# US 2013/0277331 A1 · Photonic integrated circuit having a waveguide-grating coupler

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- Number: US 2013/0277331 A1
- Document ID: US20130277331A1
- Status: Published application
- Kind: A1
- Application number: 13/919,396
- Filed: 2013-06-17
- Published: 2013-10-24
- Earliest claimed: 2009-12-17
- Assignees: Alcatel-Lucent USA Inc.
- Applicants: Alcatel-Lucent USA Inc.
- Inventors: Nicolas Dupuis; Christopher R. Doerr
- Web page: https://patentgrep.com/patent/US20130277331A1

## CPC

- 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)
- B29D 11/00663: {Production of light guides}
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- G02B 6/12002: {Three-dimensional structures}
- G02B 6/124: Geodesic lenses or integrated gratings
- G02B 6/125: Bends, branchings or intersections
- G02B 6/136: by etching
- G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide}
- G11B 5/314: {where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers (G11B5/3196 takes precedence)}
- 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}
- G11B 2005/0021: {Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## 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

### Claim at position 1

1-16. (canceled)

### Claim 17

A method of fabricating an optical device, comprising:
providing a substrate having a first optical waveguide thereon, the first optical waveguide having a first cladding layer;
forming a second cladding layer with a wedge-like portion on the first cladding layer by (i) forming a layer of cladding material over the first optical waveguide and (ii) subjecting said layer of cladding material to a wet-etch process to form from said layer of cladding material the wedge-like portion;
forming a core of a second optical waveguide on the wedge-like portion; and
forming an array of cavities in the core of the second optical waveguide to define therein a waveguide grating.

### Claim 18

(canceled)

### Claim 19 (depends on 17)

The method of claim 17, further comprising forming on the substrate an optical signal-processing (OSP) circuit, wherein:
the first optical waveguide is optically coupled to the OSP circuit;
the OSP circuit comprises at least one active optical element; and
the first and second optical waveguides, the waveguide grating, and the OSP circuit are parts of a photonic integrated circuit (PIC) formed on the substrate.

### Claim 20 (depends on 17)

The method of claim 17, wherein, for a predetermined operating wavelength, an offset distance between the waveguide grating and an interface of a cladding of the first optical waveguide with a cladding of the second waveguide is selected to cause constructive interference between (i) light of said operating wavelength diffracted by the waveguide grating toward the interface and then reflected back by the interface and (ii) light of said operating wavelength diffracted by the waveguide grating in a direction collinear with a propagation direction of the reflected light.

### Claim 21 (depends on 17)

The method of claim 17, wherein
a core of the first optical waveguide comprises a ternary, quaternary, or quinary group III-V alloy;
the first cladding layer comprises a binary group III-V compound;
the core of the second waveguide comprises silicon; and
the wedge-like portion comprises silicon oxide.

### Claim 22 (depends on 17)

The method of claim 17, further comprising forming a multilayered structure having the substrate, a core of the first optical waveguide, the first cladding layer, the second cladding layer, the core of the second optical waveguide, and a third cladding layer by:
depositing or growing a first core layer on the substrate;
patterning and etching the first core layer in accordance with a footprint layout of the first optical waveguide to form the core of the first optical waveguide;
depositing or growing the first cladding layer over the core of the first optical waveguide and the substrate;
said forming the second cladding layer with the wedge-like portion on the first cladding layer;
depositing or growing a second core layer over the first cladding layer and the second cladding layer with the wedge-like portion;
patterning and etching the second core layer in accordance with a footprint layout of the second optical waveguide to form the core of the second optical waveguide;
said forming the array of cavities in the core of the second optical waveguide; and
depositing or growing the third cladding layer over the core of the second optical waveguide, the second cladding layer with the wedge-like portion, and the first cladding layer.

### Claim 23 (depends on 22)

The method of claim 22, wherein:
the first cladding layer comprises a first material; and
the second cladding layer comprises a second material different from the first material.

### Claim 24 (depends on 23)

The method of claim 23, wherein the substrate comprises a third material different from the first material and from the second material.

### Claim 25 (depends on 23)

The method of claim 23, wherein the third cladding layer comprises a third material different from the first and second materials.

### Claim 26 (depends on 25)

The method of claim 25, wherein the substrate comprises a fourth material different from the first, second, and third materials.

### Claim 27 (depends on 22)

The method of claim 22, wherein said patterning and etching the first core layer comprises forming a laterally tapered portion of the core of the first optical waveguide.

### Claim 28 (depends on 22)

The method of claim 22, wherein:
the first core layer is directly connected to the substrate;
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.

### Claim 29 (depends on 28)

The method of claim 28, 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.

### Claim 30 (depends on 17)

The method of claim 17, wherein an index-of-refraction contrast of the second optical waveguide is greater than an index-of-refraction contrast of the first optical waveguide.

### Claim 31 (depends on 17)

The method of claim 17, wherein the first cladding layer has a thickness that causes the first and second optical waveguides to be optically coupled to each other via an evanescent field.

### Claim 32 (depends on 17)

The method of claim 17, further comprising forming a photonic integrated circuit on the substrate, wherein the photonic integrated circuit comprises the first optical waveguide, the second optical waveguide, and the waveguide grating.

### Claim 33 (depends on 33)

The method of claim 33, wherein the photonic integrated circuit comprises at least one active optical element.