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Permittivity evaluation of multilayered hyperbolic metamaterials: ellipsometry vs. reflectometry

March 14, 2015
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Journal Article
Author:
T. Tumkur
…
Published in:
J. Appl. Phys., Vol. 117, No. 10, 14 March 2015, 103104.
Topic:
advanced materials
R&D area:
R&D group:

Summary

Metal-dielectric nanolaminates represent a class of hyperbolic metamaterials with uniaxial permittivity tensor. In this study, we critically compare permittivity extraction of nanolaminate samples using two techniques: polarized reflectrometry vs. spectroscopic anisotropic ellipsometry. Both Au/MgF2 and Ag/MgF2 metal-dielectric stacks are examined. We demonstrate the applicability of the treatment of the multilayered material as a uniaxial medium and compare the derived optical parameters to those expected from the effective medium approximation. We also experimentally compare the effect of varying the material outer layer on the homogenization of the composite. Additionally, we introduce a simple empirical method of extracting the epsilon-near-zero point of the nanolaminates from normal incidence reflectance. The results of this study are useful in accurate determination of the hyperbolic material permittivity and in the ability to tune its optical properties.
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Summary

Metal-dielectric nanolaminates represent a class of hyperbolic metamaterials with uniaxial permittivity tensor. In this study, we critically compare permittivity extraction of nanolaminate samples using two techniques: polarized reflectrometry vs. spectroscopic anisotropic ellipsometry. Both Au/MgF2 and Ag/MgF2 metal-dielectric stacks are examined. We demonstrate the applicability of the treatment of the multilayered...

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Permittivity evaluation of multilayered hyperbolic metamaterials: ellipsometry vs. reflectometry

Hyperspectral Microwave Atmospheric Sounder (HyMAS) - new capability in the CoSMIR/CoSSIR scanhead

March 7, 2015
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Conference Paper
Author:
Lawrence M. Hilliard
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Published in:
2015 IEEE Aerospace Conf., 7-14 March 2015.
Topic:
sensing
R&D area:
R&D group:

Summary

MIT Lincoln Laboratory and NASA's Goddard Space Flight Center have teamed to adapt an existing instrument platform, the CoSMIR/CoSSIR system for atmospheric sensing, to develop and demonstrate a new capability in a hyperspectral microwave atmospheric sounder (HyMAS). This new sensor comprises a highly innovative intermediate frequency processor (IFP), that provides the filtering and digitization of 52 radiometric channels and the interoperable remote component (IRC) adapted to CoSMIR, CoSSIR, and HyMAS that stores and archives the data with time tagged calibration and navigation data. The first element of the work is the demonstration of a hyperspectral microwave receiver subsystem that was recently shown using a comprehensive simulation study to yield performance that substantially exceeds current state-of-the-art. Hyperspectral microwave sounders with ~100 channels offer temperature and humidity sounding improvements similar to those obtained when infrared sensors became hyperspectral. Hyperspectral microwave operation is achieved using independent RF antenna/receiver arrays that sample the same area/volume of the Earth's surface/atmosphere at slightly different frequencies and therefore synthesize a set of dense, finely spaced vertical weighting functions. The second, enabling element is the development of a compact 52-channel Intermediate Frequency processor module. A principal challenge of a hyperspectral microwave system is the size of the IF filter bank required for channelization. Large bandwidths are simultaneously processed, thus complicating the use of digital back-ends with associated high complexities, costs, and power requirements. Our approach involves passive filters implemented using low-temperature co-fired ceramic (LTCC) technology to achieve an ultra-compact module that can be easily integrated with existing RF front-end technology. This IF processor is applicable to other microwave sensing missions requiring compact IF spectrometry. The unit produces 52 channels of spectral data in a highly compact volume (
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Summary

MIT Lincoln Laboratory and NASA's Goddard Space Flight Center have teamed to adapt an existing instrument platform, the CoSMIR/CoSSIR system for atmospheric sensing, to develop and demonstrate a new capability in a hyperspectral microwave atmospheric sounder (HyMAS). This new sensor comprises a highly innovative intermediate frequency processor (IFP), that provides...

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Hyperspectral Microwave Atmospheric Sounder (HyMAS) - new capability in the CoSMIR/CoSSIR scanhead

Nanochannel fabrication based on double patterning with hydrogen silsesquioxane

March 1, 2015
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Journal Article
Author:
Kenneth A. Diest
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Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 33, No. 2, March 2015, 020601.
Topic:
microelectronics
R&D area:
R&D group:

Summary

A double patterning process is presented to pattern sub-35 nm wide channels in hydrogen silsesquioxane with near 100% pattern densities. Using aligned electron beam lithography, each side of the nanochannel structure is patterned as a separate layer. A 50000 uC/cm^2 high-dose anneal is applied to the first layer after exposure. Channels with widths below ~60 nm are shown to exhibit footing with standard tetramethyl ammonium hydroxide developers. This problem is resolved by adding surfectant during the development of the final channel structure. The resulting process produced channels
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Summary

A double patterning process is presented to pattern sub-35 nm wide channels in hydrogen silsesquioxane with near 100% pattern densities. Using aligned electron beam lithography, each side of the nanochannel structure is patterned as a separate layer. A 50000 uC/cm^2 high-dose anneal is applied to the first layer after exposure...

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Nanochannel fabrication based on double patterning with hydrogen silsesquioxane

Engineered liquid crystal anchoring energies with nanopatterned surfaces

January 26, 2015
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Journal Article
Author:
Christopher Gear
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Published in:
Opt. Express, Vol. 23, No. 2, 26 January 2015, pp. 807-14.
Topic:
optics
R&D area:
R&D group:

Summary

The anchoring energy of liquid crystals was shown to be tunable by surface nanopatterning of periodic lines and spaces. Both the pitch and height were varied using hydrogen silsesquioxane negative tone electron beam resist, providing for flexibility in magnitude and spatial distribution of the anchoring energy. Using twisted nematic liquid crystal cells, it was shown that this energy is tunable over an order of magnitude. These results agree with a literature model which predicts the anchoring energy of sinusoidal grooves.
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Summary

The anchoring energy of liquid crystals was shown to be tunable by surface nanopatterning of periodic lines and spaces. Both the pitch and height were varied using hydrogen silsesquioxane negative tone electron beam resist, providing for flexibility in magnitude and spatial distribution of the anchoring energy. Using twisted nematic liquid...

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Engineered liquid crystal anchoring energies with nanopatterned surfaces

Materials and fabrication sequences for water soluble silicon integrated circuits at the 90 nm node

January 5, 2015
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Journal Article
Author:
Lan Yin
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Published in:
Appl. Phys. Lett., Vol. 106, No. 1, 5 January 2015, 014105.
Topic:
integrated circuit
R&D area:
R&D group:

Summary

Tungsten interconnects in silicon integrated circuits built at the 90 nm node with releasable configurations on silicon on insulator wafers serve as the basis for advanced forms of water-soluble electronics. These physically transient systems have potential uses in applications that range from temporary biomedical implants to zero-waste environmental sensors. Systemic experimental studies and modeling efforts reveal essential aspects of electrical performance in field effect transistors and complementary ring oscillators with as many as 499 stages. Accelerated tests reveal timescales for dissolution of the various constituent materials, including tungsten, silicon, and silicon dioxide. The results demonstrate that silicon complementary metal-oxide-semiconductor circuits formed with tungsten interconnects in foundry-compatible fabrication processes can serve as a path to high performance, mass-produced transient electronic systems.
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Summary

Tungsten interconnects in silicon integrated circuits built at the 90 nm node with releasable configurations on silicon on insulator wafers serve as the basis for advanced forms of water-soluble electronics. These physically transient systems have potential uses in applications that range from temporary biomedical implants to zero-waste environmental sensors. Systemic...

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Materials and fabrication sequences for water soluble silicon integrated circuits at the 90 nm node

Trace aerosol detection and identification by dynamic photoacoustic spectroscopy

December 15, 2014
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Journal Article
Author:
Ryan M. Sullenberger
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Published in:
Opt. Express, Vol. 22, No. 25, 15 December 2014, pp. A1810-A1817.
Topic:
detection systems
R&D area:
R&D group:

Summary

Dynamic photoacoustic spectroscopy (DPAS) is a high sensitivity technique for standoff detection of trace vapors. A field-portable DPAS system has potential as an early warning provider for gaseous-based chemical threats. For the first time, we utilize DPAS to successfully detect the presence of trace aerosols. Aerosol identification via long-wavelength infrared (LWIR) spectra is demonstrated. We estimate the sensitivity of our DPAS system to aerosols comprised of silica particles is comparable to that of SF6 gas based on a signal level per absorbance unit metric for the two materials. The implications of the measurements are discussed.
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Summary

Dynamic photoacoustic spectroscopy (DPAS) is a high sensitivity technique for standoff detection of trace vapors. A field-portable DPAS system has potential as an early warning provider for gaseous-based chemical threats. For the first time, we utilize DPAS to successfully detect the presence of trace aerosols. Aerosol identification via long-wavelength infrared...

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Trace aerosol detection and identification by dynamic photoacoustic spectroscopy

Optical phased-array ladar

November 1, 2014
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Journal Article
Author:
Juan C. Montoya
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Published in:
Appl. Opt., Vol. 53, No. 31, 1 November 2014, pp. 7551-5.
Topic:
ladar
R&D area:
R&D group:

Summary

We demonstrate a ladar with 0.5 m class range resolution obtained by integrating a continuous-wave optical phased-array transmitter with a Geiger-mode avalanche photodiode receiver array. In contrast with conventional ladar systems, an array of continuous-wave sources is used to effectively pulse illuminate a target by electro-optically steering far-field fringes. From the reference frame of a point in the far field, a steered fringe appears as a pulse. Range information is thus obtained by measuring the arrival time of a pulse return from a target to a receiver pixel. This ladar system offers a number of benefits, including broad spectral coverage, high efficiency, small size, power scalability, and versatility.
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Summary

We demonstrate a ladar with 0.5 m class range resolution obtained by integrating a continuous-wave optical phased-array transmitter with a Geiger-mode avalanche photodiode receiver array. In contrast with conventional ladar systems, an array of continuous-wave sources is used to effectively pulse illuminate a target by electro-optically steering far-field fringes. From...

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Optical phased-array ladar

Increasing the coherence time in a magnetically-sensitive stimulated Raman transition in 85Rb

October 14, 2014
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Conference Paper
Author:
Sara A. DeSavage
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Published in:
FIO 2014: Frontiers in Optics, 14 October 2014.
Topic:
quantum
R&D area:
R&D group:

Summary

We experimentally study the Ramsey, spin echo, and CPMG pulse sequences of a magnetically sensitive transition of a cold 85Rb gas. We can increase the coherence time by up to a factor of 10 by using CPMG pulse sequences as compared to Ramsey or spin echo.
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Summary

We experimentally study the Ramsey, spin echo, and CPMG pulse sequences of a magnetically sensitive transition of a cold 85Rb gas. We can increase the coherence time by up to a factor of 10 by using CPMG pulse sequences as compared to Ramsey or spin echo.

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Increasing the coherence time in a magnetically-sensitive stimulated Raman transition in 85Rb

Energy efficiency benefits of subthreshold-optimized transistors for digital logic

October 6, 2014
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Conference Paper
Author:
Peter J. Grossmann
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Published in:
2014 IEEE SOI-3D-Subthreshold Microelectronics Technology Unified Conf. (S3S), 6-9 October 2014.
Topic:
integrated circuit
R&D area:
R&D group:

Summary

The minimum energy point of an integrated circuit (IC) is defined as the value of the supply voltage at which the energy per operation of the circuit is minimized. Several factors influence what the value of this voltage can be, including the topology of the circuit itself, the input activity factor, and the process technology in which the circuit is implemented. For application-specific ICs (ASICs), the minimum energy point usually occurs at a subthreshold supply voltage. Advances in subthreshold circuit design now permit correct circuit operation at, or even below, the minimum energy point. Since energy consumption is proportional to the square of the supply voltage, circuit design techniques and process technology choices that reduce the minimum energy point inherently improve the energy efficiency of ICs. Previous research has shown that optimizing process technology for subthreshold operation can improve IC energy efficiency. This, coupled with the energy efficiency advantages offered by fully-depleted silicon-on-insulator (FDSOI) processes, have led to the development of a subthreshold-optimized FDSOI process at MIT Lincoln Laboratory (MITLL) called xLP (Extreme Low Power). However, to date there has not been a quantitative estimate of the energy efficiency benefit of xLP or other analagous technology for complex digital circuits. This paper will show via simulation that the xLP process technology enables energy efficiency improvements that exceed that of process scaling by one generation. Specifically, the process is shown to improve power delay product by 57% vs. the IBM 90nm low power bulk process, and by 9% vs. the IBM 65 nm low power bulk technology at 0.3V.
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Summary

The minimum energy point of an integrated circuit (IC) is defined as the value of the supply voltage at which the energy per operation of the circuit is minimized. Several factors influence what the value of this voltage can be, including the topology of the circuit itself, the input activity...

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Energy efficiency benefits of subthreshold-optimized transistors for digital logic

Liquid crystal uncooled thermal imager development

September 9, 2014
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Conference Paper
Author:
Harry R. Clark Jr
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Published in:
2014 Military Sensing Symposia, (MSS 2014), Detectors and Materials, 9 September 2014.
Topic:
sensors
R&D area:
R&D group:

Summary

An uncooled thermal imager is being developed based on a liquid crystal transducer. The liquid crystal transducer changes a long-wavelength infrared scene into a visible image as opposed to an electric signal in microbolometers. This approach has the potential for making a more flexible thermal sensor. One objective is to develop imager technology scalable to large formats (tens of megapixels) while maintaining or improving the noise equivalent temperature difference (NETD) compared to microbolometers. Our work is demonstrating that the liquid crystals have the required performance (sensitivity, dynamic range, speed, etc.) to make state-of-the-art uncooled imagers. A process has been developed and arrays have been fabricated using the liquid crystals. A breadboard camera system has been assembled to test the imagers. Results of the measurements are discussed.
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Summary

An uncooled thermal imager is being developed based on a liquid crystal transducer. The liquid crystal transducer changes a long-wavelength infrared scene into a visible image as opposed to an electric signal in microbolometers. This approach has the potential for making a more flexible thermal sensor. One objective is to...

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Liquid crystal uncooled thermal imager development
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