# US 9,041,041 B2 · Optical device, optical element, and image display device

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- Number: US 9,041,041 B2
- Document ID: US9041041B2
- Status: Granted
- Kind: B2
- Application number: 14/370,886
- Filed: 2012-10-03
- Published: 2015-01-15
- Granted: 2015-05-26
- Earliest claimed: 2012-01-07
- Assignees: NEC Corporation
- Applicants: NEC Corporation
- Inventors: Masanao Natsumeda; Masao Imai; Shin Tominaga; Naofumi Suzuki; Mizuho Tomiyama; Yuji Ohno
- Web page: https://patentgrep.com/patent/US9041041B2

## CPC

- G02B 5/008: {Surface plasmon devices (diffractive gratings with a pitch less than or comparable to the wavelength G02B5/1809; surface plasmons in integrated optics G02B6/1226; optical analysis of materials by means of surface plasmons G01N21/553)}
- F21V 9/14: for producing polarised light
- G03B 21/2006: {characterised by the light source}
- G03B 21/2073: {Polarisers in the lamp house (peculiar to electronic spatial light modulators H04N9/3197)}
- G02B 5/30: Polarising elements (light-modulating devices with active elements G02F1/00)
- G02B 27/102: {for generating a colour image from monochromatic image signal sources}
- G02B 27/141: {using dichroic mirrors}
- H10H 20/00: Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

Disclosed are an optical device, an optical element, and an image display device that can achieve an improved absorption efficiency of excitation light. The optical device includes: a light-emitting element; a carrier generation layer on which light from the light-emitting element is incident and in which carriers are generated; a plasmon excitation layer that excites a plasmon, stacked on the upper side of the carrier generation layer and has a plasma frequency higher than a frequency of light generated when the carrier generation layer is excited by the light from the light-emitting element; and an exit layer that converts light or a surface plasmon generated on a surface of the plasmon excitation layer into light having a predetermined exit angle and from which the light having the predetermined exit angle exits. The optical device further includes a polarization conversion layer on the lower side of the carrier generation layer.

## Claims

### Claim 1

An optical device comprising:
a light-emitting element;
a carrier generation layer on which light from the light-emitting element is incident and in which carriers are generated;
a plasmon excitation layer that excites a plasmon, the plasmon excitation layer being stacked on an upper side of the carrier generation layer and having a plasma frequency higher than a frequency of light generated when the carrier generation layer is excited by the light from the light-emitting element; and
an exit layer that converts light or a surface plasmon generated on a surface of the plasmon excitation layer into light having a predetermined exit angle and from which the light having the predetermined exit angle exits,
wherein the optical device further comprises a polarization conversion layer on a lower side of the carrier generation layer.

### Claim 2 (depends on 1)

The optical device according to claim 1, wherein
the polarization conversion layer is a 1/4 wavelength plate.

### Claim 3 (depends on 1)

The optical device according to claim 1, wherein
a dielectric layer is stacked on at least one surface of the plasmon excitation layer.

### Claim 4 (depends on 1)

The optical device according to claim 1, wherein
the distance between a carrier generation layer side-surface of the plasmon excitation layer and a plasmon excitation layer side-surface of the carrier generation layer is shorter than an effective interaction distance of a surface plasmon excited on the carrier generation layer side-surface of the plasmon excitation layer.

### Claim 5 (depends on 4)

The optical device according to claim 4, wherein
the carrier generation layer is disposed within a distance in the range from 1 to 200 nm from the plasmon excitation layer.

### Claim 6 (depends on 1)

The optical device according to claim 1, wherein
the exit layer has a surface periodic structure.

### Claim 7 (depends on 6)

The optical device according to claim 6, wherein
the surface periodic structure is a photonic crystal structure.

### Claim 8 (depends on 1)

The optical device according to claim 1, wherein
the carrier generation layer has a surface periodic structure and serves also as the exit layer.

### Claim 9 (depends on 1)

The optical device according to claim 1, further comprising a polarization converter that sets axially symmetric polarized light exiting from the exit layer in a predetermined polarization state.

### Claim 10 (depends on 1)

The optical device according to claim 1, wherein
an incident side portion that comprises an entire structure provided on the light-emitting element side of the plasmon excitation layer and a medium in contact with the light-emitting element has a lower effective dielectric constant than an exit side portion that comprises an entire structure provided on the exit layer side of the plasmon excitation layer and a medium in contact with the exit layer.

### Claim 11 (depends on 1)

The optical device according to claim 1, wherein
an incident side portion that comprises an entire structure provided on the light-emitting element side of the plasmon excitation layer and a medium in contact with the light-emitting element has an effective dielectric constant higher than or equal to an effective dielectric constant of an exit side portion that comprises an entire structure provided on the exit layer side of the plasmon excitation layer and a medium in contact with the exit layer, and
an end of the exit layer on the plasmon excitation layer side is disposed so that a distance between the end and an exit layer side-surface of the plasmon excitation layer is within an effective interaction distance of the surface plasmon.

### Claim 12 (depends on 10)

The optical device according to claim 10, wherein
the effective dielectric constant (∈eff) is represented by either one of the following Equation (1) and Equation (7):
ɛ
eff
=
(
∫
∫
∫
D
⁢
Re
⁡
[
ɛ
⁡
(
ω
,
x
,
y
,
z
)
]
⁢
exp
⁡
(
2
⁢
⁢
j
⁢
⁢
k
spp
,
z
⁢
z
)
∫
∫
∫
D
⁢
exp
⁡
(
2
⁢
⁢
j
⁢
⁢
k
spp
,
z
⁢
z
)
)
2
(
1
)
ɛ
eff
=
∫
∫
∫
D
⁢
Re
⁡
[
ɛ
⁡
(
ω
,
x
,
y
,
z
)
]
⁢
exp
⁡
(
2
⁢
⁢
j
⁢
⁢
k
spp
,
z
⁢
z
)
∫
∫
∫
D
⁢
exp
⁡
(
2
⁢
⁢
j
⁢
⁢
k
spp
,
z
⁢
z
)
(
7
)
where an x axis and a y axis are directions parallel to an interface of the plasmon excitation layer; a z axis is a direction perpendicular to the interface of the plasmon excitation layer; ωis an angular frequency of light exiting from the carrier generation layer; ∈(ω, x, y, z) is a dielectric constant distribution of dielectric substances in the incident side portion or the exit side portion; an integration range D is a range of three-dimensional coordinates in the incident side portion or the exit side portion; kspp,z is a z component of a wave number of a surface plasmon; j is an imaginary unit; and Re[ ] is a sign indicating a real part of a numerical value in the square brackets, and
the z component kspp,z of the wave number of the surface plasmon and an x and y components kspp of the wave number of the surface plasmon are represented by the following Equation (2) and Equation (3), respectively:
k
spp
,
z
=
ɛ
eff
⁢
k
0
2
-
k
spp
2
(
2
)
k
spp
=
k
0
⁢
Re
⁡
[
ɛ
eff
⁢
ɛ
metal
ɛ
eff
+
ɛ
metal
]
(
3
)
where ∈metal is a real part of a dielectric constant of the plasmon excitation layer; and k0 is a wave number of light in a vacuum.

### Claim 13 (depends on 4)

The optical device according to claim 4, wherein
the effective interaction distance deff is represented by the following Equation (4):
d
eff
=
Im
⁡
[
1
k
spp
,
z
]
(
4
)
where Im[ ] is a sign indicating an imaginary part of a numerical value in the square brackets.

### Claim 14 (depends on 1)

The optical device according to claim 1, wherein
an incident angle of the light incident on the carrier generation layer is set to 40° or more.

### Claim 15

An optical element comprising:
a carrier generation layer on which light from a light-emitting element is incident and in which carriers are generated;
a plasmon excitation layer that excites a plasmon, the plasmon excitation layer being stacked on an upper side of the carrier generation layer and having a plasma frequency higher than a frequency of light generated when the carrier generation layer is excited by the light; and
an exit layer that converts light or a surface plasmon generated on a surface of the plasmon excitation layer into light having a predetermined exit angle and from which the light having the predetermined exit angle exits,
wherein the optical element further comprises a polarization conversion layer on a lower side of the carrier generation layer.

### Claim 16 (depends on 15)

The optical element according to claim 15, wherein
the polarization conversion layer is a ¼ wavelength plate.

### Claim 17 (depends on 1)

An image display device comprising:
the optical device according to claim 1; and
an image display section that can display an image.

### Claim 18 (depends on 17)

The image display device according to claim 17, further comprising a projection optical system that projects a projection image using light exiting from the image display section.

### Claim 19 (depends on 2)

The optical device according to claim 2, wherein a dielectric layer is stacked on at least one surface of the plasmon excitation layer.

### Claim 20 (depends on 2)

The optical device according to claim 2, wherein the distance between a carrier generation layer side-surface of the plasmon excitation layer and a plasmon excitation layer side-surface of the carrier generation layer is shorter than an effective interaction distance of a surface plasmon excited on the carrier generation layer side-surface of the plasmon excitation layer.