“Photonic crystal” is an artificial novel crystal that has been proposed in recent years and is attracting attention ever since (E. Yablonovitch, Phys. Rev. Lett., 58 (1987) 2059-2062). It can be obtained by cyclically arranging substances having different refractive indexes at intervals substantially equal to the wavelength of light. Research and development efforts are being paid to produce optical elements out of such a crystal substance because it has peculiar optical characteristics including those of showing a forbidden band of light and having an apparently abnormal refractive index that are attributable to its so-called photonic band structure resembling to the band structure of a semiconductor and can be designed artificially in terms of structure and scale.
Of these optical characteristics a phenomenon referred to as super-prism effect may be worthy of paying attention. It is a phenomenon attributable to the apparently abnormal refractive index it has as pointed out above. More specifically, photonic crystal shows an angle of refraction several to several hundreds times greater than that of an ordinary prism made of optical glass.
As an application of the above-described phenomenon, a method of controlling the angle of deflection by changing the wavelength of the laser beam striking a photonic crystal has been proposed (Japanese Patent Application Laid-Open No. 2001-13439, U.S. Pat. No. 6,448,997). There has also been proposed a method of controlling the angle of deflection by shifting the angle of a photonic crystal by means of an actuator (Japanese Patent Application Laid-Open No. 2001-42248, U.S. Patent Application Publication No. 2002/027696).
However, a variable wavelength laser needs to be used as light source in order to change the wavelength of a laser beam but such a laser is generally expensive. Additionally, the use of such a laser is in principle not suitable for applications that require a constant wavelength. Furthermore, in order to shift the angle of a photonic crystal, it is necessary to use a large mechanism for shifting the entire crystal and such a mechanism is accompanied by a problem that the operation frequency lowers in use.
In view of the above-identified circumstances, it is therefore the object of the present invention to provide an optical deflector, an optical switch and an optical scanner having a compact configuration and adapted to operate at high speed as well as an optical deflection method.