To provide a spatial optical modulation element having a long life free
from a deterioration of optical modulation characteristics even if a high
power laser beam with an ultra-short pulse is used as a modulation drive
light, and having a high response speed when e.g. a light having a
wavelength of 1.55 .mu.m is used.A spatial optical modulation element
wherein disposed between a prism 2 and an optical functional material
layer 3 made of an optical functional material with the complex index of
refraction changeable by light irradiation, is a low refractive index
layer 4 made of a transparent material with a refractive index lower than
the refractive index of the prism 2, and carbon nanotubes are used as the
optical function material.