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Broadband transparent optical phase change materials

May 14, 2017
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Conference Paper
Author:
Yifei Zhang
…
Published in:
CLEO: Conf. on Lasers and Electro-Optics, 14-19 May 2017.
Topic:
optics
R&D area:
R&D group:

Summary

We report a new group of optical phase change materials Ge-Sb-Se-Te (GSST) with low loss from telecom bands to LWIR. We further demonstrated GSST-integratedSiN photonics with significantly improved switching performance over conventional GST alloys.
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Summary

We report a new group of optical phase change materials Ge-Sb-Se-Te (GSST) with low loss from telecom bands to LWIR. We further demonstrated GSST-integratedSiN photonics with significantly improved switching performance over conventional GST alloys.

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Broadband transparent optical phase change materials

Fabrication security and trust of domain-specific ASIC processors

May 1, 2017
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Conference Paper
Author:
Mankuan Michael Vai
…
Published in:
IEEE Intl. Symp. on Hardware Oriented Security and Trust, HOST, 1-5 May 2017.
Topic:
algorithms
R&D area:
R&D group:

Summary

Application specific integrated circuits (ASICs) are commonly used to implement high-performance signal-processing systems for high-volume applications, but their high development costs and inflexible nature make ASICs inappropriate for algorithm development and low-volume DoD applications. In addition, the intellectual property (IP) embedded in the ASIC is at risk when fabricated in an untrusted foundry. Lincoln Laboratory has developed a flexible signal-processing architecture to implement a wide range of algorithms within one application domain, for example radar signal processing. In this design methodology, common signal processing kernels such as digital filters, fast Fourier transforms (FFTs), and matrix transformations are implemented as optimized modules, which are interconnected by a programmable wiring fabric that is similar to the interconnect in a field programmable gate array (FPGA). One or more programmable microcontrollers are also embedded in the fabric to sequence the operations. This design methodology, which has been termed a coarse-grained FPGA, has been shown to achieve a near ASIC level of performance. In addition, since the signal processing algorithms are expressed in firmware that is loaded at runtime, the important application details are protected from an unscrupulous foundry.
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Summary

Application specific integrated circuits (ASICs) are commonly used to implement high-performance signal-processing systems for high-volume applications, but their high development costs and inflexible nature make ASICs inappropriate for algorithm development and low-volume DoD applications. In addition, the intellectual property (IP) embedded in the ASIC is at risk when fabricated in...

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Fabrication security and trust of domain-specific ASIC processors

Seismic barrier protection of critical infrastructure

April 25, 2017
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Conference Paper
Author:
Robert W. Haupt
…
Published in:
16th Annual IEEE Int. Symp. on Technologies for Homeland Security, HST 2017, 25-26 April 2017.
Topic:
advanced materials
R&D area:
R&D group:

Summary

Each year, on average a major magnitude-8 earthquake strikes somewhere in the world. In addition, 10,000 earthquake related deaths occur annually, where collapsing buildings claim by far most lives. Moreover, in recent events, industry activity of oil extraction and wastewater reinjection are suspected to cause earthquake swarms that threaten high-value oil pipeline networks, U.S. oil storage reserves, and civilian homes. Earthquake engineering of building structural designs and materials have evolved over many years to minimize the destructive effects of seismic surface waves. However, even under the best engineering practices, significant damage and numbers of fatalities can still occur. In this paper, we present a novel concept and approach to redirect and attenuate the ground motion amplitudes caused by earthquakes by implementing an engineered subsurface seismic barrier – creating a form of metamaterial. The barrier is comprised of borehole array complexes and trench designs that impede and divert destructive seismic surface waves from a designated 'protection zone'. The barrier is also designed to divert not only surface waves in the aerial plane, but includes vertical 'V' shaped muffler structures composed of opposing boreholes to mitigate seismic waves from diffracting and traveling in the vertical plane. Computational 2D and 3D seismic wave propagation models developed at MIT Lincoln Laboratory suggest that borehole array and trench arrangements are critical to the redirection and self-interference reduction of broadband hazardous seismic waves in the vicinity of the structure to protect. The computational models are compared with experimental data obtained from large bench-scale physical models that contain scaled borehole arrays and trenches. These experiments are carried out at high frequencies, but with suitable material parameters and borehole dimensions. They indicate that effects of a devastating 7.0 Mw -magnitude earthquake can be reduced to those of a minor magnitude-4.5 or -5.5 Mw earthquake within a suitable protection zone. These results are very promising, and warrant validation in field scale tests.
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Summary

Each year, on average a major magnitude-8 earthquake strikes somewhere in the world. In addition, 10,000 earthquake related deaths occur annually, where collapsing buildings claim by far most lives. Moreover, in recent events, industry activity of oil extraction and wastewater reinjection are suspected to cause earthquake swarms that threaten high-value...

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Seismic barrier protection of critical infrastructure

Effect of surface roughness and H-termination chemistry on diamond's semiconducting surface conductance

April 10, 2017
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Journal Article
Author:
Travis C. Wade
…
Published in:
Diamond Related Mater., Vol. 76, 1 June 2017, pp. 79-85.
Topic:
advanced materials
R&D area:
R&D group:

Summary

The H-terminated surface of diamond when activated with NO2 produces a surface conduction layer that has been used to make FETs. Variations in processing can significantly affect this conduction layer. This article discusses the effect of diamond surface preparation and H termination procedures on surface conduction. Surface preparations that generate a rough surface result in a more conductive surface with the conductivity increasing with surface roughness. We hypothesize that the increase in conductance with roughness is the result of an increase of reactive sites that generate the carriers. Roughening the diamond surface is just one way to generate these sites and the rough surface is believed to be a separate property from the density of surface reactive sites. The presence of C in the H2 plasma used for H termination decreases surface conductance. A simple procedure for NO2 activation is demonstrated. Interpretation of electrical measurements and possible alternatives to activation with NO2 are discussed. Using Kasu's oxidation model for surface conductance as a guide, compounds other than NO2 have been found to activate the diamond surface as well.
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Summary

The H-terminated surface of diamond when activated with NO2 produces a surface conduction layer that has been used to make FETs. Variations in processing can significantly affect this conduction layer. This article discusses the effect of diamond surface preparation and H termination procedures on surface conduction. Surface preparations that generate...

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Effect of surface roughness and H-termination chemistry on diamond's semiconducting surface conductance

High-efficiency large-angle Pancharatnam phase deflector based on dual-twist design

March 20, 2017
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Journal Article
Author:
Kun Gao
…
Published in:
Opt. Express, Vol. 25, No. 6, 20 March 2017.
Topic:
optics
R&D area:
R&D group:

Summary

We have previously shown through simulation that an optical beam deflector based on the Pancharatnam (geometric) phase can provide high efficiency with up to 80° deflection using a dual-twist structure for polarization-state control [Appl. Opt. 54, 10035 (2015)]. In this report, we demonstrate that its optical performance is as predicted and far beyond what could be expected for a conventional diffractive optical device. We provide details about construction and characterization of a ± 40° beam-steering device with 90% diffraction efficiency based on our dual-twist design at a 633nm wavelength.
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Summary

We have previously shown through simulation that an optical beam deflector based on the Pancharatnam (geometric) phase can provide high efficiency with up to 80° deflection using a dual-twist structure for polarization-state control [Appl. Opt. 54, 10035 (2015)]. In this report, we demonstrate that its optical performance is as predicted...

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High-efficiency large-angle Pancharatnam phase deflector based on dual-twist design

Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

February 28, 2017
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Journal Article
Author:
Alla Ostrinskaya
…
Published in:
Rapid Commun. Mass Spectrom., Vol. 33, 2017, pp. 333-43.
Topic:
detection systems
R&D area:
R&D group:

Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN by mass spectrometry (MS) have not been fully investigated. METHODS: Atmospheric-pressure chemical-ionization mass spectrometry (APCI-MS) was used to detect ions characteristic of nitrated sugar alcohols. APCI time-of-flight mass spectrometry (APCI-TOF MS) and collision-induced dissociation tandem mass spectrometry (CID MS/MS) were used for confirmation of each ion assignment. In addition, the use of the chemical ionization reagent dichloromethane was investigated to improve sensitivity and selectivity for detection of MHN, SHN and XPN. RESULTS: All the nitrated sugar alcohols studied followed similar fragmentation pathways in the APCI source. MHN, SHN and XPN were detectable as fragment ions formed by the loss of NO2, HNO2, NO3, and CH2NO2 groups, and in the presence of dichloromethane chlorinated adduct ions were observed. It was determined that in MS/MS mode, chlorinated adducts of MHN and SHN had the lowest limits of detection (LODs), while for XPN the lowest LOD was for the [XPN-NO2]- fragment ion. Partially nitrated analogs of each of the three compounds were also present in the starting materials, and ions attributable to these compounds versus those formed from in-source fragmentation of MHN, SHN, and XPN were distinguished and assigned using liquid chromatography APCI-MS and ESI-MS. CONCLUSIONS: The APCI-MS technique provides a selective and sensitive method for the detection of nitrated sugar alcohols. The methods disclosed here will benefit the area of explosives trace detection for counterterrorism and forensics.
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Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN...

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Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

High-resolution, high-throughput, CMOS-compatible electron beam patterning

February 26, 2017
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Conference Paper
Author:
Melissa A. Smith
…
Published in:
SPIE Advanced Lithography, 26 February - 2 March 2017.
Topic:
lithography
R&D area:
R&D group:

Summary

Two scanning electron beam lithography (SEBL) patterning processes have been developed, one positive and one negative tone. The processes feature nanometer-scale resolution, chemical amplification for faster throughput, long film life under vacuum, and sufficient etch resistance to enable patterning of a variety of materials with a metal-free (CMOS/MEMS compatible) tool set. These resist processes were developed to address two limitations of conventional SEBL resist processes: (1) low areal throughput and (2) limited compatibility with the traditional microfabrication infrastructure.
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Summary

Two scanning electron beam lithography (SEBL) patterning processes have been developed, one positive and one negative tone. The processes feature nanometer-scale resolution, chemical amplification for faster throughput, long film life under vacuum, and sufficient etch resistance to enable patterning of a variety of materials with a metal-free (CMOS/MEMS compatible) tool...

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High-resolution, high-throughput, CMOS-compatible electron beam patterning

Spatially-resolved individual particle spectroscopy using photothermal modulation of Mie scattering

January 15, 2017
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Journal Article
Author:
Ryan M. Sullenberger
…
Published in:
Opt. Lett., Vol. 42, No. 2, 15 January 2017, pp. 203-6.
Topic:
optics
R&D area:
R&D group:

Summary

We report a photothermal modulation of Mie scattering (PMMS) method that enables concurrent spatial and spectral discrimination of individual micron-sized particles. This approach provides a direct measurement of the "fingerprint" infrared absorption spectrum with the spatial resolution of visible light. Trace quantities (tens of picograms) of material were deposited onto an infrared transparent substrate and simultaneously illuminated by a wavelength-tunable intensity-modulated quantum cascade pump laser and a continuous-wave 532 nm probe laser. Absorption of the pump laser by the particles results in direct modulation of the scatter field of the probe laser. The probe light scattered from the interrogated region is imaged onto a visible camera, enabling simultaneous probing of spatially-separated individual particles. By tuning the wavelength of the pump laser, the IR absorption spectrum is obtained. Using this approach, we measured the infrared absorption spectra of individual 3 um PMMA and silica spheres. Experimental PMMS signal amplitudes agree with modeling using an extended version of the Mie scattering theory for particles on substrates, enabling the prediction of the PMMS signal magnitude based on the material and substrate properties.
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Summary

We report a photothermal modulation of Mie scattering (PMMS) method that enables concurrent spatial and spectral discrimination of individual micron-sized particles. This approach provides a direct measurement of the "fingerprint" infrared absorption spectrum with the spatial resolution of visible light. Trace quantities (tens of picograms) of material were deposited onto...

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Spatially-resolved individual particle spectroscopy using photothermal modulation of Mie scattering

High performance, 3D-printable dielectric nanocomposites for millimeter wave devices

December 5, 2016
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Journal Article
Author:
Michael T. Lis
…
Published in:
ACS Appl. Mater. Interfaces, Vol. 8, 2016, 34019-26.
Topic:
additive manufacturing
R&D area:
R&D group:

Summary

The creation of millimeter wave, 3D-printable dielectric nanocomposite is demonstrated. Alumina nanoparticles were combined with styrenic block copolymers and solvent to create shear thinning, viscoelastic inks that are printable at room temperature. Particle loadings of up to 41 vol % were achieved. Upon being dried, the highest-performing of these materials has a permittivity of 4.61 and a loss tangent of 0.00298 in the Ka band (26.5-40 GHz), a combination not previously demonstrated for 3D printing. These nanocomposite materials were used to print a simple resonator device with predictable pass-band features.
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Summary

The creation of millimeter wave, 3D-printable dielectric nanocomposite is demonstrated. Alumina nanoparticles were combined with styrenic block copolymers and solvent to create shear thinning, viscoelastic inks that are printable at room temperature. Particle loadings of up to 41 vol % were achieved. Upon being dried, the highest-performing of these materials...

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High performance, 3D-printable dielectric nanocomposites for millimeter wave devices

Biomimetic sniffing improves the detection performance of a 3D printed nose of a dog and a commercial trace vapor detector

December 1, 2016
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Journal Article
Author:
Matthew E. Staymates
…
Published in:
Scientific Reports, Vol. 6 , art. no. 36876, December 2016. DOI: 10.1038/srep36876.
Topic:
detection systems
R&D area:
R&D group:

Summary

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog's nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the "aerodynamic reach" for inspiration of otherwise inaccessible odors. Chemical sampling and detection experiments quantified two modes of operation with the artificial nose-active sniffing and continuous inspiration-and demonstrated an increase in odorant detection by a factor of up to 18 for active sniffing. A 16-fold improvement in detection was demonstrated with a commercially-available explosives detector by applying this bio-inspired design principle and making the device "sniff" like a dog. These lessons learned from the dog may benefit the next-generation of vapor samplers for explosives, narcotics, pathogens, or even cancer, and could inform future bio-inspired designs for optimized sampling of odor plumes.
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Summary

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog's nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the "aerodynamic reach" for inspiration of...

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Biomimetic sniffing improves the detection performance of a 3D printed nose of a dog and a commercial trace vapor detector
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