| 1. |
- Hoglund, L, et al.
(författare)
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Selective optical doping to predict the performance and reveal the origin of photocurrent peaks in quantum dots-in-a-well infrared photodetectors
- 2009
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Ingår i: INFRARED PHYSICS and TECHNOLOGY. - Exeter : Elsevier BV. - 1350-4495 .- 1879-0275. ; 52:6, s. 272-275
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Tidskriftsartikel (refereegranskat)abstract
- Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. Through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots, the response was increased by a factor of 10. Low temperature photocurrent peaks observed at 120 and 148 meV were identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively by a selective increase of the electron population in the different quantum dot energy levels.
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| 2. |
- Niklaus, Frank, et al.
(författare)
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Performance model for uncooled infrared bolometer arrays and performance predictions of bolometers operating at atmospheric pressure
- 2008
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 51:3, s. 168-177
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a comprehensive calculational model for the noise equivalent temperature difference (NETD) of infrared imaging systems based on uncooled bolometer arrays. The equations are presented in a new and convenient form. The NETD model is validated and benchmarked using published performance data of a state-of-the-art uncooled infrared bolometer array. The NETD model is used to evaluate possible system and bolometer design improvements. The results of the calculations suggest that infrared imaging systems based on uncooled bolometer arrays with a bolometer pixel pitch of 28 mu m x 28 mu m have the potential to reach NETDs on the order of 12 mK. The calculations also suggest that NETDs on the order of 200 mK can be achieved with infrared imaging systems based on uncooled bolometer arrays that operate in air at atmospheric pressure.
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| 3. |
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| 4. |
- Li, N., et al.
(författare)
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Detection wavelengths and photocurrents of very long wavelength quantum-well infrared photodetectors
- 2005
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Ingår i: Infrared Physics and Technology. - : Elsevier BV. - 1350-4495. ; 47:1-2, s. 29-36
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Tidskriftsartikel (refereegranskat)abstract
- Based on detailed studies of the energy band structure and the optical transitions in very long wavelength (>14 μm) GaAs/AlGaAs quantum-well (QW) infrared photodetectors (QWIPs), we have built a practical QWIP model. We study the factors that determine photogenerated carriers and response wavelengths of photocurrents of very long wavelength QWIPs. The material structures of QWIPs are first characterized by the photoluminescence measurements (PL) at room temperature and 77 K respectively. We have found and confirmed a distinctive difference between photocurrent of QWIPs with only one confined state in the quantum well (QW) and those binding two confined states, which resulted in different dependence of detection wavelength on the quantum well width. Also, we have investigated the dependence of response wavelength on several other parameters for very long wavelength QWIPs, such as barrier width and Al mole fraction. By calculating the density of photogenerated carriers in the continuum above the energy barriers using the PL calibrated QWIP structures, we have demonstrated that due to the high sample quality, the photocarriers can be either in miniband states (Bloch states in the multiple quantum wells), or they transport from one quantum well to the next in the form of propagating waves. We have further calculated the densities of photocarriers in the QWIPs reported in the literature. It is shown that the Bloch wave boundary conditions are appropriate for QWIPs with narrow QWs, whereas propagating wave boundary conditions are appropriate for wide QWs.
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| 5. |
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| 6. |
- Swoboda, Jessica, et al.
(författare)
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Predictors of oral health quality of life in older adults.
- 2006
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Ingår i: Special care in dentistry : official publication of the American Association of Hospital Dentists, the Academy of Dentistry for the Handicapped, and the American Society for Geriatric Dentistry. - 0275-1879. ; 26:4, s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- There is limited information regarding oral health status and other predictors of oral health-related quality of life. An association between oral health status and perceived oral health-related quality of life (OHQOL) might help clinicians motivate patients to prevent oral diseases and improve the outcome of some dental public health programs. This study evaluated the relationship between older persons' OHQOL and their functional dentition, caries, periodontal status, chronic diseases, and some demographic characteristics. A group of 733 low-income elders (mean age 72.7 [SD = 4.71, 55.6% women, 55.1% members of ethnic minority groups in the U.S. and Canada) enrolled in the TEETH clinical trial were interviewed and examined as part of their fifth annual visit for the trial. OHQOL was measured by the Geriatric Oral Health Assessment Index (GOHAI); oral health and occlusal status by clinical exams and the Eichner Index; and demographics via interviews. Elders who completed the four-year assessment had an average of 21.5 teeth (SD = 6.9), with 8.5 occluding pairs (SD = 4.6), and 32% with occlusal contacts in all four occluding zones. Stepwise multiple regressions were conducted to predict total GOHAI and its subscores (Physical, Social, and Worry). Functional dentition was a less significant predictor than ethnicity and being foreign-born. These variables, together with gender, years since immigrating, number of carious roots, and periodontal status, could predict 32% of the variance in total GOHAI, 24% in Physical, 27% in Social, and 21% in the Worry subscales. These findings suggest that functional dentition and caries influence older adults' OHQOL, but that ethnicity and immigrant status play a larger role.
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