Abstract: A surface acoustic wave filter comprises a first electrode structure array which is formed on the piezoelectric substrate, and includes an input/output IDT, two receipt IDTs formed outside the input/output IDT and two reflectors formed outside the two receipt IDTs, and a second electrode structure array which is formed on the piezoelectric substrate and includes an input/output IDT, two receipt IDTs formed outside the input/output IDT and two reflectors formed outside the two receipt IDTs, which are concatenated with each other. In a case that the surface acoustic wave filter is represented by a symmetrical lattice-type circuit which is expressed by a serial arm impedance and a parallel arm impedance and is electrically equivalent to the same, at least two resonances of the serial arm impedance and at least three resonances of the parallel arm impedance are used to form a passband. The surface acoustic wave filter can have wide bands and low spurious signal.

Abstract: There is disclosed a method of producing dielectric diffraction gratings. This method comprises (a) preparing a preform by forming one upon another layers of two or more glasses having different refractive indices at a given period, and (b) cutting the preform into flat pieces.