Ultra Fast Nonlinear Optical Tuning of Photonic Crystal Cavities

We demonstrate fast (up to 20 GHz), low power (5 $\mu W$) modulation of photonic crystal (PC) cavities in GaAs containing InAs quantum dots. Rapid modulation through blue-shifting of the cavity resonance is achieved via free carrier injection by an above-band picosecond laser pulse. Slow tuning by several linewidths due to laser-induced heating is also demonstrated

The Interaction of Breaking Solitary Waves with an Armored Bed

This study investigates the interaction of breaking waves with a bed of loose angular material with a median grain size of 4.8 mm. It is motivated by the engineering problem of determining rock sizes for revetments used as protection for structures in the coastal zone and by the need for an understanding of the mechanics of material movement under waves. Both the effect of the bed on the velocities and accelerations in breaking and non-breaking waves, and the effect of breaking waves on the movement of bed material is measured. Velocities in breaking waves are measured at elevations approaching the bottom boundary, both for the case of a level bed of graded angular material and for a flat plate at the same location. By changing the water depth and the initial conditions of the incident wave, the relative size of the rock with respect to the breaking wave height is varied. Material movement resulting from the wave passage is measured and compared to the breaking wave height and to the turbulent shear determined near the bed. Using velocity and acceleration records near the rock bed together with observations of rock motion, the mechanics of material movement under waves are investigated. The roughness elements in the bed are found to have a large effect on both the mean and fluctuating velocities in the wave near the bottom. Evidence is shown of the existence of an inner layer where individual pieces of bed material influence the flow over the bed. A method for determining the maximum mean shear under a single wave is presented. Mean vertical velocities are measured to be not negligible near the bed and are shown to produce convective accelerations of the same order as the accelerations due to turbulent fluctuations. The movement of bed material is compared with the calculated shear on the bed and with local velocities and accelerations measured very close to the individual rocks. The mean size of the material moved in the bed is found to vary with the amount of shear on the bed. When adjusted for the mean size of the moved material, the calculated shears correspond well with the criterion for critical shear from the Shields curve used in steady flow. From the observed movement of particles during the passage of a wave and the measured velocities and accelerations in the wave, inertial forces are found to contribute to particle movement, especially in the regions before and after wave crest passage

The Utah Pilot Bridge, Live Load and Dynamic Testing, Modeling and Monitoring for the Long-Term Bridge Performance Program

As part of the Federal Highway Administration\u27s Long-Term Bridge Performance Program, Live Load and Dynamic tests were conducted. A long-term monitoring plan was developed and presented for the Utah Pilot Bridge based on Live Load and Dynamic tests. As one of seven pilot bridges, the Utah Pilot Bridge is one of the first bridges used to initiate the LTBP Program. A formal permit approval process, with the Utah Department of Transportation, was followed to gain permission to conduct the tests and install long-term instrumentation. Analysis provided good results for each test completed, with a summary of test results presented. A Finite Element Model was created and refined based off test data. Instrumentation was installed and checked to ensure quality data was streaming to the collection site

The solid state photomultiplier: Status of photon counting beyond the near-infrared

Rockwell International's Solid State Photomultiplier (SSPM) is an impurity-band avalanche device which can count individual photons with wavelengths between 0.4 and 28 micrometers. Its response to a photon is a pulse of between 10(exp 4) and 10(exp 5) conduction electrons, making it an important device for use in phenomenology. The characteristics of the SSPM make it a potentially important device for use in astronomical applications. Contract NAS2-12400 was initiated in June 1986 to conduct modeling and characterization studies of the SSPM to provide a basis for assessing its use in astronomical systems. Some SSPM models and results of measurements which characterize the group of SSPMs recently fabricated on this contract are discussed

Equilibrium Configurations of Homogeneous Fluids in General Relativity

By means of a highly accurate, multi-domain, pseudo-spectral method, we investigate the solution space of uniformly rotating, homogeneous and axisymmetric relativistic fluid bodies. It turns out that this space can be divided up into classes of solutions. In this paper, we present two new classes including relativistic core-ring and two-ring solutions. Combining our knowledge of the first four classes with post-Newtonian results and the Newtonian portion of the first ten classes, we present the qualitative behaviour of the entire relativistic solution space. The Newtonian disc limit can only be reached by going through infinitely many of the aforementioned classes. Only once this limiting process has been consummated, can one proceed again into the relativistic regime and arrive at the analytically known relativistic disc of dust.Comment: 8 pages, colour figures, v3: minor additions including one reference, accepted by MNRA

Negative Komar Masses in Regular Stationary Spacetimes

A highly accurate multi-domain spectral method is used to study axially symmetric and stationary spacetimes containing a black hole or disc of dust surrounded by a ring of matter. It is shown that the matter ring can affect the properties of the central object drastically. In particular, by virtue of the ring's frame dragging, the so-called Komar mass of the black hole or disc can become negative. A continuous transition from such discs to such black holes can be found

Negative Komar mass of single objects in regular, asymptotically flat spacetimes

We study two types of axially symmetric, stationary and asymptotically flat spacetimes using highly accurate numerical methods. One type contains a black hole surrounded by a perfect fluid ring and the other a rigidly rotating disc of dust surrounded by such a ring. Both types of spacetime are regular everywhere (outside of the horizon in the case of the black hole) and fulfil the requirements of the positive energy theorem. However, it is shown that both the black hole and the disc can have a negative Komar mass. Furthermore, there exists a continuous transition from discs to black holes even when their Komar masses are negative

Independent electrical tuning of separated quantum dots in coupled photonic crystal cavities

Systems of photonic crystal cavities coupled to quantum dots are a promising architecture for quantum networking and quantum simulators. The ability to independently tune the frequencies of laterally separated quantum dots is a crucial component of such a scheme. Here, we demonstrate independent tuning of laterally separated quantum dots in photonic crystal cavities coupled by in-plane waveguides by implanting lines of protons which serve to electrically isolate different sections of a diode structure.Comment: 3 pages, 3 figure