White Light Emitting Device Based on Polariton Laser

• US 20100303468A1
• Filed: 06/02/2009
• Published: 12/02/2010
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: The Government Of The United States Of America, As Represented By The Secretary Of The Navy
• Inventors: Eddy, Charles R. JR., Mastro, Michael A.
• Granted Patent: US 8,237,152 B2
• Time in Patent Office: Days
• US Class Current: 398/118
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 5/0087 for illuminating phosphorescent or fluorescent materials, e.g. using optical arrangements specifically adapted for guiding or shaping laser beams illuminating these materials
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18386 Details of the emission surface for influencing the near- or far-field, e.g. a grating on the surface
• CPC Class Codes: H01S 5/3404 influencing the polarisation
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
• CPC Class Codes: H04B 10/1121 One-way transmission
• CPC Class Codes: H04B 10/1141 One-way transmission

Abstract

A high-efficiency white-light-emitting device that includes a polariton light emitter that emits UV or blue light to a down-converting material that converts the polariton emissions to white light. The polariton light emitter includes an active region situated within a resonant optical cavity formed on a substrate. The down-converting material can comprise a luminophoric phosphor or other material. The polariton light and down-converting material can be arranged in a single apparatus to provide a white-light-emitting device that can be used for lighting and instrumentation. The device can also be configured for high-frequency modulation to provide optical signals for communications and control systems.

Claims

1. A white light-emitting device, comprising:

a polariton light emitter disposed within an optical cavity, the optical cavity having a resonant mode corresponding to a predetermined resonant photon energy, the polariton light emitter comprising an active region forming a plurality of polaritons therein, each of the plurality of polaritons comprising an exciton coupled with a resonant photon, an energy of each of the plurality of polaritons being determined by an energy of the exciton and an energy of the resonant photon coupled therewith; and

a down-converting medium disposed in close proximity to the optical cavity;

wherein the polariton light emitter emits light having a wavelength corresponding to the energy of the polaritons formed in the active region, the emitted light being received by the down-converting medium; and

wherein the down-converting medium converts the received light from the polariton laser to white light, the white light being then emitted by the down-converting medium.

2. The white light-emitting device according to claim 1, wherein optical cavity comprises a first reflector and a second reflector, the second reflector being less reflective than the first reflector,

the light emitted from the polariton light emitter traveling through the second reflector before being received by the down-converting medium.

3. The white light-emitting device according to claim 2, wherein the first and second reflectors comprise semiconductor distributed Bragg refractor (DBR) mirrors.

4. The white light-emitting device according to claim 3, wherein the first reflector comprises an n-AlN/AlGaN DBR mirror and the second reflector comprises p-AlN/AlGaN DBR mirror.

5. The white light-emitting device according to claim 2, wherein the first and second reflectors comprise dielectric distributed Bragg refractor (DBR) mirrors.

6. The white light-emitting device according to claim 1, wherein the active region in the polariton emitter comprises a multiquantum well.

7. The white light-emitting device according to claim 6, wherein the multiquantum well is formed by a semiconductor material comprising one of gallium nitride (GaN), aluminum gallium nitride (AlGaN), and indium gallium nitride (InGaN).

8. The white light-emitting device according to claim 7, wherein the GaN used in the semiconductor material is non-polar GaN.

9. The white light-emitting device according to claim 8, wherein the multiquantum well is formed on a substrate comprising one of an r-plane sapphire, a (100) lithium aluminate, an a-plane bulk GaN, and an m-plane bulk GaN.

10. The white light-emitting device according to claim 7, wherein the GaN used in the semiconductor material is polar GaN.

11. The white light-emitting device according to claim 10, wherein the multiquantum well is formed on a substrate comprising one of an a-plane sapphire, a c-plane sapphire, a (111) silicon (Si) wafer, a (100) Si wafer, (0001) 4H-silicon carbide (SiC), and (0001) 6H-SiC.

12. The white light-emitting device according to claim 1, wherein the active region in the polariton light emitter comprises a microcavity having a thickness of nλ

/2, where n is a positive integer and λ

is a wavelength of the light within the microcavity.

13. The white light-emitting device according to claim 12, wherein the microcavity is a semiconductor microcavity and λ

is a wavelength of the light within the semiconductor.

14. The white light-emitting device according to claim 13, wherein the semiconductor comprises one of GaN, AlGaN, InGaN, InAlGaN, ZnO, MgZnO, ZnSe, ZnMgSe, CdTe, and CdMnTe

15. The white light-emitting device according to claim 12, wherein the microcavity comprises an organic material selected from the group consisting of pseudoisocyanine, cyanine dyes, transition metal porpyhrins, a-conjugated polysilanes, and polyaromatic cyclic anhydrides.

16. The white light-emitting device according to claim 1, wherein the down-converting medium comprises a luminophoric phosphor.

17. The white light-emitting device according to claim 1, wherein the down-converting medium comprises one of a phosphorescent material, a fluorescent material, and a semiconductor material comprising at least one semiconductor quantum dot.

18. The white light-emitting device according to claim 1, wherein the down-converting medium comprises at least one luminescent material capable of producing a white light without light contribution from the polariton light emitter.

19. The white light-emitting device according to claim 18, wherein the down-converting medium is opaque and absorbs all of the light received from the polariton light emitter such that the light emitted from the white-light-emitting device comprises only light emitted from the down-converting medium.

20. The white light-emitting device according to claim 17, wherein the down-converting luminophoric medium is semitransparent such that the light emitted from the white light-emitting device comprises both light emitted from the polariton light emitter and light emitted from the down-converting medium.

21. The white light-emitting device according to claim 1, wherein the light emitted from the polariton light emitter has a wavelength from about 360 nm to about 500 nm.

22. The white light-emitting device according to claim 1, further comprising a transparent housing, wherein at least one polariton light emitter and the down-converting medium are situated within the housing;

and wherein the white light is emitted through the transparent housing.

23. The white light-emitting device according to claim 1, the polariton light emitter further including an n-type semiconductor contact layer and a p-type semiconductor contact layer and a voltage source operatively connected to the optical cavity, wherein the voltage source supplies electrons to the n-type semiconductor contact layer and supplies holes to the p-type semiconductor contact layer, the electrons and holes combining as bound pairs to form the excitons.

24. The white light-emitting device according to claim 22, wherein the polariton light emitter comprises a passive cavity emitter not connected to a voltage source;

and

wherein a semiconductor light emitting diode is situated in the housing along with the passive polariton light emitter to provide a source of photons to stimulate light emission from the passive polariton light emitter.

25. The white light-emitting device according to claim 22, wherein the polariton light emitter comprises a passive cavity emitter not connected to a voltage source;

and

wherein a laser diode is situated in the housing along with the passive polariton light emitter to provide a source of photons to stimulate light emission from the passive polariton light emitter.

26. An optical communications system comprising:

a first object configured with a polariton white light-emitting device comprising a polariton light emitter disposed within an optical cavity, the optical cavity having a resonant mode corresponding to a predetermined resonant photon energy, the polariton light emitter comprising an active region forming a plurality of polaritons therein, each of the plurality of polaritons comprising an exciton coupled with a resonant photon, an energy of each of the plurality of polaritons being determined by an energy of the exciton and an energy of the resonant photon coupled therewith, and a down-converting medium disposed in close proximity to the optical cavity, wherein the polariton light emitter emits light having a wavelength corresponding to the energy of the polaritons formed in the active region, the light from the polariton light emitter being received by the down-converting medium and converted to white light, the white light being then emitted by the down-converting medium, the polariton light emitter further being coupled to a voltage source providing a high-frequency modulation of power provided to the polariton light emitter to create a high-frequency modulation of the light emission from the white light-emitting device; and

a second object configured to receive the high-frequency modulated light emission from the first object.

27. The optical communications system according to claim 26, the first object effects a control over the second object by means of the wherein the high-frequency modulated light emission from the first object.