An photosensitive device, the sensor comprising: a plurality of photosensitive units distributed in an array, each photosensitive unit configured to receive and convert light signal, wherein the photosensitive unit comprises a detecting element and a polarizer, the detecting element comprises a carbon nanotube structure comprising a plurality of carbon nanotubes oriented along the same direction, and the polarizer is configured to generate polarized light to irradiate a part surface of the carbon nanotube structure; a measuring device configured to measure temperature differences or potential differences generated in the carbon nanotube structure by irradiating; a data processor configured to analyze and calculate the potential differences or the temperature differences to obtain the wavelength of the light signal.