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A new compact range facility for antenna and radar target measurements

June 1, 2007
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Journal Article
Author:
Michael W. Shields
…
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 2, June 2007, pp. 381-391.
Topic:
antennas
R&D area:
R&D group:

Summary

A new antenna and radar-cross-section measurements facility consisting of four anechoic chambers has recently been constructed at Lincoln Laboratory on Hanscom Air Force Base. One of the chambers is a large compact range facility that operates over the 400 MHz to 100 GHz band, and consists, in part, of a large temperature-controlled rectangular chamber lined with radar-absorbing material that is arranged to reduce scattering; a composite rolled-edge offset-fed parabolic reflector; a robotic multi-feed antenna system; and a radar instrumentation system. Additionally, the compact range facility includes a gantry/crane system that is used to move large antennas and radar targets onto a positioning system that provides the desired aspect angles for measurements of antenna patterns and radar cross section. This compact range system provides unique test capabilities to support rapid prototyping of antennas and radar targets.
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Summary

A new antenna and radar-cross-section measurements facility consisting of four anechoic chambers has recently been constructed at Lincoln Laboratory on Hanscom Air Force Base. One of the chambers is a large compact range facility that operates over the 400 MHz to 100 GHz band, and consists, in part, of a...

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A new compact range facility for antenna and radar target measurements

Cryogenic YB3+-doped solid-state lasers

May 1, 2007
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Journal Article
Author:
Tso Yee Fan
…
Published in:
IEEE J. Sel. Topics in Quantum Electron., Vol. 13, No. 3, May/June 2007, pp. 448-459.
Topic:
optics
R&D area:
R&D group:

Summary

Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true forYb3+ lasers because of their relatively lowquantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index at low temperature, are reviewed and data presented for YAG (ceramic and single crystal), GGG, GdVO4, and Y2O3. Spectroscopic properties of Yb:YAG and Yb:LiYF4 (YLF) including absorption cross sections, emission cross sections, and fluorescence lifetimes at cryogenic temperatures are characterized. Recent experiments have pushed the power from an end-pumped cryogenically cooled Yb:YAG laser to 455-W continuous-wave output power from 640-W incident pump power at anM2 of 1.4.
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Summary

Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true forYb3+ lasers because of their relatively lowquantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials...

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Cryogenic YB3+-doped solid-state lasers

The digital focal plane array (DFPA) architecture for data processing "on-chip"

February 5, 2007
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Conference Paper
Author:
Michael W. Kelly
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Published in:
2007 Meeting of the Military Sensing Symposia (MSS) Specialty Group on Camouflage, Concealment & Deception; Passive Sensors; Detectors; and Materials, 5-9 February 2007.
Topic:
integrated circuit
R&D area:
R&D group:

Summary

The digital focal plane array (DFPA) project seeks to develop readout integrated circuits (ROICs) utilizing aggressively scaled and commercially available CMOS. Along with focal plane scaling and readout robustness benefits, the DFPA architecture provides a very simple way to implement processing algorithms directly on image data, in real-time, and prior to read-out of the data to an external digitizer or computer. In principle, almost any linear image processing filter kernel can be convolved with the scene image prior to readout. The useful size of the filter kernel is only limited by the size of the DFPA. Time domain filters can also be implemented on the ROIC to accomplish digital time domain integration (TDI) or change detection algorithms. The unique architecture can achieve the processing capability without the use of traditional digital adders or multipliers, like those used in most signal processors. Instead, a DFPA manipulates sequential digital counters under every pixel in a unique way to achieve the desired functionality. A non-addressable readout scheme is used for data transfer in four possible directions across the array. Although we are currently targeting longwave infrared (LWIR) applications, the approach can be potentially applied to any imaging application in any band.
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Summary

The digital focal plane array (DFPA) project seeks to develop readout integrated circuits (ROICs) utilizing aggressively scaled and commercially available CMOS. Along with focal plane scaling and readout robustness benefits, the DFPA architecture provides a very simple way to implement processing algorithms directly on image data, in real-time, and prior...

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The digital focal plane array (DFPA) architecture for data processing "on-chip"

High-power, slab-coupled optical waveguide laser array packaging for beam combining

January 23, 2007
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Conference Paper
Author:
Leo J. Missaggia
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Published in:
SPIE Vol. 6478, Photonics Packaging, Integration, and Interconnects VII, 23-25 January 2007, pp. 647806-1 - 647806-12.
Topic:
optics
R&D area:
R&D group:

Summary

Linear arrays of slab coupled optical waveguide lasers (SCOWL) are ideal sources for beam combining of array elements using techniques such as wavelength beam combining (WBC) and possibly coherent beam combining (CBC). SCOWL array elements have very high brightness, low divergence nearly diffraction limited output beams. Arrays of up to 1.2 cm in width containing as many as 240 elements have been demonstrated. In this presentation, the packaging techniques developed to ensure proper performance of SCOWL arrays will be described, with particular emphasis on the application to beam combining. A commercial high performance micro impingement cooler (MIC) was used to provide thermal management for these arrays. Based on performance data for this cooler, a numerical thermal model was constructed and used to investigate the thermal performance for several packaging schemes. In order to promote uniform optical performance of SCOWL array elements, assembly procedures, which included fluxless soldering using In and AuSn solder alloys, along with the use of thermal expansion matching materials were investigated. These techniques resulted in minimal contraction ([approx] 2 um) and smile ([approx]1 um) of the laser bar during the packaging procedure. Precise control of these parameters is required in order to minimize any detrimental impact on the resultant WBC beam quality. CBC of SCOWL arrays requires phase control of the array elements. Array packaging providing for individual electrical addressability of the array elements has been developed and demonstrated, allowing for phase control by current adjustment.
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Summary

Linear arrays of slab coupled optical waveguide lasers (SCOWL) are ideal sources for beam combining of array elements using techniques such as wavelength beam combining (WBC) and possibly coherent beam combining (CBC). SCOWL array elements have very high brightness, low divergence nearly diffraction limited output beams. Arrays of up to...

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High-power, slab-coupled optical waveguide laser array packaging for beam combining

Optimized growth of lattice-matched In(x)Al(1-x)N/GaN heterostructures by molecular beam epitaxy

January 8, 2007
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Journal Article
Author:
S. Schmult
…
Published in:
Appl. Phys. Lett., Vol. 90, No. 2, 8 January 2007, pp. 021922-1 - 021922-3.
Topic:
semiconductor (CMOS)
R&D area:

Summary

The authors present a systematic study on the growth of the ternary compound In(x)Al(1-x)N by molecular beam epitaxy. This work concentrates on In mole fractions x around 0.17, as this composition is in-plane lattice matched to GaN. At a growth temperature of 540 degrees C, high quality material was obtained using a total metal to nitrogen flux ratio of ~1. Using these growth parameters, high quality GaN/InAlN superlattices were obtained without growth interruptions.
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Summary

The authors present a systematic study on the growth of the ternary compound In(x)Al(1-x)N by molecular beam epitaxy. This work concentrates on In mole fractions x around 0.17, as this composition is in-plane lattice matched to GaN. At a growth temperature of 540 degrees C, high quality material was obtained...

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Optimized growth of lattice-matched In(x)Al(1-x)N/GaN heterostructures by molecular beam epitaxy

Impact of photoacid generator leaching on optics photocontamination in 193-nm immersion lithography

January 1, 2007
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Journal Article
Author:
Vladimir Liberman
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Published in:
J. Micro/Nanolith. MEMS MOEMS, Vol. 6, No. 1, January-March 2007, pp. 013001-1 - 013001-7.
Topic:
lithography
R&D area:
R&D group:

Summary

Leaching of resist components into water has been reported in several studies. Even low dissolution levels of photoacid generator (PAG) may lead to photocontamination of the last optical surface of the projection lens. To determine the impact of this phenomenon on optics lifetime, we initiate a set of controlled studies, where predetermined amounts of PAG are introduced into pure water and the results monitored quantitatively. The study identifies the complex, nonlinear paths leading to photocontamination of the optics. We also discover that spatial contamination patterns of the optics are strongly dependent on the flow geometry. Both bare SiO2 surfaces as well as coated CaF2 optics are studied. We find that for all surfaces, at concentrations typical of leached PAG, below 500 ppb, the in situ self-cleaning processes prevent contamination of the optics.
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Summary

Leaching of resist components into water has been reported in several studies. Even low dissolution levels of photoacid generator (PAG) may lead to photocontamination of the last optical surface of the projection lens. To determine the impact of this phenomenon on optics lifetime, we initiate a set of controlled studies...

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Impact of photoacid generator leaching on optics photocontamination in 193-nm immersion lithography

Microwave-induced cooling of a superconducting qubit

December 8, 2006
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Journal Article
Author:
Sergio O. Valenzuela
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Published in:
Sci., Vol. 314, No. 5805, 8 December 2006, pp. 1589-1592.
Topic:
quantum
R&D area:
R&D group:

Summary

We demonstrated microwave-induced cooling in a superconducting flux qubit. The thermal population in the first-excited state of the qubit is driven to a higher-excited state by way of a sideband transition. Subsequent relaxation into the ground state results in cooling. Effective temperatures as low as ≈3 millikelvin are achieved for bath temperatures of 30 to 400 millikelvin, a cooling factor between 10 and 100. This demonstration provides an analog to optical cooling of trapped ions and atoms and is generalizable to other solid-state quantum systems. Active cooling of qubits, applied to quantum information science, provides a means for qubit-state preparation with improved fidelity and for suppressing decoherence in multi-qubit systems.
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Summary

We demonstrated microwave-induced cooling in a superconducting flux qubit. The thermal population in the first-excited state of the qubit is driven to a higher-excited state by way of a sideband transition. Subsequent relaxation into the ground state results in cooling. Effective temperatures as low as ≈3 millikelvin are achieved for...

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Microwave-induced cooling of a superconducting qubit

Laser-induced fluorescence-cued, laser induced- breakdown spectroscopy biological-agent detection

December 1, 2006
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Journal Article
Author:
John D. Hybl
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Published in:
Appl. Opt., Vol. 45, No. 34, 1 December 2006, pp. 8806-8814.
Topic:
detection systems
R&D area:
R&D group:

Summary

Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS test bed has been developed and used to evaluate the utility of LIBS for biological-agent detection. Analysis of these data indicates that LIBS adds discrimination capability to fluorescence-based biological-agent detectors. However, the data also show that LIBS signatures of biological agent simulants are affected by washing. This may limit the specificity of LIBS and narrow the scope of its applicability in biological-agent detection.
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Summary

Methods for accurately characterizing aerosols are required for detecting biological warfare agents. Currently, fluorescence-based biological agent sensors provide adequate detection sensitivity but suffer from high false-alarm rates. Combining single-particle fluorescence analysis with laser-induced breakdown spectroscopy (LIBS) provides additional discrimination and potentially reduces false-alarm rates. A transportable UV laser-induced fluorescence-cued LIBS...

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Laser-induced fluorescence-cued, laser induced- breakdown spectroscopy biological-agent detection

Low voltage electrowetting using thin fluoroploymer films

November 15, 2006
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Journal Article
Author:
Shaun R. Berry
…
Published in:
J. Colloid and Interface Sci., Vol. 303, No. 2, 15 November 2006, pp. 517-524.
Topic:
microfluidics
R&D area:
R&D group:

Summary

This paper investigates the nonideal electrowetting behavior of thin fluoroploymer films. Results are presented for a three phase system consisting of: (1) an aqueous water droplet containing sodium dodecyl sulfate (SDS), (2) phosphorous-doped silicon topped with SiO2 and an amorphous fluoroploymer (aFP) insulating top layer on which the droplet is situated, and (3) a dodecane oil that surrounds the droplet. The presented measurements indicate that the electrowetting equation is valid down to a 6 nm thick aFP film on a 11 nm thick SiO2. At this dielectric thickness, a remarkable contact angle change of over 100degreescan be achieved with an applied voltage less than 3 V across the system. The data also shows that for this water/surfactant/oil system, contact angle saturation is independent of the electric field, and is reached when the surface energy of the solid-water interface approaches zero.
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Summary

This paper investigates the nonideal electrowetting behavior of thin fluoroploymer films. Results are presented for a three phase system consisting of: (1) an aqueous water droplet containing sodium dodecyl sulfate (SDS), (2) phosphorous-doped silicon topped with SiO2 and an amorphous fluoroploymer (aFP) insulating top layer on which the droplet is...

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Low voltage electrowetting using thin fluoroploymer films

Contribution of photoacid generator to material roughness

November 1, 2006
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Conference Paper
Author:
Theodore H. Fedynyshyn
…
Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 24, No. 6, November/December 2006, pp. 3031-3039 (EIPBN 2006, 30 May-2 June 2006).
Topic:
microelectronics
R&D area:
R&D group:

Summary

The authors have developed an atomic-force-microscopy-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, the authors previously established that the photoacid generator (PAG) is a major material contributor of film roughness and that PAG segregation in the resist is likely responsible for nanoscale dissolution inhomogeneities. The additional roughness imparted on a test polymer by incorporation of a series of iodonium, sulfonium, diazo, and imido PAGs was measured. The roughness was then correlated to the inhibition properties of the various PAGs. This was accomplished both through a NMR technique that measures interaction of the PAG with the polymer and by evaluating the dissolution inhibition properties of the PAG through a percolation model. Several PAGs that result in significantly lower material roughness and thus the potential for significantly reduced linewidth roughness in resist imaging have been identified.
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Summary

The authors have developed an atomic-force-microscopy-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, the authors previously established that the photoacid generator (PAG)...

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Contribution of photoacid generator to material roughness
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