Light-emitting diode with hyperbolic metamaterial
A light-emitting diode includes a first semiconductor region of one of p- or n-conductivity types, a second semiconductor region of the other one of p- or n-conductivity types, forming a p-n junction with the first semiconductor region, and a quantum well layer at the p-n junction between the first and second semiconductor regions. A hyperbolic metamaterial structure is provided in the second semiconductor region. The hyperbolic metamaterial structure is coupled to the quantum well layer for extracting light from the quantum well layer. The hyperbolic metamaterial structure may be patterned to provide an array of nanoantennas to apodize the emitted beam, and to control the polarization state of the emitted beam.
1. A light-emitting diode (LED) comprising:
a first semiconductor region of one of p- or n-conductivity types;
a second semiconductor region of the other one of p- or n-conductivity types, forming a p-n junction with the first semiconductor region;
a quantum well layer at the p-n junction between the first and second semiconductor regions; and
a hyperbolic metamaterial structure in the second semiconductor region, wherein the hyperbolic metamaterial structure comprises an array of features coupled to the quantum well layer, wherein a gap between the quantum well layer and features of the array varies across the array.
2. The LED of claim 1 , wherein the hyperbolic metamaterial structure comprises a stack of alternating metal and semiconductor layers.
3. The LED of claim 1 , wherein the LED has lateral dimensions of no greater than 25×25 micrometers.
4. The LED of claim 1 , wherein a pitch of the array of features is less than a wavelength of light emitted by the LED.
5. The LED of claim 1 , wherein the array of features has a plasmonic resonance optical frequency within a spectral gain band of the quantum well layer.
6. The LED of claim 1 , wherein the array of features has a spatially variant pitch.
7. The LED of claim 1 , wherein the array of features has a spatially varying duty cycle.
8. The LED of claim 1 , wherein the array of features is two-dimensional.
9. The LED of claim 1 , wherein each feature of the array comprises at least one of a cylinder feature, a cross feature, or a chevron feature.
10. The LED of claim 1 , wherein the array comprises a plurality of sub-arrays of features.
11. The LED of claim 10 , wherein each sub-array comprises an array of grating lines.
12. The LED of claim 1 , wherein the features of the array are configured to provide a pre-defined polarization of emitted light.
13. The LED of claim 1 , wherein the gap is smaller in a center area of the array as compared to other areas of the array.
14. The LED of claim 1 , wherein at least some of the features of the array are inclined towards a center of the array.
15. A display device comprising:
an array of light-emitting diodes, each light-emitting diode comprising:
a first semiconductor region of one of p- or n-conductivity types;
a second semiconductor region of the other one of p- or n-conductivity types, forming a p-n junction with the first semiconductor region;
a quantum well layer at the p-n junction between the first and second semiconductor regions; and
a hyperbolic metamaterial structure in the second semiconductor region, wherein the hyperbolic metamaterial structure comprises an array of features coupled to the quantum well layer, wherein a gap between the quantum well layer and features of the array varies across the array; and
an element having optical power optically coupled to the array of light-emitting diodes and spaced apart therefrom for redirecting optical beams emitted by the array of light-emitting diodes.
16. The display device of claim 15 , wherein the array of features is two-dimensional.
17. The display device of claim 15 , wherein at least some of the features of the array are inclined towards a center of the array.