An image sensor includes a semiconductor layer that low-pass filters light of different wavelengths. For example, the semiconductor layer proportionately absorbs photons of shorter wavelengths and proportionately passes more photons of longer wavelengths such that the longer wavelength photons often pass through without being absorbed. An imaging pixel having a photodiode is formed on a front surface of the semiconductor layer, where the photodiode is an N− region formed within the P-type region of the semiconductor layer. A P+ layer is formed between the N− region of the photodiode and a back surface of the semiconductor layer. A mirror that primarily reflects photons of red and/or infra-red wavelengths is formed on the back surface of the semiconductor layer.