5
Optical Technology Division

MISSION AND STRATEGIC PLAN

The mission of the Optical Technology Division (OTD) is to develop and provide national measurement standards and services to advance optical technologies spanning the terahertz through the infrared, visible, and ultraviolet spectral regions. In particular, this division is charged with maintaining two primary standards: (1) the unit of luminous intensity, the candela; and (2) the unit of temperature, the kelvin, above 1234.96 K. The strategic elements of the OTD are (1) to maintain and advance optical radiation standards traceable to the SI system of units, (2) to advance optical radiation measurement science to solve problems in critical and emerging technology areas of national importance, and (3) to disseminate optical radiation measurement technology and standards to industry, government, and academia.

SCOPE

The Optical Technology Division, located at NIST’s Gaithersburg, Maryland, campus, has 42 scientists/engineers, 81 NIST associates, and 6 administrative support staff, as of January 2010. Its FY 2009 budget was about $18.5 million, 61 percent of which was STRS funding.

The division’s projects and sustained activities fall roughly into three main categories: development and refinement of optical radiation standards, optical measurement methods, and the provision of optical measurement services.

Optical Radiation Standards

The OTD provides the optical radiation measurement science and standards to aid the advancement and application of optical technology.

Unique capabilities of the division include (1) the Spectral Irradiance and Radiance Calibrations with Uniform Sources facility, coupled with cryogenic radiometry; (2) the Low-Background Infrared facility, developed to calibrate user-supplied blackbodies that are used in turn to characterize low-background IR detectors; and (3) the Spectrally Tunable Lighting Facility for studies of spectrally tunable light-emitting diode lighting.

Optical Measurement Methods

The OTD strives to improve the accuracy, quality, and utility of optical measurements in burgeoning technology areas. Its accomplishments include the following: (1) spectral and spatial stray-light correction in optical systems, (2) follow-on satellite instrument-calibration conference, (3) bacteria identification with the quantum



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5 Optical Technology Division MISSION AND STRATEGIC PLAN The mission of the Optical Technology Division (OTD) is to develop and provide national measurement standards and services to advance optical technologies spanning the terahertz through the infrared, visible, and ultraviolet spectral regions. In particular, this division is charged with maintaining two primary standards: (1) the unit of luminous intensity, the candela; and (2) the unit of temperature, the kelvin, above 1234.96 K. The strategic elements of the OTD are (1) to maintain and advance optical radiation standards traceable to the SI system of units, (2) to advance optical radiation measurement science to solve problems in critical and emerging technology areas of national importance, and (3) to disseminate optical radiation measurement technology and standards to industry, government, and academia. SCOPE The Optical Technology Division, located at NIST’s Gaithersburg, Maryland, campus, has 42 scientists/engineers, 81 NIST associates, and 6 administrative support staff, as of January 2010. Its FY 2009 budget was about $18.5 million, 61 percent of which was STRS funding. The division’s projects and sustained activities fall roughly into three main categories: development and refinement of optical radiation standards, optical measurement methods, and the provision of optical measurement services. Optical Radiation Standards The OTD provides the optical radiation measurement science and standards to aid the advancement and application of optical technology. Unique capabilities of the division include (1) the Spectral Irradiance and Radiance Calibrations with Uniform Sources facility, coupled with cryogenic radiometry; (2) the Low-Background Infrared facility, developed to calibrate user-supplied blackbodies that are used in turn to characterize low-background IR detectors; and (3) the Spectrally Tunable Lighting Facility for studies of spectrally tunable light-emitting diode lighting. Optical Measurement Methods The OTD strives to improve the accuracy, quality, and utility of optical measurements in burgeoning technology areas. Its accomplishments include the following: (1) spectral and spatial stray-light correction in optical systems, (2) follow-on satellite instrument-calibration conference, (3) bacteria identification with the quantum 33

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dot method, (4) long chains of magnetic nanoparticles, and (5) an efficient, correlated two-photon source. Optical Measurement Services The OTD builds and maintains optical radiation measurement facilities that are among the best in the world in order to meet the continued need for standards and specialized measurements by governments and industry. Selected accomplishments in this area include the following: (1) a hyperspectral image projector for the calibration of remote sensing instruments; (2) a goniospectrometer that tackles translucence and other color challenges; (3) perceived and measured colors of retroreflective materials in traffic signs; (4) the Missile Defense Transfer Radiometer, employing a cryogenic Fourier transform spectrometer and an absolute cryogenic radiometer; and (5) improvements to the transportable SIRCUS system (Traveling SIRCUS). SIRCUS is a reference calibration facility to calibrate detectors and radiometers for spectral irradiance responsivity and spectral radiance responsivity from the UV to the IR. Tunable lasers are coupled to integrating spheres with an exit port to produce either uniform irradiance at a reference plane or uniform radiance within the sphere exit port at high levels. PROJECTS The projects and sustained activities of the Optical Technology Division are listed below in the subsections on the individual groups, although there is extensive intergroup collaboration underlying much of this work. Optical Thermometry and Spectral Methods Group The Optical Thermometry and Spectral Methods Group maintains, improves, and disseminates the national scales for the spectroradiometric measurement of radiation sources and temperatures. Methods developed for extremely accurate determination of aperture areas are important for Earth-orbiting sensors of the solar irradiance. A new activity in optical medical imaging involves members of this group. They are also engaged in basic research aimed at applying new techniques in quantum optics to revolutionize future radiometry standards. Optical Properties and Infrared Technology Group The Optical Properties and Infrared Technology Group establishes and disseminates primary measurement scales for the transmittance and reflectance of materials in the IR spectral region; it studies optical properties of materials in the near-, mid-, and far-IR spectral regions; it provides blackbody calibrations, research and development of accurate, high-precision radiometric measurements in low and ambient thermal background environments; and it develops and calibrates transfer standard radiometers to be used for on-site NIST-traceable measurements of missile defense sensor test chambers. The LBIR radiometry system is used for the latter activity. It is a 34

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unique resource for calibrating sensors—a capability that must be maintained for customers of the future. Optical Sensor Group The Optical Sensor Group establishes the national measurement scale for the SI unit the candela; it provides measurements of the absolute spectral responsivity of optical detectors in the spectral region from 200 nm through the IR traceable to a high-accuracy absolute cryogenic radiometer. Solid-state lighting, a critical component of future energy-efficiency improvements, is an important thrust of this group. The group is developing novel test methods for high-power LEDs and developing new metrics to evaluate the color rendering of light sources in general. Laser Applications Group The Laser Applications Group advances laser technology for applications in optical radiation and optical properties of materials measurements. This group developed the SIRCUS facility and the Primary Optical Watt Radiometer system. The Traveling SIRCUS development is currently being used for the calibration of future space-based instruments that are designed for long-term, high-accuracy measurements of radiance and/or irradiance. It will play an increasingly important role in instrument calibration. Biophysics Group The Biophysics Group develops advanced spectroscopic and microscopic measurement methods, nano-optical probes, and imaging technologies and associated theoretical models to solve important biophysics and bio-nanotechnology measurement science problems. The new activity in optical medical imaging involves members of this group. Group members are also involved in spectroscopic studies in the terahertz spectral region. STAFFING There are 42 full-time technical staff members in the Optical Technology Division; 3 more permanent staff will be added by the end of 2010. In addition, a far greater number of temporary, contractor, and part-time personnel than of permanent staff also contribute to this division. For example, there are 81 NIST associates. In the 2008 panel report, a concern was expressed that the ratio of permanent staff to total staff was quite low. This is being addressed. MAJOR EQUIPMENT AND FACILITIES Major facilities of the Optical Technology Division associated with maintaining national standards include the following: 35

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 National Standard for Optical Power: POWR—provides the optical power standard to 0.01 percent;  LBIR Facility—maintains the NIST infrared radiometric standard for instruments that need to be calibrated in background environments that are 80 K and below;  SIRCUS—a tunable laser-based facility for the absolute calibration of optical instruments, with the companion Traveling SIRCUS, used at external sites;  Facility for Spectral Irradiance Calibration of Sources (FASCAL 2)— provides the NIST spectral irradiance scale, covering the 200 nm to 2500 nm wavelength range;  Spectral Tri-function Automated Reference Reflectometer Facility—maintains the national scale of reflectance, including the bidirectional reflectance distribution function;  Telescope Calibration Facility—for the laboratory testing and evaluation of telescopes and telescope radiometric calibration methods; and  Spectrally Tunable Lighting Facility—for the study of spectral properties of LED lighting sources related to the effects of chromaticity, color rendering, and other aspects of spectra on lighting quality. Research results are coupled with LED “wall-plug efficiency” characteristics (as they evolve with continuing improvements in LED fabrication) to evaluate the overall energy efficiency of a variety of lighting sources. These facilities are at the core of the NIST mission. Research on new methods is also being carried out, with the possibility that new approaches (e.g., single-photon source and photon-counting detection) may supplement or substitute for certain of the current facilities. ASSESSMENT OF THE DIVISION Following is the summary of the panel’s assessment of the overall quality of the Optical Technology Division (including opportunities for improvement) in terms of the three criteria as requested by the NIST Director (see Chapter 1). Assessment Relative to Technical Merit The Optical Technology Division maintains a long-term core commitment to high-accuracy measurements in radiometry, photometry, and spectroradiometry. The division’s continuing efforts to develop new approaches to calibration over a wide spectral range, from the far infrared through the ultraviolet, are commendable. The division has invested significant resources in these areas, and it justifiably places emphasis on maintaining the laboratory investments as well as careful measurement methodologies as tools for external customers in the private and government sectors. The division has the institutional responsibility for maintaining two base Système International units: the unit of temperature, the kelvin, above 1234.96 K; and the unit of luminous intensity, the candela. The division also maintains the national scales for other 36

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optical radiation measurements and ensures their relationship to the SI units. These measurement responsibilities include derived photometric and radiometric units, the radiance temperature scale, spectral source and detector scales, and optical properties of materials, such as reflectance and transmittance. The division has maintained spectral irradiance standards and has validated through international comparisons that the achieved uncertainties are the lowest in the world over a wide spectral range. The POWR system has enabled the standard for optical power to be provided with an accuracy of 0.01 percent. The division has undertaken several collaborative projects for the calibration of satellite-based sensors. Its impact on space-based climate change assessments should grow in the future owing to these collaborations with NOAA and NASA. A core activity of the Optical Technology Division is the development of technical standards for industries relying on optical technologies. The division also has research programs to develop optical and spectroscopic tools for the improved understanding of processes required to support evolving technologies in industries such as the semiconductor, solid-state lighting, biotechnology, and health science industries. The division has led efforts in the development of new American National Standards Institute (ANSI) standards of the chromaticity of solid-state lighting products. In view of the wide range of activities in optical technology, the distinctiveness and relation to similar activities elsewhere must be examined using differing criteria. Within the area of optical standards, the activities in the Optical Technology Division are clearly distinctive in the United States. The facilities for maintaining standards that have been developed in the division do not exist elsewhere in the nation. The natural technical point of comparison for the optical standards lies in the research carried out in national laboratories in Europe. The division staff members are very well aware of comparable research and, indeed, engage in ongoing international comparisons and cross-calibration. Many of the other activities in optical technology, while not involving specific international optical standards, rely on highly refined measurement capabilities. Here the uniqueness of the activities results from the choice of the problems addressed as well as from the distinctiveness of the measurement capabilities themselves. One common standard of technical merit is the number and quality of publications in the technical literature and presentations at conferences. The division has a good record in this regard. The activities of the overall program constitute forefront research in areas that are relevant to the NIST mission. Assessment Relative to Adequacy of Resources Facilities Laboratory space has been much improved over the past few years. The division appears to have adequate resources to undertake its stated mission and objectives. Several laboratories are in new locations, and in general the overall increase in floor space offers much more flexibility and a much-improved environment in which the researchers work with their equipment. In 2008 it was known that the residents of the Advanced Measurement Laboratory, in large part the new Biophysics Group, would have to move in order to create space for a new center. Laboratory moves are always 37

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disruptive to some degree. The affected personnel have made the move. There have been a few start-up transients in the new locations; however, the staff is up and running in the new locations. Equipment The equipment and instrumentation are of high quality, evidence of healthy spending on equipment over the past few years. The equipment budget appears to be adequate, and the staff appears to be making insightful decisions in the vendor-selection process. Human Resources The permanent staff is capable, experienced, and motivated. Their results attest to their commitment to high-quality research and products. The panel does not review the capabilities and productivities of the short-term staff and contractors. The percentage of the research and technical population who are permanent staff is low, much less than 50 percent. The relatively low permanent staff population appears to be partially related to the NIST overhead structure, which places the preponderant portion of the overhead on the permanent staff, with little or no overhead being attached to the other technical personnel or the office or laboratory space usage. Another factor appears to be related to the extent to which support depends on external funding sources, which can create a mood of conservatism regarding hiring. The permanent members are the leaders of the division. There are many tasks and responsibilities of an institutional nature that they alone are capable of assuming. They also direct and mentor the other technical staff. Obviously the smaller the number of permanent staff, the greater the proportion of time required to fulfill these responsibilities. The risk is high that, in the event of the loss of one or two permanent staff, a multimonth disruption in progress would occur. It takes continuity and flexibility both to maintain a laboratory of outstanding quality and to be able to respond to new needs and new opportunities. Both capabilities are at risk with a low ratio of permanent staff to total researcher population. This issue is being addressed, and progress is being made toward the hiring of additional permanent staff. The division management has exhibited the confidence in the future needed to commit to offering additional permanent positions to a select group of very capable people. This is the start of a trend that should continue. Assessment Relative to Achievement of Stated Objectives and Desired Impact The research program in the Optical Technology Division in large part reflects careful strategic planning to respond to NIST and national priorities. The existence of a vibrant and dynamic strategic planning process can be seen in the development of the division’s 2010 strategic plan. Additionally, the development of the Solid State Lighting, Vision Science, and Greenhouse Gas measurement efforts demonstrate agility in addressing national priorities. 38

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The Optical Technology Division also demonstrates a commitment to developing technology that could be foundational in future standards, as evidenced by its continued investment in its quantum measurement program and related activities. Although these single-photon-based technologies may not be integrated into the larger standards effort for some time, the compact prototype units being developed by the Optical Thermometry and Spectral Methods Group could be deployed in the near future to help streamline calibration activities for research groups relying on single-photon-counting detection. Whereas several years ago there was no OTD work related to biological sciences, staff and projects are now in place (with extensive external collaborations) to address this strategic thrust. Also, in a related vein, the frontier of optical spectroscopy of nano- and molecular-scale objects has been impressively extended. The Optical Technology Division makes use of a variety of effective means for delivering the technical output of the division. For long-term research, the means are primarily the traditional methods of publication in the technical literature and presentations at conferences. For standards work, the division’s output takes the form of providing calibrations of customer sources and detectors and making available transfer standards. Several additional forms of disseminating the technical capabilities of the division have also been implemented. Notable among these are the organizing and/or hosting of specialized courses, tutorials, and workshops and the dissemination of specialized software. The latter has been implemented very effectively with respect to the analysis of optical scattering data. This flexible analysis program, developed in the division, has been very popular, with more than 1,000 downloads. The division evidently places a healthy emphasis on publicizing and disseminating much of its technical output. The OTD has an excellent balance, meeting immediate needs while developing new long-term programs. This approach will keep the division at the technical forefront and ensure significant long-term impact. The standards work has an impact through a widespread chain of technology, since calibration is essential for a wide spectrum of applications. Similarly, fundamental advances in the optical characterization of materials have broad impact beyond the immediate field of optical science. NIST has identified biosciences as a strategic area of emphasis. Activities of the Biophysics Group in this division are distributed among diverse optical technologies in applications related to biology. This diversity is elaborated in the expanded group descriptor of “Biophysics, Nanobiotechnology, and Biophotonics.” Altogether, this is a nascent effort, still in early stages of development. It is a vigorous enterprise as is evident from its appeal to postdoctoral fellows (five NRC fellows and three National Institutes of Health [NIH] fellows currently) as well as graduate students (two currently). Although currently a small number, the research personnel are a very capable group and obviously enthusiastic about their research. The biosciences thrust in the OTD relies heavily on multidisciplinary and interdisciplinary research. Collaborations are in place with NIH and university groups. A more formalized association with biologists is recognized as beneficial, but efforts to effect such an association with the Center for Advanced Research in Biotechnology (CARB) are currently on hold, as CARB’s own association with the University of Maryland is undergoing reorganization. One particularly promising new project within the biophysics focus is a NIST Director’s Innovations in Measurement Science program in optical medical imaging. A 39

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team of division scientists is working to achieve an enhanced surgical lighting environment for obtaining images with optimal human-vision contrast. Well-calibrated hyperspectral images of normal and diseased tissues are being acquired through collaborations with partners at various universities, and algorithms are being developed for quantifying disease and tissue states. Another effort applies biophotonic-based measurement science to support research into biomolecular structure, function, and interactions in cells and tissues. Recent accomplishments include a NIST Integrated Colony Enumerator, which may be a useful tool, and developments in the molecular imaging of cells based on fluorescent nanocrystal (nanodot) probes, which have been tested in malaria-infected red blood cells. Another division effort with biological implication concerns the physicochemical characterization of engineered nanoparticles. Raman spectroscopy and other measurements are being used to characterize carbon nanotubes and other nanoparticles with an aim to establishing improved standards. Such data are key to the assessment of the environmental, health, and safety impact of nanomaterials. Another component of the group is concerned with the molecular modeling of nanoscopic properties. Quantum mechanics and molecular dynamics simulations are used in coordination with experimental observations to establish force standards. Demonstrations include work on single-molecule extensions of deoxyribonucleic acid (DNA) in comparison with observations by atomic force microscopy. Finally, the terahertz metrology project is studying applications to protein misfolding. These studies are complicated by spectroscopic challenges from water, which is typically essential for biological systems. Additional Considerations The projects and sustained activities in the Optical Technology Division are well publicized and articulated in terms of the participation of the personnel—for example, in technical conferences, workshops, and short courses—and in terms of publications. In general, the division leadership was responsive to the findings expressed in the 2008 NRC panel report. Some particulars are discussed in the following paragraphs. It was stated in the 2008 NRC panel report that although the Biophysics Group seemingly fits into the Optical Technology Division, several other division chiefs included the activities of this group in their presentations of division activities. This brought up questions about the present and future “ownership” of this promising group. The 2008 panel suggested that it would be helpful to address this issue and to articulate the understanding of the extent of the “sharing” of the objectives and products of the biophysics thrust among the various divisions. A concern was the perception of a lack of coordination of efforts in this research area. It suggested that it would be helpful for the Physics Laboratory to elucidate a comprehensive plan for organizing and staffing its expanded role in the biophysics area to optimize its effectiveness. The Optical Technology Division has been responsive to this issue. It has provided more clarity about the application in this division of its expertise in spectroscopy, imaging, and remote sensing to biophysics investigations. It was clear that personnel in the Biophysics Group are in touch with ongoing biophysics investigations in 40

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the Quantum Physics Division (e.g., in developing biological force standards capabilities). This appears to be healthy collaboration, with promising results. The Optical Technology Division has outstanding measurement capabilities in the terahertz spectral region, originally based on traditional Fourier transform techniques, more recently developing forefront capabilities for measurements using laser sources, including both frequency-domain and time-domain approaches. The suite of measurement capabilities is outstanding. A significant investment has been made in the terahertz laser source technology resident in this division, and it is attracting a number of outstanding postdoctoral fellows. It was stated in the 2008 NRC panel report that the terahertz research appeared to be at a crossroads. It was obvious (and still is) that the senior researchers in this area are very capable and are internationally recognized for their research in spectroscopy. The 2008 panel had questions about the future applications and future customers of this capability in this division. The principals on the permanent staff are associated with the new Biophysics Group and have been investigating potentially relevant applications of terahertz spectroscopy. They have been addressing the obvious problem associated with application of terahertz tools to biological research, namely, the very strong water absorption throughout the terahertz region of the spectrum. The terahertz spectroscopic study of the amino acid L-proline molecule within a reverse micelle is an interesting way of mitigating the water absorption problem. The observed terahertz resonances will be used to refine a structural model of this protein building block in an aqueous environment. Terahertz spectroscopy is also being applied to other investigations not related to biophysics. This appears to be of the nature of curiosity-driven research. One application area, related to submillimeter-wave and terahertz observations of Earth’s atmosphere from space, may become an area of emphasis as observations in this spectral region become increasingly important in climate change studies. The expansion of the Traveling SIRCUS capability is an ongoing activity. The OTD is pursuing this expansion by using American Recovery and Reinvestment Act of 2009 (ARRA; Public Law 111-5) funding to commercially acquire advanced laser systems and other associated equipment. Once the equipment is delivered, the system will be configured. The new system will permit the deployment of the Traveling SIRCUS to two additional facilities simultaneously. CONCLUSIONS AND RECOMMENDATIONS Conclusions The Optical Technology Division is successfully maintaining its long-term core commitment to high-accuracy measurements in radiometry, photometry, and spectroradiometry. This capability is central to the NIST mission. Core facilities continue to be operational, and new methods and techniques are continuing to be developed. The OTD has engaged in strategic planning that involves new areas of emphasis. The staff are capable and motivated; however, the mix between permanent 41

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staff and temporary and contract personnel appears suboptimal for long-term health and consistency in meeting strategic objectives. The calibration and sensor facilities have only two or three peers worldwide and clearly no domestic equivalents. One notable example of the use of this capability as an important element of the climate change initiative is highlighted. SIRCUS—Spectral Irradiance and Radiance Calibrations with Uniform Sources—is designed to provide a means of absolute calibration of optical instrumentation. The combination of coupling the light from stabilized tunable lasers with integrating spheres has led to a revolutionary facility for irradiance and radiance calibration. The Primary Optical Watt Radiometer system is an element of SIRCUS. The Traveling SIRCUS version can support a wide range of activities, including system calibration for satellite sensors, including calibration of total solar irradiance sensors. The staff reported that the Traveling SIRCUS and several members of staff were involved in the calibration of the NPOESS Visible Infrared Imager Radiometer Suite instrument, a very important sensor that has the potential to provide valuable data for the study of climate change, if properly calibrated. The advanced research effort in the area of Quantum Information Science is also of high quality, comparable to major academic programs throughout the country. The research into the radiometric applications of correlated photon states is unique. Concerns remain regarding the relatively small number of permanent staff—that is, those who must be counted on to continually lead the effort to achieve the core mission and realize the strategic plan of the division. The staffing issue is being addressed, and a trend in the right direction has begun. Recommendations A specific recommendation relates to the Greenhouse Gas Measurements thrust, a recent OTD initiative with the aim of quantifying greenhouse gas emissions from distributed-area sources. The instrumentation in this laboratory is in the early stages of development. At present the laboratory is developing direct absorption methods using differential absorption lidar. Although this laboratory has potential, considerable effort will be required to accomplish its objectives. Additional funding will be required to upgrade the instrumentation currently available in the laboratory. Care must also be taken in the efforts to measure quantities such as greenhouse gas fluxes using a limited number of ground-based sensors. The researchers should also take care in designing the proposed differential absorption lidar testing facilities to make certain that the test range will provide the necessary absorption paths to meet the needs for the required validation. 42