Ultraviolet radiometry with synchrotron radiation and cryogenic radiometry

Abstract

The combination of a cryogenic radiometer and synchrotron radiation enables detector scale realization in spectral regions that are otherwise difficult to access. Cryogenic radiometry is the most accurate primary detector-based standard available to date, and synchrotron radiation gives a unique broadband and continuous spectrum that extends from x ray to far IR. We describe a new cryogenic radiometer-based UV radiometry facility at the Synchrotron Ultraviolet Radiation Facility II at the National Institute of Standards and Technology. The facility is designed to perform a variety of detector and optical materials characterizations. The facility combines a high-throughput, normal incidence monochromator with an absolute cryogenic radiometer optimized for UV measurements to provide absolute radiometric measurements in the spectral range from 125 nm to approximately 320 nm. We discuss results on photodetector characterizations, including absolute spectroradiometric calibration, spatial responsivity mapping, spectroreflectance, and internal quantum efficiency. In addition, such characterizations are used to study UV radiation damage in photodetectors that can shed light on the mechanism of the damage process. Examples are also given for UV optical materials characterization.

<title>Characterization of UV-induced radiation damage to Si-based photodiodes</title>

“…For measurement of the absolute spectral responsivity in the UV and vacuum-UV, a new radiometric facility has been constructed at SURF [10]. Radiation from the synchrotron source is focused with a set of grazing-incidence, collimation optics onto the entrance slit of a 2 m norrnal-incidence-monochromator [ Fig.…”

High Accuracy Calibration Technology of UV Standard Detector

“…While it could extend the scale, its noise performance dramatically increased the uncertainties in the UV and the NIR spectral regions because of the low flux available on the comparator facilities (see the 1998 version of this document [14] for more information). The UV responsivity scale uncertainty was improved by calibrating the UV WS (UV working standard) at the NIST Synchrotron Ultraviolet Radiation Facility (SURF III) with an ACR-monochromator system [15,16] .…”

Technical Report: UV and VUV Radiometry Programs at the Synchrotron Ultraviolet Radiation Facility (SURF III)

“…Similar to the use of lamps, synchrotron radiation is typically dispersed using a monochromator. Because the throughput of a monochromator cannot be determined with high accuracy, the monochromatic synchrotron beam is no longer calculable and the scale of the beam has to be derived from an absolute detector such as a cryogenic radiometer [10,11].…”

“…The Optical Technology Division in collaboration with the Electron and Optical Physics Division of NIST operates two radiometric beamlines, beamline 3 [12] and beamline 4 [10], at SURF III. Beamline 3 takes advantage of the calculability of the synchrotron radiation and is used for measuring spectral irradiance (in W/cm 2 /nm) of sources such …”

“…Beamline 4, shown in Figures 5 and 6, is a detector-based calibration facility using radiation from SURF III as a broadband source [10]. Detector calibrations are performed by comparing the detector response to monochromatized synchrotron radiation with the response of a primary detector standard, a helium-cooled cryogenic radiometer.…”