An optical locking system comprises a light emitter, an optical wavelength identifying system, and a locking unit. The optical wavelength identifying system comprises an optical wavelength detecting device, a memory, a modulator, a comparison module, and an instruction module. The optical wavelength detecting device comprises a polarizer, a detecting element, a measuring device, and a data processor. The detecting element configured to form a temperature difference or a potential difference between two points of the detecting element when exposed to the polarized light, wherein the detecting element comprises a carbon nanotube structure comprising a plurality of carbon nanotubes oriented along the same direction, and angles between a polarizing direction of the polarized light and an oriented direction of the plurality of carbon nanotubes is adjustable.