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We have constructed, calibrated, and tested a cryogenic low-background infrared radiometer for both spectral radiance and irradiance measurements over the 4 μm to 20 μm wavelength range. The primary purpose of the Missile Defense Transfer Radiometer (MDXR) is to measure absolute irradiance or radiance from cryogenic infrared test chamber sources using a photoconductive Si:As Blocked Impurity Band (BIB) detector and a set of spectral filters. The MDXR also includes an absolute cryogenic radiometer (ACR) and a Fourier transform spectrometer (FTS). For irradiance measurements, the ACR is used to provide the primary power scale for the BIB detector in conjunction with spectral filters, while the FTS/BIB configuration derives its scale from an internal blackbody source. The two measurement scales show agreement for the irradiance of highly collimated (< 1 mrad) infrared beams from 10(−13) W/μm/cm(2) to 10(−8) W/μm/cm(2) within the combined relative uncertainties of 2.6 % (coverage factor k = 1.) We have also calibrated the radiometer for radiance measurements by using a large cavity fluid bath blackbody that overfills the spatial and angular extent of the radiometer entrance pupil. The radiometric calibration uncertainty analysis of the radiometer as well as its maintenance and stability are discussed.

Bidirectional Scattering Distribution Function (BSDF) measurements of selected specular samples were made using the Table-Top Goniometer (TTG) in the Diffuser Calibration Lab (DCL) at NASA GSFC in the support of NASA remote sensing instruments and programs. The same TTG system has also been used in the BRDF measurements for diffuse samples. The tunable laser-based TTG possesses the advantages of small incident beam profile and configuration flexibility and is able to meet various BSDF test requirements on specular samples with flat and curved surfaces. It also has a useful capability in characterizing instrument straylight due to surface roughness and in determining the scattering light distribution function of optical surfaces. The BSDF measurements on specular samples can be performed over 8 orders of linear dynamic range with correction of instrument signatures. In this paper, we present BSDF results on two types of specular samples: a witness flat fold mirror for the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) project and four Multi-Layer Insulation (MLI) samples for the Restore project at NASA GSFC. BRDF measurements in the viewing angle range of ± 90° were acquired at 500 nm, 700 nm, and 2000 nm and at incident angles of 0°, 8°, and 25° for the PACE sample, and at 500 nm, 633 nm, 700 nm, 900 nm, 1000 nm, 1550 nm, and 1800 nm at incident angles of 10° and 25° for the MLI samples. For both types of samples, the ABg model was applied to fit the BSDF data to generate the parameters for optical modeling. The ABg model is able to fit the BSDF data on the polished surface of the flat mirror very well. However, two scattering components were seen in the MLI BSDF fitting results attributed to wrinkle and surface morphology issues. Total Hemispherical Reflectance (THR) and Total Integrated Scatter (TIS) measurements were also made on the samples and were compared to the BSDF results. The details of the BSDF measurement setup and the methodology for realization of the BRDF scale for the specular samples are also described.

We report the Bidirectional Reflection Distribution Function (BRDF) and Total Hemispheric Reflectance (THR) results of several low reflectance materials using a Table-top Goniometer (TTG) and a commercial UV-VIS-NIR spectrophotometer in support of the NASA GSFC PACE project. The newly developed TTG was utilized to perform the BRDF measurements for several black candidate samples in in-plane and out-of-plane configurations from 300 nm to 2000 nm. These measurements demonstrated the BRDF capability of the TTG to calibrate the dim calibration target with a reflectance of approximately 2 % for the OCI of the PACE project. The spectral THR of the black samples from 200 nm to 2500 nm was determined using a 10 % reflectance diffuse black standard and a monochromator-based light source equipped with a 150 mm diameter integrating sphere. The THR measurement is used to compliment and validate the BRDF measurements acquired from these samples. In this presentation, we also show examples of UV induced BRDF and THR changes on two black coatings. We will discuss validation of the BRDF scale, source stability, measurement repeatability, instrument signature, and uncertainty components.

A KHz Pulsed Laser Detection System was developed employing the concept of charge integration with an electrometer, in the NASA Goddard Space Flight Center, Code 618 Calibration Lab for the purpose of using the pulsed lasers for radiometric calibration. Comparing with traditional trans-impedance (current-voltage conversion) detection systems, the prototype of this system consists of a UV-Enhanced Si detector head, a computer controlled shutter system and a synchronized electrometer. The preliminary characterization work employs light sources running in either CW or pulsed mode. We believe this system is able to overcome the saturation issue when a traditional trans-impedance detection system is used with the pulsed laser light source, especially with high peak-power pulsed lasers operating at kilohertz repetition rates (e.g. Ekspla laser or KHz OPO). The charge integration mechanism is also expected to improve the stability of measurements for a pulsed laser light source overcoming the issue of peak-to-peak stability. We will present the system characterizations including signal-to-noise ratio and uncertainty analysis and compare results against traditional trans-impedance detection systems.

We present system-level responsivity calibration results of the visible and near infrared channels of JPSS-1 VIIRS in the reflective solar band (RSB) from bands M1( 412 nm) to M7 (865 nm). A monochromator-based method based on the Spectral Measurement Assembly (SpMA), and a laser-based calibration method based on Travelling-Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources (T-SIRCUS) were applied with different illumination methods to obtain the relative and absolute spectral responses (RSR and ASR). The spectral features of RSR for each band are verified by comparing to the component-level spectral transmittance of the VIIRS bandpass filters. Variation of RSR results of a single pixel/detector with respect to the band-averaged for each band is also investigated. Utilization of RSR results from SpMA and T-SIRCUS with different illumination methods as well as the component transmittance results enables us to recognize optical and electrical cross-talk from out-of-band, which is estimated at about 3 %. We also attempted to use the ASRs from T-SIRCUS to validate the gain coefficients derived from an independent radiometric calibration test using a broadband source. Three spectral shapes of flat spectral radiance, Tungsten lamp, and solar emission are used to simulate different scenarios for baseline, pre-launch calibration, and on-orbit calibration to verify the radiometric coefficients with the more accurate NIST-traceable calibration.

The relative spectral response (RSR) characterization of the JPSS-1 VIIRS spectral bands has achieved at launch status in the VIIRS Data Analysis Working Group February 2016 Version 2 RSR release. The Version 2 release improves upon the June 2015 Version 1 release by including December 2014 NIST TSIRCUS spectral measurements of VIIRS VisNIR bands in the analysis plus correcting CO2 influence on the band M13 RSR. The T-SIRCUS based characterization is merged with the summer 2014 SpMA based characterization of VisNIR bands (Version 1 release) to yield a fused RSR for these bands, combining the strengths of the T-SIRCUS and the SpMA measurement systems. The M13 RSR is updated by applying a model-based correction to mitigate CO2 attenuation of the SpMA source signal that occurred during M13 spectral measurements. The Version 2 release carries forward the Version 1 RSR for those bands that were not updated (M8-M12, M14-M16AB, I3-I5, DNBMGS). The Version 2 release includes band average (overall detectors and subsamples) RSR plus supporting RSR for each detector and subsample. The at-launch band average RSR have been used to populate Look-Up Tables supporting the sensor data record and environmental data record at-launch science products. Spectral performance metrics show that JPSS-1VIIRS RSR are compliant on specifications with a few minor exceptions. The Version 2 release, which replaces the Version 1 release, is currently available on the password-protected NASA JPSS-1 eRooms under EAR99 control.

The National Institute of Standards and Technology (NIST) is working to extend the upper wavelength limit of the spectral power-responsivity calibration service from 1800 nm to 2500 nm. This extension is based on extended-InGaAs (EIGA) transfer- and working-standard radiometers and low-NEP pyroelectric transfer-standard detectors. The scale is traceable to the electrical-substitution cryogenic radiometer through the transfer-standard EIGA radiometers. The total uncertainty of the extended-responsivity reference scale (realized on four EIGA working-standard radiometers) is 1% (k = 2). The transfer of the reference scale from one of the four working standards to a test EIGA radiometer in direct-current (dc) measurement mode is described. The uncertainty of the transferred scale is 1.6% (k = 2) between 1200 nm and 2300 nm. The transfer was performed on the NIST Spectral Comparator Facility (SCF) without any modifications to the SCF. The EIGA radiometers have been characterized for spatial-response uniformity, temperature-dependent spectral responsivity, linearity, noise, long-term and short-term temporal stability. The preliminary results show that EIGA radiometers can be used over the spectral range between 900 nm and 2500 nm in dc mode and could eventually replace the regular InGaAs detectors in the SCF measurements. The total uncertainty budget for these measurements is discussed.

We have measured the polarization-resolved bidirectional reflectance distribution function (BRDF) for two types of graphite used in the fabrication of high-temperature fixed point blackbody cavities in and out of the plane of incidence. Measurements were made at room temperature using 405 nm and 658 nm laser sources, and the samples were illuminated at angles of incidence varying from normal incidence to 70°. All of the samples exhibited non-Lambertian behaviour, including enhanced forward scatter at high incident angles, especially for s-polarized incident light. The directional-hemispherical reflectance for unpolarized incident light, obtained by integrating the BRDF measured at individual points in a hemisphere over the sample, ranged from 0.083 to 0.101, depending upon sample and incident angle. The potential impact of these measurements on emissivity models for graphite blackbody radiators and radiance temperature scale dissemination is discussed.

This article describes a method of measuring the absolute outdoor longwave irradiance using an absolute cavity pyrgeometer (ACP), U.S. Patent application no. 13/049, 275. The ACP consists of domeless thermopile pyrgeometer, gold-plated concentrator, temperature controller, and data acquisition. The dome was removed from the pyrgeometer to remove errors associated with dome transmittance and the dome correction factor. To avoid thermal convection and wind effect errors resulting from using a domeless thermopile, the gold-plated concentrator was placed above the thermopile. The concentrator is a dual compound parabolic concentrator (CPC) with 180° view angle to measure the outdoor incoming longwave irradiance from the atmosphere. The incoming irradiance is reflected from the specular gold surface of the CPC and concentrated on the 11 mm diameter of the pyrgeometer's blackened thermopile. The CPC's interior surface design and the resulting cavitation result in a throughput value that was characterized by the National Institute of Standards and Technology. The ACP was installed horizontally outdoor on an aluminum plate connected to the temperature controller to control the pyrgeometer's case temperature. The responsivity of the pyrgeometer's thermopile detector was determined by lowering the case temperature and calculating the rate of change of the thermopile output voltage versus the changing net irradiance. The responsivity is then used to calculate the absolute atmospheric longwave irradiance with an uncertainty estimate (U95) of ±3.96 W m−2 with traceability to the International System of Units, SI. The measured irradiance was compared with the irradiance measured by two pyrgeometers calibrated by the World Radiation Center with traceability to the Interim World Infrared Standard Group, WISG. A total of 408 readings were collected over three different nights. The calculated irradiance measured by the ACP was 1.5 W/m2 lower than that measured by the two pyrgeometers that are traceable to WISG, with a standard deviation of ±0.7 W m−2. These results suggest that the ACP design might be used for addressing the need to improve the international reference for broadband outdoor longwave irradiance measurements.

Integrating-sphere-input InGaAs radiometers (ISIR) have been developed at the National Institute of Standards and Technology (NIST) to extend the detector-based calibration of radiation thermometers from the Si range to the near-infrared (NIR). These near-infrared radiometers are used to determine the reference spectral irradiance responsivity scale based on the primary-standard cryogenic radiometer. The irradiance responsivity scale is then propagated to spectral radiance at the exit port of an integrating sphere. The near-infrared radiation thermometer (NIRT) is calibrated using this detector-based radiance scale. The first phase of this research work is reported here where the relative spectral radiance responsivity of the NIRT has been determined using a monochromator-based system. Thereafter, the relative spectral responsivity of the NIRT is converted into an absolute responsivity using the radiances from the Zn fixed point blackbody. Then, the NIRT is used to extend these calibrations for temperature measurements between 157 °C and 1000 °C. The NIRT has also been calibrated in this temperature range using the five, fixed point blackbodies of the ITS-90. The two different calibration approaches for temperature measurements are compared.

Deviations from ideal blackbody (BB) behavior can be characterized by a BB’s effective emissivity. The cavity emissivity is most often obtained through a model, given a particular set of input parameters associated with the BB cavity geometry and surface optical properties. It can also be measured directly (radiance) or indirectly (reflectance). A study of BB cavity emissivity using the reflectance method is presented. Several types and designs of blackbody cavities, including those from fixed-point and water bath BBs, using our infrared total integrated scatter (ITIS) instrument for emissivity evaluation are examined. The emissivity is characterized as a function of position on the output aperture, as well as a function of output angle. The measurements have revealed emissivity values, both significantly greater than, and in confirmation of, modeling predictions. For instance, the emissivities of three fixed point BB cavity designs were found to vary significantly despite modeling predictions in the design process of similar behavior. Also, other BB cavities that exhibited poor emissivity performance were re-painted and re-machined, in one case more than once, before the predicted performance was achieved.

This paper presents a robust method for determining the calibration coefficients in polynomial calibration equations, and discusses the corresponding calibration uncertainties. An attenuator method that takes into account all measurements with and without an attenuator screen was used to restrict the impact of the absolute calibration of the light source. The originally proposed procedure attempts to simultaneously determine all unknowns nonlinearly using polynomial curve fitting. The newly proposed method divides the task into two simpler parts. For example, in the case of a quadratic calibration equation, the first part becomes a quadratic equation solely for the transmittance of attenuator, which has an analytical solution using three or four sets of measurements. Additionally, it is straightforward to determine the median value and the standard deviation of the transmittance from the solutions using all combinations of measured data points. In conjunction, the second part becomes a linear fit, with the ratio of the zeroth-order to first-order calibration coefficients as the intercept and the ratio of the second-order to first-order calibration coefficients as the slope. These ratios are unaffected by the absolute calibration of the light source and are then used in the calibration equation to calculate the first-order calibration coefficient. How the new method works is straightforward to visualize, which makes its results easier to verify. This is demonstrated using measurements from the Joint Polar Satellite System (JPSS) J1 Visible Infrared Imaging Radiometer Suite (VIIRS) reflective solar bands (RSB) pre-launch testing.

Dome-input pyroelectric radiometers with different black coatings were developed to extend the spectral responsivity scale from near infrared (NIR) to 20 μm. The reflective dome with shiny gold-coating has been known to be an efficient light trap to enhance the detector absorptance and to minimize spectral responsivity variation. The enhancement of spectral responsivity using reflective dome relies on optical characterization of black coating on detector, reflectance of dome reflector, and input aperture dimension, etc. We report a comparison of spectral responsivity of dome-input pyroelectric radiometers measured with/without dome-trap from 2.4 μm to 14 μm using the Infrared Spectral Comparator Facility (IRSCF) at NIST. The results show 4 % to 8 % gain of responsivity for two dome-input pyroelectric detectors, with reduced structure of spectral responsivity. The uncertainty of dome-input pyroelectric radiometer calibrations is approximately 2 % ( k = 2).

Spectral responsivity calibrations of two different types of pyroelectric radiometers have been made in the infrared region up to 14 μm in power mode using three different calibration facilities at NIST. One pyroelectric radiometer is a temperature-controlled low noise-equivalent-power (NEP) single-element pyroelectric radiometer with an active area of 5 mm in diameter. The other radiometer is a prototype using the same type of pyroeletric detector with dome-input optics, which was designed to increase absorptance and to minimize spectral structures to obtain a constant spectral responsivity. Three calibration facilities at NIST were used to conduct direct and indirect responsivity calibrations tied to absolute scales in the infrared spectral regime. We report the calibration results for the single-element pyroelectric radiometer using a new Infrared Spectral Comparator Facility (IRSCF) for direct calibration. Also, a combined method using the Fourier Transform Infrared Spectrophotometry (FTIS) facility and single wavelength laser tie-points are described to calibrated standard detectors with an indirect approach. For the dome-input pyroelectric radiometer, the results obtained from another direct calibration method using a circular variable filter (CVF) spectrometer and the FTIS are also presented. The inter-comparison of different calibration methods enables us to improve the responsivity uncertainty performed by the different facilities. For both radiometers, consistent results of the spectral power responsivity have been obtained applying different methods from 1.5 μm to 14 μm with responsivity uncertainties between 1 % and 2 % (k = 2). Relevant characterization results, such as spatial uniformity, linearity, and angular dependence of responsivity, are shown. Validation of the spectral responsivity calibrations, uncertainty sources, and improvements for each method will also be discussed.

Pyroelectric radiometers with noise-equivalent-power (NEP) close to 1 nW/Hz 1/2 have been developed to measure less than 1 μW radiant power levels at room temperature to 25 μm. The radiometers will be used as transfer standards for routine spectral responsivity calibrations in the infrared range at the output of a traditional monochromator. Dome inputoptics are used with multiple beam reflections to increase absorptance and to minimize structures in the spectral responsivity function. The temperature of the pyroelectric detector is stabilized with a thermoelectric cooler/heater. Spectral power responsivity calibrations were performed with two different methods. A Fourier Transform Spectrometer using it's Infrared Reference Integrating Sphere System based method was validated with a continuously variable filtermonochromator based detector-comparison method using earlier developed pyroelectric radiometer standards. A responsivity uncertainty of 1.4 % (k=2) was obtained between 2 μm and 14 μm.

We report the preliminary characterization results of a gold-coated concentrator used for longwave irradiance measurements[1]. Throughput measurements of the concentrator are conducted at 1.562 μm and 10.15 μm using two different approaches, one is referred to a transmittance measurement using the Complete Hemispherical Infrared Laserbased Reflectometer (CHILR)[2] of NIST, and the other one is a direct throughput measurement using an existing thermopile detector for longwave irradiance measurement. For the transmittance measurement using CHILR, two diffuse gold references are selected to generate a Lambertian source by shining a laser on them. Spatial variations of transmittance of the concentrator are also investigated by scanning the laser beam across the opening area of it with a gold diffuser. For the direct throughput measurement, a small diffuse gold integrating sphere of 25.4 mm in diameter is utilized to produce an ideal diffuse source. The thermopile detector measures the radiation passing through the concentrator from the small integrating sphere. The incoming irradiance is determined from signal outputs of the thermopile detector and ambient temperature changes. Comparing with the results from the two approaches, a consistent throughput of the concentrator is obtained about 91 % to 92 %. The error sources and uncertainty in the two measurements are also discussed.

Vertically aligned multiwall carbon nanotubes were grown by water-assisted chemical vapor deposition on a large-area lithium tantalate pyroelectric detector. The processing parameters are nominally identical to those by which others have achieved the "world's darkest substance" on a silicon substrate. The pyroelectric detector material, though a good candidate for such a coating, presents additional challenges and outcomes. After coating, a cycle of heating, electric field poling, and cooling was employed to restore the spontaneous polarization perpendicular to the detector electrodes. The detector responsivity is reported along with imaging as well as visible and infrared reflectance measurements of the detector and a silicon witness sample. We find that the detector responsivity is slightly compromised by the heat of processing and the coating properties are substrate dependent. However, it is possible to achieve nearly ideal values of detector reflectance uniformly less than 0.1% from 400 nm to 4 microm and less than 1% from 4 to 14 microm.

The wavelength coverage of the IR optical scattering instrument developed at the National Institute of Standards and Technology has been extended to cover the continuous range from 1 μm to 5 μm. Besides the previously available diode lasers at wavelengths of 785 nm, 1.32 μm, and 1.55 μm as well as a line tunable CO2 lasers from 9.2 μm to 11.2 μm, a PPLN OPO tunable laser is used to generate the desired IR source radiation from 1 μm to 5 μm. We present a brief description of the existing BRDF instrument, as well as the steps required to couple the tunable IR source into the BRDF system, such as improvement of beam profile, polarization control, and sample alignment. The associated results of BRDF measurements for typical specular and diffuse samples are also shown. For specular samples, the BRDF collection aperture size is varied to both 1) resolve the specular component and 2) obtain sufficient signal for the low level diffuse component. The input beam is characterized directly by a pyroelectric sensor array camera in comparison to the BRDF results. The dynamic range of detection, sample alignment, and the averaging of multiple spots for the specular sample measurement are discussed. For diffuse samples, the approach employed for speckle suppression is a combination of translation and rotation averaging. The directional-hemispherical reflectance (DHR) is calculated by integration of the BRDF data, which is found to have good agreement with the DHR results from FTIR integrating sphere measurements.

The spectral irradiance responsivity calibrations of InSb radiometers measured on the tunable-laser based Infrared Spectral Irradiance and Radiance Responsivity Calibration with Uniform Sources (IR-SIRCUS) facility are discussed. This work describes the following changes undertaken to reduce the uncertainties of the calibrations: improve the spatial uniformity, reduce the laser-induced speckle from the gold-coated integrating spheres between 1 μm and 5 μm, improve the stability of the optical parametric oscillator (OPO) tunable laser, reduce the noise from the signal-to-monitor ratio, increase the repeatability of measurements, and reduce the stray light and fringe problems of the radiometer under test. Measurements of the spatial uniformity with the use of polytetrafluoroethylene (PTFE) and gold-coated integrating spheres at different wavelengths have been performed. Different approaches for generating a uniform source, removing the speckle, stabilizing the laser, and improving the signal-to-monitor ratio are also described. The spatial nonuniformity after using these approaches has been shown to be reduced to < 1 %. The uncertainty budget of spectral irradiance responsivity calibrations is discussed, and is found to be mainly due to the measurement repeatability uncertainty component of 1 %. Calibrated radiometers are tested against a source-based scale from the calculated spectral irradiances obtained using a precision aperture and a blackbody (BB) with a known temperature.

As part of the optical detector character ization program at the Optical Technology Division at NIST, we have established a capability for the calibration of spectral radiant power responsivity in the infrared from 785 nm to 14 P m. We have used our facilities to characterize two commercial pyroelectric radiometers with KRS5 windows. The calibration methodology consists of the determination of the responsivity at single wavelength tie points together with relative spectral responsivity measurements. Responsivity tie points at 785, 1064, 1320, 1600, 2000 and 10600 nm are obtained against the NIST ACR-L1 absolu te cryogenic radiometer as well as a domed pyroelectric transfer standard, using an OPO tunable laser and a stabilized CO 2 laser as sources. The spatial variation of the responsivity of the test radiometers has also been measured. This enables us to minimize the uncertainties due to interference fringes from the KRS5 window. The relative spectral responsivity curves for the two radiometers are ob tained indirectly through measurement of the detector absorptance with an FTIR-based integrating sphere reflectometer. In order to obtain the actual absorptance at the detector from the reflectance measurements, an individual KR S5 window and a bare detector were also measured. The results are compared and th e uncertainty budgets will be discussed. Keywords: Pyroelectric radiometer with KRS5 window, spectral radiant power responsivity, absolute cryogenic radiometer, domed pyroelectric transfer st andard, OPO tunable laser, stabilized CO

Materials with similar chemical compositions often exhibit different optical properties due to their structural composition. PTFE is widely used in many applications for both its mechanical and optical properties. Low density sintered PTFE has optical properties that make it desirable for use as a white diffuser in applications such as remote sensing. The contrast between the commonly available high density material and the low density material may be useful for those interested in optical modeling of scattered light. Additionally, some applications may find high density PTFE suitable for some optical applications. This paper describes measurements of BRDF, 8o/hemispherical reflectance, and directional hemispherical transmittance for both high density (HD) and low density (LD) sintered PTFE.

An instrument, the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR), has been designed and built for the accurate characterization of the total reflectance of highly absorbing samples and cavity structures down to the level of 10 -5 . The design of CHILR employs a number of the same features of Total Integrated Scatter (TIS) measurement devices, but is used for total reflectance (both specular and diffuse components), rather than only the diffuse component. A number of features of CHILR include spatial uniformity and angular dependence of reflectance measurement capability, multiple wavelength laser sources, and the ability to measure a wide range of sample sizes and cavities with aperture sizes, ranging from 3 mm to 51 mm. We address several basic issues of alignment, background and externally scattered light, reference measurement, and laser drift, for the CHILR. We also present results of several examples, including cavities for blackbody sources, and radiometer cavities.

The reference spectral power responsivity scale of NIST is being extended from the silicon range to the infrared (IR) using pyroelectric radiometers. Two transfer standard pyroelectric radiometers have been developed at NIST. The main design consideration was to obtain only a minimal increase in the measurement uncertainty during the responsivity scale extension. Domain engineered LiNbO3 and regular LiTaO3 pyroelectric detectors were used in the two radiometers. Both detectors are gold-black coated and temperature controlled. Reflecting domes are attached to the radiometer inputs to decrease the reflectance loss and to improve the spatial uniformity of responsivity in the infrared. Four commercial pyroelectric detectors have been added to the group and used as working standards. The relative spectral responsivity of all pyroelectric detectors was determined from spectral reflectance measurements. The radiant power responsivity tie points were derived from Si trap and single element detectors traceable to the NIST reference responsivity scale. The pyroelectric radiometers have been characterized for frequency and temperature dependent responsivity, noise, spatial non-uniformity of responsivity, angular responsivity, and linearity. The expanded (relative) uncertainty of the spectral power responsivity calibrations ranged between 0.5 % and 1.2 % (k=2) within the 1 μm to 19 μm range.

Realization of a radiometric temperature scale for near ambient temperatures with accuracy at the 20 to 50 mK level is crucial for a number of demanding military and commercial applications. In support of such measurements, radiation sources with high stability and spatial uniformity must be developed as reference and working standards. Traditionally, the temperature scale, maintained at the National Institute of Standards and Technology (NIST), relies on water bath and oil bath blackbodies in this temperature range. Recently, a water heat pipe blackbody was used at NIST as a spectral radiance source in a spectral emissivity measurement facility. Now a new, more versatile high emissivity water heat pipe blackbody was designed and characterized to be used as a reference radiance source for the radiometric temperature scale realization between 50 °C and 250 °C. Furthermore, it will serve as a reference source for the infrared spectral radiance measurements between 2.5 μm and 20 μm. The calculated spectral emissivity of the painted copper alloy cavity was verified by reflectance measurements using a CO2 laser at 10.6 μm wavelength. The spatial thermal uniformity and stability of the blackbody were characterized. Two independent realizations of the radiometric temperature scale were compared in order to verify the accuracy of the scale. Radiance temperature, calculated from the cavity temperature measured with a calibrated PRT contact thermometer and from the emissivity of the cavity, was compared to the radiance temperature, directly measured with a reference pyrometer, which was calibrated with a set of fixed point blackbodies. The difference was found to be within measurement uncertainties.

An infrared (IR) optical scattering instrument for BRDF measurement has been developed at NIST with out-of-plane and retro-reflection capabilities. In this paper, a description of the BRDF instrument, its use of multi-wavelength sources (785 nm-10.6 /spl mu/m) and a retro-reflection measurement capability, and alignment techniques using a quadrant detector are presented. The related alignment results for the in- and out-of-plane geometries and reflectance of a gold mirror versus incident angle are also reported. The results of BRDF measurements for a concentric groove graphite radiator in the retro-reflection configuration are demonstrated.

Laser microprocessing has been extensively studies with applications in microelectronics, data storage and photonics. In addition to the fundamental aspects of laser materials interactions, we have investigated various applications of laser microprocessing in different areas. Laser cleaning has been studies systematically both theoretically and experimentally for dry surface cleaning and steam surface cleaning. This technology has been applied for cleaning magnetic head, magnetic sliders, suspension, laser mold cleaning and laser deflash for IC packages. Laser texturing and related processes such as laser bumping, laser tagging have been studied for magnetic recording applications. The other laser works include real-time monitoring of laser surface processing, laser-induced controllable periodic structures, laser nanopatterning by scanning probe microscope tip-enhanced laser irradiation. The further prospects of using laser microprocessing for applications in formation of ultrashallow (less than 50 nm) pn junction for next-generation MOS devices, laser generation of Si nanoparticles for quantum-dot flash memory and light emission devices are addressed.