The main aim of the research was to evaluate numeric procedures of the indirect determination of the group refractive index of air and to choose the suitable ones for requirements of ordinary and high accuracy distance measurement in geodesy and length metrology. For this purpose, 10 existing computation methods were derived from various authors' original publications and all were analysed for wide intervals of wavelengths and atmospheric parameters. The determination of the phase and the group refractive indices are essential parts in the evaluation of the first velocity corrections of laser interferometers and electronic distance meters. The validity of modern procedures was tested with respect to updated CIPM-2007 equations of the density of air. The refraction model of Leica AT401 laser tracker was analysed.
A Mach-Zehnder interferometer (MZI) that includes in an arm either a reflective image inverter or a Gouy phase shifter (RGPS) can (de)multiplex many types of modes of a few mode fiber without fundamental loss. The use of RGPSs in combination with binary phase plates for multiplexing purposes is studied for the first time, showing that the particular RGPS that shifts π the odd modes only multiplexes accurately low order modes. To overcome such a restriction, we present a new exact refractive image inverter, more compact and flexible than its reflective counterpart. Moreover, we show that these interferometers remove or reduce the crosstalk that the binary phase plates could introduce between the multiplexed modes. Finally, an experimental analysis of a MZI with both an approximated and an exact refractive image inverter is presented for the case of a bimodal multiplexing. Likewise, it is proven experimentally that a RGPS that shifts π/2 demultiplexes two odd modes which can not be achieved by any image inverter. ; Ministerio de Economía y Competitividad, Central Government of Spain, Contract number FIS2013-46584-C2-1-R; Fondo Europeo de Desenvolvemento Rexional 2007-2013 (FEDER). ; SI
1 Introduction -- 1.1 About Physical Optics -- 1.2 The Electromagnetic Spectrum -- 1.3 Overview of the Following Chapters -- References -- Problems -- 2 Maxwell's Equations and Plane Wave Propagation -- 2.1 Introduction -- 2.2 Some Preliminaries -- 2.3 Monochromatic Plane Waves -- 2.4 Polychromatic Plane Waves -- 2.5 Propagation in Polarizing Optical Systems -- 2.6 Striated Media -- References -- Problems -- 3 Material Polarization and Dispersion -- 3.1 Introduction -- 3.2 Complexity in the Microscopic World -- 3.3 A Derivation of the Lorentz-Lorenz Relation -- 3.4 The Spring Model of Matter -- 3.5 Wave Propagation in Dispersive Media -- 3.6 Macroscopic Models of More Exotic Effects -- References -- Problems -- 4 Wave Propagation in Anisotropic Media -- 4.1 Introduction -- 4.2 Microscopic Basis for the Existence of an Index Tensor -- 4.3 Fresnel's and the Index Ellipsoids -- 4.4 The Normal Surface and the Ray Surface -- 4.5 Some Propagation Effects in Crystals -- 4.6 Some Polarization Devices -- References -- Problems -- 5 Geometrical Optics -- 5.1 Introduction -- 5.2 The WKB Approximation as it Relates to Geometrical Optics -- 5.3 The Eikonal Equation -- 5.4 Energy Flow and Radiometry -- 5.5 Paraxial Ray Optics -- 5.6 About Optical Instruments -- 5.7 Phase Space and Liouville's Theorem -- References -- Problems -- 6 Interferenee -- 6.1 Introduction -- 6.2 The Michelson Interferometer -- 6.3 Other Interferometers -- 6.4 The Fabry-Perot Interferometer -- 6.5 Young's Interferometer and Spatial Coherence -- 6.6 Hanbury-Brown and Twiss Interferometer -- References -- Problems -- 7 Diffraetion -- 7.1 Introduction -- 7.2 Green's Theorem and Scalar Diffraction -- 7.3 Rayleigh-Sommerfeld Theory -- 7.4 Van Cittert-Zemicke Theorem -- 7.5 Diffraction Gratings and Spectrometers -- References -- Problems.
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VTT's well-proven 3 μm SOI (Silicon Over Insulator) photonic integration platform is particularly suitable for passive optical functionalities such as Multiplexers, De-Multiplexers, Power Splitters, Delay Lines, Mach-Zehnder Interferometers (MZI), also for active operations such as phase tuning through Thermo-optic Switches and optical power monitoring or high-speed detection with integrated Ge Photo-Detectors (Ge-PD) etc. In combination with integrated up-reflecting mirrors and solder coated cavities it's enabling heterogeneous integration of III-V active devices; both Wafer Level Packaging (WLP) and E/O Wafer Level Tests can be fully exploited, scaling up in volume manufacturing while dramatically reducing assembly costs. Here heterogeneous integration of 40 Vertical Cavity Surface Emitting Lasers (VCSELs) and a SOI 40:1 multiplexer Photonic Integrated Circuit (PIC) is exploited with flip-chip techniques, coupling VCSEL emitting spots on top of respective up-reflective mirrors. VCSELs can be directly modulated up to 50 Gb/s reaching a 2 T/ls full transmission capacity. Additional 40 linear VCSEL drivers are flip-chip bonded onto a suitable Land Grid Array (LGA) interposer designed to provide interconnection and thermal decoupling capabilities to the Si-PIC, realizing a very compact, thermally efficient packaging solution. The exit waveguide from the PIC is also terminated with an up-reflective mirror and furthermore coupled with a 90 deg. tilting fiber optic pigtail designed to minimize the form-factor impact, improving mechanical reliability of the overall transmitter module. ; This work was partially supported by a project that has received funding from the European Union's Horizon 2020 research and innovation programme, under grant agreement PASSION No 780326.
Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements. ; European project Synaptic Molecular Networks for Bioinspired Information Processing (SYMONE) (318597); German Research Foundation (DFG); European Union; The Science Academy, Turkey; TUBITAK-BIDEB (113C032); TUBITAK-ULAKBIM High Performance and Grid Computing Center (TRUBA Resources); EU (318516)
709 786 12 3 ; S ; [EN] Programmable integrated photonics is an emerging new paradigm that aims at designing common integrated optical hardware resource configurations, capable of implementing an unconstrained variety of functionalities by suitable programming, following a parallel but not identical path to that of integrated electronics in the past two decades of the last century. Programmable integrated photonics is raising considerable interest, as it is driven by the surge of a considerable number of new applications in the fields of telecommunications, quantum information processing, sensing, and neurophotonics, calling for flexible, reconfigurable, low-cost, compact, and low-power-consuming devices that can cooperate with integrated electronic devices to overcome the limitation expected by the demise of Moore¿s Law. Integrated photonic devices exploiting full programmability are expected to scale from application-specific photonic chips (featuring a relatively low number of functionalities) up to very complex application-agnostic complex subsystems much in the same way as field programmable gate arrays and microprocessors operate in electronics. Two main differences need to be considered. First, as opposed to integrated electronics, programmable integrated photonics will carry analog operations over the signals to be processed. Second, the scale of integration density will be several orders of magnitude smaller due to the physical limitations imposed by the wavelength ratio of electrons and light wave photons. The success of programmable integrated photonics will depend on leveraging the properties of integrated photonic devices and, in particular, on research into suitable interconnection hardware architectures that can offer a very high spatial regularity as well as the possibility of independently setting (with a very low power consumption) the interconnection state of each connecting element. Integrated multiport interferometers and waveguide meshes provide regular and periodic geometries, formed by ...
The three infrared atmospheric sounding interferometers (IASIs), launched in 2006, 2012, and 2018, are key instruments to weather forecasting, and most meteorological centres assimilate IASI nadir radiance data into atmospheric models to feed their forecasts. The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) recently released a reprocessed homogeneous radiance record for the whole IASI observation period, from which 13 years (2008-2020) of temperature profiles can be obtained. In this work, atmospheric temperatures at different altitudes are retrieved from IASI radiances measured in the carbon dioxide absorption bands (654-800 and 2250-2400gcm-1) by selecting the channels that are the most sensitive to the temperature at different altitudes. We rely on an artificial neural network (ANN) to retrieve atmospheric temperatures from a selected set of IASI radiances. We trained the ANN with IASI radiances as input and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis version 5 (ERA5) as output. The retrieved temperatures were validated with ERA5, with in situ radiosonde temperatures from the Analysed RadioSoundings Archive (ARSA) network and with EUMETSAT temperatures retrieved from IASI radiances using a different method. Between 750 and 7ghPa, where IASI is most sensitive to temperature, a good agreement is observed between the three datasets: the differences between IASI on one hand and ERA5, ARSA, or EUMETSAT on the other hand are usually less than 0.5gK at these altitudes. At 2ghPa, as the IASI sensitivity decreases, we found differences up to 2gK between IASI and the three validation datasets. We then computed atmospheric temperature linear trends from atmospheric temperatures between 750 and 2ghPa. We found that in the past 13 years, there is a general warming trend of the troposphere that is more important at the poles and at mid-latitudes (0.5gK/decade at mid-latitudes, 1gK/decade at the North Pole). The stratosphere is globally cooling on average, ...
An interesting approach in cooperative control is to design distributed control strategies which use only local information so that a multi-agent system achieves specified behaviors. A basic behavior in cooperative control is the consensus. Given a multi-agent system, like a multiple robot network, it is said that the agents reach a consensus if the state of each agent converges to a common state. Examples of cooperative tasks in which consensus algorithms are employed include formation control, flocking theory, rendezvous problems and synchronization. These cooperative tasks have several possible applications, like: transportation systems (intelligent highways, air-traffic control); military systems (formation flight, surveillance, reconnaissance, cooperative attack and rendezvous) and mobile sensor networks (space-based interferometers, environmental sampling). The solution to the consensus problems involves the design of control algorithms such that the agents can reach an agreement on their states. There are two main problems that are studied in consensus, the leader-follower consensus and the leaderless consensus. In the leader-follower consensus problem, there exists a leader that specifies the state for the whole group while in a leaderless consensus problem, there is not a priori reference state. The main goal of this thesis is the design of operational space controllers that solve the leader-follower and the leaderless consensus problems in networks composed of multiple heterogeneous robots. Furthermore, this document proposes novel operational space control schemes for bilateral teleoperation systems. In both scenarios, different conditions are studied, such as the absence of robot velocity measurements, constant and variable time-delays in the robot's interconnection, and uncertainty in the robot's physical parameters. Most of the previous consensus control algorithms, only work with the position or orientation but not with both. On the contrary, this dissertation deals with the entire pose of the ...
Regenerated Fibre Bragg Gratings have the potential for high-temperature monitoring. In this paper, the inscription of Fibre Bragg Gratings (FBGs) and the later regeneration process to obtain Regenerated Fiber Bragg Gratings (RFBGs) in high-birefringence optical fiber is reported. The obtained RFBGs show two Bragg resonances corresponding to the slow and fast axis that are characterized in temperature terms. As the temperature increases the separation between the two Bragg resonances is reduced, which can be used for low cost interrogation. The proposed interrogation setup is based in the use of optical filters in order to convert the wavelength shift of each of the Bragg resonances into optical power changes. The design of the optical filters is also studied in this article. In first place, the ideal filter is calculated using a recursive method and defining the boundary conditions. This ideal filter linearizes the output of the interrogation setup but is limited by the large wavelength shift of the RFBG with temperature and the maximum attenuation. The response of modal interferometers as optical filters is also analyzed. They can be easily tuned shifting the optical spectrum. The output of the proposed interrogation scheme is simulated in these conditions improving the sensitivity. ; The authors wish to acknowledge the financial support of the Infraestructura FEDER UPVOV08-3E-008, FEDER UPVOV10-3E-492, the Spanish MCINN through the project TEC2011-29120-C05-05 and the Valencia Government through the Ayuda Complementaria ACOMP/2013/146. The authors also acknowledge the collaboration of Alvarez from Fibercore for providing the high birefringence optical fiber. ; Barrera Vilar, D.; Sales Maicas, S. (2013). A high-temperature fiber sensor using a low cost interrogation scheme. Sensors. 13(9):11653-11659. https://doi.org/10.3390/s130911653 ; S ; 11653 ; 11659 ; 13 ; 9 ; Erdogan, T., Mizrahi, V., Lemaire, P. J., & Monroe, D. (1994). Decay of ultraviolet‐induced fiber Bragg gratings. Journal of Applied Physics, ...
We consider k-essence, a scalar-tensor theory with first-order derivative self-interactions that can screen local scales from scalar fifth forces, while allowing for sizeable deviations from general relativity on cosmological scales. We construct fully nonlinear static stellar solutions that show the presence of this screening mechanism, and we use them as initial data for simulations of stellar oscillations and gravitational collapse in spherical symmetry. We find that for k-essence theories of relevance for cosmology, the screening mechanism works in the case of stellar oscillation and suppresses the monopole scalar emission to undetectable levels. In collapsing stars, we find that the Cauchy problem, although locally well posed, can lead to diverging characteristic speeds for the scalar field. By introducing a "fixing equation"in the spirit of J. Cayuso et al. [Phys. Rev. D 96, 084043 (2017)PRVDAQ2470-001010.1103/PhysRevD.96.084043], inspired in turn by dissipative relativistic hydrodynamics, we manage to evolve collapsing neutron stars past the divergence of the characteristic speeds. We show that, in these systems, the screening mechanism is less efficient than for oscillating and static stars, because the collapsing star must shed away all of its scalar hair before forming a black hole. For k-essence theories of relevance for cosmology, the characteristic frequency of the resulting scalar monopole signal is too low for terrestrial detectors, but we conjecture that space-borne interferometers such as the Laser Interferometer Space Antenna might detect it if a supernova explodes in the Galaxy. ; We thank L. Lehner for enlightening conversations on the well-posedness of the Cauchy problem. M. B., L. t. H., M. C., and E. B. acknowledge support from the European Union's H2020 ERC Consolidator Grant "Gravity from Astrophysical to Microscopic Scales" (Grant No. GRAMS-815673). C. P. acknowledges support from the Spanish Ministry of Economy and Competitiveness Grants No. AYA2016-80289-P and No. PID2019–110301 GB-I00 (AEI/FEDER, UE). M. B. acknowledges the support of the PHAROS COST Action (CA16214).
This paper presents an extensive intercomparison and validation for the ozone (O3) product measured by the two Infrared Atmospheric Sounding Interferometers (IASIs) launched on board the MetOp-A and MetOp-B satellites in 2006 and in 2012 respectively. IASI O3 total columns and vertical profiles obtained from Fast Optimal Retrievals on Layers for IASI (FORLI) v20140922 software (running up until recently) are validated against independent observations during the period 2008-2014 on a global scale. On average for the period 2013-2014, IASI-A and IASI-B total ozone columns (TOCs) retrieved using FORLI are consistent, with IASI-B providing slightly lower values with a global difference of only 0.2±0.8%. The comparison between IASI-A and IASI-B O3 vertical profiles shows differences within ±2% over the entire altitude range. Global validation results for 7 years of IASI TOCs from FORLI against the Global Ozone Monitoring Experiment-2 (GOME-2) launched on board MetOp-A and Brewer-Dobson data show that, on average, IASI overestimates the ultraviolet (UV) data by 5-6% with the largest differences found in the southern high latitudes. The comparison with UV-visible SAOZ (Système d'Analyse par Observation Zénithale) measurements shows a mean bias between IASI and SAOZ TOCs of 2-4% in the midlatitudes and tropics and 7% at the polar circle. Part of the discrepancies found at high latitudes can be attributed to the limited information content in the observations due to low brightness temperatures. The comparison with ozonesonde vertical profiles (limited to 30km) shows that on average IASI with FORLI processing underestimates O3 by ∼ 5-15% in the troposphere while it overestimates O3 by ∼ 10-40% in the stratosphere, depending on the latitude. The largest relative differences are found in the tropical tropopause region; this can be explained by the low O3 amounts leading to large relative errors. In this study, we also evaluate an updated version of FORLI-O3 retrieval software (v20151001), using look-up tables recalculated ...
The authors report on the realization of a novel methodology for refractometry - GAs modulation refractometry (GAMOR) - that decreases the influence of drifts in Fabry Perot cavity refractometry. The instrumentation is based on a dual Fabry-Perot cavity refractometer in which the beat frequency between the light fields locked to two different cavities, one measurement and one reference cavity, is measured. The GAMOR methodology comprises a process in which the measurement cavity sequentially is filled and evacuated while the reference cavity is constantly evacuated. By performing beat frequency measurements both before and after the finite-pressure measurement, zero point references are periodically created. This opens up for high precision refractometry under nontemperature-stabilized conditions. A first version of an instrumentation based on the GAMOR methodology has been realized and its basic performance has been scrutinized. The refractometer consists of a Zerodur cavity-block and tunable narrow linewidth fiber lasers operating within the C34 communication channel (i.e., around 1.55 μm) at which there are a multitude of fiber coupled off-the-shelf optical, electro-optic, and acousto-optic components. The system is fully computer controlled, which implies it can perform unattended gas assessments over any foreseeable length of time. When applied to a system with no active temperature stabilization, the GAMOR methodology has demonstrated a 3 orders of magnitude improvement of the precision with respect to conventional static detection. When referenced to a dead weight pressure scale the instrumentation has demonstrated assessment of pressures in the kilo-Pascal range (4303 and 7226 Pa) limited by white noise with standard deviations in the 3.2 N - 1 / 2 - 3.5 N - 1 / 2 mPa range, where N is the number of measurement cycles (each being 100 s long). For short measurement times (up to around 103 s), the system exhibits a (1 σ) total relative precision of 0.7 (0.5) ppm for assessment of pressures in the 4 kPa region and 0.5 (0.4) ppm for pressures around 7 kPa, where the numbers in parentheses represent the part of the total noise that has been attributed to the refractometer. As long as the measurement procedure is performed over short time scales, the inherent properties of the GAMOR methodology allow for high precision assessments by the use of instrumentation that is not actively temperature stabilized or systems that are affected by outgassing or leaks. They also open up for a variety of applications within metrology; e.g., transfer of calibration and characterization of pressure gauges, including piston gauges. ; Funding details: 621-2011-4216, VR, Vetenskapsrådet; Funding details: 621-2015-04374, VR, Vetenskapsrådet; Funding details: 2015-0647, Umeå Universitet; Funding details: 2014-06095, Umeå Universitet; Funding text: This research was supported by the EMPIR initiative, which is cofounded by the European Union's Horizon 2020 research and innovation program and the EMPIR Participating States; the Swedish Research Council (VR), Project Nos. 621-2011-4216 and 621-2015-04374; the Umeå University program VFS (Verifiering for samverkan), 2016:01; and the Vinnova Metrology Programme, Project Nos. 2015-0647 and 2014-06095.
Context. The innermost astronomical unit (au) in protoplanetary disks is a key region for stellar and planet formation, as exoplanet searches have shown a large occurrence of close-in planets that are located within the first au around their host star. Aims. We aim to reveal the morphology of the disk inner rim using near-infrared interferometric observations with milli-arcsecond resolution provided by near-infrared multitelescope interferometry. Methods. We provide model-independent reconstructed images of 15 objects selected from the Herbig AeBe survey carried out with PIONIER at the Very Large Telescope Interferometer, using the semi-parametric approach for image reconstruction of chromatic objects. We propose a set of methods to reconstruct and analyze the images in a consistent way. Results. We find that 40% of the systems (6/15) are centrosymmetric at the angular resolution of the observations. For the rest of the objects, we find evidence for asymmetric emission due to moderate-to-strong inclination of a disk-like structure for similar to 30% of the objects (5/15) and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (4/15, similar to 27%). Among the systems with a disk-like structure, 20% (3/15) show a resolved dust-free cavity. Finally, we do not detect extended emission beyond the inner rim. Conclusions. The image reconstruction process is a powerful tool to reveal complex disk inner rim morphologies, which is complementary to the fit of geometrical models. At the angular resolution reached by near-infrared interferometric observations, most of the images are compatible with a centrally peaked emission (no cavity). For the most resolved targets, image reconstruction reveals morphologies that cannot be reproduced by generic parametric models (e.g., perturbed inner rims or complex brightness distributions). Moreover, the nonaxisymmetric disks show that the spatial resolution probed by optical interferometers makes the observations of the near-infrared emission (inside a few au) sensitive to temporal evolution with a time-scale down to a few weeks. The evidence of nonaxisymmetric emission that cannot be explained by simple inclination and radiative transfer effects requires alternative explanations, such as a warping of the inner disks. Interferometric observations can therefore be used to follow the evolution of the asymmetry of those disks at an au or sub-au scale. ; French National Research Agency (ANR) ANR-10-BLAN-0511 European Union (EU) SH-06192 Philip Leverhulme Prize PLP-2013-110 KU Leuven C14/17/082 National Science Foundation (NSF) 1210972 1616483 European Research Council (ERC) 639889 European Union (EU) 284405 French National Research Agency (ANR) ANR-16-CE31-0013 Australian Research Council FT170100040 DP180104235 Universite Joseph Fourier (UJF, Grenoble) through its Pole TUNES Universite Joseph Fourier (UJF, Grenoble) through its Pole SMING Institut de Planetologie et d'Astrophysique de Grenoble French National Research Agency (ANR) French National Research Agency (ANR) Institut National des Science de l'Univers (INSU) via the "Programme National de Physique Stellaire" Institut National des Science de l'Univers (INSU) via "Programme National de Planetologie"
United States National Science Foundation (NSF) ; Science and Technology Facilities Council (STFC) of the United Kingdom ; Max-Planck-Society (MPS) ; State of Niedersachsen/Germany ; Australian Research Council ; International Science Linkages program of the Commonwealth of Australia ; Council of Scientific and Industrial Research of India ; Department of Science and Technology, India ; Science & Engineering Research Board (SERB), India ; Ministry of Human Resource Development, India ; Spanish Ministerio de Economia y Competitividad ; Conselleria d'Economia i Competitivitat and Conselleria d'Educaci, Cultura i Universitats of the Govern de les Illes Balears ; Foundation for Fundamental Research on Matter - Netherlands Organization for Scientific Research ; Polish Ministry of Science and Higher Education ; FOCUS Programme of Foundation for Polish Science ; European Union ; Royal Society ; Scottish Funding Council ; Scottish Universities Physics Alliance ; National Aeronautics and Space Administration ; Hungarian Scientific Research Fund (OTKA) ; Lyon Institute of Origins (LIO) ; National Research Foundation of Korea ; Industry Canada ; Province of Ontario through the Ministry of Economic Development and Innovation ; National Science and Engineering Research Council Canada ; Brazilian Ministry of Science, Technology, and Innovation ; Carnegie Trust ; Leverhulme Trust ; David and Lucile Packard Foundation ; Research Corporation ; Alfred P. Sloan Foundation ; NSF ; STFC ; MPS ; INFN ; CNRS ; Science and Technology Facilities Council ; Science and Technology Facilities Council: ST/L000938/1 ; Science and Technology Facilities Council: ST/I006285/1 ; Science and Technology Facilities Council: ST/I006269/1 ; Science and Technology Facilities Council: ST/L000946/1 ; Science and Technology Facilities Council: ST/L000962/1 ; Science and Technology Facilities Council: ST/L003465/1 ; Science and Technology Facilities Council: ST/K000845/1 ; Science and Technology Facilities Council: ST/J00166X/1 ; Science and Technology Facilities Council: ST/L000911/1 Gravitational Waves ; Science and Technology Facilities Council: Gravitational Waves ; Science and Technology Facilities Council: PPA/G/S/2002/00652 ; Science and Technology Facilities Council: ST/I006269/1 Gravitational Waves ; Science and Technology Facilities Council: ST/L000911/1 ; Science and Technology Facilities Council: 1362895 ; Science and Technology Facilities Council: ST/I006277/1 ; Science and Technology Facilities Council: ST/H002359/1 ; Science and Technology Facilities Council: ST/K005014/1 ; Science and Technology Facilities Council: ST/K00137X/1 ; Science and Technology Facilities Council: ST/M006735/1 ; Science and Technology Facilities Council: ST/M000931/1 ; Science and Technology Facilities Council: ST/L000938/1 Gravitational Waves ; We describe directed searches for continuous gravitational waves (GWs) in data from the sixth Laser Interferometer Gravitational-wave Observatory (LIGO) science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the remnants are associated with non-pulsing suspected neutron stars. One target ' s parameters are uncertain enough to warrant two searches, for a total of 10. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering. -statistic. We found no evidence of GW signals. We set 95% confidence upper limits as strong (low) as 4 x 10(-25) on intrinsic strain, 2 x 10(-7) on fiducial ellipticity, and 4 x 10(-5) on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.