# US 9,753,219 B2 · Optical coupler with forked grating structure

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- Number: US 9,753,219 B2
- Document ID: US9753219B2
- Status: Granted
- Kind: B2
- Application number: 15/044,602
- Filed: 2016-02-16
- Published: 2016-08-18
- Granted: 2017-09-05
- Earliest claimed: 2015-02-13
- Assignees: Clarkson University
- Applicants: Christopher T. Nadovich
- Inventors: Christopher T. Nadovich
- Web page: https://patentgrep.com/patent/US9753219B2

## CPC

- G02B 6/124: Geodesic lenses or integrated gratings
- G02B 6/1225: {comprising photonic band-gap structures or photonic lattices}
- G02B 6/1228: {Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305)}
- G02B 6/30: for use between fibre and thin-film device
- G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A device and system for coupling light into and out of a photonic integrated circuit. The forked grating coupler device applies a forked grating structure to the design of the diffracting lines in an integrated optics grating coupler to make the device compatible with vortex light beams to or from free space, bulk optics, or special optical fiber that can propagate vortex modes. These diffracting lines, which can be grooves, or ridges, or a photonic metamaterial discontinuity arranged in a continuous or intermittent curve, follow the forked diffraction pattern lobes over a two-dimensional surface. The resulting device can therefore absorb or radiate a vortex beam mode at near-normal incidence to a PIC and transform that vortex mode to a transverse electric (TE) or transverse magnetic (TM) waveguide mode traveling along a slab or strip optical waveguide parallel to the surface of the IC.

## Claims

### Claim 1

An optical coupler configured to couple an incident optical vortex light beam to or from a waveguide mode, the optical coupler comprising:
a forked grating structure configured to receive the optical vortex light beam, wherein the forked grating structure comprises at least one forked region and a plurality of grooves, and further wherein the at least one forked region is positioned amidst the plurality of grooves;
an optical waveguide; and
a tapered portion connecting the forked grating structure and the optical waveguide.

### Claim 2 (depends on 1)

The optical coupler of claim 1, wherein the optical vortex light beam is in free space.

### Claim 3 (depends on 1)

The optical coupler of claim 1, wherein the optical vortex light beam is received from an optic.

### Claim 4 (depends on 1)

The optical coupler of claim 1, wherein the optical vortex light beam is received from an optical fiber.

### Claim 5 (depends on 1)

The optical coupler of claim 1, wherein the plurality of grooves comprise a constant width.

### Claim 6 (depends on 1)

The optical coupler of claim 1, wherein at least some of the plurality of grooves are segmented.

### Claim 7 (depends on 1)

The optical coupler of claim 1, wherein the coupler comprises at least two optical waveguides and at least two tapered portions.

### Claim 8 (depends on 1)

The optical coupler of claim 1, further comprising a reflector.

### Claim 9 (depends on 1)

The optical coupler of claim 1, wherein the at least one forked region is coated.

### Claim 10

An optical coupling system configured to couple an incident optical vortex light beam to or from a waveguide mode, the system comprising:
an optical coupler comprising: (i) a forked grating structure configured to receive the optical vortex light beam, wherein the forked grating structure comprises at least one forked region and a plurality of grooves, and further wherein the at least one forked region is positioned amidst the plurality of grooves; (ii) an optical waveguide; and (iii) a tapered portion connecting the forked grating structure and the optical waveguide; and
a photonic integrated circuit configured to receive light from the optical coupler.

### Claim 11 (depends on 10)

The optical coupling system of claim 10, further comprising an optic configured to provide the light beam to the optical coupler.

### Claim 12 (depends on 10)

The optical coupling system of claim 10, further comprising an optical fiber configured to provide the light beam to the optical coupler.

### Claim 13 (depends on 10)

The optical coupling system of claim 10, wherein the plurality of grooves comprise a constant width.

### Claim 14 (depends on 10)

The optical coupling system of claim 10, wherein at least some of the plurality of grooves are segmented.

### Claim 15 (depends on 10)

The optical coupling system of claim 10, wherein the coupler comprises at least two optical waveguides and at least two tapered portions.

### Claim 16 (depends on 10)

The optical coupling system of claim 10, wherein the at least one forked region is coated.