# US 12,601,922 B2 · Waveguides with enhanced modal densities

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,601,922 B2
- Document ID: US12601922B2
- Status: Granted
- Kind: B2
- Application number: 19/089,083
- Filed: 2025-03-25
- Published: 2025-10-23
- Granted: 2026-04-14
- Earliest claimed: 2024-04-19
- Assignees: Corning Incorporated
- Applicants: Corning Incorporated
- Inventors: Robert Adam Modavis
- Web page: https://patentgrep.com/patent/US12601922B2

## CPC

- G02B 27/0172: {characterised by optical features}
- G02B 6/30: for use between fibre and thin-film device
- G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)}
- G02B 27/0176: {characterised by mechanical features}
- G02B 2027/0123: {comprising devices increasing the field of view}
- G02B 2027/0152: {involving arrangement aiming to get lighter or better balanced devices}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A device for projecting a virtual- or augmented-reality image may include a waveguide and an in-coupler directing light into the waveguide such that the light is propagated through the waveguide via total internal reflection. The waveguide may include a core, a substrate, and a stack of thin films overlaying a surface of the core. A refractive index of at least one of the thin films of the stack may differ from that of the core. Adjacent thin films may have different refractive indices from one another.

## Claims

### Claim 1

A device for projecting a virtual-or augmented-reality image, the device comprising:
a waveguide; and
an in-coupler directing light into the waveguide such that the light is propagated through the waveguide via total internal reflection;
wherein the waveguide comprises:
a core;
a substrate having a thickness greater than or equal to 20 μm and less than or equal to 600 μm; and
a stack of thin films overlaying a surface of the core, wherein:
the stack comprises at least three thin films overlaying one another in the stack;
the stack has a thickness less than 50 μm;
a refractive index of at least one of the thin films differs from that of the core;
adjacent thin films have different refractive indices from one another; and
the stack of thin films is configured to satisfy one of the following:
wherein the stack of thin films overlays a first major surface of the core, wherein the substrate is disposed on a second major surface of the core opposite the first major surface of the core, and
wherein
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the stack of thin films over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where q is an incidence angle of the light propagating inside the core of the waveguide via total internal reflection, and øc represents a phase change of the light upon reflection from the first major surface of the core; or
wherein the stack of thin films overlays the second major surface of the core, and wherein the stack of thin films is disposed between the core and the substrate,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the stack of thin films over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where Øs represents a phase change of the light upon reflection from the second major surface of the core.

### Claim 2 (depends on 1)

The device of claim 1, wherein the stack of thin films increases the density of modes of the light propagated through the waveguide relative to that of the core without the stack of thin films, and wherein the propagation of the light through the waveguide via total internal reflection satisfies the following:
κ
1
⁢
h
-
∅
c
-
∅
s
=
m
⁢
π
where κ1=n1k cos θ, n1 is the refractive index of the core, k=2π/λ, λ is the wavelength of the light, h is the thickness of the core, and m is an integer and specifies a mode number associated with the incidence angle θ.

### Claim 3 (depends on 1)

The device of claim 1, wherein the stack of thin films is configured such that:
when the light propagates in transverse electric (TE) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where n1 is the refractive index of the core, and nB represents a refractive index of a medium directly overlaying the stack of thin films; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
B
2
n
B
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
B
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
B
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 4 (depends on 1)

The device of claim 1, wherein the stack of thin films is configured such that:
when the light propagates in transverse electric (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where n1 is the refractive index of the core, and ns represents a refractive index of the substrate; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
s
2
n
s
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
s
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
s
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 5 (depends on 1)

The device of claim 1, wherein the refractive index of the core is greater than or equal to 1.6.

### Claim 6 (depends on 1)

The device of claim 1, wherein the stack comprises:
a first thin film overlaying the core and having a first refractive index that is less than the refractive index of the core;
a second thin film overlaying the first thin film and having a second refractive index that is greater than the first refractive index; and
a third thin film overlaying the second thin film and having a third refractive index that is less than the second refractive index.

### Claim 7

A head-mounted device, comprising:
a display;
a waveguide;
an in-coupler configured for coupling light emitted by the display into the waveguide at a first location of the waveguide such that the light is propagated through the waveguide via total internal reflection to a second location of the waveguide; and
an out-coupler configured for coupling the light out of the waveguide at the second location of the waveguide and for projecting the light into a user's eye;
wherein the waveguide comprises:
a core comprising:
a first major surface, a second major surface opposite the first major surface, and a thickness defined by a distance between the first major surface and the second major surface, wherein the thickness of the core is less than or equal to 2,000 μm; and
a coating comprising:
a thickness that is less than or equal to 50 μm;
a first layer disposed on the first major surface of the core and having a first refractive index that is different from the refractive index of the core; and
a second layer disposed on the first layer and having a second refractive index that is different from the first refractive index of the first layer; and
wherein the propagation of the light through the waveguide via total internal reflection satisfies the following: κ1h−Øc−Øs=mπ, where κ1=n1k cos θ, n1 is the refractive index of the core, k=2π/λ, λ is the wavelength of the light, θ is an incidence angle of the light propagating inside the core of the waveguide via internal reflection, h is the thickness of the core, Øc represents a phase change of the light upon reflection from the first major surface of the core, and Øs represents a phase change of the light upon reflection from the second major surface of the core, and m is an integer and specifies a mode number associated with the incidence angle θ; and
wherein the coating is configured such that
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the coating over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 8 (depends on 7)

The head-mounted device of claim 7, wherein the coating is configured such that:
when the light propagates in transverse electric (TE) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where nB represents a refractive index of a medium directly overlaying the coating; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
s
2
n
B
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
B
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
B
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 9 (depends on 7)

The head-mounted device of claim 7, wherein the waveguide further comprises:
a substrate, wherein:
the core is disposed on a major surface of the substrate;
a refractive index of the substrate is less than the refractive index of the core; and
the coating and the substrate are disposed on opposite sides of the core.

### Claim 10 (depends on 9)

The head-mounted device of claim 9, wherein the coating disposed on the first major surface of the core is a first coating, the waveguide further comprising:
a second coating disposed on the second major surface of the core, wherein the second coating is configured such that
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the second coating over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 11 (depends on 10)

The head-mounted device of claim 10, wherein the second coating comprises a stack of thin films having a thickness less than 50 μm, and wherein adjacent thin films have different refractive indices from one another.

### Claim 12 (depends on 10)

The head-mounted device of claim 10, wherein the second coating is configured such that:
when the light propagates in transverse electric (TE) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where ns represents a refractive index of the substrate; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
s
2
n
s
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
s
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
2
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 13 (depends on 7)

The head-mounted device of claim 7, wherein:
the refractive index of the core is greater than the first refractive index of the first layer of the coating; and
the second refractive index of the second layer is greater than the first refractive index of the first layer of the coating.

### Claim 14

A waveguide for transporting a virtual-or augmented-reality image, comprising:
a core comprising:
a first major surface, a second major surface opposite the first major surface, and a thickness defined by a distance between the first major surface and the second major surface, wherein the thickness of the core is greater than or equal to 5 μm to 2,000 μm; and
a coating disposed on the first major surface of the core, wherein the coating comprises:
a first layer disposed on the first major surface of the core and having a first refractive index less than or equal to 1.6 and different from the refractive index of the core;
a second layer disposed on the first layer and having a second refractive index that is greater than or equal to 1.6 and different from the first refractive index of the first layer;
a third layer disposed on the second layer and having a third refractive index that is less than or equal to 1.6 and different from the second refractive index of the second layer; and
a thickness that is greater than or equal to 1 nm and less than or equal to 50 μm;
wherein propagation of light through the waveguide via total internal reflection satisfies the following:
κ
1
⁢
h
-
∅
c
-
∅
s
=
m
⁢
π
where k1=n1k cos θ, n1 is the refractive index of the core, k=2π/λ, λ is the wavelength of the light, θ is an incidence angle of the light propagating inside the core of the waveguide via internal reflection, h is the thickness of the core, Øc represents a phase change of the light upon reflection from the first major surface of the core, and Øs represents a phase change of the light upon reflection from the second major surface of the core, and m is an integer and specifies a mode number associated with the incidence angle θ; and
wherein the coating is configured such that
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the coating over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 15 (depends on 14)

The waveguide of claim 14, wherein the coating is configured such that:
when the light propagates in transverse electric (TE) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where nB represents a refractive index of a medium directly overlaying the coating; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
c
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
B
2
n
B
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
B
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
B
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
B
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 16 (depends on 14)

The waveguide of claim 14, wherein the coating disposed on the first major surface of the core is a first coating, the waveguide further comprises a second coating, wherein the first coating and the second coating are disposed on opposite sides of the core;
wherein the second coating comprises:
a first layer disposed on the second major surface of the core and having a first refractive index different from the refractive index of the core; and
a second layer disposed on the first layer and having a second refractive index different from the first refractive index of the first layer;
wherein the second coating is configured such that
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater relative to that of the core without the second coating over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 17 (depends on 16)

The waveguide of claim 16, wherein the second coating is configured such that:
when the light propagates in transverse electric (TE) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
n
1
⁢
sin
⁢
θ
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°, where ns represents a refractive index of a medium directly overlaying the second coating; and/or
when the light propagates in transverse magnetic (TM) mode,
❘
"\[LeftBracketingBar]"
d
⁢
∅
s
d
⁢
θ
❘
"\[RightBracketingBar]"
is greater than
❘
"\[LeftBracketingBar]"
[
n
s
2
n
s
4
⁢
cos
2
⁢
θ
+
n
1
4
⁢
sin
2
⁢
θ
-
n
1
2
⁢
n
s
2
]
[
n
1
⁢
sin
⁢
θ
⁡
(
n
1
2
-
n
s
2
)
n
1
2
⁢
sin
2
⁢
θ
-
n
s
2
]
❘
"\[RightBracketingBar]"
over one or more or a range of incidence angles between the critical angle θcritical of the core and 90°.

### Claim 18 (depends on 14)

The waveguide of claim 14, further comprising at least one of:
a substrate;
an in-coupler configured to couple light into the waveguide; or
an out-coupler configured to couple light out of the waveguide;
wherein:
the substrate has a refractive index less than the refractive index of the core;
the substrate has a thickness greater than or equal to 20 μm and less than or equal to 1,500 μm;
the substrate comprises a plastic substrate or a glass substrate; and
at least one of the in-coupler or the out-coupler comprises a grating.