# US 11,609,365 B2 · Fabricating non-uniform diffraction gratings

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- Number: US 11,609,365 B2
- Document ID: US11609365B2
- Status: Granted
- Kind: B2
- Application number: 16/535,965
- Filed: 2019-08-08
- Published: 2019-12-05
- Granted: 2023-03-21
- Earliest claimed: 2016-10-05
- Assignees: Magic Leap, Inc.
- Applicants: Magic Leap, Inc.
- Inventors: Mauro Melli; Christophe Peroz
- Web page: https://patentgrep.com/patent/US11609365B2

## CPC

- G02B 5/1857: {using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams}
- G02B 6/124: Geodesic lenses or integrated gratings
- G02B 6/136: by etching
- G02B 27/0172: {characterised by optical features}
- G02B 27/4205: {having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant}
- G02B 27/4272: {having plural diffractive elements positioned sequentially along the optical path}
- H01J 37/3056: {for microworking, e. g. etching of gratings or trimming of electrical components}
- H01J 37/3171: {for ion implantation}
- G02B 2006/12188: {Ion implantation}
- G02B 2027/0125: {Field-of-view increase by wavefront division}
- H01J 2237/31708: unpatterned
- H01J 2237/31711: using mask
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A method of fabricating non-uniform gratings includes implanting different densities of ions into corresponding areas of a substrate, patterning, e.g., by lithography, a resist layer on the substrate, etching the substrate with the patterned resist layer, and then removing the resist layer from the substrate, leaving the substrate with at least one grating having non-uniform characteristics associated with the different densities of ions implanted in the areas. The method can further include using the substrate having the grating as a mold to fabricate a corresponding grating having corresponding non-uniform characteristics, e.g., by nanoimprint lithography.

## Claims

### Claim 1

A device comprising:
a diffractive optical element (DOE) having one or more layers on at least partially in a substrate, each layer including an orthogonal pupil expansion (OPE) diffractive element and an exit pupil expansion (EPE) diffractive element,
wherein the OPE diffractive element comprises a first non-uniform grating configured to deflect part of input light beams propagating in the substrate into the EPE diffractive element in the substrate,
wherein the EPE diffractive element comprises a second non-uniform grating configured to deflect part of deflected light beams from the OPE diffractive element out of the substrate, and
wherein the first non-uniform grating has a first characteristic that varies along a first direction, and the first non-uniform grating has increasing diffraction efficiencies along the first direction associated with the first characteristic that corresponds to linearly varying densities of ions implanted in a medium of the substrate along the first direction.

### Claim 2 (depends on 1)

The device of claim 1, wherein the second non-uniform grating has a second characteristic that varies along a second direction different from the first direction, and the second non-uniform grating has increasing diffraction efficiencies along the second direction.

### Claim 3 (depends on 2)

The device of claim 2, wherein an angle between the first direction and the second direction is between 45 degrees and 90 degrees.

### Claim 4 (depends on 2)

The device of claim 2, wherein the first non-uniform grating has a third characteristic that varies along a third direction different from the first direction, and wherein an angle between the first direction and the third direction is larger than 0 degree and less than 180 degrees.

### Claim 5 (depends on 2)

The device of claim 2, wherein the second non-uniform grating has a fourth characteristic that varies along a fourth direction different from the second direction, and wherein an angle between the second direction and the fourth direction is larger than 0 degree and less than 180 degrees.

### Claim 6 (depends on 2)

The device of claim 2, further comprising an in-coupling element (ICO) integrated in the substrate and configured to receive the input light beams from outside of the substrate and transmit the input light beams to the DOE in the substrate.

### Claim 7 (depends on 2)

The device of claim 2, wherein the first non-uniform grating has first linearly varying depths along the first direction, and the second non-uniform grating has second linearly varying depths along the second direction.

### Claim 8 (depends on 1)

The device of claim 1, wherein at least one of the first non-uniform grating or the second non-uniform grating comprises a binary grating with non-uniform depths.

### Claim 9 (depends on 1)

The device of claim 1, wherein at least one of the first non-uniform grating or the second non-uniform grating comprises a blazed grating with non-uniform depths.

### Claim 10 (depends on 1)

The device of claim 1, wherein at least one of the first non-uniform grating or the second non-uniform grating comprises at least one of a linear diffractive structure, a circular diffractive structure, or a radially symmetric diffractive structure.

### Claim 11 (depends on 1)

The device of claim 1, wherein at least one of the first non-uniform grating or the second non-uniform grating has a lateral resolution of no more than 5000 nm.

### Claim 12 (depends on 1)

The device of claim 1, wherein at least one of the first non-uniform grating or the second non-uniform grating has an area with a dimension of at least 1 mm.

### Claim 13 (depends on 1)

The device of claim 1, wherein the OPE diffractive element and the EPE diffractive element are arranged as co-planar or side-by-side on each layer of the one or more layers.

### Claim 14 (depends on 1)

The device of claim 1, wherein the DOE comprises at least one dithering feature along at least one of the first non-uniform grating or the second non-uniform grating.

### Claim 15 (depends on 1)

The device of claim 1, wherein the DOE is configured to deflect the input light beams out across an area of the DOE with a substantially uniform diffraction efficiency.

### Claim 16

A device comprising:
a substrate; and
a non-uniform grating formed at least partially in the substrate, the non-uniform grating having a first characteristic that varies along a first direction, wherein the non-uniform grating has increasing diffraction efficiencies along the first direction associated with the first characteristic that corresponds to linearly varying densities of ions implanted in a medium of the substrate along the first direction.

### Claim 17 (depends on 16)

The device of claim 16, wherein the non-uniform grating has a second characteristic that varies along a second direction different from the first direction, and
wherein an angle between the first direction and the second direction is larger than 0 degree and less than 180 degrees.

### Claim 18 (depends on 16)

The device of claim 16, wherein the non-uniform grating has linearly varying depths along the first direction.

### Claim 19 (depends on 16)

The device of claim 16, wherein the first characteristic comprises a series of grooves along the first direction, and wherein varying densities of ions implanted in the substrate are between adjacent grooves along the first direction.

### Claim 20 (depends on 16)

The device of claim 16, wherein the first characteristic comprises a series of grooves along the first direction, and wherein varying densities of ions implanted in the substrate are under the series of grooves along the first direction.