Method and apparatus for optical waveguide-to-semiconductor coupling and optical vias for monolithically integrated electronic and photonic circuits
First Claim
1. An optical out-of-plane coupler on a monolithically integrated metal-oxide-semiconductor (MOS) integrated circuit comprising:
- a waveguide; and
a grating coupled to the waveguide, the grating comprising a plurality of scattering units,each scattering unit further comprising;
a first scattering element formed of a first shape formed in a polysilicon gate layer of the integrated circuit, anda second scattering element formed of a second shape formed in an active layer of the integrated circuit,each shape having width smaller than two microns,the polysilicon gate layer being also used to form gates of MOS transistors of the integrated circuit;
the waveguide being formed in a layer comprising a layer selected from the group consisting of the polysilicon gate layer and the active layer;
the first scattering element in each scattering unit having a first side (E1) disposed towards the waveguide and a second side (E2) disposed more distant from the waveguide than side E1;
the second scattering element in each scattering unit having a first side (E3) disposed towards the waveguide and a second side (E4) disposed more distant from the waveguide than side E3;
wherein sides E1 and E3 are offset along the in-plane propagation direction from the waveguide W to the grating;
wherein sides E2 and E4 are offset along the in-plane propagation direction from the waveguide to the grating;
wherein;
if side E1 is closer to the waveguide than side E3, then side E2 is closer to the waveguide than side E4 and light will be scattered with constructive interference out-of-plane toward the second scattering elements,and if side E3 is closer to the waveguide than side E1, then side E4 is closer to the waveguide than side E2 and light will be scattered with constructive interference out-of-plane toward the first scattering elements; and
wherein a distance from E1 to E3 is less than a design wavelength of light, the design wavelength being less than 1650 nanometers;
and a distance measured in an axis perpendicular to a plane of the integrated circuit between the first and second scattering element being less than 500 nanometers.
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Abstract
An optical coupler has a waveguide coupled to a grating of multiple scattering units, each scattering unit having a first scattering element formed of a shape in a polysilicon gate layer and a second scattering element formed of a shape in a body silicon layer of a metal-oxide-semiconductor (MOS) integrated circuit (IC). The couplers may be used in a system having a coupler on each of a first and second IC, infrared light being formed into a beam passing between the couplers. Vias may be interposed in third ICs between the first and second ICs. The couplers may be configured with nonuniform width of scattering elements to produce Gaussian or focused beams.
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Citations
23 Claims
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1. An optical out-of-plane coupler on a monolithically integrated metal-oxide-semiconductor (MOS) integrated circuit comprising:
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a waveguide; and a grating coupled to the waveguide, the grating comprising a plurality of scattering units, each scattering unit further comprising; a first scattering element formed of a first shape formed in a polysilicon gate layer of the integrated circuit, and a second scattering element formed of a second shape formed in an active layer of the integrated circuit, each shape having width smaller than two microns, the polysilicon gate layer being also used to form gates of MOS transistors of the integrated circuit; the waveguide being formed in a layer comprising a layer selected from the group consisting of the polysilicon gate layer and the active layer; the first scattering element in each scattering unit having a first side (E1) disposed towards the waveguide and a second side (E2) disposed more distant from the waveguide than side E1; the second scattering element in each scattering unit having a first side (E3) disposed towards the waveguide and a second side (E4) disposed more distant from the waveguide than side E3; wherein sides E1 and E3 are offset along the in-plane propagation direction from the waveguide W to the grating; wherein sides E2 and E4 are offset along the in-plane propagation direction from the waveguide to the grating; wherein; if side E1 is closer to the waveguide than side E3, then side E2 is closer to the waveguide than side E4 and light will be scattered with constructive interference out-of-plane toward the second scattering elements, and if side E3 is closer to the waveguide than side E1, then side E4 is closer to the waveguide than side E2 and light will be scattered with constructive interference out-of-plane toward the first scattering elements; and wherein a distance from E1 to E3 is less than a design wavelength of light, the design wavelength being less than 1650 nanometers; and a distance measured in an axis perpendicular to a plane of the integrated circuit between the first and second scattering element being less than 500 nanometers. - View Dependent Claims (2, 3, 10, 21, 22)
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4. An interlayer out-of-plane optical coupling system comprising:
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a first integrated circuit having a first coupler, the first coupler comprising; a first waveguide; and a first grating coupled to the first waveguide, the first grating comprising a plurality of scattering units, each scattering unit further comprising at least a first scattering element formed of; a shape in an active silicon layer of the first integrated circuit; and a shape in a polysilicon gate layer of the first integrated circuit, wherein; each of the shape in the active silicon layer and the shape in the polysilicon gate layer have a leading edge, in at least one scattering unit the leading edge of the shape in the active silicon layer being offset by at least 100 nm from the leading edge of the shape in the polysilicon gate layer, each of the shape in the active silicon layer and the shape in the polysilicon gate layer have a trailing edge, in at least one scattering unit the trailing edge of the shape in the active silicon layer being offset by at least 100 nm from the trailing edge of the shape in the polysilicon gate layer, if the leading edge of the shape in the polysilicon layer is closer to the waveguide than the leading edge of the shape in the active layer, then the trailing edge of the shape in the polysilicon layer is closer to the waveguide than the trailing edge of the shape in the active layer and light will be scattered with constructive interference out-of-plane toward the shape in the active layer, and if the leading edge of the shape in the active layer is closer to the waveguide than the leading edge of the shape in the polysilicon layer, then the trailing edge of the shape in the active layer is closer to the waveguide than the trailing edge of the shape in the polysilicon layer and light will be scattered with constructive interference out-of-plane toward the shape in the polysilicon layer; and a second integrated circuit having a second coupler, the second coupler comprising a second waveguide coupled to a second grating comprising a plurality of second scattering units, each second scattering unit further comprising at least a second scattering element, the first grating configured to divert light out-of-plane from the first waveguide primarily along a light path directed to the second optical coupler. - View Dependent Claims (5, 6, 7, 8, 9)
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11. An out-of-plane grating coupler comprising:
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a waveguide coupled to a grating comprising a plurality of scattering units, at least a subset of the scattering units each further comprising; a first structure formed of a first core material layer having a first thickness, adjacent a second structure formed of a second core material layer having a second thickness; wherein the first and second core material layer are different material layers; wherein; E1 is a first edge of the first structure other than top and bottom edges, E2 is a second edge of the first structure other than top or bottom edges, E3 is a first edge of the second structure other than top or bottom edges, and E4 is a second edge of the second structure other than top or bottom edges, wherein edges E1 and E3 are offset, and edges E2 and E4 are offset along a direction of propagation in a plane of the first material layer from an edge of the waveguide toward the grating such that; E1 is closer to the waveguide than E3, and E2 is closer to the waveguide than E4, the offset from edge E1 to edge E3 is less than 2000 nanometers, and light will be scattered with constructive interference out-of-plane toward the second core material layer. - View Dependent Claims (12, 13, 23)
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14. An optical system comprising:
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a first integrated circuit having a first out-of-plane coupler, the first out-of-plane coupler comprising; a first waveguide; and a first grating coupled to the first waveguide, the first grating comprising a plurality of scattering units; a second out-of-plane coupler comprising; a second waveguide; and a second grating coupled to the second waveguide, the second grating comprising a plurality of second scattering units and located in a plane different from a plane of the first out-of-plane coupler; wherein the first out-of-plane coupler is configured as a focusing coupler for producing a focused optical beam having a beam waist between the first out-of-plane coupler and the second out-of-plane coupler, the second out-of-plane coupler being aligned to receive the focused optical beam produced by the first out-of-plane coupler; and
wherein the scattering units of the first out-of-plane coupler comprise a first portion of silicon and gap, the first portion of silicon having a first thickness and formed on a first layer of silicon, adjacent a second portion of silicon and gap, the second portion of silicon having a second thickness and formed on a second layer of silicon, the first waveguide comprising a silicon structure formed on the first or second layer of silicon, there being an offset of 100 nm to 2000 nm in a plane of the waveguide between the first portion of silicon and the second portion of silicon such that light will be scattered with constructive interference out-of-plane toward whichever of the first portion of silicon and the second portion of silicon is farther from the waveguide;wherein, when viewed from a point perpendicular to a plane of the coupler, the first portion of silicon having a first section overlapping the corresponding second portion of silicon, and a second section not overlapping the corresponding second portion of silicon; and wherein the second portion of silicon has a first section overlapping the first portion of silicon, and a second section portion not overlapping the first portion of silicon. - View Dependent Claims (15, 16)
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17. A planar, unidirectional out-of-plane optical coupler on a chip, for coupling light at an operating wavelength, the planar, unidirectional out-of-plane optical coupler on a chip comprising:
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a first grating comprising an array of lithographically defined elements in a first material layer; a second grating comprising an array of lithographically defined elements in a second planar material layer different from the first material layer; and a waveguide; wherein; the waveguide comprises a portion of a lithographically patterned material layer selected from the first and second planar material layers; the first grating being displaced from the second grating in a direction normal to the plane of the first planar material layer by a distance that is between 25 nm and 500 nm such that light will be scattered with constructive interference out-of-plane toward whichever of the first grating and the second grating is farther from the waveguide; the lithographically defined elements forming the first grating are spaced in the plane of the first planar material by a distance of between 100 nm and 2000 nm; and the lithographically defined elements forming the second grating being spaced in the plane of the second planar material by a distance between 100 nm and 2000 nm; wherein, when viewed from a point perpendicular to a plane of the coupler, a lithographically defined element of the second grating has a first portion overlapping a corresponding lithographically defined element of the first grating, and a second portion not overlapping the corresponding lithographically defined element of the first grating; and wherein the corresponding lithographically defined element of the first grating has a third portion overlapping the lithographically defined element of the second grating, and a fourth portion not overlapping the corresponding lithographically defined element of the second grating. - View Dependent Claims (18, 19, 20)
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Specification