We investigate the magnetoresistance of a nonplanar two-dimensional electron gas (2DEG) fabricated by growth GaAs/(AlGa)As heterojunction on wafer prepatterned with facets at 20\ifmmode^\circ\else\textdegree\fi{} to substrate. Applying uniform magnetic field (B) produces spatially nonuniform component perpendicular 2DEG. With in plane substrate, resistance measured across an etched facet shows oscillations that are periodic 1/B. This measurement is equivalent two-terminal planar Hall bar...

During 1951-1952 Arthur Prior wrote a column of firstly public comment, and then, in 1952, theological discussion under the nom-de plume Naphtali Outlook, magazine New Zealand Presbyterian Church. This article discusses these columns, putting them wider Prior’s life, thought Christian beliefs; his early work as thinker.

This article discusses 30 letters between Arthur Prior and Charles Brasch, the editor of Landfall, over period 1946-1958. The contain new important information on Prior’s view logic philosophy, what he was reading at this time, his reflections Popper C.S. Lewis, contributions to preference for Polish notation. They also provide insight as how writings, ideas suggestions including that Landfall regularly discuss were received responded by Brasch.

We have investigated experimentally an open semiconductor system in which electron confinement around obstacle is obtained using a magnetic field. The field gives rise to Landau levels, and each associated edge state circulates the obstacle, forming set of quantized states. Tunable constrictions are fabricated by technique enables us control transport out these states, producing Aharonov-Bohm oscillations as swept. Surprisingly, strong extra oscillation with same h/e frequency develops,...

Recent efforts to improve the reliability of high-power broad-area diode lasers operating in 9xx nm wavelength band have yielded single emitter devices with excellent >15 W. However, applications requiring fiber coupling, coupling power a device is rather limited by its linear density, and hence brightness device. Unfortunately, due rapid increase slow-axis divergence, typical laser offers much lower an earlier rollover than output power. In this work, we show that thermal lensing (rather...

Focused development under the DARPA SHEDs program has lead to extremely high power conversion efficiency in 9xx-nm wavelength band, leading bars with excess of 74%. We review progress advancing and detail route > 85% at room temperature. The band is commercially used for pumping Ytterbium-doped solid-state crystals fiber lasers - only one many diode laser markets. Fortunately, lessons learned are transferable other wavelengths. report breakthrough results 8xx-nm example showing 71% from...

We have studied the in-plane magnetoresistance of coupled double-quantum-well structures, in which each well has a different mobility and where values carrier concentration can be varied independently. Resistance resonances, observed at zero magnetic field, were suppressed with an field 1 T, provided was perpendicular to current. The showed structure changed systematically front-gate back-gate voltages, due deformation both wave functions Fermi surfaces field.

We have used a torque magnetometer to measure de Haas - van Alphen oscillations in the magnetization of two-dimensional electrons GaAs/AlGaAs heterostructures and multiple-quantum-well systems for temperatures ranging from 0.125 K 4.2 magnetic fields up 15 T. Our results indicate that high density states can be described by series Lorentzian-broadened Landau levels with broadening is independent field, B, level index, n. However, at low becomes indistinguishable Gaussian one proportional ....

Using the techniques of in situ focused ion beam lithography and molecular epitaxy regrowth high quality, patterned back gate, double quantum well devices have been fabricated. Independent ohmic contacts were made to two two-dimensional electron gases (2DEGs) using a ‘‘selective depletion’’ scheme, further gates carrier densities each controlled. Resonant tunneling between was observed as function density 2DEG, bias applied wells. Extremely large peak-to-valley ratios observed, resulting...

We have studied Coulomb-blockade effects through a quantum dot formed by an impurity potential near two-dimensional electron gas (2DEG) defined at GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterojunction. compared the energy-level spacing within obtained two methods: from magnetic-field-induced gate-voltage shifts of conductance peaks, and applying source-drain voltage across dot. The use latter method in magnetic field allows us to distinguish...

Improved performance and reliability of 9xx nm single emitter laser diodes are presented. To date, over 15,000 hours accelerated multi-cell lifetest data has been collected, with drive currents from 14A to 18A junction temperatures ranging 60°C 110°C. Out 208 devices, 14 failures have observed so far. Using established analysis techniques, the effects temperature power acceleration assessed. The Mean Time Failure (MTTF) is determined be >30 years, for use condition 10W 353K (80°C), 90%...

We have used MBE regrowth technology to produce a non-planar 2DEG at GaAs/AlGaAs heterojunction grown over an etched facet. By applying uniform magnetic field this structure we obtain spatially varying component normal the 2DEG. When is applied in plane of substrate, resistance measured from one side facet other found be quantized approximately quantum Hall plateaux. Rotating sample with respect allows us investigate edge state propagation and reflection different regions sample. making...

We have developed a new technique to contact submicrometer metal dot gate independently of surrounding gates. With this we made two ballistic channels in parallel on GaAs-AlGaAs heterostructure. Independent control over all the gates allows unprecedented flexibility adjust both size and widths channels. In perpendicular magnetic field can obtain extremely large Aharonov–Bohm oscillations double-frequency oscillation indicative edge state charging an open system. At low fields see no evidence...

There is a great interest in the development of high-power, high-efficiency, and low-cost quasicontinuous wave (QCW) diode laser bars arrays for pumping solid state lasers. We report on kW-class 88x-nm that are based bipolar cascade design, which multiple lasers epitaxially grown electrical series single substrate separated by low-resistance tunnel junctions with resistance as low 8.0×10−6 Ω-cm2. QCW power 630 W was demonstrated 3-mm-wide minibar 3-mm cavity length. Peak efficiency 61%...

Optimized single stripe 975-nm broad area devices deliver 76% power conversion efficiency at 10degC. Cooling the material leads to 85% -50degC. External differential quantum is dominant term.

This paper presents reliable high power and brightness 9xx-nm single emitter laser diodes, which have been designed for various multi-emitter fiber-coupled modules. Diode lasers from legend generation life-tested with currents up to 14A at heat-sink junction temperatures of 50°C 80°C respectively, accumulated more than 15,000 hours life-test duration. In order further improve operational optimize beam quality, new devices developed. The demonstrated 20W CW rollover without catastrophic...

We report on continued progress in the development of high power and brightness single emitter laser diodes from 790 nm to 980 for reliable use industrial pumping applications. High performance has been demonstrated nLIGHT's diode technology this spectral range with corresponding peak electrical-to-optical conversion efficiency ~65%. These pumps have incorporated into fiber-coupled pump module, elementTM. latest updates reliability chips modules. This paper also includes a new chip design...

Abstract Digital society has been lauded as emancipatory and freeing individuals from the constrictions of time place yet also critiqued introducing a type techno-feudalism data extraction. The vaunted freedom work leisure time, work-space leisure-place, occurred to some, for many others it created collapse non-work space into digital surveillance work, identity social interaction. There are issues technological inequality generational differences. This paper introduces some questions that...

High power GaAs-based high diode bars produce wavelengths in the range of 780 to 980 nm and are widely used for pumping a broad rare earth doped solid-state lasers. As markets these laser systems mature, lasers that operate at higher levels, greater overall efficiency, reliability demand. In this paper we report efficiencies over 70% 9xx-nm band, continuous wave levels 340 Watts 8xx-nm data or above 100 Watts. We will also review latest advances performance detail basic physics material...

Performance, lifetest data, as well failure modes from two different device structures will be discussed in this paper, with emitting wavelengths 780nm to 800nm. The first structure, designed for high temperature operation, has demonstrated good reliability on various packages output power up 10W a 200μm area. structure can operated 60°C heatsink temperatures under CW conditions. Then efficiency is shown further improvement operation and reliability, room operation. With ongoing at 12A 50°C...

Facets of high-power broad area diode lasers are typically coated with one high-reflecting and partially reflecting layer to improve slope efficiency maximize output power. The typical cavity lengths commercial devices have also been progressively increasing, mainly reduce temperature rise at the active region laser performance reliability. asymmetric reflectivities long length, however, result in a highly inhomogeneous longitudinal profile photon density, which induces spatially non-uniform...

Abstract This article proceeds in two distinct parts. The first section engages with a deliberately small number of popular texts written by discriminating and interrogative consumers producers digital culture society. While these may be dismissed as journalistic sources those more focused academic intent, here are used because they the connection between engagement wider public readership. As such, frame what can termed critical capitalism. These read tandem my thesis immaterial capitalism...

We show that a system of two closely separated two-dimensional electron gases in GaAs/AlGaAs which one is formed into quantum dot can be used as Coulomb blockade electrometer. The to explore the density states other gas patterned wire. Electron localization observed and shows behavior magnetic field arising from destruction interference subsequent wave-function shrinkage. dimensionality transport changes carrier concentration increased, with inferred changing quasi-one-dimensional dimensional.