| 61. |
- Zhou, Weidong, et al.
(författare)
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On-Chip Photonic Crystal Surface-Emitting Membrane Lasers
- 2019
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1077-260X .- 1558-4542. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- Photonic crystal lasers can be realized either based on photonic bandgap defect mode or defect-free bandedge mode, while the bandgap is not essential for the latter. We review here defect-free bandedge mode based photonic crystal surface-emitting lasers (PCSELs) for on-chip integration. We first discuss ultra-thin membrane reflector vertical-cavity surface-emitting lasers (MR-VCSELs), where single layer photonic crystal slabs can be designed as a broadband membrane reflector. Later, we discuss another type of defect-free PCSELs where the lasing cavity is formed based on evanescent coupling of gain medium with the photonic crystal bandedge mode near bandedge. Cavity designs were carried out for the optimal modal overlap and high confinement factors. Lateral cavity size scaling was also investigated both theoretically and experimentally in PCSELs. Buried tunnel junction based InGaAsP quantum well heterostructures were also designed and incorporated into electrically injected PCSELs. Finally, discussions are given toward energy efficient lasers.
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| 62. |
- Zhou, Yi, et al.
(författare)
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Black Polymers in Bulk-Heterojunction Solar Cells
- 2010
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Ingår i: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 16:6, s. 1565-1572
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Tidskriftsartikel (refereegranskat)abstract
- The active materials in polymer solar cells have a decisive role on the performance of the cells. Polymers with extended absorption, i.e., black polymers with absorption covering the whole visible region are desired in order to capture the important parts of the solar irradiation. Different ways of achieving black active materials are discussed and two new alternating polyfluorene (APFO) copolymers with broad absorption, APFO-Black 1 and APFO-Black 2, using two different design strategies are described. The UV-Vis absorption spectra of the polymers extend to approximately 850 nm, and the polymers were used as donors and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)[60] or PCBM[70] as acceptors in solar cell devices in various mixing ratios. The best combinations yielded an overall power conversion efficiency of 1.2% for APFO-Black 1 and 1.5% for APFO-Black 2.
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| 63. |
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| 64. |
- Borgström, Magnus, et al.
(författare)
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Nanowires With Promise for Photovoltaics
- 2011
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X. ; 17:4, s. 1050-1061
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Tidskriftsartikel (refereegranskat)abstract
- Solar energy harvesting for electricity production is regarded as a fully credible future energy source: plentiful and without serious environmental concerns. The breakthrough for solar energy technology implementation has, however, been hampered by two issues: the conversion efficiency of light into electricity and the solar panel production cost. The use of III-V nanowires (NWs) in photovoltaics allows to respond to both these demands. They offer efficient light absorption and significant cost reduction. These low-dimensional structures can be grown epitaxially in dense NW arrays directly on silicon wafers, which are abundant and cheaper than the germanium substrates used for triple-junction solar cells today. For planar structures, lattice matching poses a strong restriction on growth. III-V NWs offer to create highly efficient multijunction devices, since multiple materials can be combined to match the solar spectrum without the need of tightly controlled lattice matching. At the same time, less material is required for NW-based solar cells than for planar-based architecture. This approach has potential to reach more than 50% in efficiency. Here, we describe our work on NW tandem solar cells, aiming toward two junctions absorbing different parts of the solar spectrum, connected in series via a tunnel diode.
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| 65. |
- Brizuela, Fernando, et al.
(författare)
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Imaging at the Nanoscale With Practical Table-Top EUV Laser-Based Full-Field Microscopes
- 2012
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X. ; 18:1, s. 434-442
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Tidskriftsartikel (refereegranskat)abstract
- The demonstration of table-top high average power extreme-ultraviolet (EUV) lasers combined with the engineering of specialized optics has enabled the demonstration of full-field microscopes that have achieved tens of nanometer spatial resolution. This paper describes the geometry of the EUV microscopes tailored to specific imaging applications. The microscope illumination characteristics are assessed and an analysis on the microscope's spatial resolution is presented. Examples of the capabilities of these table-top EUV aerial microscopes for imaging nanostructures and surfaces are presented.
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| 66. |
- Brydegaard, Mikkel, et al.
(författare)
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High Dynamic Range in Entomological Scheimpflug Lidars
- 2021
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- Minimizing insecticide use, preventing vector diseases and facilitating biodiversity assessments are suitable applications of recent advances in photonic insect surveillance and entomological lidar. The tools also comprise a new window into fundamental aspect of the fascinating life and ecology of insects and their predators in situ. At the same time, it is evident that lidars are subject to finite detection range given by the instrument noise and saturation levels, and therefore, intervals of the biomass spectra are sectioned at different ranges. The Scheimpflug lidar allows an interesting trade-off between high sample rate and low pulse energy for retrieving wing beat harmonics and slow sample rates with high pulse energy for detecting small species far away. In this paper, we review and revise calibration, sizing and associated deficiencies, and report count rates to 104 insects/minute up to 2 km range. We investigate if and how high dynamic range can be exploited in entomological lidar and also how fast and slow sample rates could complement each other and capture a wider span of the biomass spectrum. We demonstrate that smaller insect can be detected further away by long exposures and show consistency between the captured biomass size spectra. However, we find unexpected discrepancies between short and long exposures in the range distributions. We found that vertebrates as well as specular insects can saturate signals. Error sources and limitations are elaborated on.
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| 67. |
- Caroff, Philippe, et al.
(författare)
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Crystal Phases in III-V Nanowires: From Random Toward Engineered Polytypism
- 2011
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X. ; 17:4, s. 829-846
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Tidskriftsartikel (refereegranskat)abstract
- III-V nanowires (NWs) are promising for a wide range of applications, ranging from optics to electronics, energy, and biological sensing. The structural quality of NWs is of paramount importance for the performance of such future NW-based devices. Random structural defects and polytypism occur naturally in semiconductor NWs, but progress both on the theoretical understanding and experimental control have been achieved recently. Here, we review progress towards the realization of perfect wurtzite and zinc-blende phases in III-VNWs, eventually leading to true phase engineering in single NWs.
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| 68. |
- Gratz, M, et al.
(författare)
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Time-gated imaging in radiology: Theoretical and experimental studies
- 1996
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X. ; 2:4, s. 1041-1048
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Tidskriftsartikel (refereegranskat)abstract
- Novel short-pulse X-ray sources, e.g., laser-produced plasmas, offer new approaches to the solution of the scatter-reduction problem in X-ray imaging, by the use of time-gated detection techniques. Monte Carlo simulations are used to estimate the scatter-reduction performance of time-gated imaging techniques within a range of X-ray energies, gating times and tissue parameters, Significant improvements can be achieved for thick tissues combined with high photon energies, Experimental studies on water phantoms are performed using a laser-produced plasma X-ray source. Problems arising on the technical realization are discussed.
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| 69. |
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| 70. |
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