In the invention, light incident onto an end surface of one-dimensional
photonic crystal is phase-modulated in the same period and direction as
those of the photonic crystal to thereby propagate only specific
high-order band light in the photonic crystal. That is, a phase modulation
unit for generating phase-modulated wave having the same period as that of
the periodic structure is disposed adjacent or close to a light incident
surface of the periodic structure.
