An Assessment of the National Institute of Standards and Technology Physics Laboratory: Fiscal Year 2008 (2008)

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Optical Technology Division DESCRIPTION OF THE DIVISION Mission The Optical Technology Division’s mission is to provide the foundation for optical radiation measurements for the nation. In particular, this division is charged with maintaining two primary standards: the candela, and the kelvin above 1234.96 K, the freezing point of silver. The division’s strategy is to develop and disseminate national measurement standards and services to advance optical technologies spanning the terahertz through the ultraviolet (UV) spectral regions. The division’s approach to implementing this strategy has three main elements. The first is to develop and provide optical radiation standards based on the Système International (SI units). The second is to develop novel measurement methods for solving problems in critical and emerging technology areas. The third is to disseminate optical radiation measurements and standards to commerce, industry, government, and academia. Scope The division activities fall into three main categories—the development and refinement of optical radiation standards, optical measurement methods, and optical measurement services. The division provides the optical radiation measurement science and standards to aid the advancement and application of optical technology. Its accomplishments include new spectral irradiance standards from the SURF III facility; the development of total spectral radiant flux standards; and the development of the Low Background Infrared (LBIR) Facility for missile defense sensors. The division strives to improve the accuracy, quality, and utility of optical measurements in burgeoning technology areas. Its accomplishments include spectral and spatial stray light correction in optical systems, satellite instrument calibration, bacteria identification with a variation of the quantum dot method, assembling magnetic nanoparticles into long chains, and construction of an efficient two-photon source. The delivery and refinement of core radiometric calibrations to external customers, including other government agencies, have been ongoing accomplishments. The division builds and maintains state-of-the-art optical radiation measurement facilities to meet the continued need for standards and specialized measurements by government and industry. Its accomplishments include the development of a hyperspectral image projector for the calibration of remote sensing instruments; research in the area of tackling translucence and other color challenges with the goniospectrom- eter, an instrument for precisely measuring the intensity of light reflected from the surface of a sample; and the study of perceived and measured colors of retroreflective materials in traffic signs. 33 

Projects The Optical Thermometry and Spectral Methods Group maintains, improves, and disseminates the national scales for the spectroradiometric measurement of radiation sources and temperatures. This group is also engaged in basic research aimed at applying new techniques in quantum optics to revolutionize future radiometry standards. The Optical Properties and Infrared Technology Group establishes and disseminates primary measurement scales for the transmittance and reflectance of materials in the infrared (IR) spectral region; studies optical properties of materials in the near-, mid-, and far-infrared spectral regions; provides blackbody calibrations; performs research and development work to achieve accurate, high-precision radiometric measurements at low and ambient thermal background environments; and develops and calibrates transfer standard radiometers to be used for on-site NIST-traceable measurements of missile defense sensor test chambers. The Optical Sensor Group establishes the national measurement scale for the SI unit the candela and provides measurements of the absolute spectral responsivity of optical detectors in the spectral region from 200 nm through the IR using a high-accuracy absolute cryogenic radiometer. The Laser Applications Group advances laser and synchrotron radiation technology for applications in optical radiation and measurements of optical properties of materials. The Biophysics Group develops advanced spectroscopic and microscopic measurement methods, nano-optical probes, and imaging technologies and associated theoretical models to solve important science problems in biophysics and bionanotechnology. Staffing The division has 35 permanent technical staff members and 6 permanent support staff members across its groups—the Optical Thermometry and Spectral Methods Group, the Optical Properties and Infrared Technology Group, the Optical Sensor Group, the Laser Applications Group, and the Biophysics Group. Major Equipment, Facilities, Ancillary Support, and Resources The facilities of the Optical Technology Division associated with maintaining national standards include the following: • The National Standard for Optical Power: the Primary Optical Watt Radiometer (POWR) provides the optical power standard to 0.01 percent; • The LBIR Facility maintains the NIST infrared radiometric standard for instruments that need to be calibrated in background environments that are 20 K and below; • SIRCUS (Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources) is a tunable laser-based facility for the absolute calibration of optical instruments; the companion Traveling SIRCUS is used at external 34 

sites; • FASCAL 2 (Facility for Automated Spectroradiometric Calibrations) provides the NIST spectral irradiance scale, covering the 200 nm to 2,500 nm wavelength range; • The Spectral Tri-function Automated Reference Reflectometer Facility maintains the national scale of reflectance, including bidirectional reflectance distribution function; and • SURF III is used for detector power response calibration, and for irradiance calibration from 130 nm to 600 nm applications in materials characterization and semiconductor physics and technology. These facilities are at the core of the division’s mission. At present these are mature facilities, although incremental improvements continue to be made. 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 The mission of the Optical Technology Division is to provide the foundation for optical radiation measurements for the United States. Its approach is to develop and disseminate national measurement standards and services to advance optical technologies spanning the terahertz through the infrared, visible, and ultraviolet spectral regions. The division’s main responsibility is to advance, maintain, and disseminate standards for the candela and kelvin base SI units and related radiometric quantities. Its core competency in this area is evident through its execution of several high-profile projects, including SIRCUS, Traveling SIRCUS, SURF III, and the LBIR Facility. The Optical Technology Division’s major accomplishment is the continued refinement of core radiometric calibrations at the LBIR Facility and SIRCUS and their delivery to external customers, including other government sponsors through the Missile Defense Agency program. The division’s highly qualified and productive staff executes a diverse program of applied research and calibration services. The facilities and equipment are of the highest caliber and appear to be well maintained. The division appears to be delivering on its stated mission as witnessed by its external sponsor base, which includes other U.S. government agencies, foreign national metrology organizations, and prestigious U.S. industry and academic institutions. Additionally, the division’s leadership and participation in international standards organizations and conferences, its capture of a relatively large number of competed NRC postdoctoral fellows, and its overall publication record also indicate the high quality of its delivered products, services, and research accomplishments. The calibration and sensor facilities and expertise of the division have two or three peers worldwide and clearly no domestic equivalents. Their advanced research effort in the area of quantum information science is also of high quality, comparable to major academic programs throughout the country, and their research into the radiometric applications of correlated photon states is unique. 35 

Concerns include the level to which the division relies on nonpermanent staff to achieve its core mission, the apparent divergence of the new (and very impressive) Biophysics Group from the division’s core mission, the future prospects for the terahertz research effort, the distraction of staff effort in order to address administrative issues (namely, the IT burden and other unfunded mandates), and the potential disruption in service that will potentially accompany the planned laboratory relocations. Technical Merit Relative to State of the Art The Optical Technology Division maintains a long-term core commitment to high-accuracy measurements in radiometry, photometry, and spectroradiometry. The division continues its successful efforts to develop new approaches to calibration over a wide spectral range, from the far infrared through the UV. The division has invested significant resources in these areas and 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 SI 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 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. A core activity of the division is the development of technical standards for industries relying on optical technologies. The division also has research programs for developing optical and spectroscopic tools for the improved understanding of processes required to support evolving technologies in, for example, the semiconductor, solid-state lighting, and biotechnology and health science industries. Within the area of optical standards, the activities within the division are clearly distinctive within the United States. The facilities for maintaining standards that have been developed within 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 staff in the division is well aware of comparable research and engages in 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 division’s activities results from the choice of the problems addressed as well as from the distinctiveness of the measurement capabilities themselves. The division’s overall activities constitute forefront research in areas that are relevant to the NIST mission. Adequacy of Infrastructure Laboratory space has been much improved. Five years ago, some of the division’s laboratories were severely cramped to the point of being borderline dangerous—that is, laboratory safety was an issue in laboratories that housed major radiometric instrumentation resources. Now several laboratories are in new locations in 36 

the AML, and in general the overall increase in floor space offers much more flexibility and a much improved environment for the researchers to work in with their equipment. Unfortunately the occupants of the AML, many of whom are in the new Biophysics Group, will have to move in order to create space for a new NIST Center for Nanoscale Science and Technology. Laboratory moves are always disruptive. Although the affected staff is facing this with a positive attitude, it will slow the progress of their research for a time. It is important that a plan be in place to prepare their destination laboratories adequately prior to the move and to minimize the disruption. The equipment and instrumentation of the division are of high quality. There is evidence of healthy equipment spending 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. The permanent staff is capable, experienced, and motivated. Their results attest to their commitment to high-quality research and products. The percentage of the researchers who are permanent staff is low—less than 50 percent. This percentage is uneven from group to group, with one notable group having only four permanent staff and more than a dozen short-term or contract personnel. The permanent staff 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 multiple-month disruption in progress will occur in related research. Most groups depend on external customers for a portion of their funding support, with deliverables to these customers being a central aspect of these task plans. Customer satisfaction would likely be put at risk in the event of a staff loss because of the shallow bench strength. It takes continuity and flexibility to maintain a laboratory of outstanding quality and to be able to respond to new needs and new opportunities. Both capabilities are threatened by the staffing trends of the past few years. Visiting researchers are major contributors to the quality of a laboratory, bringing in new ideas, establishing close working relationships that continue after the individuals have returned to their own institutions, and filling gaps in expertise in particular projects. There is an impressively large number of NRC postdoctoral fellows in this division. This is evidence of the attractiveness of the division’s activities to early-career scientists, as well as of the commitment of the division’s staff in making the effort to attract and mentor these young scientists. 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. A NIST committee is addressing the NIST overhead structure. The panel looks forward to seeing that committee’s report. Another related factor appears to be the extent to which support depends on external funding sources, which can create a mood of conservatism regarding hiring. The Optical Technology Division and the Physics Laboratory should be more aggressive in hiring early-career talent. 37 

Achievement of Objectives and Impact The research program in the Optical Technology Division reflects careful technical strategic planning aimed at responding to NIST and to national priorities. The existence of a vibrant and dynamic technical strategic planning process can be seen in the realignment of many of the activities that were in the Laser Applications Group. Whereas several years ago there was no 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 issue of customer focus is particularly relevant within the standards area. In this respect, a special role is filled by the Council for Optical Radiation Measurements, which periodically evaluates national needs in optical metrology and provides feedback on the services and standards supplied by the division. CORM is a body originally instituted by NIST to provide guidance and prioritization on technical needs in industry and research. The laboratory’s colorimetry facility, for example, was developed in response to CORM recommendations. The impressive level of customer satisfaction with the division can be gauged by the high level of other-agency research support. A continued high level of such external support is the ultimate test of attention to the customer. The Optical Technology Division makes use of a variety of effective means for delivering its technical output. 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 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 holding specialized courses and tutorials and making available specialized software. The latter has been implemented very effectively with respect to the analysis of optical scattering data. A 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 division has an excellent balance with respect to meeting immediate needs and at the same time developing new long-term programs. This approach will keep the division at the technical forefront and will 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. Excellent work in this field is already underway in a number of NIST’s laboratories, including the Physics Laboratory, where the new, impressive Biophysics Group has been formed in this division. Although currently small in number, the research personnel are a very capable group, enthusiastic about their research. The overall group objectives appear to be in line with the NIST mission. The bioscience thrust in the division relies heavily on multidisciplinary and interdisciplinary research. The collaborations with the National 38 

Institutes of Health and the appointments of several NIST personnel as participants at the Center for Advanced Research in Biotechnology (CARB) are consistent with strategic goals.8 As pointed out in the previous NRC assessment, there is an increasing need for interdisciplinary approaches in the biosciences.9 Although this group fits into the Optical Technology Division (which seems appropriate), several other divisions include the activities of this group in their portfolios. This brings up questions about the present and future ownership of this promising group. It would be helpful to address this issue and articulate the understanding of the extent of the sharing of the objectives and products of this group among the various divisions. Addressing this issue would help to alleviate the perception of a lack of coordination of efforts in this research area. The level of coordination or overlap among these divisions should be clarified. The Physics Laboratory has the potential to play an increasingly important role in collaborating with other external organizations to exploit the new technologies and methods in many facets of the biosciences. However, it will be necessary for the Physics Laboratory to elucidate a comprehensive plan for organizing and staffing its expanded role in this area if it is to optimize its effectiveness. The division has outstanding measurement capabilities in the terahertz spectral region, originally based on traditional Fourier-transform techniques, and more recently it has been 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. The terahertz research appears, however, to be at a crossroads. There are questions about the future applications: Who are the customers of the future? What biological problems do the principals on the permanent staff who are now associated with the new Biophysics Group plan to address in the future? The problem associated with the application of terahertz tools to biological research is the very strong water absorption throughout the terahertz region of the spectrum. It is timely for the terahertz technical leads and the division management to enunciate applications areas for their unusual capabilities in which they will have desirable impact. Particularly interesting would be the application of such a tunable terahertz source to microscopic apertures. High pressure physics is one such area. The small aperture associated with the highest pressure diamond anvil cells could make tunable terahertz the ideal probe for exploring the appearance of pressure-induced insulator-metal transitions in front-line materials like solid hydrogen. There is an effort in the division to explore such new applications areas. 8 CARB is located at the University of Maryland Shady Grove campus near NIST. CARB was initially a joint collaboration of the NIST Biochemical Science Division, within the NIST Chemical Science and Technology Laboratory, and the University of Maryland Biotechnology Institute. 9 National Research Council, 2005, An Assessment of the National Institute of Standards and Technology Measurements and Standards Laboratories: Fiscal Years 2004-2005, Washington, D.C.: The National Academies Press. 39 

CONCLUSIONS The Optical Technology Division is successfully maintaining its long-term core commitment to high-accuracy measurements in radiometry, photometry, and spectroradiometry. This commitment is in line with the NIST mission. Core facilities continue to be operational, and new methods and techniques are continuing to be developed. The division has engaged in strategic planning that involves new areas of emphasis. One notable example is biophysics. A new Biophysics Group has been formed, collaborations with external organizations have been put in place, and the future looks bright. The staff are capable and motivated; however, the mix between permanent staff and temporary and contract personnel appears suboptimal for long-term health and consistency in meeting strategic objectives. The Optical Technology Division and the Physics Laboratory should be more aggressive in hiring early-career talent. The Physics Laboratory should elucidate a comprehensive plan for organizing and staffing its expanded role in the biophysics area if it is to optimize its effectiveness. The terahertz technical leads and the division management should enunciate the applications areas for the unusual capabilities of terahertz tools in which they will have desirable impact. The Optical Technology Division should adequately prepare the destination laboratories prior to the move of the Biophysics Group personnel and minimize the disruption from the move. 40