Integrated optical mode shape transformer and method of fabrication

• US 20060285797A1
• Filed: 05/31/2006
• Published: 12/21/2006
• Est. Priority Date: 10/09/2003
• Status: Active Grant

• Current Assignee: Infinera Corp.
• Original Assignee: Infinera Corp.
• Inventors: Little, Brent E.
• Granted Patent: US 7,359,593 B2
• Time in Patent Office: Days
• US Class Current: 385/43
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide

Abstract

An integrated optical mode transformer provides a low loss interconnection between an optical fiber and an integrated optic waveguide having a spot size different from that of the fiber. The mode transformer is comprised of two waveguide layers, an upper layer and a lower layer, with the upper layer being contiguous to the lower layer. The lower layer is the integrated optic waveguide layer forming the optical circuit. The input dimensions of the composite two-waveguide structure supports a fundamental mode that accepts all of the light present on the optical fiber. The upper waveguide layer is tapered down from an input width to an output width and then terminates in such a way that at the termination substantially all of the input optical power resides in the lower waveguide layer. The two-waveguide layer structure is fabricated by deposition and planarization techniques.

Claims

1. An optical mode transformer, comprising:

a first waveguide having a first thickness; and

a second waveguide having a second thickness, at least a portion of the second waveguide being contiguous with at least a portion of the first waveguide, the first and second waveguides cooperating to form an adiabatic region in which the second waveguide is tapered and a lightwave evanescently couples into the first waveguide.

2. The optical mode transformer of claim 1 wherein the first waveguide has an input, and the second waveguide has an input and an output, the input of the first and second waveguides configured to receive light, and the output of the second waveguide configured to provide light.

3. The optical mode transformer of claim 2 further comprising:

an input fiber having a predetermined fiber spot size and wherein at least a portion of the input of the first waveguide having a width corresponding to that of the fiber spot size and at least a portion of the input of the second waveguide having a width corresponding to that of the fiber spot size.

4. The optical mode transformer of claim 1 wherein the first and second waveguides are constructed of materials having a similar refractive index.

5. The optical mode transformer of claim 1 wherein the first and second waveguides are constructed of materials having different refractive indexes.

6. A method of fabricating an optical mode transformer, comprising the steps of:

depositing a first waveguide on a substrate, the first waveguide having a first thickness and a first refractive index; and

fabricating a second waveguide having a second thickness and a second refractive index, at least a portion of the second waveguide being contiguous with at least a portion of the first waveguide and wherein the second waveguide having a width that is tapered.

7. The method of claim 6 wherein the first and second waveguides are constructed of materials having a similar refractive index.

8. The method of claim 6 wherein the first and second waveguides are constructed of materials having different refractive indexes.

9. The method of claim 6 further comprising the step of:

providing an input fiber having a predetermined fiber spot size wherein at least a portion of an input of the first waveguide having a width corresponding to that of the fiber spot size and at least a portion of an input of the second waveguide having a width corresponding to that of the fiber spot size.

10. The method of claim 9 wherein the sum of the first thickness of the first waveguide and the second thickness of the second waveguide are similar to the fiber spot size.