TECHNICAL ACTIVITIES 1998 -
NISTIR 6268
OPTICAL TECHNOLOGY DIVISION
MISSION
ORGANIZATION
CURRENT DIRECTIONS
TECHNICAL HIGHLIGHTS
FUTURE DIRECTIONS
FUTURE DIRECTIONS
- Machining Process Metrology and Simulation. In collaboration with
the Manufacturing Engineering Laboratory (MEL) and the Information Technology
Laboratory (ITL), the Optical Technology Division was recently funded by the
Advanced Technology Program (ATP) to support research on fundamental
predictive modeling and simulation of machining processes. The goal is to
achieve accurate measurements of the temperature and stress fields near the
tool-chip interface in order to validate machining simulations. The validation
of the modeling will improve the predictive capabilities of these models,
which is in great demand because of rapid progress in machining processes. The
Optical Technology Division is responsible for the development of an accurate
infrared pyrometer that will be used for non-contact thermometry of the
tool-chip interface in test bed experiments at NIST. The range of temperatures
to be studied is from room temperature to about 700 K. High spatial
resolution and fast response time requirements have led to a design that
incorporates an all reflective objective, an x-y galvo scanner, and an InGaAs
detector. This Scanning MicroPyrometer (SCAMPY) will be radiometrically
calibrated using blackbody standards in the Optical Technology Division. The
emissivity of the tool and the stock material will also be characterized.
- Terahertz Dynamical Measurements of Proteins and DNA. Determining
the time-dependent variation in tertiary structure and molecule-biopolymer
interactions is crucial towards obtaining a better picture of the biological
function of enzymes, protein-drug interactions and DNA helix transitions. The
new THz Competence Program will develop a joint research program involving the
Optical Technology Division and the Center for Neutron Research in the
Materials Science and Engineering Laboratory. We plan to employ
state-of-the-art, pulsed, terahertz (THz) optical techniques and high
resolution, neutron scattering, techniques to explore the microscopic,
concerted, nuclear motions associated with molecular structural changes over
various timescales (picoseconds to milliseconds). It is envisioned that, in
FY 1999, alterations to the current, pulsed-THz, laser apparatus will
enable acquisition of time sequenced spectra after imparting a sample
temperature jump by a laser pulse. Application of modern, molecular dynamics,
modeling simulations will be used to aid in the assignment of observed,
low-frequency, spectroscopic structure and the origin of their measured,
time-dependent changes.
- Single Molecules as a Probe of the Local Environment. The behavior
of a single molecule depends on its immediate environment in a way that is not
well understood. Single dye molecules adsorbed onto a surface exhibit
time-dependent spectra and changes in lifetime presumed to be dependent on the
details of the surface in the close vicinity, as well as conformal or
positional changes in the molecule or the surface. In principle, it should be
possible to use the spectra or lifetime of a single molecule to investigate
the nanoscale structure of the surface or film that the molecule is on or in.
In order to test this hypothesis and begin to understand single molecule
spectra, we are building a confocal microscope capable of imaging single
molecules. Test samples consisting of dye molecules embedded in self-organized
films will be constructed and the spectra and/or lifetime studied and modeled.
- Continuous-Wave Mid-infrared Cavity Ringdown Saturation
Spectroscopy. Cavity ringdown spectroscopy has been shown at NIST and
elsewhere to be a sensitive technique for measuring the linear absorption
spectra of atoms and molecules in the near infrared and visible at optical
pathlengths on the order of kilometers. We have recently extended the
capabilities of cavity ringdown spectroscopy to the mid-infrared using a
CO2 laser with tunable microwave sidebands. Molecular vibrational
absorption coefficients are orders of magnitude larger in the mid-infrared
than in the near infrared or visible. Thus, mid-infrared, cavity ringdown
spectroscopy offers the opportunity for significantly increased sensitivity
for concentration measurements over near infrared and visible measurements.
The large absorption coefficients in the mid-infrared have led to the
observation of saturation dips on the absorption lines, which improves the
frequency precision of the cavity ringdown measurements by more than a factor
of 10. In addition, measurements of the linewidths of the saturation dips,
which arise primarily from power broadening, furnish a method for the absolute
determination of transition moments without knowledge of species
concentration. Cavity ringdown spectroscopy thus offers exciting potential for
determining the absolute absorption coefficients of many unstable molecules.
- Spectral Irradiance and Radiance Calibrations with Uniform Sources
(SIRCUS). A reference calibration facility is being developed to realize a
detector spectral irradiance response scale directly against the High Accuracy
Cryogenic Radiometer (HACR). This high accuracy, detector-based scale will be
the basis for the illuminance (candela), the color temperature, the radiance
temperature, and the spectral radiance response scales of NIST. High
performance, transfer- and working-standard radiometers will be developed to
realize the irradiance response scale for the UV, VIS, NIR, and IR ranges. The
monochromatic source is being realized with stabilized tunable lasers and
different size integrating spheres. This versatile, high intensity, radiation
source, in addition to the collimated beam geometry, can be used as a point
source and/or a large area Lambertian source. The point source geometry and
the inverse square law will be utilized to further minimize the illuminance
scale uncertainties. The Lambertian sources will be calibrated against the
standard irradiance meters. Standards quality radiance meters, calibrated
against the Lambertian sources will provide the spectral radiance response
scale. A new facility for spectroradiometric source calibration is being
designed that will utilize detectors calibrated on SIRCUS.
- New Source-based Radiometry Beamline at SURF III. Synchrotron
radiation from SURF has been used as an accurate standard light source for
NIST because of its predictable nature. With the upgrade of SURF II to
SURF III, this facility will further improve its accuracy as a light
source to an unprecedented level. To fully utilize SURF for source-based
radiometry, we are developing a new, white-light beamline for SURF III.
This beamline will allow unobstructed synchrotron radiation to irradiate
detectors (such as spectrally dispersed radiometers) to measure their
response. These radiometers are then used to intercompare synchrotron
radiation with other standard light sources, such as blackbody radiation, arc
lamps, and FEL lamps. The intercomparison between SURF and other NIST standard
light sources can improve and maintain NIST scales, especially in the
ultraviolet region where SURF has higher radiant power than any other standard
light sources. The new beamline can also be used as a general facility for
absolute light source calibration.
- Development of a Second Generation Cryogenic Radiometer:
HACR 2. A new cryogenic radiometer with a lower uncertainty and
greater dynamic range is being developed to replace the present absolute
standard, HACR, as the basis for NIST optical calibration scales. The
improvements designed into HACR 2 are its operation at 2 K to reduce
the noise in the temperature measurements, its operation over a greater
dynamic range to avoid nonlinearity corrections to the calibration transfers,
and a receiving cavity with a horizontal geometry to facilitate calibration
transfers. The dynamic range of HACR 2 will be from 1 µW to
1 mW with an intended uncertainty of 0.01% or better. The fully automated
HACR 2 facility will be sharing the laser resources of SIRCUS and be able
to provide calibrations at wavelengths from 180 nm to 11 µm. By
designing HACR 2 to operate at the power levels of other optical
facilities, to be accessible to the wide range of laser resources, and to ease
the method of calibration transfers, the overall uncertainty in the optical
calibration scales based on the cryogenic radiometer is reduced.
- UV Radiometry for Semiconductor Lithography. A new UV Fourier
Transform Spectrometer is nearing completion and will be used to characterize
the index of fused silica and calcium fluoride with a target accuracy of
1 part in 106. The UV FTS will also be used to characterize
the refractive index of purge gasses (such as nitrogen at 157 nm) with an
accuracy that is consistent with the needs of the stepper manufacturers which
has not been previously been measured. Efforts are being made to upgrade the
goniometric refractometer and measure the refractive index of calcium fluoride
to an accuracy of 1 part in 105. Various photodetectors will
be characterized and their stability towards irradiation from an excimer laser
operating at 193 nm and at 157 nm will be measured. An improved UV
responsivity scale will be realized with the use of synchrotron radiation from
SURF III in conjunction with a cryogenic radiometer.
Mission | Organization | Current Directions | Technical Highlights |
Future Directions
TECHNICAL ACTIVITIES 1998
- Contents
Pages designed and maintained by the Office of ECSED.
Inquiries or comments: Feedback.
Online: April 1999