A rhodopsin family protein is inserted into an etalon type cavity having partially reflecting mirrors as principal components having a reflectivity of 50% to less than 100% for light having a wavelength in the 650-800 nm region and a transmissivity of 30% or more for light having a wavelength in the 400-600 nm region to form a photo-controlled spatial modulator. By utilizing a change in the refractive index by light of the photo-sensitive protein, near infrared light of a stronger intensity can be controlled by weaker visible light, and the information contained in the light signal on a two-dimension plane can be rapidly controlled by a light signal of weaker intensity of another two-dimension plane by using an optical switch of a simple construction.