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The
National Institute of Standards and Technology (NIST), in cooperation
with the National Research Council (NRC), offers awards for postdoctoral
research in many fields. These awards provide a select group of scientists
and engineers an opportunity for research in many of the areas that are
of deep concern to the scientific and technological community of the nation.
NIST, with direct responsibilities for the nation’s measurement network,
involves its laboratories in the most modern developments in the physical,
engineering, and mathematical sciences and the technological development
that proceed from them. The NRC, through its Associateship Programs office,
conducts a bi-annual national competition to recommend and make awards
to outstanding scientists and engineers at the postdoctoral level for
tenure as guest researchers at participating laboratories. The first deadline
for applications is February 1, 2006 for appointments beginning between
July 1 and December 31, 2006; the second competition's deadline will be
August 1, 2006 for appointments beginning between January 1 and June 30,
2007.
The
Objectives of the Programs are:
- To
provide postdoctoral scientists and engineers of unusual promise and
ability opportunities for research on problems, largely of their own
choosing, that are compatible with the interest of the sponsoring
laboratories.
- To
contribute thereby to the overall efforts of the federal laboratories.
Eligibility requirements include U.S. citizenship and receipt of Ph.D.
within 5 years of application. NRC positions involve a two-year tenure
at NIST in Boulder Colorado, and the annual basic salary for the 2006
program year is $55,700 plus $5,500 to support professional travel,
books, incidental research expenses. Other benefits include: relocation
expenses, health and life insurance and a retirement plan.
For more detailed
information, including instructions for applicants, please contact the
Optoelectronics Division Office and request a copy of the NRC Postdoctoral
Opportunities booklet. You may also visit the NRC Research Associateship
Program web page (http://national-academies.org/rap) to see a list of
opportunities within our division. A PDF copy of the Associateship Program
Brochure can be found here.
Opportunities
for the Year 2006 with the Optoelectronics Division Through the NRC Research
Associateship Program:
Quantum
Dot Morphology
Advisor: A. Roshko
RO#: 50.81.52.B4379
Quantum dots have attracted a great deal of interest because of their
unique properties and possibilities for optoelectronic applications. However,
control of dot density, composition, position, size, and shape remain
major obstacles for many device applications. We invite proposals to address
these issues through an investigation of quantum dot morphology as a function
of growth parameters, such as temperature, rate, thickness, composition,
and dot stacking. Studies of the interrelations between these variables
and strain state are also of interest. State-of-the-art molecular beam
epitaxy with reflected high-energy electron diffraction, atomic force
microscopy, high-resolution x-ray diffraction, and transmission electron
microscopy are available for analyzing quantum dot distributions, heights,
shapes, spacings, and strain fields. Correlation with optical properties,
such as photoluminescence, is also of interest. The work will contribute
to a more complete understanding of quantum dot morphology, how it correlates
with device performance, and how it can be controlled through the choice
of growth conditions.
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Molecular
Spectroscopy Using Ring-Down Cavities and its Application to Semiconductor
Crystal Growth
Advisor: K.A. Bertness
RO#: 50.81.52.B5883
Gases such as phosphine, ammonia, arsine, nitrogen, silane, and germane
are widely used in semiconductor synthesis and processing. Most of these
processes are highly sensitive to contamination, although the precise
incorporation mechanisms and concentrations of concern are poorly known.
We have developed cavity ring-down spectroscopy as a tool for high sensitivity
measurements of impurities in gases along with the capability of using
many of these gases in gas-source molecular beam epitaxy growth. The system
has a sensitivity for measuring water as an impurity down to approximately
30 ppb in phosphine and 10 ppb in nitrogen using laser light near 935
nm. We anticipate the availability of new laser sources in the next few
years that will significantly enhance the flexibility and sensitivity
of the instrument. Because of its fast time response, cavity ring-down
spectroscopy is also useful for measuring time-dependent effects and confirming
the efficacy of purifiers. We invite proposals extending the capability
of the instrument to new impurities or host gases (e.g, novel studies
of correlations of gas properties with semiconductor crystal properties
and fundamental studies of the impurity incorporation process).
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Photonic
Crystals
Advisor: R. Mirin
RO#: 50.81.52.B3901
Photonic crystals are meta-materials whose optical properties are determined
by the photonic band structure that arises from resonant photon scattering
off the nanometer-scale physical structure, in direct analogy with well-established
concepts of electronic bands in semiconductors. Photonic crystals offer
the new possibility of creating materials with custom-tailored bandgaps
and dispersion curves, liberating light-emitting devices from the constraints
caused by the underlying material dispersion. We are pursuing an active
program of photonic crystal dispersion engineering with the aim of vastly
enhancing the performance of semiconductor light emitters. Specifically,
we are designing, fabricating, and measuring photonic crystal nanocavities
for Purcell-enhanced single-photon sources, circular Bragg gratings for
enhanced light extraction in LEDs, chirped waveguide gratings for dispersion
control in semiconductor mode-locked lasers, and waveguide arrays for
nonlinear soliton formation. Our capabilities include electromagnetic
modeling, nanofabrication, quantum-optical measurements and ultrafast
measurements.
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Semiconductor
Quantum Optics
Advisor: R. Mirin
RO#: 50.81.52.B4380
We are developing a regulated source of single photons by fabricating
a single photon turnstile with a single quantum dot. Our goals include
spontaneous emission control and delivery of the individual photons to
any other on-chip location through photonic crystal waveguides. Important
technologies for this project include microcavities, microdisks, photonic
crystals, and nonlinear optics. We invite experimental and/or theoretical
proposals that can complement and expand on this ongoing effort. Available
resources include epitaxial semiconductor growth, e-beam lithography,
fabrication facilities, and finite difference time domain software for
electromagnetic modeling.
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Optical
Spectroscopy of Quantum Dots
Advisor: R. Mirin
RO#: 50.81.52.B5884
Self-assembled semiconductor quantum dots have been demonstrated for many
optoelectronic devices (lasers, optical amplifiers, and photodetectors)
and proposed for novel applications such as quantum computing. However,
there is still a lack of fundamental knowledge about the optical and electronic
properties of these quantum dots, such as homogeneous linewidth, oscillator
strength, coupling, and carrier escape mechanisms, especially at the single
quantum dot level. We invite proposals that will investigate these or
other fundamental characteristics of self-assembled quantum dots.
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Coherent
Spectroscopy of Quantum Dots
Advisor:
R. Mirin
RO#: 50.81.52.B6459
We are currently
performing high-resolution optical spectroscopy on self-assembled semiconductor
quantum dots. Our technique employs narrow linewidth tunable lasers and
heterodyne detection. Recent results from our group have shown that these
structures are almost purely radiatively broadened at 9 K. We are soliciting
proposals to extend this experimental method to investigate multi-exciton
and charged exciton complexes. We are interested in the fundamental properties
of these transitions as well as the coherence in these coupled-state systems.
Optical phenomena such as electromagnetic-induced transparency (EIT) should
be observable.
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MBE
Growth of Quantum Dots
Advisor: R. Mirin
RO#: 50.81.52.B5885
We are developing single photon sources based on epitaxially grown single
quantum dots. Many quantum dots are deposited during growth and individual
dots are isolated by masking and etching. The goal of this project is
to use novel methods of controlling the exact placement and size of the
quantum dots. This will enable schemes of coupling two or more quantum
dots for applications in quantum information and quantum optics.
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Engineered
Quantum States of Light
Advisors: R. Mirin, T. Clement
RO#: 50.81.52.B6460
We are investigating methods of creating new quantum states of light such
as Schrodinger cat states, NOON states, and Fock states. These new states
have a variety of applications, including linear optical quantum computing,
quantum metrology (for example, Heisenberg limited interferometry), and
fundamental physics (loop-hole free Bell measurements). We are particularly
interested in utilizing our high quantum efficiency photon number resolving
detectors to enable creation of these states. Our group includes both
experimentalists and theorists. We invite proposals to further develop
and utilize quantum states of light.
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Nanoscopic
Wide-Bandgap Materials Characterization by CW and Ultrafast Nonlinear
Optics
Advisor: N.A. Sanford, J.B. Schlager
RO#: 50.81.52.B4766
Near-field and confocal microscopies provide unique methods of characterizing
a wide variety of semiconductor, dielectric, and hybrid optoelectronic
materials and interfaces. We are developing methods of nanoscopic multi-photon
spectroscopy and nonlinear optics for examining local structural and electronic
properties of the wide-bandgap III-nitride alloy semiconductors. The techniques
include ultraviolet (UV) second-harmonic generation in addition to cw
and time-resolved, multi-photon UV spectroscopy that employ NSOM and confocal
techniques. We are particularly interested in the study of local defects,
polytyping, inversion domains, and alloy segregation; spectroscopy on
the scale of defect separation (roughly 100 nm); and ultrafast processes
involving interactions with strong static polarization fields in these
materials. The spectroscopic results are correlated with x-ray diffraction
imaging, high-resolution cathodoluminescence, and TEM.
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Metrology
and Prototyping of Wide-Bandgap Semiconductor Quantum Nanowire Structures
and Devices
Advisor: N.A. Sanford, K. Bertness, A. Roshko
RO#: 50.81.52.B5887
Semiconductor quantum nanowires offer new applications in areas such as
chemical sensors, NEMs, nanolasers, and nanoscale thermoelectric devices.
A key aspect of these structures that makes the research challenging and
enables the utility of various nanowire devices is that many physical
phenomena do not scale from the macro to nano regimes. Our research primarily
focuses on nanowires grown from wide-bandgap semiconductors including
the group III-nitride (GaN, AlN, InN) and ZnO material systems. We are
interested in nanowire growth techniques that include MBE, vapor transport,
and catalyst methods. We are interested in a range of research topics,
from the applied to the fundamental, covering such areas as understanding
the evolution of the microstructure of nitride semiconductors; development
of nanotemplates for patterned growth of nanowires; optimization of p-type
doping in nanostructures; developing methods of making electrical contact
to single nanowires or arrays of nanowires; and development of new measurement
methods for quantifying nanoscale piezoelectric, transport, and optoelectronic
phenomena. Current device interests include nanowire lasers, LEDs, photodetectors
(primarily in the UV), UV and visible light emitters (i.e., for solid
state lighting and water purification), and field emitting ion sources
for mass spectrometry. We are also working on the design and fabrication
of prototype nanowire electronic devices such as FETs. We welcome proposals
aimed at new technological aspects of semiconductor quantum nanowire research
and application. Our characterization resources include triple-axis x-ray
diffraction, atomic force microscopy, scanning electron microscopy, ultrafast
nonlinear optical characterization, near-field scanning optical microscopy,
cw and time-resolved photoluminescence, device processing, and electrical
measurements. Opportunities exist for collaborative work within NIST for
more specialized characterization such as TEM, field-emission SEM, STM,
cathodoluminescence, nanoscale electrical and thermal measurements.
Our existing programs use gas-source molecular beam epitaxy growth of
nitrides, phosphides, and arsenides with a focus on nanostructures. Other
in-house collaboration includes vapor phase and catalyst growth methods
for nanowire growth. Also, a wide range of clean room processing equipment
is available in order to carry out prototyping of specialized nanostructures.
Our
existing programs use gas-source molecular beam epitaxy growth of nitrides,
phosphides, and arsenides with a focus on nanostructures. Other in-house
collaboration includes vapor phase and catalyst growth methods for nanowire
growth. Also, a wide range of clean room processing equipment is available
in order to carry out prototyping of specialized nanostructures.
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In-Situ
Metrology of Epitaxial Crystal Growth for Semiconductor Optoelectronics
Advisor: K.A. Bertness, R.K. Hickernell
RO#: 50.81.52.B1560
Semiconductor optoelectronic devices are being employed in a variety of
applications, including telecommunications, computer interconnects, data
storage, display, printing, and sensor systems. Most of these devices
rely on accurate, reproducible epitaxial crystal growth; however, further
reductions in growth cost will require further development of in situ
and ex situ measurement tools. Our research focuses on optical in situ
material probes (i.e., pyrometry, atomic absorption spectroscopy, and
broadband normal-incidence optical reflectance) correlated with reflectance
high-energy electron diffraction, ex situ x-ray diffractometry, photoluminescence
spectroscopy, optical reflectance, and extensive modeling capabilities.
Other resources include in situ mass spectrometry, atomic force microscopy,
transmission electron microscopy, electrochemical profiling, and clean
room facilities for processing test and device structures. We have recently
demonstrated growth of GaN nanowires, and proposals specific to plasma
nitrogen characterization and monitoring of rough surfaces are encouraged.
We also examine the practical utility of various measurement tools through
the growth of device structures, with emphasis placed on vertical-cavity
surface-emitting lasers, in-plane lasers, quantum dot lasers, and saturable
Bragg absorbers.
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Superconducting
and Nanometer-Scale Devices for Infrared to Millimeter-Wave Applications
Advisor: E. Grossman
RO#: 50.81.42.B1533
Our goal is to explore the physical mechanisms and limitations of devices
operating in the frequency range from 0.1 to 100 THz, and to develop novel
devices and measurement techniques. For the short wavelength end, we use
electron-beam lithography to fabricate the submicron structures required
to minimize parasitic impedances. One specific research area includes
mixers and harmonic mixers for frequency synthesis and high-resolution
spectroscopy; another research area involves IR to millimeter-wave imaging
radiometry. Our main focus is on high-sensitivity bolometers and superconducting
multiplexers based on SQUIDS. Other devices of interest include high-Tc
superconducting bolometers; room-temperature, thin-film bolometers; lithographic
and/or micromachined coupling structures, particularly antennas and integrating
cavities; superconducting mixers/rectifiers; and room-temperature mixers/rectifiers
(e.g., lithographic metal-insulator-metal diodes).
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Flat
Panel Display Metrology
Advisor: E.F. Kelley (Boulder), P.A.
Boynton (Gaithersburg)
RO#: 50.81.11.B4369
NIST's flat panel display laboratory serves the display industry by developing
and quantifying good electronic display metrology for industrial use.
With the explosion of the information age, the Internet, and e-commerce,
the use of flat panel displays has become a growing need for US industries.
Good display measurement methods are needed for several reasons: (1) specification
language needs to rest solidly upon good metrology, (2) fierce competition
between technologies requires good metrology to distinguish features,
(3) users and implementers of displays need accurate characterizations
of displays for selection purposes. NIST is doing research in (1) equipment
on improving measurements made on displays; (2) development of display
metrology with various standards organizations; (3) development of display
metrology assessment methods and equipment to provide guidance for the
implementation of good measurement methods in the display industry; and(4)
display reflectance characterization, measurements, and modeling using
the bi-directional reflectance distribution function. Opportunities are
available at both Boulder and Gaithersburg campuses.
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High
Speed Optoelectronics Measurements
Advisor: P.D. Hale, D.F. Williams
RO#: 50.81.52.B4008
Increasing data rates and bandwidths of optical telecommunications, cable
television systems, remote microwave antenna links, and computer data
interconnections all require advanced techniques for accurately determining
optical transmitter and receiver frequency response in both magnitude
and phase. Methods being investigated at NIST include heterodyne and ultrashort
pulse technologies. Current research focuses on fully calibratable measurement
of frequency response with low uncertainty to 110 GHz and extension to
400 GHz in the near future. We are especially interested in the measurement
of response phase with low uncertainty using high-speed sampling techniques
and in methods for verifying these measurements in a coaxial or on-wafer
environment. Future calibration artifacts will require fabrication of
ultrafast photodetectors. We are also interested in theoretical studies
of the modulation characteristics, frequency response, spectral response,
saturation, and electrical characteristics of optical receivers that would
further enhance our metrology effort.
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High-Speed
Optical Receivers and Optoelectronic Integrated Circuits
Advisor: P.D. Hale, R.P. Mirin, D.F. Williams
RO#: 50.81.52.B4767
The need for ever smaller size and increased bandwidth of optoelectronic
devices is requiring these devices to be packaged in hybrid modules and
optoelectronic integrated circuits. Characterization of the frequency
response and electrical properties of these devices requires a change
in measurement strategy away from coaxially connected modular devices
to on wafer measurements. We are developing a new fully calibratable on-wafer
measurement paradigm for calibrating optoelectronic and electronic devices
to bandwidths exceeding 110 GHz. We are interested in fabricating new
high-speed receivers that will be used as calibration artifacts in this
new measurement strategy. Possible designs might include metal-semiconductor-metal
photoconductive switches or p-i-n photodiodes grown in low-temperature
GaAs or InGaAs. The work will result in artifacts that will be used to
calibrate high-speed measurement equipment.
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Optical
Pulse Characterization and System Monitoring
Advisor: P.D. Hale, K.B. Rochford, C.M. Wang, K.A. Remley, D.F.
Williams
RO#: 50.81.52.B4381
Optical component measurements alone will not be adequate to design and
operate the next generation of optical communications, which will include
dynamic channel add/drop switching, routing, gain control, equalization,
and dispersion compensation. Accurate methods to dynamically characterize
system impairment through measurements of optical signal amplitude, phase,
jitter, and noise are needed. We are soliciting proposals for methods
that will assess system impairment, particularly methods that will discriminate
between failure modes and offer insight into the strengths and weaknesses
of various modulation, error correction, and dispersion compensation schemes.
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Characterization
of Dispersion Compensation and Equalization Schemes
Advisor: P.D. Hale, K.B. Rochford, C.M. Wang, K.A. Remley, D.F.
Williams
RO#: 50.81.52.B6461
Various optical and electrical methods of dispersion compensation and
gain equalization are now being employed to extend the length of short
and long reach optical communications systems. Electrical impairments
known as frequency dependent loss and multipath interference also appear
in board level electrical interconnects, wireless communications, and
data storage. Although the impairments appear in systems that differ greatly
and can affect vastly different time scales, they can be addressed through
similar techniques of equalization and filtering. We are soliciting methods
for characterizing equalization and dispersion compensation methods, and
particularly their efficacy for correcting low probability impairments.
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Waveform
Metrology
Advisor: P.D. Hale
RO#: 50.81.52.B5521
Current techniques used by industry for characterizing digital waveforms,
both electrical and optical, are qualitative at best. As a result, the
specifications for test equipment and communication systems are conservative
and are not well understood. For example, the computer and communications
industries both need measurements of different types of jitter and inter-symbol
interference because these effects could cause erroneous bit transmission.
We have developed a world-class capability for characterizing and calibrating
equipment used in the acquisition of high-speed waveforms. We are looking
for proposals that will investigate calibrated waveform measurement and
the quantitative study of waveform metrics that characterize parameters
such as random jitter, inter-symbol interference, and eye margin.
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Tunable
Laser Ensemble Development for Laser Radiometry
Advisor: J.H. Lehman
RO#: 50.81.52.B5888
The calibration of laser and optical fiber meters over wavelengths ranging
from 200 nm to 1800 nm requires laser sources that are stable, broadly
tunable, and having well defined optical properties (e.g., polarization,
beam quality). Our goal is to go beyond merely demonstrating what wavelengths
may be produced by novel methods. We will demonstrate a variety of sources
that are continuously tunable over the entire wavelength of interest (200
nm to 1800 nm) and deliver the output of these sources to various laboratories
using optical fiber. This will enable cost-efficient, routine, calibration
services having low uncertainties. We may employ new methods and equipment
or optimize existing methods and equipment to ensure that NIST can provide
laser power measurement comparisons with standards laboratories around
the world as well as manufacturers of laser and optical fiber power measurement
equipment. Several new projects are under consideration to provide novel,
robust methods for the generation and transportation of tunable laser
light.
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Carbon
Nanotube Coatings for Laser Power and Energy Measurements
Advisor: J.H. Lehman
RO#: 50.81.52.B5889
Several areas of research are currently being pursued: improved coatings
for thermal detectors, ultraviolet detectors resistant to damage and aging,
and improved transfer standards for pulsed-laser radiation measurements.
In each case, our goal is to develop and maintain optical detectors that
are traceable to electrical standards for the purpose of maintaining calibration
services in the area of laser power and energy measurements. Nearly all
of the primary standards for laser power and energy measurements at NIST
are based on thermal detectors. Our goal is to establish carbon nanotube
coatings as a practical choice for the next generation of standards. We
also employ a variety of photodiode-based detectors as transfer standards
for routine laser power calibrations for our customers. In each of these
areas, the practical matters of providing cost-efficient, routine calibrations
having low uncertainties must be considered. Topics of interest also include
new technologies and/or methods for developing and transferring detector-calibration
information from one area to another.
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Ultraviolet
Laser Metrology
Advisor: J.H. Lehman, M.L. Dowell
RO#: 50.81.52.B1563
In recent years, ultraviolet (UV) laser-specifically diode lasers-have
found increased use in a variety of industrial, commercial, homeland security
and medical applications. For example applications range from high definition
digital video to detection of chemical and biological aerosols. Presently
there is no primary standard for calibration of high-power continuous
laser power meters. Aging and hardening of materials exposed to UV laser
radiation is among the challenges to developing new measurement tools.
Presently we are pursuing carbon nanotube based coatings for thermal detectors
as well as optoelectronic means of creating artificial spectra for calibration
of chemical, biological and explosive sensors. Our work includes the development
of high-accuracy UV primary and transfer standard detectors, beam profile
characterization, laser power, energy and dose measurement services.
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Optical
Coherence Tomography
Advisor: S.D. Dyer, P.A. Williams
RO#: 50.81.52.B5890
Optical coherence tomography (OCT) is an exciting technique to achieve
high-resolution, three-dimensional, in vivo images of human tissue. OCT
has excellent spatial resolution (1-10 micrometers), which is two orders
of magnitude better than ultrasound. OCT has applications ranging from
early detection of glaucoma to measuring the morphology of the arterial
plaques that may be responsible for 70 % of heart attacks. Our work is
focused on developing accurate, high-resolution OCT measurements. We are
applying OCT to measurements of tissue dispersion and absorption for tissue
identification and early disease diagnosis. We are particularly interested
in proposals on the topic of Mie scattering theory applied in a multiple
scattering geometry. Another interest is minimum phase and non-minimum
phase filters, and their applications to tissue measurements. We are also
developing high-accuracy polarization sensitive OCT measurements to assess
tissue anisotropy as a measure of tissue health.. We are also studying
the sources of the polarization speckle noise that degrades these measurements.
The accuracy of OCT distance measurements is limited by the scattering,
absorption, dispersion, and birefringence of the tissue, as well as the
lack of high-accuracy data on the refractive indices of various human
tissues. The refractive index is important because OCT measures the optical
path length, which is the product of the layer thickness with the group
refractive index. To address this problem, we would like to develop techniques
to accurately measure both thickness and refractive index.
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Fiber-Optic
Sensors
Advisor: S.D. Dyer
RO#: 50.81.52.B5522
Fiber-optic sensors are lightweight, tiny, and flexible, with low power
requirements and large dynamic range. They can detect a variety of measurands,
including strain, temperature, pressure, and electromagnetic quantities.
Much of our research focuses on fiber Bragg gratings (FBGs) for strain,
temperature, and pressure sensing. We are interested in developing high-accuracy
wavelength measurements for sensor calibration. Because hysteresis and
nonlinearity due to the FBG's polymer coating and adhesives affects sensor
calibration, we are also interested in novel measurement techniques to
characterize these effects. Other important topics include techniques
for distributed sensing with high-spatial resolution (<100 micrometers),
and understanding and improving the process of writing Bragg gratings
in optical fibers.
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Infrared
Frequency Comb Development and Applications
Advisor: N.R. Newbury
RO#: 50.81.52.B5523
A supercontinuum of light that spans over an octave in frequency can be
generated by launching pulses from femtosecond fiber lasers into highly
nonlinear optical fiber. Through recently developed techniques, this supercontinuum
can be phase-locked to a reference and thereby provide a stable frequency
comb with a spacing equal to that of the laser repetition rate. These
frequency combs have the potential to revolutionize optical frequency
metrology in the telecommunication band since optical frequencies can
now easily be measured relative to the time standard. We invite proposals
that explore the generation, properties, and applications of infrared
frequency combs. We are particularly interested in the generation of stable
frequency combs in the telecommunications band using either Femtosecond
fiber lasers or other laser technology that could be used for wavelength
metrology. Other examples of proposals include developing a better understanding
of the noise properties of the frequency comb, and exploring other uses
of the frequency comb related to LADAR, coherent communication or optical
coherence tomography applications.
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