438 research outputs found
Thermal surveillance of Cascade Range volcanoes using ERTS-1 multispectral scanner, aircraft imaging systems, and ground-based data communication platforms
A combination of infrared images depicting areas of thermal emission and ground calibration points have proved to be particularly useful in plotting time-dependent changes in surface temperatures and radiance and in delimiting areas of predominantly convective heat flow to the earth's surface in the Cascade Range and on Surtsey Volcano, Iceland. In an integrated experiment group using ERTS-1 multispectral scanner (MSS) and aircraft infrared imaging systems in conjunction with multiple thermistor arrays, volcano surface temperatures are relayed daily to Washington via data communication platform (DCP) transmitters and ERTS-1. ERTS-1 MSS imagery has revealed curvilinear structures at Lassen, the full extent of which have not been previously mapped. Interestingly, the major surface thermal manifestations at Lassen are aligned along these structures, particularly in the Warner Valley
Postsurgical Rehabilitation of a Rotator Cuff Tear
The purpose of this project is to determine a rehab protocol for a postsurgical rotator cuff tear. The structure under investigation is a newly repaired torn rotator cuff, that is in a very delicate state and will require treatment and rehabilitation immediately following surgery. Rehabilitation will continue until the rotator cuff has completely healed, and range of motion, strength, and stability have been restored to the glenohumeral joint
Fully quantum mechanical dynamic analysis of single-photon transport in a single-mode waveguide coupled to a traveling-wave resonator
We analyze the dynamics of single photon transport in a single-mode waveguide
coupled to a micro-optical resonator using a fully quantum mechanical model. We
examine the propagation of a single-photon Gaussian packet through the system
under various coupling conditions. We review the theory of single photon
transport phenomena as applied to the system and we develop a discussion on the
numerical technique we used to solve for dynamical behavior of the quantized
field. To demonstrate our method and to establish robust single photon results,
we study the process of adiabatically lowering or raising the energy of a
single photon trapped in an optical resonator under active tuning of the
resonator. We show that our fully quantum mechanical approach reproduces the
semi-classical result in the appropriate limit and that the adiabatic invariant
has the same form in each case. Finally, we explore the trapping of a single
photon in a system of dynamically tuned, coupled optical cavities.Comment: 24 pages, 10 figure
Truly unentangled photon pairs without spectral filtering
We demonstrate that an integrated silicon microring resonator is capable of
efficiently producing photon pairs that are completely unentangled; such pairs
are a key component of heralded single photon sources. A dual-channel
interferometric coupling scheme can be used to independently tune the quality
factors associated with the pump and signal and idler modes, yielding a
biphoton wavefunction with Schmidt number arbitrarily close to unity. This will
permit the generation of heralded single photon states with unit purity.Comment: 5 pages, 3 figure
Development of a 50 kw cw L-band rectangular window for Jefferson Lab FEL cryomodule
A 50 kW CW L-Band Rectangular Ceramic Window has been developed for the Jefferson Lab FEL quarter cryomodule. RF properties of the windows were optimized using high-frequency simulation codes and S-parameter measurements confirmed the predicted broad band matching properties of the structure. Metallized AL 995 alumina ceramic was brazed to a thin copper eyelet and the eyelet to a copper plated stainless steel flange. Losses in the metallization were removed efficiently by a water cooling circuit. High power tests in a resonant ring showed that the ceramic temperature rise was very low at 50 kW CW level
Observation of a stronger-than-adiabatic change of light trapped in an ultrafast switched GaAs-AlAs microcavity
We study the time-resolved reflectivity spectrum of a switched planar
GaAs-AlAs microcavity. Between 5 and 40 ps after the switching (pump) pulse we
observe a strong excess probe reflectivity and a change of the frequency of
light trapped in the cavity up to 5 linewidths away from the cavity resonance.
This frequency change does not adiabatically follow the fast-changing cavity
resonance. The frequency change is attributed to an accumulated phase change
due to the time-dependent refractive index. An analytical model predicts
dynamics in qualitative agreement with the experiments, and points to crucial
parameters that control future applications.Comment: Discussed effect of probe bandwidth. Included functional forms of
n(z) and R(z
Nonlinear Photon Pair Generation in a Highly Dispersive Medium
Photon pair generation in silicon photonic integrated circuits relies on four wave mixing via the third order nonlinearity. Due to phase matching requirements and group velocity dispersion, this method has typically required TE polarized light. Here, we demonstrate TM polarized photon pair production in linearly uncoupled silicon resonators with more than an order of magnitude more dispersion than previous work. We achieve measured rates above 2.8 kHz and a heralded second order correlation of . This method enables phase matching in dispersive media and paves the way for novel entanglement generation in silicon photonic device
Carrier velocity in InAlN/AlN/GaN heterostructure field effect transistors on Fe-doped bulk GaN substrates
We report microwave characteristics of field effect transistors employing InAlN/AlN/GaN heterostructures grown on low-defect-density bulk Fe-doped GaN substrates. We achieved unity current gain cutoff frequencies of 14.3 and 23.7 GHz for devices with gate lengths of 1 and 0.65 μm, respectively. Measurements as a function of applied bias allow us to estimate the average carrier velocity in the channel to be ∼1.0×107 cm/sec for a 1 μm device. Additionally, we found nearly no gate lag in the devices, which is considered a precondition for good performance under large signal operation
- …