Physical Sciences

Ring-Down Spectroscopy for Characterizing a CW Raman Laser

Parameters of operation can be obtained from a single ringdown scan. A relatively simple technique for characterizing an all-resonant intracavity continuous- wave (CW) solid-state Raman laser involves the use of ring-down spectroscopy. As used here, “characterizing” signifies determining such parameters as threshold pump power, Raman gain, conversion efficiency, and quality factors (Q values) of the pump and Stokes cavity modes.

Posted in: Physical Sciences, Briefs, TSP

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Interferometric Quantum-Nondemolition Single-Photon Detectors

These detectors would function independently of frequency. Two interferometric quantum-nondemolition (QND) devices have been proposed: (1) a polarization- independent device and (2) a polarization- preserving device. The prolarization- independent device works on an input state of up to two photons, whereas the polarization- preserving device works on a superposition of vacuum and single-photon states. The overall function of the device would be to probabilistically generate a unique detector output only when its input electromagnetic mode was populated by a single photon, in which case its output mode would also be populated by a single photon.

Posted in: Physical Sciences, Briefs, TSP

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Complex Type-II Interband Cascade MQW Photodetectors

Multiple active subregions, each optimized for a different color, would enable multicolor operation. Multiple-quantum-well (MQW) photodetectors of a proposed type would contain active regions comprising multiple superlattice subregions. These devices would have complex structures: The superlattice of each subregion would be designed for enhanced absorption of photons in a desired wavelength band (typically in the infrared) and multiple subregions of different design would be cascaded for multicolor operation.

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Simplified Generation of High-Angular-Momentum Light Beams

Inherent properties of a WGM resonator and optical fiber are exploited. A simplified method of generating a beam of light having a relatively high value of angular momentum (see figure) involves the use of a compact apparatus consisting mainly of a laser, a whispering gallery mode (WGM) resonator, and optical fibers. The method also can be used to generate a Bessel beam. (“Bessel beam” denotes a member of a class of non-diffracting beams, so named because their amplitudes are proportional to Bessel functions of the radii from their central axes. High-order Bessel beams can have high values of angular momentum.)

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Alignment Cube With One Diffractive Face

Only one theodolite is needed instead of two. An enhanced alignment cube has been invented for use in a confined setting (e.g., a cryogenic chamber) in which optical access may be limited to a single line of sight. Whereas traditional alignment-cube practice entails the use of two theodolites aimed along two lines of sight, the enhanced alignment cube yields complete alignment information through use of a single theodolite aimed along a single line of sight.

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Surface Acoustic Wave Sensor for Viscosity Measurement

Acoustic wave solid-state viscometers can be integrated into in-line, real-time monitoring and process control systems. Viscosity is a measure of the resistance of a liquid to flow, and is an important measurement requirement in industrial process control and OEM applications. Viscosity describes the retarding force that is proportional to the rate of deformation. This so-called shear rate has units of s-1 and describes the crossstream gradient of the flow speed.

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Forecasting of Storm-Surge Floods Using ADCIRC and Optimized DEMs

Maximum water levels are mapped for Hurricanes Camille and Katrina. Increasing the accuracy of storm-surge flood forecasts is essential for improving preparedness for hurricanes and other severe storms and, in particular, for optimizing evacuation scenarios. An interactive database, developed by WorldWinds, Inc., contains atlases of storm-surge flood levels for the Louisiana/Mississippi gulf coast region. These atlases were developed to improve forecasting of flooding along the coastline and estuaries and in adjacent inland areas. Storm-surge heights depend on a complex interaction of several factors, including: storm size, central minimum pressure, forward speed of motion, bottom topography near the point of landfall, astronomical tides, and, most importantly, maximum wind speed.

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