Facility for spectral irradiance and radiance responsivity calibrations using uniform sources

Area of Science:

• Radiometry
• Optical Metrology
• Instrumentation

Background:

• Traditional detector calibration methods using lamp-monochromators face limitations in accuracy for spectral irradiance and radiance responsivity.
• Existing techniques result in significantly increased uncertainties when measuring instruments in irradiance or radiance modes.

Purpose of the Study:

• To introduce a novel laser-based calibration facility, Spectral Irradiance and Radiance Responsivity Using Uniform Sources (SIRCUS).
• To enable direct calibration of instruments in irradiance or radiance mode with high accuracy.

Main Methods:

• Utilizing high-power, tunable lasers coupled into an integrating sphere via optical fibers to create uniform, high-radiant-flux sources.
• Employing reference standard irradiance detectors traceable to national primary standards for calibration.
• Determining source radiance from measured irradiance and known geometry.

Main Results:

• The SIRCUS facility achieves combined standard uncertainties of less than 0.1% for irradiance and radiance responsivity calibrations.
• The laser-based system provides uniform, quasi-Lambertian sources suitable for precise radiometric measurements.
• Calibration uncertainties approach or exceed those of traditional spectral power responsivity calibrations.

Conclusions:

• The SIRCUS facility represents a significant advancement in radiometric calibration capabilities.
• Direct calibration in irradiance and radiance modes with high accuracy is now achievable.
• This technology enhances the precision of radiometric scales and measurements for scientific applications.