OPTICAL ELEMENT, ILLUMINATION DEVICE, IMAGE DISPLAY DEVICE, METHOD OF OPERATING OPTICAL ELEMENT

• US 20150301282A1
• Filed: 04/22/2013
• Published: 10/22/2015
• Est. Priority Date: 07/31/2012
• Status: Abandoned Application

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: IMAI, Masao, SUZUKI, Naofumi, NATSUMEDA, Masanao, TOMINAGA, Shin, TOMIYAMA, Mizuho, OHNO, Yuji
• Application Number:
  US14/417,849
• Publication Number:
  US 20150301282A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2006/12123 Diode
• CPC Class Codes: G02B 6/1226 involving surface plasmon interaction
• CPC Class Codes: G03B 21/2006 characterised by the light source
• CPC Class Codes: G03B 21/204 using secondary light emission, e.g. luminescence or fluorescence using different colours G03B33/00; if related to video signals H04N9/3197
• CPC Class Codes: G03B 21/206 Control of light source other than position or intensity
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/15 Hole transporting layers
• CPC Class Codes: H10K 50/155 comprising dopants
• CPC Class Codes: H10K 50/156 comprising a multilayered structure
• CPC Class Codes: H10K 50/157 between the light-emitting layer and the cathode
• CPC Class Codes: H10K 50/16 Electron transporting layers
• CPC Class Codes: H10K 50/165 comprising dopants
• CPC Class Codes: H10K 50/166 comprising a multilayered structure
• CPC Class Codes: H10K 50/167 between the light-emitting layer and the anode
• CPC Class Codes: H10K 50/81 Anodes
• CPC Class Codes: H10K 50/818 Reflective anodes, e.g. ITO combined with thick metallic layers
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices

Abstract

Provided is an optical element that highly efficiently radiates light with high directivity at low etendue. The optical element includes a light emission layer (103) generating an exciton to emit light, a plasmon excitation layer (105) having a higher plasma frequency than a light emission frequency of the light emission layer (103), an output layer (107) converting light or a surface plasmon generated on an upper surface of the plasmon excitation layer (105) into light with a predetermined output angle to output the light, and a dielectric layer (102). In the optical element, a real part of an effective dielectric constant with respect to the surface plasmon is higher in an upper side portion than the plasmon excitation layer (105) than in a lower side portion than the plasmon excitation layer (105); a dielectric constant with respect to the light emission frequency of the light emission layer (103) is higher in a lowest layer than in a layer adjacent to a lower side of the plasmon excitation layer (105); and assuming that a radiation angle of a surface plasmon-derived highly directional radiation from the plasmon excitation layer (105) to the output layer (107) side is θ_out,spp and a radiation angle of an optical waveguide fundamental mode-derived highly directional radiation is θ_out,light, an absolute value of a difference between the θ_out,spp and the θ_out,light is less than 10 degrees.

Claims

1. An optical element comprising:

a light emission layer, a plasmon excitation layer, an output layer, and a dielectric layer, wherein the light emission layer generates an exciton to emit light;

the plasmon excitation layer is arranged on an upper side than the light emission layer and has a higher plasma frequency than a light emission frequency of the light emission layer;

the output layer is arranged on an upper side than the plasmon excitation layer and converts light or a surface plasmon generated on an upper surface of the plasmon excitation layer into light with a predetermined output angle to output the light;

the dielectric layer is arranged at least one of on a lower side than the light emission layer and between the light emission layer and the plasmon excitation layer;

a real part of an effective dielectric constant with respect to the surface plasmon is higher in an upper side portion than the plasmon excitation layer than in a lower side portion than the plasmon excitation layer;

a dielectric constant with respect to the light emission frequency of the light emission layer is higher in a lowest layer than in a layer adjacent to a lower side of the plasmon excitation layer; and

assuming that, in a highly directional radiation from the plasmon excitation layer to the output layer side, a radiation angle of a surface plasmon-derived highly directional radiation is θ

_out,spp and a radiation angle of an optical waveguide fundamental mode-derived highly directional radiation is θ

_out,light, an absolute value of a difference between the θ

_out,spp and the θ

_out,light is less than 10 degrees.

2. The optical element according to claim 1, further comprising a positive hole transport layer, an electron transport layer, and an electrode, wherein current is injectable from outside through the electrode;

the positive hole transport layer is arranged on either of an upper side or a lower side of the light emission layer;

the electron transport layer is arranged on either of an upper side or a lower side of the light emission layer and on a side opposite to the positive hole transport layer; and

the light emission layer generates the exciton by coupling of a positive hole injected from the positive hole transport layer and an electron injected from the electron transport layer to emit light.

3. The optical element according to claim 1, wherein an effective dielectric constant (∈

_eff,spp) with respect to the surface plasmon is represented by the following formula (1);

a z component k_spp,z of a wavenumber of the surface plasmon is represented by the following formula (2); and

x and y components k_spp of the wavenumber of the surface plasmon are represented by the following formula (3);

4. An illumination device comprising the optical element according to claim 1 and a light projection unit, the illumination device being capable of projecting light by inputting light from the optical element to the light projection unit and outputting light from the light projection unit.

5. The illumination device according to claim 4, further comprising a projection optical system projecting a projected image by the light output from the light projection unit.

6. The illumination device according to claim 4, wherein the optical element is arranged relative to the light projection unit in a direction different from a direction of light output from the light projection unit.

7. An image display device comprising the optical element according to claim 1 and an image display unit, the image display device being capable of displaying an image by inputting light from the optical element to the image display unit and outputting light from the image display unit.

8. The image display device according to claim 7, further comprising a projection optical system projecting a projected image by the light output from the image display unit.

9. The image display device according to claim 7, wherein the optical element is arranged relative to the light projection unit in a direction different from a direction of light output from the light projection unit.

10. An operation method for the optical element according to claim 1 the method comprising:

causing the light emission layer of the optical element according to claim 1 generate an exciton, coupling power of the generated exciton to a surface plasmon-derived mode and an optical waveguide mode in the optical element, and then, emitting, as light, the power of the exciton coupled to each mode.