| 1. |
- Willander, Magnus, et al.
(författare)
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UV detectors and LEDs in different metal oxide nanostructures
- 2014
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Konferensbidrag (refereegranskat)abstract
- Different composite nanostructures based pn-junctions have been synthesized using the low temperature hydrothermal chemical growth. The composite nanostructures based pn junctions demonstrated here include p-NiO/n-ZnO, p-CuO/n-ZnO, and p-NiO/n-TiO2. Structural characterization of these composite nanostructures based pn-junctions was performed by different complementary tools and the results indicated that reasonable device quality crystals have been achieved. His act was also confirmed by the rectifying electrical behavior observed from these junctions. Further, the different composite nanostructures based junctions were used to demonstrate UV detectors and visible light emitting diodes (LEDs) operating with acceptable performance.
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| 2. |
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| 3. |
- Zhang, Miao, et al.
(författare)
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Optical detection of two-color-fluorophore barcode for nanopore DNA sensing
- 2015
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Konferensbidrag (refereegranskat)abstract
- A simple schematic on parallel optical detection of two-fluorophore barcode for single-molecule nanopore sensing is presented. The chosen two fluorophores, ATTO-532 and DY-521-XL, emitting in well-separated spectrum range can be excited at the same wavelength. A beam splitter was employed to separate signals from the two fluorophores and guide them to the same CCD camera. Based on a conventional microscope, sources of background in the nanopore sensing system, including membranes, compounds in buffer solution, and a detection cell was characterized. By photoluminescence excitation measurements, it turned out that silicon membrane has a negligible photoluminescence under the examined excitation from 440 nm to 560 nm, in comparison with a silicon nitrite membrane. Further, background signals from the detection cell were suppressed. Brownian motion of 450 bps DNA labelled with single ATTO-532 or DY-521-XL was successfully recorded by our optical system.
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| 4. |
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| 5. |
- Bratkovsky, A. M., et al.
(författare)
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Properties of nanostructured metamaterials at optical frequencies
- 2008
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Konferensbidrag (refereegranskat)abstract
- A variety of metamaterials has been demonstrated recently that support backward waves and negative refraction (Negative Index Materials, NIM.) In particular, these materials enable sub-wavelength resolution that makes them even more interesting, especially in optical domain rather than at microwave frequencies where their unusual properties were known for decades. We describe below theoretical and experimental studies of the so-called 'fishnet' metal-spacer holearray metamaterials, which exhibit NIM behavior at optical frequencies, having unit cell size of a few 100s nm. We demonstrate experimentally that their refractive index can be modulated very fast and very strongly (from -2.4 to -1.5) around the communication wavelength of =1.55 um, in good agreement with the FDTD results. We also discuss a problem of loss compensation in those materials with hefty Ohmic losses by using gain media and local field enhancement in metallic nanoparticles ensembles that enable SERS.
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| 6. |
- Fredenberg, Erik, PhD, 1979-, et al.
(författare)
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Contrast-enhanced dual-energy subtraction imaging using electronic spectrum-splitting and multi-prism x-ray lenses
- 2008
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Ingår i: Medical Imaging 2008 - Physics of Medical Imaging. - San Diego, CA, USA : SPIE. - 9780819470973 ; , s. 91310-91310
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Konferensbidrag (refereegranskat)abstract
- Dual-energy subtraction imaging (DES) is a method to improve the detectability of contrast agents over a lumpy background. Two images, acquired at x-ray energies above and below an absorption edge of the agent material, are logarithmically subtracted, resulting in suppression of the signal from the tissue background and a relative enhancement of the signal from the agent. Although promising, DES is still not widely used in clinical practice. One reason may be the need for two distinctly separated x-ray spectra that are still close to the absorption edge, realized through dual exposures which may introduce motion unsharpness. In this study, electronic spectrum-splitting with a silicon-strip detector is theoretically and experimentally investigated for a mammography model with iodinated contrast agent. Comparisons are made to absorption imaging and a near-ideal detector using a signal-to-noise ratio that includes both statistical and structural noise. Similar to previous studies, heavy absorption filtration was needed to narrow the spectra at the expense of a large reduction in x-ray flux. Therefore, potential improvements using a chromatic multi-prism x-ray lens (MPL) for filtering were evaluated theoretically. The MPL offers a narrow tunable spectrum, and we show that the image quality can be improved compared to conventional filtering methods.
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| 7. |
- Kamp, M., et al.
(författare)
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Technology and properties of photonic crystal based active and passive optoelectronic devices
- 2004
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Konferensbidrag (refereegranskat)abstract
- We have investigated tunable photonic crystal waveguide lasers and their integration with a photonic crystal based combiner. The devices were fabricated on a layer structure with active and passive sections. The lasers are formed in the active part and consist of two longitudinally coupled photonic crystal waveguide segements. Photonic crystals based waveguides and a combiner, both defined in the passive sections, are used to direct the light of the two sources into a single output waveguide. Tuning over a 30 nm range is demonstrated. The two sources can be operated independently, allowing the simultaneous transmission of two freely selectable wavelengths.
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| 8. |
- Landré, Jérôme, et al.
(författare)
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Visual browsing in image collections using wavelets
- 2006
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Konferensbidrag (refereegranskat)abstract
- Visual browsing is an important way of searching for images in large databases. In image retrieval, a lot of problems have to be solved to get a good system: dimensionality curse, users' search context, size of the database, visual features. In this article, a method trying to attenuate these problems is proposed. Each features vector is organized into four signature vectors used in the classification process while building a fuzzy search tree that is proposed to users for visual browsing. Our system gives good results in terms of speed and accuracy by solving several problems of classical image retrieval methods.
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| 9. |
- Lysak, V. V., et al.
(författare)
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The influence of gain nonlevearities on distortion in semiconductor lasers
- 2004
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Konferensbidrag (refereegranskat)abstract
- The modulation response and second harmonic distortion was analyzed for different gain models and compared with exact integral gain models. It was shown that if we modulate the laser around steady state with a signal, it would induce carrier and photon fluctuations. The second order distortion depended on the carrier and photon modulation response, the internal mixing process determined by the Hessian matrix creating a fictive injection signal and the carrier and photon modulation response at intermodulation frequency. It was found that the approximate model has a reasonable good agreement with an exact comprehensive gain model at all frequencies and pumping currents.
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| 10. |
- Noharet, Bertrand, et al.
(författare)
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Spectroscopy-based photonic instrumentation for the manufacturing industry: Contactless measurements of distances, temperatures, and chemical composition
- 2014
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Konferensbidrag (refereegranskat)abstract
- The steady progress in photonic components in terms of cost-to-performance ratio, maturity and robustness opens new avenues for the commercial deployment of photonic sensor systems in a wide range of industrial applications. Advanced sensing can be used to optimize complex processes and thereby enable significant savings in energy consumption. Three cases of robust photonic instrumentation for process optimization and quality control in manufacturing industries are presented: improved metal recycling with laser-induced breakdown spectroscopy, quality control in precision machining by white-light interferometry with optical fiber probes embedded in machining tools, and process optimization in steel foundries by stand-off temperature measurements in blast furnaces with optical fiber lances and spectral analysis techniques. Each of these methods utilizes a low-cost spectrometer, and requires dedicated calibration and signal processing methods to guarantee robust operation in industrial environments with varying conditions. Experimental results are presented, including on-line steel alloy analysis with correct classification rates in excess of 95%, distance measurements with axial resolution of +/- 2nm over a 75μm range, and continuous temperature monitoring of molten steel in oxygen blast furnaces with temperature measurement accuracy better than 1%.
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