Disclosed are a functional material and a functional device, each of which
is capable of changing a wavelength of a transmission electromagnetic wave such
as transmission light or a transmission sound wave such as a transmission ultrasonic
wave through the device on the basis of a signal supplied from external. Each of
the functional material and the functional device includes a periodic structure
having a periodicity with a unit cycle on the order of a wavelength of an electromagnetic
wave or a sound wave, and means for disturbing the periodicity which is inserted
in at least one portion of the periodic structure, wherein a wavelength of the
electromagnetic wave or sound wave passing through the periodic structure by controlling
the means on a signal supplied from external.