Photonic integrated circuit having a waveguide-grating coupler

• US 8,494,315 B2
• Filed: 12/17/2009
• Issued: 07/23/2013
• Est. Priority Date: 12/17/2009
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Doerr, Christopher R., Dupuis, Nicolas
• Primary Examiner(s): Le, Uyen Chau N
• Assistant Examiner(s): TRAN, HOANG Q
• Application Number:
  US12/640,151
• Publication Number:
  US 20110150386A1
• Time in Patent Office: 1,314 Days
• Field of Search: 385/14, 385/37
• US Class Current: 385/14
• CPC Class Codes: B29D 11/00663 Production of light guides
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/29332 Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency non wavelength-selective light guide couplers G02B6/28
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G11B 2005/0021 Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
• CPC Class Codes: G11B 5/314 where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers G11B5/3196 takes precedence

Abstract

A photonic integrated circuit (PIC) having a waveguide-grating coupler with two evanescently coupled waveguides. The first waveguide is fabricated using materials suitable for manufacturing active optical elements in the PIC. The second waveguide is fabricated using materials capable of providing a relatively high index-of-refraction contrast for the constituent waveguide grating. The waveguide-grating coupler is compatible with the III-V semiconductor technology while being relatively easy to fabricate on an industrial scale.

Claims

1. An apparatus, comprising:

a multilayered structure having a substrate layer, a first core layer, a first cladding layer, a second cladding layer, a second core layer, and a third cladding layer, wherein;

the first cladding layer comprises a first material; and

the second cladding layer has a wedge-like portion and comprises a second material different from the first material;

a first optical waveguide having a first core and a first cladding, wherein;

the first core comprises a portion of the first core layer; and

the first cladding comprises a portion of the substrate layer and a portion of the first cladding layer;

a second optical waveguide having a second core and a second cladding, wherein;

the second core comprises a portion of the second core layer; and

the second cladding comprises at least the wedge-like portion of the second cladding layer and a portion of the third cladding layer;

an optical coupler optically coupling the first and second waveguides, wherein the optical coupler comprises a portion of the first cladding layer; and

a waveguide grating being adapted to transfer optical power between one or more waveguide modes of the second waveguide and an optical beam formed by or applied to the waveguide grating, wherein the waveguide grating comprises a portion of the second core layer.

2. The apparatus of claim 1, wherein an index-of-refraction contrast of the second waveguide is greater than an index-of-refraction contrast of the first waveguide.

3. The apparatus of claim 1, wherein:

the substrate layer comprises the first material; and

the third cladding layer comprises the second material.

4. The apparatus of claim 3, wherein:

the first core layer comprises a ternary, quaternary, or quinary group III-V alloy;

the first material comprises a binary group III-V compound;

the second core layer comprises silicon; and

the second material comprises silicon oxide.

5. The apparatus of claim 1, wherein the optical coupler couples the first and second optical waveguides via evanescent fields.

6. The apparatus of claim 5, wherein the optical coupler has a length that causes optical energy to spatially beat one or more times between the first and second optical waveguides.

7. The apparatus of claim 1, wherein a portion of the second cladding layer adjacent to the waveguide grating has a thickness that causes the apparatus to produce constructive interference between (i) light diffracted by the waveguide grating toward an interface between the first cladding layer and the second cladding layer and then reflected back by the interface and (ii) light diffracted by the waveguide grating in a direction collinear with a propagation direction of the reflected light.

8. The apparatus of claim 1, wherein the first core comprises a laterally tapered portion connected to the optical coupler.

9. The apparatus of claim 1, further comprising an optical signal-processing (OSP) circuit supported on the substrate layer, wherein the first waveguide is optically coupled to the OSP circuit.

10. The apparatus of claim 9, wherein the OSP circuit comprises at least one active optical element.

11. The apparatus of claim 9, wherein the first and second waveguides, the waveguide grating, and the OSP circuit are parts of a photonic integrated circuit (PIC) formed on the substrate layer.

12. The apparatus of claim 1, wherein:

the first core layer is directly connected to the substrate layer;

the first cladding layer is directly connected to the first core layer;

the second cladding layer is directly connected to the first cladding layer;

the second core layer is directly connected to the second cladding layer; and

the third cladding layer is directly connected to the second core layer.

13. The apparatus of claim 12, wherein:

a portion of the second core layer is directly connected to the first cladding layer; and

a portion of the third cladding layer is directly connected to the first cladding layer.