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We investigate a kilometer‐scale steep relay rampstructure in the Galilee, northern Israel. The data indi-cate an asymmetric fold above the buried tip of thesouthern boundary fault as well as at the lower partof the ramp. Structural analysis suggests that the buriedtip of the bounding fault is only a few hundred metersbelow the surface. A sequence of colluvial wedges,exposed at the base of the southern flank of the relayramp over the blind tip of the boundary fault, presentssuccessively decreasing angles from 67° at the bottomto 30° at the top. The lower three wedges rest at anglesgreater than the angle of repose, suggesting tilting dur-ing and after deposition. We suggest that the increasingangle of the wedges is the result of the development ofthe monocline over the buried tip ofthe boundaryfault,which in turn reflects the development of the entirerelay ramp structure. Paleomagnetic measurements testthis hypothesis. Samples from three of the four lowerwedges and the carbonate fill in the fractured bedrockyield northerly declination and positive inclination.Inclination anomalies are 19.4° ± 3.3° and 11.3° ±1.8° for the fractured bedrock and the wedges, respec-tively. These anomalies reflect part of the tilt. Paleo-magnetic measurements and optically stimulatedluminescence (OSL) constrain the time of initial defor-mation of the monocline above the southern boundaryfault between 780 ka and 461 ± 75 ka (OSL age ofwedge 1) and the termination of deformation to 176 ±22 ka (OSL age of wedge 5). These bounding agessuggest tilting rates that range between 1°/16 kyrand 1°/8 kyr. Termination of tilting along the south-ern flank of the relay ramp and the fact that the tipof the buried normal fault is only a few hundreds ofmeters below the surface suggest that the relay rampmay be close to being breached by a connecting fault.

The origins of line broadening in the far-infrared spectrum of phosphorus donors in SiGe are investigated. Using a combination of Fourier transform infrared FT-IR spectroscopy and time-resolved pump-probe measurements, we show that the line shapes are dominated by inhomogenous broadening. Experimental FT-IR absorbance spectra measured in the temperature range 6–150 K are presented for three different Ge contents. Additional spectra of pure phosphorus doped silicon recorded under similar experimental conditions are presented and compared with the SiGe results. We propose a simple quantitative model to simulate the line broadening in our experimental spectra. Our model takes into account the compositional variations in the random SiGe binary alloy and its effect on the permittivity of the environment around each donor. We also show that the addition of small amounts Ge to Si single crystals has little detrimental effect on the lifetime of the excited infrared electronic energy levels, despite the observed line broadening.

[1] We use in situ-produced and meteoric 10Be, analyzed in soils from 28 pits on four hillcrest-parallel transects along a 14° hillslope in the Great Smoky Mountains, North Carolina, as tracers of soil production and transport. We rely upon amalgamation both to investigate and smooth spatial variability in 10Be concentrations. Lidar indicates that the hillslope is topographically complex and that soil is moved downslope diffusively until it encounters the ephemeral channel network and is rapidly exported. In situ-produced 10Be, measured in depth profiles, indicates that over millennial timescales, soils are mixed above the soil-saprolite boundary. In contrast, meteoric 10Be concentrations increase with depth and are correlated to concurrent increases of dithionite-extractable Al and pH, observations explained by similar Al and Be mobility in the soil. The concentrations of both meteoric and in situ-produced 10Be increase downslope proportional to the maximum soil particle path length. The data suggest virtual downslope soil velocities of 1.1–1.7 cm yr−1 in a well-mixed active transport layer ∼60 cm thick. The thickness of this transport layer is constant downslope and depends on the rooting depth and consequent root wad thickness of downed trees on the slope, both of which reflect depth to the soil/saprolite boundary. Both meteoric and in situ-produced 10Be suggest that soil production is balanced by surface denudation at rates between 10 and 13 m Myr−1. Soil residence times on the slope range from 21 to 33 kyr based on the meteoric 10Be inventories. Major element geochemical analysis suggests little if any elemental loss during soil transport downslope.

Over the last eight years, we have developed several paleoenvironmental records from a broad geographic region spanning the Altiplano in Bolivia (18°S–22°S) and continuing south along the western Andean flank to ca. 26°S. These records include: cosmogenic

Si0.5Ge0.5/Si quantum cascade structures have been deposited by low-energy plasma-enhanced CVD according to a bound-to-continuum design and characterized by high resolution x-ray diffraction and transmission electron microscopy. Electroluminescence from the active region is peaked around 2.5 THz (~10 meV) and exhibits Stark shift and polarization dependence.

Producing an electrically pumped silicon-based laser at terahertz frequencies is gaining increased attention these days. This paper reviews the recent advances in the search for a silicon-based terahertz laser. Topics covered include resonant tunneling in p-type Si/SiGe, terahertz intersubband electroluminescence from quantum cascade structures, intersubband lifetime measurements in Si/SiGe quantum wells, enhanced optical guiding using buried silicide layers, and the potential for exploiting common impurity dopants in silicon such as boron and phosphorus to realize a terahertz laser.

�� erosion rate at the upstream end of the flow acceleration zone above a waterfall, Fr is the Froude number at this setting, and n ranges between 0.5–1.7. This amplification expression suggests that erosion at the lip could be as much as 2–5 times higher relative to erosion at a normal setting with identical hydraulic geometry. Utilizing this erosion amplification expression in numerical simulations, we demonstrate its impact on reach-scale morphology above waterfalls. Amplified erosion at the lip of a waterfall can trigger the formation of an oversteepened reach whose length is longer than the flow acceleration zone, provided incision wave velocity (Vi) at the upstream edge of the flow acceleration zone is higher than the retreat velocity of the waterfall face. Such an oversteepened reach is expected to be more pronounced when Vi increases with increasing slope. The simulations also suggest that oversteepening can eventually lead to steady state gradients adjacent to a waterfall lip provided Vi decreases with increasing slope. Flow acceleration above waterfalls can thus account, at least partially, for prevalent oversteepened bedrock reaches above waterfalls. Using the cosmogenic isotope Cl-36, we demonstrate that incision wave velocity upstream of a waterfall at the Dead Sea western escarpment is probably high enough for freefall-induced oversteepening to be feasible.

We present here the results of 44 paleomagnetic measurements, and single cosmogenic burial and optically stimulated luminescence ages for the Earlier Stone Age deposits from Wonderwerk Cave, Northern Cape, South Africa. The resulting paleomagnetic sequence: NRNRN constrains the Earlier Stone Age strata in this part of the site to between approximately 0.78-1.96 Ma. A single cosmogenic date of approximately 2.0 Ma from the base of the section offers some corroboration for the paleomagnetic sequence. Preliminary results indicate that the small lithic assemblage from the basal stratum may contain an Oldowan facies. This is overlain by several strata containing Acheulean industries. The preliminary radiometric dates reported here place the onset of the Acheulean at this site to approximately 1.6 Ma, which is roughly contemporaneous with that of East Africa.

[1] The Peru frontal prism represents a contrasting hydrologic setting to the better characterized systems of Nankai and Barbados. The high taper angle and convergence rate result in rapid burial of low-permeability sediments. Critical taper stability calculations were combined with a flow model to understand how a steep taper angle could be stable under these conditions. Constant rate flow tests of the slope and prism sediments gave permeability values ranging from a low of ∼10−18 m2 to a high of ∼10−16 m2. Estimated compaction fluid sources exceed 5 × 10−13 s−1 near the toe and remain above 10−14 s−1 for 20 km arcward in the underthrust sediments. These data were used to constrain a two-dimensional, steady state model of pore pressure along a cross section at 9°S. The model domain is composed of a 15-km-wide frontal prism with a crystalline buttress at the back and 500 m of permeable basement at the base. The combined mechanical stability and flow model analysis yielded a feasible basement permeability of ∼10−16 m2 and a decollement permeability range of 10−15–10−17 m2. The model results demonstrate that basement flow and use of different pressure ratio values for the wedge and the base in stability calculations are important for systems with steep taper angles.

The emission and absorption characteristics of boron-doped and phosphorous-doped silicon at terahertz frequencies are investigated. Different doping concentrations are considered and individual terahertz optical transitions are identified. The effect of temperature is considered.

The emission and absorption characteristics of boron-doped and phosphorous-doped silicon at terahertz frequencies are investigated. Different doping concentrations are considered and individual terahertz optical transitions are identified. The effect of temperature is considered.

We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router’s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described. The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel. Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization. Finally, we will present some of our current research work on a next-generation optical switch. The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

There has been considerable interest in using impurity dopants in silicon, such as boron and phosphorus, since it was demonstrated that such materials can show emission in the THz region of the electromagnetic spectrum. The measured temperature dependence of these transitions in this letter shows that the most optimistic maximum operating temperature of such an impurity-based laser is 90 K. In a real device with current flowing and associated Joule heating, the actual operating range is likely to be much narrower and it is therefore unlikely that such a device would have a maximum operating temperature above 40 K.

This paper covers some recent advances in the search for a silicon quantum cascade laser. These include intersubband lifetime measurements, growth of high quality structures on buried suicide layers, and demonstration of THz electroluminescence.

Nanosecond routing in a 64/spl times/64 optical phased array switch is reported. Further testing of the switch shows transmission capability of four 40 Gb/s WDM channels through a single switch path, with power penalty of 0.3 dB per channel. The optical path performance at high bit rate and data rate scalability of the switch is demonstrated for the first time. This performance indicates the possibility of switch implementation in Terabit routing systems. Furthermore, the results presented demonstrate the wavelength, data rate and format transparency of the switch, opening the possibility for the switch to be used in optical IP networks.

The reported unit satisfies all requirements in order to function as switching core of a high-capacity packet switching backbone router. IP format packet-switching is acheived. At the time of writing this report, the switch demonstrated the transport of 12.5 Gbit/sec data into a single channel.

Most research focuses on varying the resonator and dielectric spacer to configure the absorption and resonant frequency of terahertz (THz) metamaterial absorbers (MAs), where a metal ground plane is used as a perfect reflector of incident THz waves. In this paper, we modulate the MAs absorption by varying the conductivity of the ground plane. Two THz MAs were fabricated by replacing the gold ground planes with cobalt silicide films, and the measured absorptivity decreases by 4% for the electric resonance and increases by 44% for the dipole resonance. Our quantitative analysis reveals that when the conductivity of the ground plane decreases from 1.8 × 107 S/m to 3.0 × 105 S/m, the absorptivity of the electric resonance decreases by 23%, while that of the dipole resonance increases by 62%. Our approach also provides a practical method to measure the electric conductivity of conductive films in the THz regime.

We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser. The noise equivalent power was 1 × 10−11 W Hz−1/2. The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing.

A planar broadband metamaterial absorber with high absorptivity working at terahertz frequencies was designed and fabricated in this work. Two nested back-to-back split-ring resonators (BSRRs) constitute a single resonator, which achieves three strong resonances, with two of them merged into a broadband peak. Cobalt silicide and parylene-C were innovatively applied as ground plane and dielectric spacer. The nested BSRR absorber experimentally realizes a bandwidth of 0.66 THz with the absorptivity above 0.8, and the highest absorptivity reaches 0.97. Taking the central frequency at 2.74 THz, the measured FWHM is 47% and the Q factor is 2.13.

We design, fabricate, and characterize dual-band terahertz (THz) metamaterial absorbers with high absorption based on structures consisting of a cobalt silicide (Co-Si) ground plane, a parylene-C dielectric spacer, and a metal top layer. By combining two periodic metal resonators that couple separately within a single unit cell, a polarization-independent absorber with two distinct absorption peaks was obtained. By varying the thickness of the dielectric layer, we obtain absorptivity of 0.76 at 0.76 THz and 0.97 at 2.30 THz, which indicates the Co-Si ground plane absorbers present good performance.