Luminescent detector for free-space optical communication

1. An apparatus comprising:

a wavelength-shifting element comprising:

a photoluminescent wavelength-shifting material configured to:

receive, from a first direction, an input-light data signal comprising a first range of wavelengths;

absorb at least a portion of the received input-light data signal; and

produce, based on an upper-state lifetime of the photoluminescent wavelength-shifting material, an emitted-light data signal comprising a second range of wavelengths;

a plasmonic structure that emits the emitted-light data signal in an opposite direction from the first direction;

a focusing element configured to:

receive, from the opposite direction, at least a portion of the emitted-light data signal;

concentrate the received portion of the emitted-light data signal; and

produce a concentrated-light data signal; and

a photodetector configured to:

receive the concentrated-light data signal; and

produce an electrical current corresponding to the concentrated-light data signal.

2. The apparatus of claim 1 , wherein the input-light data signal is a free-space optical-communication signal sent from an optical transmitter.

3. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material has an upper-state lifetime of less than or equal to 10 nanoseconds.

4. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material is contained within an encapsulant material.

5. The apparatus of claim 4 , wherein an upper-state lifetime of the photoluminescent wavelength-shifting material is reduced due to properties of the encapsulant material.

6. The apparatus of claim 4 , wherein a quantum efficiency of the photoluminescent wavelength-shifting material is increased due to properties of the encapsulant material.

7. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material has a thickness between 0.05 μm and 1 mm.

8. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material comprises a fluorescent-dye material or a plurality of quantum dots.

9. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material is a non-isotropic emitter that radiates the emitted-light data signal in a forward direction or a backward direction.

10. The apparatus of claim 1 , wherein the photoluminescent wavelength-shifting material absorbs greater than or equal to 70% of the input-light data signal.

11. The apparatus of claim 1 , wherein the absorbed portion of the received input-light data signal comprises visible or near-infrared light and the emitted-light data signal has a wavelength range that is longer than a wavelength range of the absorbed portion of the received input-light data signal.

12. The apparatus of claim 1 , wherein:

the photoluminescent wavelength-shifting material comprises an input aperture configured to receive the input-light data signal, wherein the input aperture has a diameter or width of greater than or equal to 1 cm; and

the photodetector has an active element with a diameter or width of less than or equal to 1 mm.

13. The apparatus of claim 1 , wherein:

the photoluminescent wavelength-shifting material comprises an input aperture configured to receive the input-light data signal, wherein the input aperture has a diameter or width of greater than or equal to 1 mm; and

the photodetector has an active element with a diameter or width of less than or equal to 20 micrometers.

14. The apparatus of claim 1 , wherein the portion of the emitted-light data signal received by the focusing element comprises greater than or equal to 25% of the emitted-light data signal.

15. The apparatus of claim 1 , wherein the plasmonic structure comprises a plurality of plasmonic-structure elements having diameters between 10 nm and 1 μm.

16. The apparatus of claim 15 , wherein the plurality of plasmonic structure elements extends perpendicular to a side of the photoluminescent wavelength-shifting material.

17. The apparatus of claim 15 , wherein the plasmonic structure is configured to cause the emitted-light data signal to be radiated in one or more collimated beams, one of the collimated beams directed in the opposite direction toward the focusing element.

18. A method comprising:

receiving, from a first direction by a photoluminescent wavelength-shifting material, an input-light data signal comprising a first range of wavelengths;

absorbing at least a portion of the received input-light data signal;

producing based on an upper-state lifetime of the photoluminescent wavelength-shifting material, an emitted-light data signal comprising a second range of wavelengths;

emitting, by a plasmonic structure, the emitted-light data signal in an opposite direction from the first direction;

receiving, from the opposite direction by a focusing element, at least a portion of the emitted-light data signal;

concentrating the received portion of the emitted-light data signal;

producing a concentrated-light data signal;

receiving, by a photodetector, the concentrated-light data signal; and

producing an electrical current corresponding to the concentrated-light data signal.

19. The apparatus of claim 1 , wherein the photodetector has a response time that is faster than the upper-state lifetime of the photoluminescent wavelength-shifting material.