Luminescent detector for free-space optical communication

1. An apparatus comprising:

a wavelength-shifting element configured to receive an input-light signal, wherein the wavelength-shifting element comprises a wavelength-shifting material configured to:

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

produce an emitted-light signal from the absorbed portion of the received input-light signal;

a plasmonic grating comprising a plurality of plasmonic-structure elements, wherein each plasmonic-structure element extends perpendicular to a side of the wavelength-shifting element, the plasmonic grating configured to:

receive at least a portion of the emitted-light signal; and

concentrate the received portion of the emitted-light signal onto a photodetector; and

the photodetector configured to:

receive the concentrated portion of the emitted-light signal; and

produce an electrical current corresponding to the concentrated portion of the emitted-light signal.

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

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

4. The apparatus of claim 1 , wherein the wavelength-shifting element further comprises a substantially transparent encapsulant material, wherein the wavelength-shifting material is contained within the encapsulant material.

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

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

7. The apparatus of claim 1 , wherein the wavelength-shifting element has a thickness of approximately 0.05 μm to approximately 1 mm.

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

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

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

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

12. The apparatus of claim 1 , wherein:

the wavelength-shifting element comprises an input aperture configured to receive the input-light 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 wavelength-shifting element comprises an input aperture configured to receive the input-light 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 signal received by the plasmonic grating comprises greater than or equal to 25% of the emitted-light signal.

15. The apparatus of claim 1 , wherein the plasmonic grating is incorporated into the wavelength-shifting element.

16. The apparatus of claim 1 , wherein the plasmonic grating is configured to cause the emitted-light signal to be radiated in one or more collimated beams.

17. A method comprising:

receiving an input-light signal;

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

producing an emitted-light signal from the absorbed portion of the received input-light signal;

receiving at least a portion of the emitted-light signal;

concentrating the received portion of the emitted-light signal by using a plasmonic grating, the plasmonic grating comprising a plurality of plasmonic-structure elements, wherein each plasmonic-structure element extends perpendicular to a side of a wavelength shifting element;

receiving the concentrated portion of the emitted-light signal; and

producing an electrical current corresponding to the concentrated portion of the emitted-light signal.

18. An apparatus comprising:

means for receiving an input-light signal;

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

means producing an emitted-light signal from the absorbed portion of the received input-light signal;

means for receiving at least a portion of the emitted-light signal;

means for concentrating the received portion of the emitted-light signal comprising a plasmonic grating, the plasmonic grating comprising a plurality of plasmonic-structure elements, wherein each plasmonic-structure element extends perpendicular to a side of a wavelength shifting element;

means for receiving the concentrated portion of the emitted-light signal; and

means for producing an electrical current corresponding to the concentrated portion of the emitted-light signal.

19. The apparatus of claim 1 , wherein the plurality of plasmonic structure elements are affixed to a side of the wavelength-shifting element that is opposite to a side that absorbs the emitted-light signal.

20. The apparatus of claim 1 , wherein receiving at least a portion of the emitted-light signal comprises coupling one or more photons of the emitted light signal to one or more of the plasmonic-structure elements to generate one or more plasma oscillations.