J.; Bixel, Alex; ACCESS Team; Earths in Other Solar Systems Team

    2017-01-01

    We present results from the ACCESS survey, a large optical transmission spectroscopy survey of transiting planets. With over 40 transits observed using the IMACS multi-object spectrograph on Magellan, ACCESS is building up the most comprehensive spectral database for transiting exoplanets. The goals of ACCESS are to probe the composition of exoplanet atmospheres as a function planet mass and insolation and stellar properties.We will present a brief overview of the survey and highlight results on multiple targets, including hot jupiters and the sub-nepture GJ1214. I will also report on our study of how stellar heterogeneity impact the transmission spectrum of transiting exoplanets and discuss approaches to correct for this important effect to improve the diagnostic power of transit spectroscopcy.

  6. Magic Wavelength for the Hydrogen 1S-2S Transition

    NASA Astrophysics Data System (ADS)

    Kawasaki, Akio

    2016-05-01

    The state of the art precision measurement of the transition frequencies of neutral atoms is performed with atoms trapped by the magic wavelength optical lattice that cancels the ac Stark shift of the transitions. Trapping with magic wavelength lattice is also expected to improve the precision of the hydrogen 1S-2S transition frequency, which so far has been measured only with the atomic beam. In this talk, I discuss the magic wavelength for the hydrogen 1S-2S transition, and the possibility of implementing the optical lattice trapping for hydrogen. Optical trapping of hydrogen also opens the way to perform magnetic field free spectroscopy of antihydrogen for the test of CPT theorem.

  7. Gas turbine combustor transition

    DOEpatents

    Coslow, Billy Joe; Whidden, Graydon Lane

    1999-01-01

    A method of converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit.

  8. Gas turbine combustor transition

    DOEpatents

    Coslow, B.J.; Whidden, G.L.

    1999-05-25

    A method is described for converting a steam cooled transition to an air cooled transition in a gas turbine having a compressor in fluid communication with a combustor, a turbine section in fluid communication with the combustor, the transition disposed in a combustor shell and having a cooling circuit connecting a steam outlet and a steam inlet and wherein hot gas flows from the combustor through the transition and to the turbine section, includes forming an air outlet in the transition in fluid communication with the cooling circuit and providing for an air inlet in the transition in fluid communication with the cooling circuit. 7 figs.

  9. Optical Metacages

    NASA Astrophysics Data System (ADS)

    Mirzaei, Ali; Miroshnichenko, Andrey E.; Shadrivov, Ilya V.; Kivshar, Yuri S.

    2015-11-01

    We suggest a novel strategy for spectrally selective optical shielding of arbitrary shaped volumes by arranging specifically designed two- or three-layer nanowires around an area that needs to be protected. We show that such nanowire shields preserve their functionality for almost arbitrary geometry, and we term such structures optical metacages. We analyze several designs of such optical metacages made from either metallic or dielectric materials with experimentally measured parameters. We employ a semianalytical approach and also verify our results by numerical simulations. We further study optical properties of the introduced metacages in both near- and far-field regions, as well as analyze their frequency selectivity and the vanishing backscattering regime.

  10. Optical engineering

    SciTech Connect

    Saito, T T

    1998-01-01

    The Optical Engineering thrust area at Lawrence Livermore National Laboratory (LLNL) was created in the summer of 1996 with the following main objectives: (1) to foster and stimulate leading edge optical engineering research and efforts key to carrying out LLNL's mission and enabling major new programs; (2) to bring together LLNL's broad spectrum of high level optical engineering expertise to support its programs. Optical engineering has become a pervasive and key discipline, with applications across an extremely wide range of technologies, spanning the initial conception through the engineering refinements to enhance revolutionary application. It overlaps other technologies and LLNL engineering thrust areas.

  11. Optical trapping

    PubMed Central

    Neuman, Keir C.; Block, Steven M.

    2006-01-01

    Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. PMID:16878180

  12. Optical computing.

    NASA Technical Reports Server (NTRS)

    Stroke, G. W.

    1972-01-01

    Applications of the optical computer include an approach for increasing the sharpness of images obtained from the most powerful electron microscopes and fingerprint/credit card identification. The information-handling capability of the various optical computing processes is very great. Modern synthetic-aperture radars scan upward of 100,000 resolvable elements per second. Fields which have assumed major importance on the basis of optical computing principles are optical image deblurring, coherent side-looking synthetic-aperture radar, and correlative pattern recognition. Some examples of the most dramatic image deblurring results are shown.

  13. Phase diagram and incommensurate antiferroelectric structure in (Pb{sub 1−1.5x}La{sub x})(Zr{sub 0.42}Sn{sub 0.40}Ti{sub 0.18})O{sub 3} ceramics discovered by band-to-band optical transitions

    SciTech Connect

    Ding, X. J.; Xu, L. P.; Hu, Z. G. Chu, J. H.; Chen, X. F.; Wang, G. S.; Dong, X. L.

    2014-09-29

    Optical properties and phase transitions of (Pb{sub 1−1.5x}La{sub x})(Zr{sub 0.42}Sn{sub 0.40}Ti{sub 0.18})O{sub 3} (PLZST 100x/42/40/18) ceramics with different compositions have been investigated by temperature dependent spectroscopic ellipsometry. Two interband critical points (E{sub cp1} and E{sub cp2}) located at about 3.9 and 5.1 eV can be obtained by fitting standard line shapes to the second derivatives of the complex dielectric functions. Based on the band-to-band transitions, the phase diagram of PLZST ceramics can be well presented. Moreover, a peculiar incommensurate antiferroelectric state has been found to exist above the temperature of the normal commensurate antiferroelectric tetragonal structure. It can be stable below Curie temperature, evolving slowly with decreasing temperature towards the commensurate structure, which is due to strong pinning of incommensurate domain walls. The phenomena can result from a competition between ferroelectric ordering and antiferroelectric ordering caused by the lanthanum modification.

  14. Kinetics of an oxygen – iodine active medium with iodine atoms optically pumped on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition

    SciTech Connect

    Zagidullin, M V; Azyazov, V N; Malyshev, M S

    2015-08-31

    The kinetics of the processes occurring in an O{sub 2} – I{sub 2} – He – H{sub 2}O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen – iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O{sub 2}(a{sup 1}Δ) exceeding 10%. Having formed a supersonic gas flow with a temperature ∼100 K from this medium, one can reach a small-signal gain of about 10{sup -2} cm{sup -1} on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition in iodine atoms. The specific power per unit flow cross section in the oxygen – iodine laser with this active medium may reach ∼100 W cm{sup -2}. (active media)

  15. Magnetic hyperbolic optical metamaterials

    PubMed Central

    Kruk, Sergey S.; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N.; Kivshar, Yuri S.; Zhang, Xiang

    2016-01-01

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light. PMID:27072604

  16. Magnetic hyperbolic optical metamaterials.

    PubMed

    Kruk, Sergey S; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N; Kivshar, Yuri S; Zhang, Xiang

    2016-04-13

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light.

  17. Magnetic hyperbolic optical metamaterials

    NASA Astrophysics Data System (ADS)

    Kruk, Sergey S.; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N.; Kivshar, Yuri S.; Zhang, Xiang

    2016-04-01

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light.

  18. Layer thinning transition in an achiral four-ring hockey stick shaped liquid crystal

    NASA Astrophysics Data System (ADS)

    Paul, Manoj Kr.; Nath, Rahul K.; Moths, Brian; Pan, LiDong; Wang, Shun; Deb, Rajdeep; Shen, Yongqiang; Rao, Nandiraju V. S.; Huang, C. C.

    2012-12-01

    Depolarized reflected light microscopy and high resolution optical reflectivity measurements have been conducted on free-standing films of an achiral four-ring hockey stick shaped liquid crystal exhibiting SmA-B2-SmX* transition sequence. A layer thinning transition above the bulk isotropic-SmA phase transition has been observed. This behaviour was highly irreproducible, indicating an irregular layer thinning transition. From optical reflectivity data, both thickness of the free-standing films and the smectic interlayer spacing were determined. This is the first report of the layer thinning transition in a hockey stick shaped liquid crystal.

  19. Optically pumped microplasma rare gas laser.

    PubMed

    Rawlins, W T; Galbally-Kinney, K L; Davis, S J; Hoskinson, A R; Hopwood, J A; Heaven, M C

    2015-02-23

    The optically pumped rare-gas metastable laser is a chemically inert analogue to three-state optically pumped alkali laser systems. The concept requires efficient generation of electronically excited metastable atoms in a continuous-wave (CW) electric discharge in flowing gas mixtures near atmospheric pressure. We have observed CW optical gain and laser oscillation at 912.3 nm using a linear micro-discharge array to generate metastable Ar(4s, 1s(5)) atoms at atmospheric pressure. We observed the optical excitation of the 1s(5) → 2p(9) transition at 811.5 nm and the corresponding fluorescence, optical gain and laser oscillation on the 2p(10) ↔ 1s(5) transition at 912.3 nm, following 2p(9)→2p(10) collisional energy transfer. A steady-state kinetics model indicates efficient collisional coupling within the Ar(4s) manifold.

  20. Conceptualizing Transitions to Adulthood

    ERIC Educational Resources Information Center

    Wyn, Johanna

    2014-01-01

    This chapter provides an overview of theories of the transition to young adulthood. It sets out the argument for conceptual renewal and discusses some implications of new patterns of transition for adult education.

  1. Transition to Adulthood

    MedlinePlus

    ... fix that! Keep reading… Back to top IDEA’s Definition of Transition Services Any discussion of transition services ... from special education. Back to top Considering the Definition A number of key words in the definition ...

  2. Unified Model Deformation and Flow Transition Measurements

    NASA Technical Reports Server (NTRS)

    Burner, Alpheus W.; Liu, Tianshu; Garg, Sanjay; Bell, James H.; Morgan, Daniel G.

    1999-01-01

    The number of optical techniques that may potentially be used during a given wind tunnel test is continually growing. These include parameter sensitive paints that are sensitive to temperature or pressure, several different types of off-body and on-body flow visualization techniques, optical angle-of-attack (AoA), optical measurement of model deformation, optical techniques for determining density or velocity, and spectroscopic techniques for determining various flow field parameters. Often in the past the various optical techniques were developed independently of each other, with little or no consideration for other techniques that might also be used during a given test. Recently two optical techniques have been increasingly requested for production measurements in NASA wind tunnels. These are the video photogrammetric (or videogrammetric) technique for measuring model deformation known as the video model deformation (VMD) technique, and the parameter sensitive paints for making global pressure and temperature measurements. Considerations for, and initial attempts at, simultaneous measurements with the pressure sensitive paint (PSP) and the videogrammetric techniques have been implemented. Temperature sensitive paint (TSP) has been found to be useful for boundary-layer transition detection since turbulent boundary layers convect heat at higher rates than laminar boundary layers of comparable thickness. Transition is marked by a characteristic surface temperature change wherever there is a difference between model and flow temperatures. Recently, additional capabilities have been implemented in the target-tracking videogrammetric measurement system. These capabilities have permitted practical simultaneous measurements using parameter sensitive paint and video model deformation measurements that led to the first successful unified test with TSP for transition detection in a large production wind tunnel.

  3. Jumping phase control in interband photonic transition.

    PubMed

    Liu, Ye; Zhu, Jiang; Gao, Zhuoyang; Zhu, Haibin; Jiang, Chun

    2014-03-10

    Indirect interband photonic transition provides a nonmagnetic and linear scheme to achieve optical isolation in integrated photonics. In this paper, we demonstrate that the nonreciprocal transition can be induced through two pathways respectively by different modulation designs. At the end of those pathways, the two final modes have π phaseshift. We call this phenomenon jumping phase control since this approach provides a method to control the mode phase after the conversion. This approach also yields a novel way to generate nonreciprocal phaseshift and may contribute to chip-scale optoelectronic applications.

  4. Bowen fluorescence in the solar transition region

    NASA Technical Reports Server (NTRS)

    Raymond, J. C.

    1978-01-01

    In Bowen fluorescence, a 304-A photon of He II is converted into two optical photons and an EUV photon of O III. The fluorescent contribution to the intensity of the O III 374-A line is a measure of the column density of O III in the solar transition region. Division of the column density into the emission measure derived from other lines of O III allows determination of the electron density. The accuracy of this technique is roughly a factor of 2, which is comparable to the accuracy of the density diagnostics for the solar transition region.

  5. Phase Transition of DNA Coated Nanogold Networks

    NASA Astrophysics Data System (ADS)

    Kiang, Ching-Hwa; Sun, Young; Harris, Nolan; Wickremasinghe, Nissanka

    2004-03-01

    Melting and hybridization of DNA-coated gold nanoparticle networks are investigated with optical absorption spectroscopy and tansmission electron microscopy. Single-stranded DNA-coated nanogold are linked with complementary, single-stranded linker DNA to form particle networks. Network formation results in a solution color change, which can be used for DNA detection. Compared to free DNA, networked DNA-nanoparticle systems result in a sharp melting transition. Melting curves calculated from percolation theory agree with our experimental results(1). (1) C.-H. Kiang, ``Phase Transition of DNA-Linked Gold Nanoparticles,'' Physica A, 321 (2003) 164--169.

  6. Transition in Turbines

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The concept of a large disturbance bypass mechanism for the initiation of transition is reviewed and studied. This mechanism, or some manifestation thereof, is suspected to be at work in the boundary layers present in a turbine flow passage. Discussion is presented on four relevant subtopics: (1) the effect of upstream disturbances and wakes on transition; (2) transition prediction models, code development, and verification; (3) transition and turbulence measurement techniques; and (4) the hydrodynamic condition of low Reynolds number boundary layers.

  7. Cosmological phase transitions

    SciTech Connect

    Kolb, E.W. |

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  8. Optically controlled integrated optical switch

    NASA Astrophysics Data System (ADS)

    Soref, R. A.

    1986-02-01

    This invention relates to an optically controlled integrated optical switch having a body made up of entirely crystalline silicon. More specifically, the body has a pair of channel waveguides intersecting at an X-like configuration forming therein an intersection crossover region. An electrically controlled optical source is positioned over the crossover region to shine intense, short-wave light on the crossover region in order to generate numerous electron-hole pairs in the waveguide material. These charge carriers alter the refractive index of the intersection region. A controllable current source is used to adjust the optical output power of the optical source. This, in turn, changes the amount of optical cross coupling of light between the intersecting waveguides.

  9. Optical Lattice Clocks

    NASA Astrophysics Data System (ADS)

    Oates, Chris

    2012-06-01

    Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths << 1 Hz). To suppress the effects of atomic motion/recoil, the atoms in the sample (˜10^4 atoms) are confined tightly in the potential wells of an optical standing wave (lattice). The wavelength of the lattice light is tuned to its ``magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates

  10. Transition: Preschool to Kindergarten

    ERIC Educational Resources Information Center

    Arizona Department of Education, 2007

    2007-01-01

    Transition is movement or change without interruption. It should be a smooth flow from one place or condition to another. While the transition plan for a student receiving special education services is designed to prepare him or her for life after high school, transition can start when a child enters preschool. The second of six distinct stages of…

  11. Transition. Feature Issue.

    ERIC Educational Resources Information Center

    Wallace, Teri, Ed.; And Others

    1992-01-01

    This feature issue of a quarterly bulletin on community integration addresses the topic of transition services for preparing youth with disabilities for adult community living. It contains articles with the following titles and authors: "Transition: The Next Five Years" (David R. Johnson and others); "Transition Policy in the 1990s:…

  12. Optical interconnection of optical modules

    NASA Astrophysics Data System (ADS)

    Schamschula, Marius P.; Caulfield, H. J.; Shamir, Joseph

    1990-12-01

    The most plausible possible uses of nonlinear optics as the bases for interconnections among complex optical modules are evaluated, with a view to such applications as neural networks that entail large numbers of interconnections and numerous stages. Optical interconnection allows such a system to be composed of many modules as well as to incorporate switching- and amplification-function optical nonlinearities. While it is possible to achieve a pixel-by-pixel, diffraction-limited flat-field relay with nonlinearity, where the interconnect allows for cascadability, the wave-particle duality is destroyed between stages.

  13. Optical testing

    NASA Technical Reports Server (NTRS)

    Wyant, James; Hochberg, Eric; Breault, Robert; Greivenkamp, John; Hunt, Gary; Mason, Pete; Mcguire, James; Meinel, Aden; Morris, Mike; Scherr, Larry

    1992-01-01

    Optical testing is one of the most vital elements in the process of preparing an optical instrument for launch. Without well understood, well controlled, and well documented test procedures, current and future mission goals will be jeopardized. We should keep in mind that the reason we test is to provide an opportunity to catch errors, oversights, and problems on the ground, where solutions are possible and difficulties can be rectified. Consequently, it is necessary to create tractable test procedures that truly provide a measure of the performance of all optical elements and systems under conditions which are close to those expected in space. Where testing is not feasible, accurate experiments are required in order to perfect models that can exactly predict the optical performance. As we stretch the boundaries of technology to perform more complex space and planetary investigations, we must expand the technology required to test the optical components and systems which we send into space. As we expand the observational wavelength ranges, so must we expand our range of optical sources and detectors. As we increase resolution and sensitivity, our understanding of optical surfaces to accommodate more stringent figure and scatter requirements must expand. Only with research and development in these areas can we hope to achieve success in the ever increasing demands made on optical testing by the highly sophisticated missions anticipated over the next two decades. Technology assessment and development plan for surface figure, surface roughness, alignment, image quality, radiometric quantities, and stray light measurement are presented.

  14. Camera Optics.

    ERIC Educational Resources Information Center

    Ruiz, Michael J.

    1982-01-01

    The camera presents an excellent way to illustrate principles of geometrical optics. Basic camera optics of the single-lens reflex camera are discussed, including interchangeable lenses and accessories available to most owners. Several experiments are described and results compared with theoretical predictions or manufacturer specifications.…

  15. Atomistic tight-binding study of electronic structure and interband optical transitions in GaBi{sub x}As{sub 1−x}/GaAs quantum wells

    SciTech Connect

    Usman, Muhammad; O'Reilly, Eoin P.

    2014-02-17

    Large-supercell tight-binding calculations are presented for GaBi{sub x}As{sub 1−x}/GaAs single quantum wells (QWs) with Bi fractions x of 3.125% and 12.5%. Our results highlight significant distortion of the valence band states due to the alloy disorder. A large full-width-half-maximum (FWHM) is estimated in the ground state interband transition energy (≈33 meV) at 3.125% Bi, consistent with recent photovoltage measurements for similar Bi compositions. Additionally, the alloy disorder effects are predicted to become more pronounced as the QW width is increased. However, they are less strong at the higher Bi composition (12.5%) required for the design of temperature-stable lasers, with a calculated FWHM of ≈23.5 meV at x = 12.5%.

  16. On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E{sub 1} and E{sub 1} + Δ{sub 1} optical transitions

    SciTech Connect

    Gluba, L. Yastrubchak, O.; Kulik, M.; Żuk, J.; Sęk, G.; Rudno-Rudziński, W.; Misiewicz, J.; Sadowski, J.; Rzodkiewicz, W.; Andrearczyk, T.; Wosinski, T.

    2014-07-21

    The dilute (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. In this paper, we verify the ellipsometric results and compare them with more precise photoreflectance method, which gives an important insight into the interaction of the Mn-related states with the ones of GaAs valence band. No spectral shifts observed for the E{sub 1} and E{sub 1} + Δ{sub 1} interband transitions in highly doped and annealed (Ga,Mn)As epitaxial layers indicate that the coupling between a detached Mn impurity band and the valence band does not occur. Our findings are supported by the characterizations of the (Ga,Mn)As epitaxial layers with the high resolution transmission electron microscopy and magnetization measurements.

  17. Optical biosensors

    PubMed Central

    Damborský, Pavel; Švitel, Juraj

    2016-01-01

    Optical biosensors represent the most common type of biosensor. Here we provide a brief classification, a description of underlying principles of operation and their bioanalytical applications. The main focus is placed on the most widely used optical biosensors which are surface plasmon resonance (SPR)-based biosensors including SPR imaging and localized SPR. In addition, other optical biosensor systems are described, such as evanescent wave fluorescence and bioluminescent optical fibre biosensors, as well as interferometric, ellipsometric and reflectometric interference spectroscopy and surface-enhanced Raman scattering biosensors. The optical biosensors discussed here allow the sensitive and selective detection of a wide range of analytes including viruses, toxins, drugs, antibodies, tumour biomarkers and tumour cells. PMID:27365039

  18. A cloaking device for transiting planets

    NASA Astrophysics Data System (ADS)

    Kipping, David M.; Teachey, Alex

    2016-06-01

    The transit method is presently the most successful planet discovery and characterization tool at our disposal. Other advanced civilizations would surely be aware of this technique and appreciate that their home planet's existence and habitability is essentially broadcast to all stars lying along their ecliptic plane. We suggest that advanced civilizations could cloak their presence, or deliberately broadcast it, through controlled laser emission. Such emission could distort the apparent shape of their transit light curves with relatively little energy, due to the collimated beam and relatively infrequent nature of transits. We estimate that humanity could cloak the Earth from Kepler-like broad-band surveys using an optical monochromatic laser array emitting a peak power of ˜30 MW for ˜10 hours per year. A chromatic cloak, effective at all wavelengths, is more challenging requiring a large array of tunable lasers with a total power of ˜250 MW. Alternatively, a civilization could cloak only the atmospheric signatures associated with biological activity on their world, such as oxygen, which is achievable with a peak laser power of just ˜160 kW per transit. Finally, we suggest that the time of transit for optical Search for Extraterrestrial Intelligence (SETI) is analogous to the water-hole in radio SETI, providing a clear window in which observers may expect to communicate. Accordingly, we propose that a civilization may deliberately broadcast their technological capabilities by distorting their transit to an artificial shape, which serves as both a SETI beacon and a medium for data transmission. Such signatures could be readily searched in the archival data of transit surveys.

  19. Transiting Exoplanet Survey Satellite (TESS)

    NASA Astrophysics Data System (ADS)

    Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland; Latham, David W.; Bakos, Gáspár. Á.; Bean, Jacob L.; Berta-Thompson, Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David; Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty, John; De Lee, Nathan; Dressing, Courtney; Dunham, E. W.; Endl, Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon; Jernigan, Garrett; Johnson, John A.; Kaltenegger, Lisa; Kawai, Nobuyuki; Kjeldsen, Hans; Laughlin, Gregory; Levine, Alan M.; Lin, Douglas; Lissauer, Jack J.; MacQueen, Phillip; Marcy, Geoffrey; McCullough, P. R.; Morton, Timothy D.; Narita, Norio; Paegert, Martin; Palle, Enric; Pepe, Francesco; Pepper, Joshua; Quirrenbach, Andreas; Rinehart, S. A.; Sasselov, Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti, Alessandro; Stassun, Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew; Torres, Guillermo; Udry, Stephane; Villasenor, Joel

    2014-08-01

    The Transiting Exoplanet Survey Satellite (TESS ) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with IC (approximately less than) 13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.

  20. Transiting Exoplanet Survey Satellite (TESS)

    NASA Astrophysics Data System (ADS)

    Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland; Latham, David W.; Bakos, Gáspár Á.; Bean, Jacob L.; Berta-Thompson, Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David; Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty, John; De Lee, Nathan; Dressing, Courtney; Dunham, Edward W.; Endl, Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon M.; Jernigan, Garrett; Johnson, John Asher; Kaltenegger, Lisa; Kawai, Nobuyuki; Kjeldsen, Hans; Laughlin, Gregory; Levine, Alan M.; Lin, Douglas; Lissauer, Jack J.; MacQueen, Phillip; Marcy, Geoffrey; McCullough, Peter R.; Morton, Timothy D.; Narita, Norio; Paegert, Martin; Palle, Enric; Pepe, Francesco; Pepper, Joshua; Quirrenbach, Andreas; Rinehart, Stephen A.; Sasselov, Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti, Alessandro; Stassun, Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew; Torres, Guillermo; Udry, Stephane; Villasenor, Joel

    2015-01-01

    The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its 2-year mission, TESS will employ four wide-field optical charge-coupled device cameras to monitor at least 200,000 main-sequence dwarf stars with IC≈4-13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from 1 month to 1 year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10 to 100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every 4 months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.