Process for fabricating an optical device for generating a second harmonic optical beam

Claim 1

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate (1) that has a second, opposite polarization, characterized by the steps of: applying a proton exchange process for exchanging cations in said ferroelectric substrate with protons selectively in correspondence to a region (4) in which said inversion region is to be formed; providing electrodes (5, 6) on upper and lower major surfaces of said ferroelectric substrate; and growing said inversion region (4) selectively in a direction vertical to said upper major surface of the ferroelectric substrate by applying a d.c. voltage across the electrode on the upper major surface of the ferroelectric substrate and the electrode on the lower major surface of the ferroelectric substrate to induce an electric field acting in a direction coincident to a direction of said first polarization in said ferroelectric substrate.

Claim 8

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate (1) that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (42a, 42b, 6) respectively on upper and lower major surfaces of a ferroelectric substrate (1); patterning the upper electrode such that a plurality of electrode fingers (42a) forming a first electrode group are formed on the upper major surface of the substrate in correspondence to a region (4) in which said inversion region is to be formed and such that a plurality of electrode fingers (42b) forming a second electrode group are formed such that each of said electrode fingers forming said second electrode group are formed adjacent to but in separation from said electrode fingers that form the first electrode group; causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said electrode fingers (42a) that form said first group electrode are provided; characterized in that said step of causing the inversion comprising: a step of applying a first voltage (V₁) to the electrode fingers (42a) that forms the first electrode group and a step of applying a second voltage (V₂) to the electrode finger (42b) that forms the second electrode group, such that said first voltage has a magnitude larger than a magnitude of said second voltage (V₁ > V₂), said magnitude of said first voltage being set sufficient to cause the inversion of polarization in the ferroelectric substrate, while said magnitude of said second voltage being set not to cause the inversion of polarization in the ferroelectric substrate.

Claim 10

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (21, 6) respectively on upper and lower major surfaces of a ferroelectric substrate (1); patterning the upper electrode such that a plurality of electrode patterns (21) are left on the upper major surface of the substrate in correspondence to a region (4) in which said inversion region is to be formed; and causing an inversion of polarization in said ferroelectric substrate in correspondence to said region wherein said electrode patterns are provided by applying a voltage to the electrode fingers on the upper major surface of the substrate; characterized in that said step of applying the voltage is achieved in a reduced pressure environment.

Claim 11

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (21, 42a, 42b, 6) respectively on upper and lower major surfaces of a ferroelectric substrate (1); patterning the upper electrode such that a plurality of electrode fingers (42a, 21) are formed on the upper major surface of the substrate (1) in correspondence to a region in which said inversion region (4) is to be formed; and causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said electrode fingers are provided by applying a voltage to the electrode fingers; characterized in that an insulation layer (24b, 41b) is provided on said upper major surface of said substrate (1) such that said insulation layer covers at least those parts of the upper major surface of the substrate that are exposed between the electrode fingers of said electrode pattern.

Claim 12

A method for forming an inversion region having a first polarization in a ferroelectric substrate that has a second, opposite polarization, characterized by the steps of: providing a first insulation layer (24a, 41a) to cover an upper major surface of the ferroelectric substrate (1); providing an upper electrode (21, 41a) on said first insulation layer that covers the upper major surface of the ferroelectric substrate; providing a lower electrode (6) on a lower major surface of the ferroelectric substrate; patterning the upper electrode such that a plurality of electrode fingers (21, 41a) are formed on the upper major surface of the substrate in correspondence to a region in which said inversion region is to be formed; providing a second insulation layer (24b, 41b) on said first insulation layer (24a, 41a) such that said second insulation layer covers at least those parts of the upper major surface of the ferroelectric substrate (1) that are exposed between the electrode fingers of said electrode pattern; and causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said electrode fingers are provided by applying a voltage to the electrode fingers.

Claim 13

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate (1) that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (51, 6) respectively on upper and lower major surfaces of a ferroelectric substrate; patterning the upper electrode (51) such that a plurality of electrode fingers (51a) are formed on the upper major surface of the substrate in correspondence to a region (4) in which said inversion region is to be formed; and causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said electrode patterns are provided by applying a voltage to the electrode fingers on the upper major surface of the substrate; characterized in that said method further comprises a step of modifying said electrode finger (51a) on said upper major surface of said substrate to form a buffer structure (52, 53) for eliminating an electric discharge occurring at the electrode fingers.

Claim 16

A method for forming an inversion region having a first polarization in a ferroelectric substrate that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (51, 6) respectively on upper and lower major surfaces of a ferroelectric substrate (1); patterning the upper electrode such that a plurality of electrode fingers (51a) are formed on the upper major surface of the substrate in correspondence to a region in which said inversion region is to be formed; and causing an inversion of polarization in said ferroelectric substrate in correspondence to said region (4) wherein said electrode fingers are provided; characterized in that said step of causing the inversion of polarization comprises a step of irradiating said electrode (6) at the lower major surface by a charged particle beam.

Claim 17

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate (1) that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (61, 6) respectively on upper and lower major surfaces of a ferroelectric substrate; patterning the upper electrode such that a plurality of finger patterns (61a) are formed on the upper major surface of the substrate to extend parallel with each other in correspondence to a region in which said inversion region (4) is to be formed, and causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said finger patterns (61a) are provided by applying a predetermined voltage across the electrode (61) provided on the upper major surface of the substrate and the electrode (6) at the lower major surface of the substrate; characterized in that said step of patterning being conducted such that said finger patterns (61a) have an elongate rectangular shape extending with a size (L) of less than 50 µm in an elongating direction thereof.

Claim 20

A method for forming an inversion region (4) having a first polarization in a ferroelectric substrate (1) that has a second, opposite polarization, comprising the steps of: providing upper and lower electrodes (61, 6) respectively on upper and lower major surfaces of a ferroelectric substrate; patterning the upper electrode such that a plurality of finger patterns (61a) are formed on the upper major surface of the substrate to extend parallel with each other in correspondence to a region in which said inversion region (4) is to be formed, and causing an inversion of polarization in said ferroelectric substrate (1) in correspondence to said region (4) wherein said finger patterns (61a) are provided by applying a predetermined voltage across the electrode (61) provided on the upper major surface of the substrate and the electrode (6) at the lower major surface of the substrate; characterized in that said step of patterning is conducted such that said finger patterns have an elongate rectangular shape extending with a size of less than 50 µm in an elongating direction; said step of forming the finger patterns comprising the steps of: forming a plurality of finger-shaped openings (61a) in said upper electrode (61) as said finger patterns such that each of said finger-shaped openings extends in a direction coincident to said elongating direction of said finger patterns and such that said plurality of finger-shaped openings are arranged to form a row extending in a direction different from said elongating direction of said finger patterns; and forming a pair of elongating openings (61b) in said upper electrode to extend parallel with each other in a direction coincident to the direction of said row at both sides thereof; said step of patterning further comprising a step for forming a structure (6a, 6b) for avoiding electric discharge between said upper and lower electrodes (61, 6); said step of applying the predetermined voltage being conducted in a reduced pressure environment for avoiding electric discharge occurring between said upper and lower electrodes (61, 6).