Improved Near-Infrared Spectral Responsivity Scale

Area of Science:

• Metrology
• Optical Engineering
• Detector Physics

Background:

• Accurate spectral power responsivity scales are crucial for optical detector calibration.
• Existing methods in the near-infrared (NIR) range have limitations in uncertainty and scope.
• Advancements in detector technology necessitate improved calibration standards.

Purpose of the Study:

• To develop and characterize a new cryogenic radiometer-based system for absolute radiometric measurements.
• To improve the detector spectral power responsivity scales in the 900 nm to 1800 nm wavelength range.
• To calibrate various photodetectors with enhanced accuracy.

Main Methods:

• Construction of a system featuring a liquid-helium-cooled cryogenic radiometer.
• Integration of a 100 W quartz-tungsten-halogen lamp and a 1 m monochromator for wavelength selection.
• Characterization of the system and evaluation of measurement uncertainty for spectral power responsivity.

Main Results:

• The system enables spectral power responsivity measurements with a combined relative standard uncertainty of 0.4% or less over most of the spectral range.
• Successful calibration of indium gallium arsenide (InGaAs) photodiodes, germanium (Ge) photodiodes, and pyroelectric detectors.
• Demonstrated a factor of two improvement in measurement uncertainty compared to previous capabilities.

Conclusions:

• The new cryogenic radiometer system significantly enhances the NIR spectral power responsivity scale at NIST.
• The achieved uncertainty levels represent a substantial advancement for radiometric measurements.
• The system provides a reliable platform for calibrating diverse photodetector types in the NIR spectrum.