COMPARISON BETWEEN CRYOGENIC RADIOMETRY AND THE PREDICTED QUANTUM EFFICIENCY OF PN SILICON PHOTODIODE LIGHT TRAPS

In an earlier publication a silicon photodiode self-calibration boot-strap technique was demonstrated in a 633 nm laser power intercomparison with a cryogenic radiometer. The experiment involved individual silicon photodiodes whose quantum efficiency was determined at 633 nm from quantum efficiency measurements made at 442 nm. Although the results were quite good, there were some problems with that intercomparison that warranted further experimental work, the biggest problem being the instability of the reflectance of the silicon photodiodes. In this paper we report a second comparison of the boot-strap technique with a cryogenic radiometer where the reflectance stability problem has been solved by using three-detector light traps instead of individual silicon photodiodes. For five different trap detectors the average difference between the predicted absolute responsivity at 633 nm and that measured by comparison to a cryogenic radiometer was 0.010 % within a combined uncertainty of 0,025 %.