Optical device using photonic crystal and light beam deflection method using the same

An optical device comprising:

• a photonic crystal designed to have a shape of a dispersion surface with a strong direction dependence at a frequency;
• light input means configured to allow a light beam having a wavelength determined by said frequency to be incident on said photonic crystal at an incident angle determined from a region with a large change of direction dependence in the shape of the dispersion surface according to the law of conservation of momentum;
• and
• a deflection controller configured to apply an energy to said photonic crystal in order to switch between a first optical path for allowing the light beam incident on said photonic crystal to pass through said photonic crystal, thereby obtaining a first transmitted light beam, and a second optical path, which is angularly different from said first optical path, for allowing the light beam incident on said photonic crystal to pass through said photonic crystal, thereby obtaining a second transmitted light beam.