Aperiodic nano-optical array for angular shaping of incoherent emissions
Disclosed herein are a number of dielectric pillars, arranged to form a close-packed aperiodic array, such as a Vogel spiral, where the geometries of the aperiodic array produce azimuthally isotropic scattering of luminescence within a restricted angular cone of extraction. The aperiodic array can be formed, attached or placed on a converting material, such as, phosphor, to restrict emission to within the angular cone of extraction. The phosphor could be part of a converting illumination device, such as a phosphor coated light emitting diode, or a laser activated remote phosphor converting device.
1. An illumination device comprising:
a light source configured to emit a first light beam having a wavelength within a first range of wavelengths;
a converting material arranged in a phosphor layer such that the first light beam is incident on the converting material, the converting material configured to emit a second light beam having a wavelength within a second range of wavelengths, and the second range of wavelengths different from the first range of wavelengths; and
a dielectric aperiodic array disposed on the phosphor layer, the aperiodic array comprising a plurality of sub-wavelength scattering pillars arranged to form an aperiodic pattern, the aperiodic array configured to restrict emission of the second light beam to within a restricted angular cone,
wherein the aperiodic pattern of the dielectric aperiodic array is configured to produce azimuthally isotropic scattering of incident luminescence within the restricted angular cone,
wherein the phosphor layer is a flat plate and optically thick, and
wherein each of the plurality of dielectric pillars comprises a transparent dielectric.
2. The illumination device of claim 1 , wherein the aperiodic array comprises circularly symmetric Fourier k-space configured to produce azimuthally isotropic scattering of luminescence within the restricted angular cone.
3. The illumination device of claim 1 , wherein the plurality of pillars forms a Vogel spiral.
4. The illumination device of claim 3 , wherein the plurality of pillars forms a golden angle Vogel spiral.
5. The illumination device of claim 1 , wherein the converting material comprises phosphor.
6. The illumination device of claim 5 , wherein the converting material has a composition A 3 B 5 O 12 :Ce, and wherein A is selected from the group consisting of Y, Sc, La, Gd, Lu, Tb and B is selected from the group consisting of Al, Ga and Sc.
7. The illumination device of claim 5 , wherein the second range of wavelengths is between 500 nanometers and 600 nanometers.
8. The illumination device of claim 1 , wherein the light source is a light emitting diode (LED).
9. The illumination device of claim 8 , wherein the first range of wavelengths is between 430 nanometers and 495 nanometers or between 375 nanometers and 410 nanometers.
10. The illumination device of claim 8 , wherein the converting material is disposed on a top surface of the LED.
11. The illumination device of claim 1 , wherein the light source is a laser.
12. The illumination device of claim 11 , further comprising collection optics arranged downstream from the converting material.
13. The illumination device of claim 1 , wherein a mean center-to-center spacing between each of the plurality of pillars is between 300 and 500 nanometers.
14. The illumination device of claim 1 , wherein each of the plurality of pillars has a height of between 100 nanometers and 1,000 nanometers.
15. The illumination device of claim 1 , wherein each of the plurality of pillars is cylindrically shaped and has a diameter of between 100 nanometers and 300 nanometers.
16. The illumination device according to claim 1 , wherein each of the plurality of dielectric pillars consists of titanium dioxide (TiO 2 ), titanium nitride (TiN) or silicon (Si).
17. The illumination device according to claim 1 , wherein each of the plurality of pillars is cylindrically shaped and has a diameter of between 100 nanometers and 300 nanometers, a height of between 100 nanometers and 1,000 nanometers, and a mean center-to-center spacing between each of the plurality of pillars of between 300 and 500 nanometers.
18. An arrangement comprising:
a substrate being a phosphor layer, wherein the phosphor layer is a flat plate and optically thick; and
a plurality of dielectric sub-wavelength scattering pillars disposed on the substrate and arranged to form a dielectric aperiodic array with an aperiodic pattern, the plurality of dielectric pillars of the aperiodic pattern configured to cooperate to produce azimuthally isotropic scattering of incident luminescence to within a restricted angular cone,
wherein the aperiodic array is configured to restrict illumination emissions to within the restricted angular cone, and
wherein each of the plurality of dielectric pillars comprises a transparent dielectric.
19. The arrangement of claim 18 , wherein the aperiodic array is a Vogel spiral.
20. The arrangement of claim 19 , wherein a mean center-to-center spacing between each of the plurality of dielectric pillars is between 0.25 and 2.5 times a wavelength of the incident luminescence.
21. The arrangement of claim 19 , wherein each of the plurality of dielectric pillars is cylinder shaped, cone shaped, pyramid shaped, or rectangular shaped.
22. The arrangement of claim 19 , wherein each of the plurality of dielectric pillars is cylindrically shaped and has a height of between 100 nanometers and 1,000 nanometers and a diameter of between 100 nanometers and 300 nanometers.
23. The arrangement of claim 18 , wherein the substrate comprises phosphor.
24. A method of manufacturing an arrangement, the method comprising:
applying a pattern, to mark a plurality of sub-wavelength scattering pillars arranged in an aperiodic array, onto a substrate comprising a wavelength converting material arranged in a phosphor layer and arranged to emit light of a first wavelength responsive to incidence of light of a second, different, wavelength; and
forming the plurality of sub-wavelength scattering pillars from the substrate,
wherein the phosphor layer is a flat plate and optically thick,
wherein each of the plurality of dielectric pillars comprises a transparent dielectric,
wherein the aperiodic array is configured to restrict illumination emissions to within a restricted angular cone, and
wherein the pattern of the plurality of sub-wavelength scattering pillars is configured to produce azimuthally isotropic scattering of incident luminescence within the restricted angular cone.
25. The method of claim 24 , further comprising:
depositing a dielectric material into the wavelength converting material; and
etching the dielectric material to form the plurality of pillars.
26. The method of claim 24 , wherein the aperiodic array is a Vogel spiral.
27. The method of claim 24 , wherein each of the plurality of pillars is cylindrically shaped and has a height of between 100 nanometers and 1,000 nanometers and a diameter of between 100 nanometers and 300 nanometers, and wherein a mean center-to-center spacing between each of the plurality of pillars is between 0.25 and 2.5 times the first wavelength.