Waveguides and devices incorporating optically functional cladding regions

• US 20030169958A1
• Filed: 03/21/2003
• Published: 09/11/2003
• Est. Priority Date: 07/26/2001
• Status: Active Grant

• Current Assignee: David William Nippa, Richard William Ridgway, Van Earl Wood
• Original Assignee: David William Nippa, Richard William Ridgway, Van Earl Wood
• Inventors: Ridgway, Richard William, Nippa, David William, Wood, Van Earl
• Granted Patent: US 6,785,435 B2
• Time in Patent Office: Days
• US Class Current: 385/14
• CPC Class Codes: G02F 1/0113 Glass-based, e.g. silica-based, optical waveguides
• CPC Class Codes: G02F 1/065 in an optical waveguide structure
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 1/3136 of interferometric switch type
• CPC Class Codes: G02F 1/3558 Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
• CPC Class Codes: G02F 2203/06 Polarisation independent
• CPC Class Codes: Y10S 977/788 Of specified organic or carbon-based composition
• CPC Class Codes: Y10S 977/834 Optical properties of nanomaterial, e.g. specified transparency, opacity, or index of refraction
• CPC Class Codes: Y10S 977/897 Polymerization

Abstract

Waveguides and integrated optical devices incorporating optically functional cladding regions are provided. In accordance with one embodiment of the present invention, an electrooptic clad waveguide is provided with an optical waveguide core and first and second electrooptic cladding regions. The optical waveguide core is a substantially non-electrooptic material. The cladding regions are electrooptic polymers defining a refractive index that is less than that of the core. The first and second cladding regions may be configured such that their polar axes are oriented in opposite directions, different directions, or along a contour of an electric field. Additional embodiments of the present invention utilize other types of optically functional materials in the cladding regions. Integrated optical devices according to the present invention comprise phase modulators, intensity modulators, 2×2 polarization independent optical switches, high-frequency modulators, wavelength-dependent optical switches, directional couplers employing electrooptic gaps and electrooptic cladding regions, and optical devices with thinned-down waveguide channels and phase compensating elements.

Claims

1. An electrooptic clad waveguide comprising an optical waveguide core defining a primary axis of propagation z, a first cladding region offset from said z axis in a first direction along an x axis perpendicular to said z axis, and a second cladding region offset from said z axis in a second direction along said x axis, wherein:

said optical waveguide core comprises a substantially non-electrooptic material defining a refractive index n₁;

said first cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said second cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said electrooptic polymer of said first cladding region is configured such that its polar axes are oriented in a direction opposite a direction in which polar axes of said electrooptic polymer of said second cladding region are oriented.

2. A waveguide as claimed in claim 1 wherein said polar axes of said first and second cladding regions are oriented parallel to said x-axis.

3. A waveguide as claimed in claim 1 wherein said polar axes of said first and second cladding regions are oriented parallel to a y-axis perpendicular to said x-axis and said z axis

4. A waveguide as claimed in claim 1 wherein:

said electrooptic clad waveguide further comprises first and second control electrodes arranged to create an electric field in said first and second cladding regions; and

said control electrodes are arranged such that a quantitative combination of said electric field and said orientation of said polar axes in said first cladding region is substantially equivalent to a quantitative combination of said electric field and said orientation of said polar axes in said second cladding region.

5. A waveguide as claimed in claim 4 wherein said quantitative combination of said electric field and said orientation of said polar axes is represented by the following equation

Δ

n=−

½

n³r_ijE_j

where r_ij is the electrooptic coefficient of the cladding region at issue and E_j represents the strength and orientation of the electric field.

6. A waveguide as claimed in claim 1 further comprising an outer optical cladding layer defined about a periphery of said core and positioned between said first cladding region and said core and between said second cladding region and said core.

7. A waveguide as claimed in claim 6 wherein said outer optical cladding layer comprises a substantially non-electrooptic material.

8. An electrooptic clad waveguide comprising an optical waveguide core defining a primary axis of propagation z, a first cladding region offset from said z axis in a first direction along an x axis perpendicular to said z axis, a second cladding region offset from said z axis in a second direction along said x axis, and first and second control electrodes, wherein:

said optical waveguide core comprises a substantially non-electrooptic material defining a refractive index n₁;

said first cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said second cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said first and second control electrodes are arranged to enable electrooptic modification of said refractive indices of said first and second cladding regions by creating a contoured electric field in said first and second cladding regions;

said electrooptic polymer of said first cladding region is configured such that its polar axes are oriented substantially along the contour of said electric field;

said electrooptic polymer of said second cladding region is configured such that its polar axes are oriented substantially along the contour of said electric field; and

said contoured electric field and said respective directions of polarization in said first and second cladding regions define a polarization-independent waveguide structure along said primary axis of propagation of said electrooptic clad waveguide; and

9. A waveguide as claimed in claim 8 wherein said contoured electric field is substantially symmetric relative to a plane defined by said z axis and a y axis perpendicular to said x axis and said z axis.

10. An integrated optical device comprising first and second electrooptic clad waveguides arranged to define a directional coupling region, a set of control electrodes, first and second optical inputs, and first and second optical outputs, wherein:

said first electrooptic clad waveguide comprises a substantially non-electrooptic optical waveguide core defining a refractive index n₁;

said waveguide core of said first waveguide is disposed between a first outer electrooptic cladding region and an electrooptic gap region in said directional coupling region;

said first outer cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said electrooptic polymer of said first outer cladding region is configured such that its polar axes are oriented along a common contour;

said electrooptic gap region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said electrooptic polymer of said gap region is configured such that its polar axes are oriented in a common direction;

said second electrooptic clad waveguide comprises a substantially non-electrooptic optical waveguide core defining a refractive index n₁;

said waveguide core of said second waveguide is disposed between a second outer electrooptic cladding region and said electrooptic gap region in said directional coupling region;

said second outer cladding region comprises an electrooptic polymer defining a refractive index that is less than n₁;

said electrooptic polymer of said second outer cladding region is configured such that its polar axes are oriented along a common contour;

said control electrodes are arranged to create an electric field across said outer cladding regions and said electrooptic gap region, whereby an optical signal incident in one of said waveguides may be switched to the other of said waveguides.

11. An integrated optical device as claimed in claim 10 wherein said respective orientations of said polar axes of said first and second outer cladding regions and said electrooptic gap region render said directional coupling region polarization-independent.

12. An optical waveguide comprising an optical input, an optical output, and a waveguide core, wherein:

said waveguide core defines a core height dimension h that remains substantially constant between said optical input and said optical output;

said core width dimension defines an input width w₁ at said optical input, an output width w₂ at said optical output, an increased-width w₀ along a phase compensating element of said waveguide core, and a decreased-width w₃ along a thinned-down portion of said waveguide core;

said increased-width w₀ is greater than said input width; and

said decreased-width w₃ is less than said input width.

13. An integrated optical device as claimed in claim 12 wherein said input width w₁ and said output width w₂ are substantially equal to said core height dimension h.

14. An integrated optical device as claimed in claim 12 wherein said input width w₁ and said output width w₂ are about 5 μ

m, said increased-width w₀ is about 10 μ

m, and said decreased-width w₃ is about 3 μ

m.

15. An integrated optical device as claimed in claim 12 wherein said phase compensating element and said thinned-down portion of said waveguide are coupled to adjacent waveguide portions via tapered transitions.

16. An integrated optical device as claimed in claim 15 wherein said thinned-down portion defines a length of about 2 cm, said compensating element defines a length of at least about 2 cm, and said tapered transitions define a length of about 0.3 cm.

17. An integrated optical device as claimed in claim 12 wherein said thinned-down portion defines a length of about 2 cm, said compensating element defines a length of at least about 2 cm.

18. An electrooptic clad waveguide comprising an optical waveguide core defining a primary axis of propagation z, a first cladding region offset from said z axis in a first direction along an x axis perpendicular to said z axis, and a second cladding region offset from said z axis in a second direction along said x axis, wherein:

said optical waveguide core comprises an optically non-functional material defining a refractive index n₁;

said first cladding region comprises an optically functional material defining a refractive index that is less than n₁;

said second cladding region comprises an optically functional material defining a refractive index that is less than n₁; and

said optically functional material of said first cladding region is configured such that its polar axes are oriented in a direction different than a direction in which polar axes of said optically functional material of said second cladding region are oriented.