Light emitting diode device

1. A light emitting diode device, comprising:

a transmissive optical element configured to collimate incident beams of light;

a reflective optical element configured to reflect incident beams of light along a direction opposite to an incidence direction;

a cavity between the transmissive optical element and the reflective optical element formed by the transmissive optical element and the reflective optical element; and

a light emitter within the cavity and configured to emit beams of light, such that some of the light is to be directed toward the transmissive optical element and some of the light is to be directed towards the reflective optical element, which is then to be redirected back along a path from which the light came and towards the transmissive optical element;

wherein at least one of the transmissive optical element and the reflective optical element is a planar non-periodic high-index-contrast grating.

2. A device as in claim 1 , wherein the beams of light emitted from the light emitter comprise a plurality of wavelengths.

3. A device as in claim 1 , wherein the transmissive optical element is a collimating lens configured to transmit light from a plurality of incident angles in parallel.

4. A device as in claim 1 , wherein the reflective optical element is a parabolic reflector configured to reflect incident beams of light from a plurality of different directions back along the plurality of directions of incidence.

5. A device in accordance with claim 1 , wherein the light emitter comprises a transparent light emitter.

6. A light emitting diode device, comprising:

a first planar non-periodic high-index-contrast grating configured as a transmissive collimating optical element;

a second planar non-periodic high-index-contrast grating configured as a parabolic reflective optical element;

a cavity between the transmissive collimating optical element and the parabolic reflective optical element formed by the transmissive collimating optical element and the parabolic reflective optical element; and

a light emitter within the cavity and configured to emit light, such that some of the light is to be directed toward the transmissive collimating optical element and some of the light is to be directed towards the parabolic reflective optical element, which is then to be redirected back along a path from which the light came and towards the transmissive collimating optical element.

7. A device as in claim 6 , wherein the parabolic reflective optical element comprises a reflective sub-wavelength grating comprising a grating layer, the grating layer having a planar geometry and configured with lines, the lines widths, line thicknesses and line period spacing selected to control phase changes in different portions of the emitted light which is reflected from the grating such that the phase changes collectively produce a desired wavefront shape in the emitted light reflected from the grating.

8. A device as in claim 7 , wherein the lines width, line thickness and line period spacing are selected such that the reflective sub-wavelength grating forms a converging parabolic reflector.

9. A device as in claim 7 , further comprising a substrate, wherein the grating layer is disposed on the substrate and the grating layer is composed of a material having a relatively higher refractive index than the refractive index of the substrate.

10. A device as in claim 6 , wherein the transmissive collimating optical element further comprises:

a first substantially planar reflective structure;

a second substantially planar reflective structure; and

a substantially planar sub-wavelength grating layer disposed between the first reflective structure and the second reflective structure, wherein the grating layer is configured with lines having line widths, line thicknesses, and line period spacing selected to control phase changes in different portions of a beam of light transmitted through the transmissive collimating optical element.

11. A device as in claim 10 , wherein at least one of the first reflective structure and the second reflective structure are configured as sub-wavelength grating layers configured with lines having line widths, line thicknesses, and line period spacing selected to control phase changes in different portions of a beam of light transmitted through the transmissive collimating optical element.

12. A device as in claim 11 , wherein the lines widths, line thickness, and line period spacing of the sub-wavelength grating layer and the first or second substantially planar reflective surface are selected to form a transmissive collimating optical element.

13. A device as in claim 6 , wherein the cavity comprises air.