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- Andersson, J. Y., et al.
(författare)
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Quantum structure based infrared detector research and development within Acreo's centre of excellence IMAGIC
- 2010
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 53:4, s. 227-230
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Tidskriftsartikel (refereegranskat)abstract
- Acreo has a long tradition of working with quantum structure based infrared (IR) detectors and arrays. This includes QWIP (quantum well infrared photodetector), QDIP (quantum dot infrared photodetector), and InAs/GaInSb based photon detectors of different structure and composition. It also covers R&D on uncooled microbolometers. The integrated thermistor material of such detectors is advantageously based on quantum structures that are optimised for high temperature coefficient and low noise. Especially the SiGe material system is preferred due to the compatibility with silicon technology. The R&D work on IR detectors is a prominent part of Acreo's centre of excellence "IMAGIC" on imaging detectors and systems for non-visible wavelengths. IMAGIC is a collaboration between Acreo, several industry partners and universities like the Royal Institute of Technology (KTH) and Linkoping University. (C) 2010 Elsevier B.V. All rights reserved.
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- Gustafsson, Oscar, et al.
(författare)
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Long-wavelength infrared quantum-dot based interband photodetectors
- 2011
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 54:3, s. 287-291
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Tidskriftsartikel (refereegranskat)abstract
- We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.
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- Junique, Stéphane, et al.
(författare)
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Multiple quantum well spatial light modulators design-fabrication-characterization
- 2001
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - San Diego, CA : SPIE. ; , s. 62-71
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Konferensbidrag (refereegranskat)abstract
- Multiple quantum well spatial light modulators (MQW SLMs) are promising devices for future high-speed applications. We present results obtained with a single-pixel amplitude modulator. We discuss the status of our work on a 128x—128-pixel ternary SLM. This SLM will run at 10 kHz and have one low-reflectance level and two high reflectance levels with a phase difference of Ï€. We also present a study of the relation between the coding domain and the structural design of modulators.
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| 13. |
- Karim, Amir, et al.
(författare)
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Characterization of InSb QDs grown on InAs (100) substrate by MBE and MOVPE
- 2012
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 9780819491312
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Konferensbidrag (refereegranskat)abstract
- We report on the optical and structural characterization of InSb QDs in InAs matrix, grown on InAs (100) substrates, for infrared photodetection. InSb has 7% lattice mismatch with InAs forming strained QDs, which are promising for longwave IR applications, due to their type-II band alignment. This report contains material development results of InSb QDs for increasing their emission wavelength towards long-wave IR region. Samples were grown by two techniques of MBE and MOVPE, with different InSb coverage on InAs (100) substrates. Structures grown by MBE reveal QD related photoluminescence at 4 μm. AFM investigations of the MBE grown structures showed uncapped dots of ∼ 35 nm in size and ∼ 3 nm in height, with a density of about 2 × 1010 cm -2. Cross-section TEM investigations of buried InSb layers grown by MBE showed coherently strained QDs for nominal InSb coverage in the range of 1.6 - 2 monolayers (MLs). Layers with InSb coverage more than 2MLs contain relaxed QDs with structural defects due to large amount of strain between InSb and InAs. Samples with such large dots did not show any InSb related luminescence. The MOVPE grown InSb samples exhibit a strong QD related emission between 3.8 to 7.5 μm, depending on the amount of InSb coverage and other growth parameters. We report the longest wavelength observed so far in this material system.
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| 14. |
- Marpaung, D, et al.
(författare)
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Development of a Broadband and Squint-Free Ku-Band Phased Array Antenna System for Airborne Satellite Communications
- 2011
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Ingår i: Future Aeronautical Communications, Edited by Simon Plass, Chapter 10. - 9789533076256
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Future Aeronautical Communications, Edited by Simon Plass, Chapter 10: Development of a Broadband and Squint-Free Ku-Band Phased Array Antenna System for Airborne Satellite CommunicationsNovel avionic communication systems are required for various purposes, for example to increase the flight safety and operational integrity as well as to enhance the quality of service to passengers on board. To serve these purposes, a key technology that is essential to be developed is an antenna system that can provide broadband connectivity within aircraft cabins at an affordable price. Currently, in the European Commission (EC) 7th Framework Programme SANDRA project (SANDRA, 2011), a development of such an antenna system is being carried out. The system is an electronically-steered phased-array antenna (PAA) with a low aerodynamic profile. The reception of digital video broadcasting by satellite (DVB-S) signal which is in the frequency range of 10.7-12.75 GHz (Ku-band) is being considered. In order to ensure the quality of service provided to the passengers, the developed antenna should be able to receive the entire DVB-S band at once while complying with the requirements of the DVB-S system (Morello & Mignone, 2006). These requirements, as will be explained later, dictate a broadband antenna system where the beam is squint-free, i.e. no variation of beam pointing direction for all the frequencies in the desired band. Additionally, to track the satellite, the seamless tunability of the beam pointing direction of this antenna is also required. In this work, a concept of optical beamforming (Riza & Thompson, 1997) is implemented to provide a squint-free beam over the entire Ku-band for all the desired pointing directions. The optical beamformer itself consists of continuously tunable optical delay lines that enable seamless tunability of the beam pointing direction.
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| 24. |
- Wang, Q., et al.
(författare)
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Multilayer InAs/InGaAs quantum dot structure grown by MOVPE for optoelectronic device applications
- 2006
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Ingår i: Nanoengineering: Fabrication, Properties, Optics, and Devices III. - : SPIE. ; , s. L3270-L3270
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Konferensbidrag (refereegranskat)abstract
- We report on a quantum dot (QD) structure grown on a 4" GaAs substrate by metal organic vapor phase epitaxy (MOVPE), which consists of five stacked InAs/InGaAs/GaAs QD layers embedded in the center of a typical in-plane waveguide. The density of the QDs is about 2.5 × 1010 cm -2 per QD layer. The photoluminescence (PL) peak wavelength at 1322 nm corresponding to the interband transition of the QD ground states was observed at room temperature with a full width at half-maximum of 49 meV. A good uniformity of the QD structure across the 4" wafer was verified with a variation of the PL peak wavelength of 0.9 % from the wafer center to the edge. Top p-contacts and a bottom n-contact were processed on the QD structure, and electroluminescence (EL) spectra were measured at different temperatures. An EL peak corresponding to the QD ground states emission was obtained at 1325 nm at room temperature.
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| 26. |
- Wang, Q., et al.
(författare)
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Wide-aperture GaAs/AlGaAs multiple quantum well electro-optic modulators
- 2002
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 4947, s. 59-67
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present design and fabrication methods for surface normal monolithic amplitude modulators with an aperture up to 14 × 14 mm2, a contrast ratio of 6:1 and for low driving voltages (=8 V). The modulators consist of undoped GaAs/AlGaAs quantum wells embedded in a Fabry-Perot (FP) resonance cavity grown by MOVPE. To improve the device performance the FP cavity, the period and thickness of the quantum well and doping concentration were optimised. Also, the dimension of the modulator were varied from 0.5 × 0.5 to 14 × 14 mm2. The results show that the yield of the modulators increases significantly when decreasing the size of the modulators. To remedy the low yield issue for wide aperture modulator, a pixelated approach was used to divide the mono pixel in a monolithic modulator into several pixels, for example from 4 to 48. The modulation speed of the modulators with different dimensions was characterised by electro-optic (EO) response measurements. The temporal optical response of the large modulators was satisfactory up to the order of MHz modulation frequency where the RC constant limited the performance. A few of the modulators with wide apertures are to be assembled into an optical link system for free-space communication.
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