Waveguide line electrode structure and electro-optic modulator

1 . A waveguide line electrode structure, comprising:

a first ground electrode, a signal electrode, and a second ground electrode, wherein the first ground electrode, the signal electrode, and the second ground electrode are sequentially arranged spaced apart from each other;

an optical waveguide comprising a first branch and a second branch, the first branch being arranged in a first gap formed between the first ground electrode and the signal electrode, and the second branch being arranged in a second gap formed between the second ground electrode and the signal electrode;

a first covering layer at least partially covering the first branch;

a second covering layer at least partially covering the second branch; and

at least one electrode extension portion, wherein each electrode extension portion extends from a first side of the signal electrode facing the first ground electrode, a second side of the signal electrode facing the second ground electrode, a third side of the first ground electrode facing the signal electrode or a fourth side of the second ground electrode facing the signal electrode to the first gap or the second gap adjacent to the signal electrode, and each electrode extension portion extends to an upper surface of the first covering layer or the second covering layer,

wherein the upper surface of at least one of the first covering layer or the second covering layer comprises at least one inclined section, each inclined section extending obliquely upward in a direction from the signal electrode, the first ground electrode, or the second ground electrode toward the first branch or the second branch adjacent to the signal electrode,

wherein only corresponding portions of the at least one electrode extension portion are configured to directly contact the first covering layer or the second covering layer, and the first ground electrode, the signal electrode, and the second ground electrode are not in direct contact with the first covering layer or the second covering layer.

2 . The waveguide line electrode structure according to claim 1 ,

wherein

the electrode extension portion extends to the upper surface of the first covering layer or the second covering layer via the inclined section; or

the electrode extension portion and at least a part of the signal electrode connected to the electrode extension portion extend to the upper surface of the first covering layer or the second covering layer via the inclined section.

3 . The waveguide line electrode structure according to claim 2 , wherein the electrode extension portion comprises:

a plurality of extension sub-electrodes, each of the extension sub-electrodes extending from one side of the first ground electrode, the second ground electrode or the signal electrode toward the first gap or the second gap adjacent to the side.

4 . The waveguide line electrode structure according to claim 3 , wherein each of the extension sub-electrodes comprises:

an extension portion extending from one side of the first ground electrode, the second ground electrode or the signal electrode toward the first gap or the second gap adjacent to the side.

5 . The waveguide line electrode structure according to claim 4 , wherein each of the extension sub-electrodes further comprises:

an electrode portion arranged at an extended end portion of the extension portion and extending in a direction parallel to the first branch or the second branch.

6 . The waveguide line electrode structure according to claim 3 , wherein at least one of the upper surface of the first covering layer or the second covering layer further comprises:

a platform section contiguous to a higher side edge of the inclined section, wherein

the optical waveguide is arranged below the platform section, and an end of the extension sub-electrode is arranged on the platform section or the inclined section.

7 . The waveguide line electrode structure according to claim 3 , wherein

in each electrode extension portion, electrode portions of two adjacent extension sub-electrodes are spaced apart from each other.

8 . The waveguide line electrode structure according to claim 3 , wherein

in each electrode extension portion, electrode portions of two adjacent extension sub-electrodes are connected end to end.

9 . The waveguide line electrode structure according to claim 1 , wherein the at least one electrode extension portion comprises:

a first electrode extension portion arranged on the first side of the signal electrode facing the first ground electrode;

a second electrode extension portion arranged on the second side of the signal electrode facing the second ground electrode;

a third electrode extension portion arranged on the third side of the first ground electrode facing the signal electrode; and

a fourth electrode extension portion arranged on the fourth side of the second ground electrode facing the signal electrode.

10 . The waveguide line electrode structure according to claim 9 , wherein

the first electrode extension portion comprises a plurality of first extension sub-electrodes, and each of the first extension sub-electrodes extends from the first side toward the first gap; and

the second electrode extension portion comprises a plurality of second extension sub-electrodes, and each of the second extension sub-electrodes extends from the second side toward the second gap.

11 . The waveguide line electrode structure according to claim 9 , wherein

the third electrode extension portion comprises a plurality of third extension sub-electrodes, and each of the third extension sub-electrodes extends from the third side toward the first gap; and

the fourth electrode extension portion comprises a plurality of fourth extension sub-electrodes, and each of the fourth extension sub-electrodes extends from the fourth side toward the second gap.

12 . The waveguide line electrode structure according to claim 9 , wherein

the first electrode extension portion comprises a plurality of first extension sub-electrodes, and each of the first extension sub-electrodes extends from the first side toward the first gap;

the second electrode extension portion comprises a plurality of second extension sub-electrodes, and each of the second extension sub-electrodes extends from the second side toward the second gap;

the third electrode extension portion comprises a plurality of third extension sub-electrodes, and each of the third extension sub-electrodes extends from the third side toward the first gap; and

the fourth electrode extension portion comprises a plurality of fourth extension sub-electrodes, and each of the fourth extension sub-electrodes extends from the fourth side toward the second gap.

13 . The waveguide line electrode structure according to claim 12 , wherein

each of the first extension sub-electrodes in the first electrode extension portion is arranged opposite the corresponding third extension sub-electrode in the third electrode extension portion; and

each of the second extension sub-electrodes in the second electrode extension portion is arranged opposite the corresponding fourth extension sub-electrode in the fourth electrode extension portion.

14 . The waveguide line electrode structure according to claim 9 , wherein

the upper surface of the first covering layer comprises a first inclined section, a first platform section, and a second inclined section, wherein the first inclined section, the first platform section, and the second inclined section are sequentially contiguous to each other, the first inclined section facing the first ground electrode, and the second inclined section facing the signal electrode; and

the upper surface of the second covering layer comprises a third inclined section, a second platform section, and a fourth inclined section, wherein the third inclined section, the second platform section, and the fourth inclined section are sequentially contiguous to each other, the third inclined section facing the signal electrode, and the fourth inclined section facing the second ground electrode, wherein

the first electrode extension portion extends to the first platform section via the second inclined section, the second electrode extension portion extends to the second platform section via the third inclined section, the third electrode extension portion extends to the first platform section via the first inclined section, and the fourth electrode extension portion extends to the second platform section via the fourth inclined section.

15 . The waveguide line electrode structure according to claim 1 , wherein

a refractive index of at least one of the first covering layer or the second covering layer is less than that of the optical waveguide.

16 . An electro-optic modulator, comprising:

a substrate;

an isolation layer arranged on an upper surface of the substrate;

a thin film layer arranged on an upper surface of the isolation layer, the thin film layer being made of a photoelectric material;

a waveguide line electrode structure, wherein the waveguide line electrode structure is arranged on an upper surface of the thin film layer and wherein the waveguide line electrode structure comprises:

a first ground electrode, a signal electrode, and a second ground electrode, wherein the first ground electrode, the signal electrode, and the second ground electrode are sequentially arranged spaced apart from each other;

an optical waveguide comprising a first branch and a second branch, the first branch being arranged in a first gap formed between the first ground electrode and the signal electrode, and the second branch being arranged in a second gap formed between the second ground electrode and the signal electrode;

a first covering layer at least partially covering the first branch;

a second covering layer at least partially covering the second branch; and

at least one electrode extension portion, wherein each electrode extension portion extends from a first side of the signal electrode facing the first ground electrode, a second side of the signal electrode facing the second ground electrode, a third side of the first ground electrode facing the signal electrode or a fourth side of the second ground electrode facing the signal electrode to the first gap or the second gap adjacent to the signal electrode, and each electrode extension portion extends to an upper surface of the first covering layer or the second covering layer,

wherein the upper surface of at least one of the first covering layer or the second covering layer comprises at least one inclined section, each inclined section extending obliquely upward in a direction from the signal electrode, the first ground electrode or the second ground electrode toward the first branch or the second branch adjacent to the signal electrode,

wherein only corresponding portions of the at least one electrode extension portion are configured to directly contact the first covering layer or the second covering layer, and the first ground electrode, the signal electrode, and the second ground electrode are not in direct contact with the first covering layer or the second covering layer; and

an optical assembly arranged on the upper surface of the thin film layer and configured to:

split light propagating in the optical waveguide into light in the first branch and light in the second branch, and

combine the light in the first branch and the light in the second branch into the light propagating in the optical waveguide again.

17 . The electro-optic modulator according to claim 16 , wherein

lower surfaces of the signal electrode, the first ground electrode and the second ground electrode penetrate through the thin film layer and are in direct contact with the isolation layer.

18 . The electro-optic modulator according to claim 16 , wherein the thin film layer is an etched X-cut, Y-cut, or Z-cut thin film of lithium niobate.