Multidecade linearity measurements on Si photodiodes

It is often claimed that silicon photodiodes are linear over many decades, but very little evidence on the experimental verification can be found in the literature. Therefore, an effort was made to investigate the linearity of Si photodiodes over as many decades as possible. Optically, the experiments are based on a cascaded use of the linearity tester described by Sanders, which utilizes the double-aperture method. The electronics include an operational amplifier, a voltage-to-frequency converter, and a counter. Details of the optical and electronic instrumentation will be presented. The measurements are extended to cover a range of about 9 decades, from 10 mA to about 10 pA. Measurements were made on Si photodiodes from various manufacturers, and the results are given.