InGaAs trap detector: advancing toward a short-wave infrared standard with 1% uncertainty

Trap detectors are effective as transfer or secondary standards in radiometry, with silicon photodiodes commonly used for visible and germanium for near-infrared (NIR) light detection due to their cost-effectiveness and simple fabrication. However, indium gallium arsenide (InGaAs) photodiodes offer superior performance in the short-wave infrared, 1-1.65 µm range, featuring high internal quantum efficiency, excellent temperature stability, and enhanced durability. In this work, we developed and evaluated a small-footprint InGaAs-based trap detector using an optical trap configuration with two off-the-shelf InGaAs photodiodes and a high-reflectivity mirror. The prototype trap demonstrated excellent stability, low polarization dependence, and good responsivity stability, achieving system detection efficiency exceeding 98% for wavelengths between 1 and 1.3 µm. This versatile detector is suitable for both free-space and optical fiber measurements. The near-unity efficiency of the optical trap configuration shows potential as a primary standard with 1% uncertainty for short-wave infrared standard (SWIR) detection. While the 1% uncertainty of the trap detector is 2 orders of magnitude higher than the 0.01% possible with cryogenic radiometry, the latter requires an expensive cryostat and very specialized expertise. The trap detector, with its robust design and its 1% uncertainty, provides a practical and cost-effective alternative as a standard detector for a wide range of applications, offering a viable solution to reduce reliance on cryogenic radiometry for photodiode calibration.