An optical element for controlling light propagation including:
transparent material; and inorganic fine particles dispersed in the
transparent material, wherein the transparent material and the inorganic
fine particles meet at least one of following a) and b): a) a rate of
change of a refractive index of the transparent material with temperature
and a rate of change of a refractive index of the inorganic fine
particles with temperature are opposite in sign; b) a thermal expansion
coefficient of the transparent material and a thermal expansion
coefficient of the inorganic fine particles are opposite in sign.