Jeanne M. Houston

Realization of a scale of absolute spectral response using the National Institute of Standards and Technology high-accuracy cryogenic radiometer

Using the National Institute of Standards and Technology high-accuracy cryogenic radiometer (HACR), we have realized a scale of absolute spectral response between 406 and 920 nm. The HACR, an electrical-substitution radiometer operating at cryogenic temperatures, achieves a combined relative standard uncertainty of 0.021%. Silicon photodiode light-trapping detectors were calibrated against the HACR with a typical relative standard uncertainty of 0.03% at nine laser wavelengths between 406 and 920 nm. Modeling of the quantum efficiency of these detectors yields their responsivity throughout this range with comparable accuracy.

National Institute of Standards and Technology High-Accuracy Cryogenic Radiometer

A high-accuracy cryogenic radiometer has been developed at the National Institute of Standards and Technology to serve as a primary standard for optical power measurements. This instrument is an electrical-substitution radiometer that can be operated at cryogenic temperatures to achieve a relative standard uncertainty of 0.021% at an optical power level of 0.8 mW. The construction and operation of the high-accuracy cryogenic radiometer and the uncertainties in optical power measurements are detailed.

NIST reference cryogenic radiometer designed for versatile performance

We describe the concept of modularity and versatility in the construction of a new cryogenic radiometer developed at the National Institute of Standards and Technology. We address the benefits of the modular design in the construction and development and discuss some of the device characterizations and results of a cryogenic radiometer intercomparison.

Comparison of the NIST high Accuracy Cryogenic Radiometer and the NIST scale of Detector Spectral Response

Two independent methods of measurement were used to determine the absolute spectral responsivity and external quantum efficiency of light-trapping silicon photodiode packages. These trap packages were calibrated first by the NIST High Accuracy Cryogenic Radiometer at laser wavelengths of 633 nm and 442 nm. They were also measured in the NIST Spectral Comparator Facility with working standards traceable to a 100% quantum efficient radiometer (QED-200). The two sets of measurements agree to better than 0,1% at 633 nm and 0,25% at 442 nm.

Calibration of a pyroelectric detector at 10.6 µm with theNational Institute of Standards and Technology high-accuracy cryogenicradiometer

The National Institute of Standards and Technology (NIST) is establishing an infrared detector calibration facility to improve radiometric standards at infrared wavelengths. The absolute response of the cryogenic bolometer that serves as the transfer standard for this facility is being linked to the NIST high- accuracy cryogenic radiometer (HACR) at a few laser wavelengths. At the 10.6-microm CO(2) laser line, this link is being established through a pyroelectric detector that has been calibrated against the HACR. We describe the apparatus, methods, and uncertainties for the calibration of this pyroelectric detector.

Comparison of Two Cryogenic Radiometers at NIST

Two cryogenic radiometers from NIST, one from the Optical Technology Division and the other from the Optoelectronics Division, were compared at three visible laser wavelengths. For this comparison, each radiometer calibrated two photodiode trap detectors for spectral responsivity. The calibration values for the two trap detectors agreed within the expanded (k = 2) uncertainties. This paper describes the measurement and results of this comparison.

Argon mini-arc meets its match: use of a laser-driven plasma source in ultraviolet-detector calibrations

The National Institute of Standards and Technology operates two spectral comparator facilities, both of which are used to provide detector calibrations from the ultraviolet to the near-infrared spectral range. One, the Ultraviolet Spectral Comparator Facility (UV SCF), has been in operation for more than two decades, providing one of the core calibration services. Recently, the illumination source used in the UV SCF has been changed from an argon mini-arc source to a laser-driven plasma light source. This new source has higher brightness, a smaller source size, better temporal stability, and much better conversion efficiency than the previous source. The improvements in the capabilities are summarized.

IR-enhanced Si reference detectors for one-step scale transfers from 300?nm to 1000?nm

IR-enhanced Si photodiodes have improved radiometric and electronic characteristics as compared to other widely used Si photodiodes and can be used as responsivity standards in the wavelength range from 300 nm to 1000 nm. Their low predicted uncertainty for radiant power responsivity measurements can result in improvements in the existing monochromator-based Si responsivity scales. They have several advantages over traditionally used Si-trap detectors, such as wider acceptance angle, higher shunt resistance, and higher responsivity in the NIR region. Radiometric and electronic measurement results are discussed to illustrate these characteristics. The spectral power responsivity scales can be improved using a set of the IR-enhanced Si photodiodes not only to transfer the calibration from the cryogenic radiometer, but for use in the monochromator facility as working standards. This improvement will reduce the length of the calibration chain and create a one-step scale transfer between the cryogenic radiometer- and the monochromator-based facility.

Results of a pyroelectric detector calibration by a cryogenic radiometer at 10.6 mm

A pyroelectric detector was calibrated against the National Institute of Standards and Technology (NIST) High Accuracy Cryogenic Radiometer (HACR) at 10.6 mm using a CO2 laser as a source. The purpose of this calibration was to link the NIST infrared (IR) radiometric detector scales to the HACR. Issues addressed in this calibration included the spatial non- uniformity of the pyroelectric detector, the transport and alignment of the IR laser beam, and the measurement of ac signals. The final combined relative standard uncertainty of the calibration is 0.48%, with the largest uncertainty component arising from the spatial non-uniformity of the pyroelectric detector. The apparatus, measurement procedures, and results of the calibration will be discussed.