Nanostructured meta-materials and meta-surfaces to collimate light emissions from LEDs
A system, method and device for collimating the output of a light emitting diode (LED) are disclosed. The system, method and device include an LED substrate including a top surface from which the light is emitted, and an array of subwavelength scattering antennas positioned within the emitted light path, the array of subwavelength scattering antennas configured to select directions of scatter of the LED emitted light to provide collimated light output from the device. The array may be aligned perpendicular to the plane of propagation of the light emitted from the LED and may be positioned adjacent to the top surface. The array may be at least partially, or completely, positioned within the LED substrate. The array may be spaced a distance from the top surface and the spacing may be achieved using a dielectric spacer adjacent to the top surface. The array may be positioned within the dielectric spacer.
1. A light emitting device comprising:
a light emitting diode (LED) having a light emitting surface through which light is emitted from active light regions of the LED during operation thereof;
at least a first array of light scattering elements arranged in a plane parallel to the light emitting surface, each light scattering element having dimensions in the plane of the first array less than or equal to a free space wavelength of light emitted by the LED, the light scattering elements having structural, optical, or structural and optical properties that vary with position along the plane of the first array; and
a dielectric spacer, at least a portion of the dielectric spacer being positioned between the light emitting surface and the first array,
the scattering elements of the first array and the dielectric spacer being arranged so as to impart collectively spatially varying phase or amplitude onto light emitted from the active light regions of the LED and result in collimation or partial collimation of the emitted light by forming a far-field image of the active light regions of the LED.
2. The light emitting device of claim 1 , the dielectric spacer including a solid, substantially transparent dielectric substrate having opposed first and second surfaces with the first surface of the substrate facing the light emitting surface, the first array being positioned within the substrate or at the second surface of the substrate.
3. The light emitting device of claim 1 , at least some of the scattering elements being arranged as resonant scattering elements.
4. The light emitting device of claim 1 , at least some of the scattering elements being arranged as non-resonant scattering elements.
5. The light emitting device of claim 1 , the scattering elements including one or more materials among gold, silver, copper, aluminum, other metals or metal alloys, silicon, silicon dioxide, titanium dioxide, gallium arsenide, aluminum gallium arsenide, other dielectric materials, or one or more hybrid metallo-dielectric material combinations.
6. The light emitting device of claim 1 , the light emitting device including a phosphor layer between the dielectric spacer and the light emitting diode.
7. The light emitting device of claim 1 , spacing of the light scattering elements varying with spatial location of the light scattering elements in the plane of the first array.
8. The light emitting device of claim 1 , shapes or sizes, or both, of the light scattering elements varying with spatial location of the light scattering elements in the plane of the first array.
9. The light emitting device of claim 1 , refractive indices of the light scattering elements varying with spatial location of the light scattering elements in the plane of the first array.
10. The light emitting device of claim 1 , the light scattering elements having structural, optical, or structural and optical properties that vary with distance from a center of the first array of light scattering elements.
11. The light emitting device of claim 1 , the light scattering elements having dimensions perpendicular to the plane of the first array less than or equal to the free space wavelength of light emitted by the light emitting diode.
12. The light emitting device of claim 1 , further comprising a second array of light scattering elements arranged (i) in a plane parallel to and spaced apart from the plane of the first array and (ii) between the first array and at least a portion of the light emitting diode, each light scattering element of the second array having dimensions in the plane of the second array less than or equal to the free space wavelength of light emitted by the LED, the light scattering elements of the second array having structural, optical, or structural and optical properties that vary with position along the plane of the second array, the scattering elements of the second array being arranged so as to impart collectively spatially varying phase or amplitude onto light emitted from the active light regions of the LED and, in combination with the dielectric spacer and the scattering elements of the first array, result in collimation or partial collimation of the emitted light by forming a far-field image of the active light regions of the LED.
13. The light emitting device of claim 12 , the light scattering elements of the second array being positioned (i) at the light emitting surface and located external to the LED or within the LED, or (ii) within or at the first surface of the dielectric spacer and spaced apart from the light emitting surface.
14. The light emitting device of claim 12 , (i) at least some of the scattering elements of the second array being arranged as resonant scattering elements, or (ii) at least some of the scattering elements of the second array being arranged as non-resonant scattering elements.
15. The light emitting device of claim 12 , the scattering elements of the second array including one or more materials among gold, silver, copper, aluminum, other metals or metal alloys, silicon, silicon dioxide, titanium dioxide, gallium arsenide, aluminum gallium arsenide, other dielectric materials, or one or more hybrid metallo-dielectric material combinations.
16. The light emitting device of claim 12 , spacing of the light scattering elements of the second array varying with spatial location of the light scattering elements in the plane of the second array.
17. The light emitting device of claim 12 , shapes or sizes, or both, of the light scattering elements of the second array varying with spatial location of the light scattering elements in the plane of the second array.
18. The light emitting device of claim 12 , refractive indices of the light scattering elements of the second array varying with spatial location of the light scattering elements in the plane of the second array.
19. The light emitting device of claim 12 , the light scattering elements of the second array having structural, optical, or structural and optical properties that vary with distance from a center of the second array of light scattering elements.
20. The light emitting device of claim 12 , the light scattering elements of the second array having dimensions perpendicular to the plane of the second array less than or equal to the free space wavelength of light emitted by the light emitting diode.