Mid-infrared Spectral Responsivity Scale Based on an Absolute Cryogenic Radiometer and a Tunable Quantum Cascade Laser

The spectral optical radiant power of a quantum cascade laser (QCL) in the (7.35-10.6) mu m spectral range has been measured using a Y-shape absolute cryogenic radiometer (ACR). The spectral responsivity (SR) of a transfer detector based on an integrating-sphere-coupled mercury-cadmium-telluride (IS-MCT) photoconductive detector has been calibrated. The optical radiant power of the QCL can be adjusted and stabilized in the range of (0.035-0.6) mW. The relative uncertainty of the ACR-based optical radiant power measurement was evaluated to be 0.023%-0.04% (k = 1). The relative uncertainty of the SR calibration of the IS-MCT transfer detector was analyzed to be 0.097%-0.16% (k = 1). The spectral range for the SR calibration can be extended to cover (3-12) mu m using commercially available QCLs.