Intercomparison of a correlated-photon-based method to measure detector quantum efficiency

Area of Science:

• Quantum optics
• Metrology
• Photodetector characterization

Background:

• Accurate photodetector quantum efficiency (QE) calibration is crucial for optical measurements.
• Existing calibration methods often have limitations in accuracy and traceability.
• Correlated photon sources offer a promising avenue for absolute QE determination.

Purpose of the Study:

• To perform absolute calibration of photodetector QE using correlated photon sources.
• To demonstrate the interlaboratory consistency and setup independence of the photon correlation technique.
• To develop a robust measurement protocol for QE calibration.

Main Methods:

• Absolute QE calibration using entangled photon pairs generated via spontaneous parametric down-conversion.
• Interlaboratory comparison of measurements between the National Institute of Standards and Technology (NIST) and Istituto Elettrotecnico Nazionale (IEN).
• Calibration of both free-space and fiber-coupled avalanche photodiode modules.

Main Results:

• The photon correlation technique demonstrated inherent absoluteness, with detector nonuniformity being the primary limitation, not the method's uncertainty.
• Successful interlaboratory comparison between NIST and IEN, validating the technique's robustness.
• Improved accuracy in QE calibration at IEN using an optimized nonlinear crystal for photon generation.

Conclusions:

• The correlated photon source technique is a reliable method for absolute photodetector QE calibration.
• Detector nonuniformity needs careful consideration for high-accuracy comparisons.
• The developed protocol enables experimental determination and operational verification of measurement uncertainties.