Patent ID: 6879739

Claim:
An optical modulator comprising: an optical waveguide formed of a dielectric material having electrooptical effect and formed of (Pb 1-w M w )(Zr 1-x-y Ti x Sn y ) z O 3 (wherein 0≦w≦0.5 0<x≦0.5, 0<y≦0.5, 0.8≦z≦1.2; and M is one kind, or two or more kinds of elements selected from the group consisted of lanthanum, niobium, tantalum, barium and strontium), and electrodes opposed to each other across the optical waveguide, an electric field being applied between the electrodes to change a refractive index of the dielectric material to thereby control a propagating direction of a signal light propagating in the optical waveguide, the dielectric material having a first refractive index in its initial state, having a second refractive index by application of an electric field of a first polarity, and retaining a third refractive index obtained after the electric field has been removed, and the dielectric material having the third refractive index having the first refractive index by the application of an electric field of a second polarity different from the first polarity and removal of the electric field.