J.J. Talghader

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (81)105.75 Total impact

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    ABSTRACT: A method has been devised and tested for measuring the c-axis orientation of crystal grains in thin sections of glacier ice. The crystal orientation and grain size of ice are of great interest to glaciologists since these parameters contain information on the prior thermal and flow history of the ice. The traditional method of determining c-axis orientation involves a transmission measurement through an ice sample, a process that is time-consuming and therefore impractical for obtaining a continuous record. A reflection-or backscatter-based method could potentially be used inside boreholes, with bubbles as reflectors to avoid such drawbacks. The concept demonstration of this paper is performed on ice slices, enabling a direct comparison of accuracy with traditional methods. Measurements of the crystal orientations (�, �) in 11 grains showed an average error of �0.8° in �, with no grain error >1.4°. Measurements of � showed an average error of �8.2° on ten grains, with unexplained disagreement on the remaining grain. Although the technique is applied specifically to glacier ice, it should be generally applicable to any transparent birefringent polycrystalline material.
    Journal of Glaciology 11/2014; 60(224):1135. · 2.88 Impact Factor
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    ABSTRACT: Most thermoluminescent materials are created using crystal growth techniques; however, it would be of great utility to identify those few thermoluminescent materials that can be deposited using simpler methods, for example to be compatible with the early portions of a silicon integrated circuit or microelectromechanical fabrication process. In this work, thin films of yttrium oxide with a terbium impurity (Y2O3:Tb) were deposited on silicon wafers by electron beam evaporation. The source for the Y2O3:Tb was made by combining Y2O3 and Tb4O7 powders. The approximate thicknesses of the deposited films were 350 nm. After deposition, the films were annealed at 1100 °C for 30 s to improve crystallinity. There is a strong correlation between the x-ray diffraction (XRD) peak intensity and the thermoluminescent glow curve intensity. The glow curve displays at least two peaks at 140 °C and 230 °C. The emission spectra was measured using successive runs with a monochromator set to a different wavelength for each run. There are two main emission peaks at 490 nm and 540 nm. The terbium impurity concentration of approximately 1 mol% was measured using Rutherford backscattering spectrometry (RBS). The Y2O3:Tb is sensitive to UV, x-ray, and gamma radiation. The luminescent intensity per unit mass of UV irradiated Y2O3:Tb was about 2 times that of x-ray irradiated TLD-100.
    Journal of Luminescence 04/2014; 148:225–229. · 2.14 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
    Journal of Microelectromechanical Systems 01/2014; 23(3):549-554. · 2.13 Impact Factor
  • R. Shea, A. Gawarikar, J. Talghader
    Journal of Microelectromechanical Systems 01/2014; 23(3):681-688. · 2.13 Impact Factor
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    ABSTRACT: 3D Meta-Optics are optical components that are based on the engineering of the electromagnetic fields in 3D dielectric structures. The results of which will provide a class of transformational optical components that can be integrated at all levels throughout a High Energy Laser system. This paper will address a number of optical components based on 2D and 3D micro and nano-scale structures and their performance when exposed to high power lasers. Specifically, results will be presented for 1550 nm and 2000 nm spectral bands and power densities greater than100 kW/cm 2 .
    Laser-Induced Damage in Optical Materials; 11/2013
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    ABSTRACT: The laser-damage thresholds of single material and nanolaminate thin films were compared under continuous-wave (CW) illumination conditions. Nanolaminate films consist of uniform material interrupted by the periodic insertion of one or more atomic layers of an alternative material. Hafnia and titania were used as the base materials, and the films were deposited using atomic-layer deposition. The nanolaminates were less polycrystalline than the uniform films, as quantified using x-ray diffraction. It was found that the nanolaminate films had reduced laser-damage thresholds on smooth and patterned substrates as compared to uniform single-material films. This behavior is unusual as prior art indicates that amorphous (less polycrystalline) materials have higher laser-damage thresholds under short-pulse excitation. It is speculated that this may indicate that local thermal conduction affects breakdown more strongly under CW excitation than the dielectric properties that are important for short-pulse excitation.
    Optics Letters 11/2013; 38(21):4292-5. · 3.39 Impact Factor
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    ABSTRACT: It is well known that thermal gradients penetrating deep into a material can preserve a memory of the temperature history of the surface. To date, this concept has been largely applied in the earth sciences, but there are many applications where a memory of rapid thermal events would be useful. For example, multiple layers of thermoluminescent films could serve as temperature sensors that indicate temperature versus depth in a microfabricated structure. As an advance toward this goal, this paper examines the effect of nonuniform temperature profiles on the thermoluminescence of heterogeneous multilayers. A Nd:YAG laser is used to create a known thermal event and apply pulses of heat energy of varying duration to a metalized thermoluminescent multilayer composed of LiF:Mg,Ti and CaF2:Dy. The thermoluminescence of the system is measured before and after the applied laser pulse. To model the process, a finite-difference time-domain method is used to calculate the dynamic heat transfer, and the temperature distribution is plugged into a first order kinetics model of the thermoluminescence of each film to get a final luminescent intensity. A thermal contact conductance between the critical layers is also introduced. Dynamic temperatures in durations of hundreds of milliseconds are resolved with the technique, and simulation curves match experimental measurements to within 6% at 250 ms.
    Journal of Applied Physics 08/2013; 114(5). · 2.21 Impact Factor
  • Wing S. Chan, Mika J. Saarinen, Joseph J. Talghader
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    ABSTRACT: Vertical electrostatic wedge actuators are described that control nanometer-scale gaps between surfaces. Standard parallel-plate electrostatic actuators become difficult to stabilize across extremely small gaps because the nature of the forces and the force laws that describe them often deviate from a Coulomb's law dependence. In this work, a nanometer-scale air gap between a collapsed cantilever structure formed by two facing In0.53Ga0.47As surfaces, with areas of tens of microns, was controlled by a wedge electrostatic actuator. Upon actuation, the gap spacing between the surfaces was tuned over a maximum range of 55 nm with an applied voltage of 60 V.
    Applied Physics Letters 06/2013; 102(24). · 3.52 Impact Factor
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    ABSTRACT: We compared the laser damage performance of uniform versus nanolaminate thin films for hafnia and titania-based coatings. Our experiments showed that the films with higher crystallinity appeared to have better performance for CW systems.
    Optical Interference Coatings; 06/2013
  • M.L. Mah, P.R. Armstrong, J.J. Talghader
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    ABSTRACT: The thermoluminescence characteristics of a thin film of terbium-doped yttrium oxide change upon repeated stress application through electrostatic actuation. A maximum 42% decrease in the intensity of two thermoluminescent peaks is seen when voltage is applied in 5V increments to 25V, translating to 0.15 μm of center deflection. While the overall intensity decreases, the higher temperature peak - corresponding to deeper traps - is affected more than the lower temperature one. Two possible physical explanations for the behavior are mechanical stress and dielectric charging.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: A spectrally selective uncooled long wave infrared detector with peak detectivity between 3×109 cm Hz1/2/W and 4.4×109 cm Hz1/2/W is reported. The detector is fabricated using silicon microfabrication techniques and integrates a thermoelectric readout with a resonant optical cavity to achieve wavelength selective absorption.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: We describe uncooled thermal detectors with a peak detectivity of at least 3 ×109 cm √{Hz}/W with spectrally selective absorption in the long-wave infrared. The spectral selectivity in absorption is achieved through resonant cavity coupling of a thin metal film with a low-order air-gap optical cavity. The electrical readout uses thermoelectric thin films with a Johnson noise limited performance. The detectors are of multiple sizes but those with 100- μm2 area have time constants of 58 ms and thermal conductances of 2.3 ×10-7 W/K.
    IEEE Transactions on Electron Devices 01/2013; 60(8):2586-2591. · 2.06 Impact Factor
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    ABSTRACT: Thermoluminescent LiF:Mg, Ti (TLD-100) micro- particle sensors are demonstrated to record the thermal history of the environment around a high-explosive detonation. Microparticles are gamma-irradiated to fill their charge-carrier traps and then exposed to the detonation of 20 g of a plastic bonded HMX and Al explosive formulation at a test distance of approximately 22 cm from the center of the detonation. The thermal history of the microparticles is reconstructed by iteratively matching the degree of trap depopulation, derived from luminescence measurements, with that projected by theoretical simulations using appropriate models. Measurements and modeling indicate that the particles experienced a maximum temperature of 240°C, then cooled to 1°C above ambient temperature within 0.4 seconds. The resulting glow curve intensity is calculated to match the observed post-detonation signal to 3% averaged over the comparison values used for reconstruction.
    IEEE Sensors Journal 01/2013; 13(5):1742-1747. · 1.85 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: Fabrication and characterization of high detectivity thermopile infrared detectors with spectrally selective absorption operating at room temperature is described. The detector architecture consists of a Johnson noise limited thermoelectric readout scheme integrated with a resonant cavity coupled absorber and a low thermal conductance support structure. A resonant responsivity enhancement of 4.3 and a peak detectivity of 1.3×109 cm Hz1/2 Watt-1 at 10.5 μm wavelength are demonstrated.
    Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS & EUROSENSORS XXVII), 2013 Transducers & Eurosensors XXVII: The 17th International Conference on; 01/2013
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    Joseph J Talghader, Anand S Gawarikar, Ryan P Shea
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    ABSTRACT: A review is made of the physics and technology of spectrally selective thermal detectors, especially those operating at non-cryogenic temperatures. The background radiation noise fluctuations are rederived for arbitrary spectral characteristics. Infrared absorption due to phonons and free carriers is discussed followed by a review of published works on artificial infrared absorption materials such as patterned grids, nanoparticles, plasmonic structures, metamaterials and others. Subsequently, the literature of the spectral characteristics of broadband thermal detectors and spectrally selective thermal detectors is reviewed. Finally, the authors speculate on the directions that future research and development in the area will take regarding architectures, sensitivity and spectral characteristics.
    Light: Science & Applications. 08/2012; 1(8).
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    Anand S. Gawarikar, Ryan P. Shea, Joseph J. Talghader
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    ABSTRACT: The far field radiation efficiency achievable in narrowband thermal emitters is investigated, taking into account the full spatial and spectral variation of the emissivity. A coupled Fabry-Perot cavity model is used to develop an insight into the efficiency variation with cavity coherence and device temperature. It is found that the spatial variation of emissivity has to be explicitly included in the radiation power calculations to accurately estimate the achievable power efficiencies. The calculated radiation efficiencies of an ideal coherent cavity coupled emitter were found to vary from 0.1% to 9%, with a corresponding increase in the emission linewidth from 6.3 nm to 930 nm, and were much lower than that estimated without accounting for effects of spatial coherence. The analysis presented here can be used to determine the optimal operating temperature of a coherent thermal emitter once its emission characteristics and conduction losses are known and it is demonstrated that this optimum temperature is different from the temperature of peak blackbody emission at the resonant absorption wavelength.
    AIP Advances 07/2012; 2(3). · 1.35 Impact Factor
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    Kyle D Olson, Joseph J Talghader
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    ABSTRACT: The optimum transition wavelength between high absorption and low emissivity for selective solar absorbers has been calculated in several prior treatises for an ideal system, where the emissivity is exactly zero in the infrared. However, no real coating can achieve such a low emissivity across the entire infrared with simultaneously high absorption in the visible. An emissivity of even a few percent radically changes the optimum wavelength separating the high and low absorption spectral bands. This behavior is described and calculated for AM0 and AM1.5 solar spectra with an infrared emissivity varying between 0 and 5%. With an emissivity of 5%, solar concentration of 10 times the AM1.5 spectrum the optimum transition wavelength is found to be 1.28 µm and have a 957K equilibrium temperature. To demonstrate typical absorptions in optimized solar selective coatings, a four-layer sputtered Mo and SiO₂ coating with absorption of 5% across the infrared is described experimentally and theoretically.
    Optics Express 07/2012; 20 Suppl 4:A554-9. · 3.55 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: This paper presents the design and fabrication of narrowband resonant cavity absorbers in the long wave infrared. Absorption in multiple spectral bands is demonstrated with a structure whose thermal mass is compatible with thermal detectors.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
  • W.S. Chan, J.J. Talghader, M.J. Saarinen
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    ABSTRACT: An actuator was designed and fabricated to actively tune the nanometer-scaled gap between quantum wells in a collapsed cantilever structure. Maximum actuation of 55nm was achieved. Photoluminescence from the quantum wells at the collapsed cantilever was observed at cryogenic temperature, indicating that the wells remained intact after fabrication.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
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    Nicholas T. Gabriel, Joseph J. Talghader
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    ABSTRACT: Hafnia-alumina nanolaminates show improved smoothness and reduced crystallinity relative to pure hafnia in films formed by atomic layer deposition (ALD). However, typical nanolaminates also show reduced cross-plane thermal conductivity due to the much larger interface density relative to continuous films. We find that the interface thermal resistance in hafnia-alumina nanolaminates is very low and does not dominate the film thermal conductivity, which is 1.0 to 1.2 W/(m K) at room temperature in 100 nm thin films regardless of the interface density. Measured films had a number of interfaces ranging from 2 to 40, equivalent to interface spacing varying from about 40 to 2 nm. The degree of crystallinity of these films appears to have a much larger effect on thermal conductivity than that of interface density. Cryogenic measurements show good agreement with both the minimum thermal conductivity model for disordered solids and the diffuse mismatch model of interface resistance down to about 80 K before diverging. We find that the films are quite smooth through a 400:5 ratio of hafnia to alumina in terms of ALD cycles, and the refractive index scales as expected with increasing alumina concentration.
    Journal of Applied Physics 08/2011; 110(4):043526-043526-8. · 2.21 Impact Factor

Publication Stats

118 Citations
105.75 Total Impact Points

Institutions

  • 2002–2014
    • University of Minnesota Duluth
      • Department of Electrical Engineering
      Duluth, Minnesota, United States
  • 2000–2013
    • University of Minnesota Twin Cities
      • Department of Electrical and Computer Engineering
      Minneapolis, Minnesota, United States