Dynamic instability in the transmission field of an optical ring cavity containing three-level Λ-type rubidium atoms is studied in detail both experimentally and theoretically. The onset and periodicity of such dynam...
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Dynamic instability in the transmission field of an optical ring cavity containing three-level Λ-type rubidium atoms is studied in detail both experimentally and theoretically. The onset and periodicity of such dynamic oscillations in the cavity field can be controlled by the experimental parameters, such as intensity and frequency detuning of the coupling field and∕or cavity field. Such nonlinear dynamic behavior is caused by competition between optical saturation of the cavity field and optical population pumping by the coupling field in the three-level atomic system.
Molecular beam epitaxy growth of lattice mismatched In0.53Ga0.47As/GaAs(100) system is studied by in situ scanning tunneling microscope (STM) and reflection high energy electron diffraction. InGaAs layers with a thick...
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Molecular beam epitaxy growth of lattice mismatched In0.53Ga0.47As/GaAs(100) system is studied by in situ scanning tunneling microscope (STM) and reflection high energy electron diffraction. InGaAs layers with a thickness ranging up to 250 nm do not exhibit a smooth surface when grown under In-rich conditions. RHEED and STM confirm the well-ordered (4×2) reconstruction and mono-layer steps associated with this unique planar growth mode. Large STM scans reveal a characteristic morphology of rectangular shaped islands distributed on large flat terraces which are typically more than 300 nm width but only monolayer steps.
To achieve a high degree of functional density and efficiency, some of the micro actuators in MEMS can be replaced by active biological elements. An example of this is the cellular motor micro pump (CMMP) currently un...
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ISBN:
(纸本)0791837211
To achieve a high degree of functional density and efficiency, some of the micro actuators in MEMS can be replaced by active biological elements. An example of this is the cellular motor micro pump (CMMP) currently under development at the University of Arkansas. The CMMP is realized through the tethering of a harmless strain of Escherichia coli cells to a MEMS-based micro fluidic channel. In a free moving state, an *** cell 'swims' by rotating its' flagella, driven at the base by a rotary motor. When a cell is attached to a surface by a single shortened flagellar filament (∼0.5 micron long), the motor turns the entire cell body at a high rotational speed. The CMMP utilizes this mechanism to transport liquid in a micro fluidic channel through viscous pumping. This paper describes two important areas in the CMMP development process: cell tethering in micro channels fabricated from various substrate materials and visualization of tethered cell behavior through fluorescent microscopy.
We report on intersubband transitions in InxGa1-xAs/AlGaAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The conduction band offset for this material system is larger than that of the well known GaAs/...
We report on intersubband transitions in InxGa1-xAs/AlGaAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The conduction band offset for this material system is larger than that of the well known GaAs/AlGaAs system, thus making it possible to design, grow, and fabricate quantum well infrared photodetectors operational beyond the 14 μm spectral region with minimized dark current. We have grown InxGa1-xAs/AlGaAs MQWs with indium compositions ranging from x = 0.08 to 0.20 verified by in situ RHEED oscillations, band offset measurements, and high-resolution X-ray diffraction. Band-to-band transitions were verified by photoluminescence measurements, and intersubband transitions were measured using Fourier transform infrared (FTIR) spectroscopy. Due to the high strain and introduction of dislocations associated with the high indium content, wells with indium compositions above ∼ 0.12 did not result in intersubband transitions at silicon doping levels of 2×1018 cm-3. A thick linear graded InxGa1-xAs buffer was grown below the MQW structures to reduce the strain and resulting dislocations. Intersubband transitions were measured in InxGa1-xAs wells with indium compositions of x = 0.20 and greater when grown on top of the linear graded buffer. In addition to these results, FTIR measurements on InGaAs/AlGaAs MQW multi-color, long-wavelength infrared detector structures are reported.
This paper presents the results of the computational fluid dynamic (CFD) modeling of viscous fluid flow in a novel cell motor actuated micropump. A cell motor is a bacterial flagellar cell tethered to a surface by a s...
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ISBN:
(纸本)0791837211
This paper presents the results of the computational fluid dynamic (CFD) modeling of viscous fluid flow in a novel cell motor actuated micropump. A cell motor is a bacterial flagellar cell tethered to a surface by a single flagellum, this flagellum acts as a pivot around which the cell body rotates. As a test case for investigation, the micropump consisted of two Escherichia coli cell motors tethered to the bottom of a microchannel with fixed dimensions. The CFD modeling of the micropump was performed using CFD-ACE+ simulation software (CFD Research Corporation). The biological cell motor was modeled as an ellipse with constant rotational speed of 10 Hz clockwise. The results of this model demonstrated the effect of the biological cell motor placement within the microchannel, as well as the rotational phase between the two biological cell motors, on the volumetric flowrate. Pumping action was observed as the cell motor location was moved adjacent to the sidewall of the microchannel. The rates of fluid pumping were of the order of 11 pL/hr when the cell motors were rotating in phase and their placement was close to the sidewall of the microchannel.
In this paper the authors describe the design considerations including force and tolerance analysis and mechanism and tip design, for a novel, dynamic scanning probe microscopy tip directly insertable into today's...
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In this paper the authors describe the design considerations including force and tolerance analysis and mechanism and tip design, for a novel, dynamic scanning probe microscopy tip directly insertable into today's existing atomic force microscopy tools. This tool is the first of its kind and is a major step in the field of nanomanufacturing enabling the use of nanomechanical machining operations for nanostructure top-down manufacturing. The application of this device is the nanomechanical drilling and milling of III-V semiconductor substrates for various applications such as nanovias for electrical interconnection of next generation electronic and photonic applications, as well as reservoirs and capillaries for nano-fluidics. Results to date indicate that device performance parameters allow a normal drilling force of 25 μN, tangential drilling force of 35 μN, maximum rotational speed of 100,000 rpm, and minimum machined feature size of less than 200 nm. This device is currently being fabricated at Sandia National Laboratories, SUMMIT MEMS foundry and being packaged at the University of Arkansas, Fayetteville High Density Electronics Center (HiDEC).
We report on intersubband transitions in InxGa1-xAs/AlGaAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The conduction band offset for this material system is larger than that of the well known GaAs/...
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We report on intersubband transitions in InxGa1-xAs/AlGaAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The conduction band offset for this material system is larger than that of the well known GaAs/AlGaAs system, thus making it possible to design, grow, and fabricate quantum well infrared photodetectors operational beyond the 14 μm spectral region with minimized dark current. We have grown InxGa1-xAs/AlGaAs MQWs with indium compositions ranging from x = 0.08 to 0.20 verified by in situ RHEED oscillations, band offset measurements, and high-resolution X-ray diffraction. Band-to-band transitions were verified by photoluminescence measurements, and intersubband transitions were measured using Fourier transform infrared (FTIR) spectroscopy. Due to the high strain and introduction of dislocations associated with the high indium content, wells with indium compositions above ∼ 0.12 did not result in intersubband transitions at silicon doping levels of 2×1018 cm-3. A thick linear graded InxGa1-xAs buffer was grown below the MQW structures to reduce the strain and resulting dislocations. Intersubband transitions were measured in InxGa1-xAs wells with indium compositions of x = 0.20 and greater when grown on top of the linear graded buffer. In addition to these results, FTIR measurements on InGaAs/AlGaAs MQW multi-color, long-wavelength infrared detector structures are reported.
In this paper the authors describe the design considerations including force and tolerance analysis and mechanism and tip design, for a novel, dynamic scanning probe microscopy tip directly insertable into today's...
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