Reducing photodiode reflectance by Brewster-angle operation

摘要

Methods for reducing reflectance losses at multiple wavelengths with a silicon photodiode detector are described. Using thick oxide layer and Brewster-angle operation it is shown that specular reflectance losses can be theoretically decreased below 1 ppm (part per million) in a simple measurement arrangement. Additionally, a detector structure is presented which can be used to reduce the measurement uncertainties due to diffuse reflectance below 1 ppm, even if the total diffuse reflectance losses from a plain photodiode would be two orders of magnitude larger.