Accordingly, the provision of the sub-pillar 24 is a contributing factor for increasing the number of channels to be accommodated and keeping high light transmittance. [0111] As described above, since five or six resonant pillars such as the main pillar 21 and the sub-pillars, 22, 23 and 24 constituting the resonator 51 are formed of the same medium as that of the pillars 62 forming the periodic s