Optical integrated modulator
First Claim
1. An optical modulator comprising:
- a substrate formed of a material which has a refractive index that changes when an electric field is applied;
an optical waveguide formed in contact with said substrate;
a plurality of insulating buffer layers formed on surfaces of the optical waveguide and of the substrate, andmeans for applying an electric field which causes a radio frequency electric field onto said optical waveguide via said insulating buffer layer, said applying means including a first electrode arranged along said optical waveguide and a second electrode arranged in parallel to said first electrode,wherein said insulating buffer layers include a first region formed between said first electrode and said optical waveguide having a width equal to or narrower than a width of the first electrode, and a second region formed between said second electrode and said substrate,wherein the first and second electrodes are formed in such a shape and with such an interval distance therebetween as to establish a relation of C0 =1/(c·
n0 ·
Z0) among a static capacitance C0 of a time when said substrate, optical waveguide and insulating buffer layers are assumed not to exist, a refractive index n0 of said optical waveguide against transmitting light, a velocity of light c, and a characteristic impedance Z0 required between said first and second electrodes, and that said substrate, said optical waveguide and said insulating buffer layers are formed in such a form and arrangement of such a material as to substantially establish the relation of C=n0 /(Z0 ·
c) with the static capacitance C between said first and second electrodes.
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Accused Products
Abstract
This invention enables low voltage operation and improves matching in velocities of the radio frequency and of light by lowering effective index and to thereby expand modulation frequency bandwidth by structuring an optical modulator where a substrate of the material of which refractive index changes by an application of electric field description, and the insulating buffer layers are eliminated from the regions other than the electrodes. By structuring the modulator in a manner to satisfy the prescribed conditions with dimensions of each unit, the light can be matched in complete phase matching (group velocity matching) with radio frequency while characteristic impedance of the electrodes is fixed at a desired value.
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Citations
8 Claims
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1. An optical modulator comprising:
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a substrate formed of a material which has a refractive index that changes when an electric field is applied; an optical waveguide formed in contact with said substrate; a plurality of insulating buffer layers formed on surfaces of the optical waveguide and of the substrate, and means for applying an electric field which causes a radio frequency electric field onto said optical waveguide via said insulating buffer layer, said applying means including a first electrode arranged along said optical waveguide and a second electrode arranged in parallel to said first electrode, wherein said insulating buffer layers include a first region formed between said first electrode and said optical waveguide having a width equal to or narrower than a width of the first electrode, and a second region formed between said second electrode and said substrate, wherein the first and second electrodes are formed in such a shape and with such an interval distance therebetween as to establish a relation of C0 =1/(c·
n0 ·
Z0) among a static capacitance C0 of a time when said substrate, optical waveguide and insulating buffer layers are assumed not to exist, a refractive index n0 of said optical waveguide against transmitting light, a velocity of light c, and a characteristic impedance Z0 required between said first and second electrodes, and that said substrate, said optical waveguide and said insulating buffer layers are formed in such a form and arrangement of such a material as to substantially establish the relation of C=n0 /(Z0 ·
c) with the static capacitance C between said first and second electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification