This is a unique photo detector with two vertically stacked P-N junctions on a single silicon chip. One junction is response enhanced for blue/visible light, the other enhanced for red/near IR. Monochromatic light between 480nm and 850nm generates different amounts of photocurrent in each junction. This produces a unique photocurrent ratio that can be correlated to the exact wavelength of radiation.

The PSS silicon “sandwich” detector consists of two vertically stacked 3.6mm diameter active area silicon PIN photodiodes. The top silicon detector acts as a long-pass filter, only allowing wavelengths greater than 950nm to pass through it to the bottom detector. The unique signature created by the dual current outputs can be used to identify source wavelength or Color temperature by comparing ratios with the standard black body radiation curves.