Polarization inversion method for ferroelectric substances

1. A polarization inversion method for a ferroelectric substance, comprising the steps of:

i) forming a pattern electrode, which has a predetermined pattern, and a connecting electrode, which is electrically connected to the pattern electrode, on one surface of a single-polarized ferroelectric substance crystal,

ii) locating a corona wire at a position which stands facing the other surface of the ferroelectric substance crystal, and

iii) applying an electric field across the ferroelectric substance crystal with a corona charging technique by use of the corona wire and the pattern electrode, forming a polarization inversion region having a shape corresponding to the predetermined pattern of the pattern electrode in the ferroelectric substance crystal,

wherein the application of the electric field is performed in a state, in which an electrical insulating material is located on the other surface of the ferroelectric substance crystal and at a position that corresponds to at least a position of a certain area of the connecting electrode.

2. A polarization inversion method for a ferroelectric substance as defined in claim 1 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode.

3. A polarization inversion method for a ferroelectric substance as defined in claim 1 wherein the pattern electrode comprises a plurality of periodic electrodes, which are arrayed with a predetermined period, and

the connecting electrode is electrically connected to each of the periodic electrodes in order to connect the periodic electrodes to one another.

4. A polarization inversion method for a ferroelectric substance as defined in claim 3 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode, which bent area is electrically connected to the periodic electrodes.

5. A process for producing an optical wavelength converting device, in which a polarization inversion method for a ferroelectric substance as defined in claim 3 is employed, the process comprising the steps of:

a) utilizing a nonlinear optical crystal as the single-polarized ferroelectric substance crystal, and

b) forming a periodic polarization inversion structure, which corresponds to a pattern of the periodic electrodes, in the nonlinear optical crystal.

6. A process for producing an optical wavelength converting device as defined in claim 5 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode, which bent area is electrically connected to the periodic electrodes.

7. A process for producing an optical wavelength converting device as defined in claim 5 wherein the ferroelectric substance crystal is a crystal selected from the group consisting of an LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, an MgO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, a ZnO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, and an Sc-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1.

8. A polarization inversion method for a ferroelectric substance as defined in claim 1 wherein the ferroelectric substance crystal is a crystal selected from the group consisting of an LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, an MgO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, a ZnO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, and an Sc-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1.

9. A polarization inversion method for a ferroelectric substance, comprising the steps of:

i) forming a pattern electrode, which has a predetermined pattern, and a connecting electrode, which is electrically connected to the pattern electrode, on one surface of a single-polarized ferroelectric substance crystal, and

ii) applying an electric field across the ferroelectric substance crystal with irradiation of an electron beam to the ferroelectric substance crystal from the side of the other surface of the ferroelectric substance crystal, forming a polarization inversion region having a shape corresponding to the predetermined pattern of the pattern electrode in the ferroelectric substance crystal,

wherein the application of the electric field is performed in a state, in which an electrical insulating material is located on the other surface of the ferroelectric substance crystal and at a position that corresponds to at least a position of a certain area of the connecting electrode.

10. A polarization inversion method for a ferroelectric substance as defined in claim 9 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode.

11. A polarization inversion method for a ferroelectric substance as defined in claim 9 wherein the pattern electrode comprises a plurality of periodic electrodes, which are arrayed with a predetermined period, and

the connecting electrode is electrically connected to each of the periodic electrodes in order to connect the periodic electrodes to one another.

12. A polarization inversion method for a ferroelectric substance as defined in claim 11 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode, which bent area is electrically connected to the periodic electrodes.

13. A process for producing an optical wavelength converting device, in which a polarization inversion method for a ferroelectric substance as defined in claim 11 is employed, the process comprising the steps of:

a) utilizing a nonlinear optical crystal as the single-polarized ferroelectric substance crystal, and

b) forming a periodic polarization inversion structure, which corresponds to a pattern of the periodic electrodes, in the nonlinear optical crystal.

14. A process for producing an optical wavelength converting device as defined in claim 13 wherein the electrical insulating material is located at a position that corresponds to at least a position of a bent area of the connecting electrode, which bent area is electrically connected to the periodic electrodes.

15. A process for producing an optical wavelength converting device as defined in claim 13 wherein the ferroelectric substance crystal is a crystal selected from the group consisting of an LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, an MgO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, a ZnO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, and an Sc-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1.

16. A polarization inversion method for a ferroelectric substance as defined in claim 9 wherein the ferroelectric substance crystal is a crystal selected from the group consisting of an LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, an MgO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, a ZnO-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1, and an Sc-doped LiNb x Ta 1−x O 3 crystal, where 0≦x≦1.