Photonic structures for efficient light extraction and conversion in multi-color light emitting diodes

Abstract

A high efficiency light emitting diode (LED) comprised of a substrate, a buffer layer grown on the substrate (if such a layer is needed), a first active region comprising primary emitting species (PES) that are electrically-injected, a second active region comprising secondary emitting species (SES) that are optically-pumped by the light emitted from the PES, and photonic crystals, wherein the photonic crystals act as diffraction gratings to provide high light extraction efficiency, to provide efficient excitation of the SES, and/or to modulate the far-field emission pattern.

1 . A phosphor that is patterned with one or more photonic crystals. 
     
     
         2 . The phosphor of  claim 1 , wherein the photonic crystals are patterned to extract light emitted by the phosphor. 
     
     
         3 . The phosphor of  claim 2 , wherein the phosphor is positioned on or above a light emitting diode (LED) and the phosphor emits the light when optically-pumped by light emitted by the LED. 
     
     
         4 . The phosphor of  claim 3 , wherein the photonic crystals are patterned to extract the light emitted by the LED. 
     
     
         5 . The phosphor of  claim 4 , wherein the photonic crystals are patterned for extracting total internal reflection (TIR) or waveguided (WG) modes of the light emitted by the phosphor and the LED. 
     
     
         6 . The phosphor of  claim 5 , wherein the phosphor is positioned relative to a low refraction index layer to prevent coupling of the phosphor's evanescent waves to the TIR or WG modes of the light emitted by the LED or the phosphor. 
     
     
         7 . The phosphor of  claim 5 , wherein the photonic crystals are one-dimensional (1D) gratings having a periodicity, such that the TIR or WG modes of the LED light emitted by the LED, or the light emitted by the phosphors, are diffracted at angles nearly parallel to the LED's layers, so that the diffracted light propagates nearly in-plane in the phosphor. 
     
     
         8 . The phosphor of  claim 5 , further comprising means for confining or thinning one or more layers containing the TIR or WG modes, in order to increase the TIR or WG modes' overlap with the photonic crystals. 
     
     
         9 . The phosphor of  claim 3 , further comprising a plurality of the phosphors, wherein different ones of the phosphors are positioned on different regions of the LED to form multi-color pixels, and each type of pixel in the multi-color pixels has a different photonic crystal to obtain homogeneous efficiency and directionality for all colors. 
     
     
         10 . The phosphor of  claim 3 , wherein the photonic crystals increase excitation of the phosphors by the light emitted by the LED. 
     
     
         11 . The phosphor of  claim 3 , wherein the photonic crystals are one-dimensional (1D) gratings that diffract differently different components of the light emitted by the LED or the phosphors. 
     
     
         12 . The phosphor of  claim 3 , wherein the photonic crystals are one-dimensional (1D) gratings integrated at different positions on the LED, with different orientations, to diffract the light emitted by the LED or the phosphor in more than one direction. 
     
     
         13 . The phosphor of  claim 3 , wherein the photonic crystals are two-dimensional (2D) gratings that improve extraction of the light emitted by the LED or the phosphors in more than one direction. 
     
     
         14 . The phosphor of  claim 3 , wherein the photonic crystals are fabricated on separate membranes and then are positioned on the LED. 
     
     
         15 . A method of fabricating a phosphor, comprising patterning the phosphor with one or more photonic crystals. 
     
     
         16 . The method of  claim 15 , wherein the photonic crystals are patterned to extract light emitted by the phosphor. 
     
     
         17 . The method of  claim 16 , further comprising positioning the phosphor on or above a light emitting diode (LED) such that the phosphor emits the light when optically-pumped by light emitted by the LED. 
     
     
         18 . The method of  claim 17 , wherein the photonic crystals are patterned to extract the light emitted by the LED. 
     
     
         19 . The method of  claim 18 , wherein the photonic crystals are patterned for extracting total internal reflection (TIR) or waveguided (WG) modes of the light emitted by the phosphor and the LED. 
     
     
         20 . The method of  claim 19 , wherein the phosphor is positioned relative to a low refraction index layer to prevent coupling of the phosphor's evanescent waves to the TIR or WG modes of the light emitted by the LED or the phosphor. 
     
     
         21 . The method of  claim 19 , wherein the photonic crystals are one-dimensional (1D) gratings having a periodicity, such that the TIR or WG modes of the LED light emitted by the LED, or the light emitted by the phosphors, are diffracted at angles nearly parallel to the LED's layers, so that the diffracted light propagates nearly in-plane in the phosphor. 
     
     
         22 . The method of  claim 19 , further comprising confining or thinning one or more layers containing the TIR or WG modes, in order to increase the TIR or WG modes' overlap with the photonic crystals. 
     
     
         23 . The method of  claim 17 , further comprising fabricating a plurality of the phosphors, wherein different ones of the phosphors are positioned on different regions of the LED to form multi-color pixels, and each type of pixel in the multi-color pixels has a different photonic crystal to obtain homogeneous efficiency and directionality for all colors. 
     
     
         24 . The method of  claim 17 , wherein the photonic crystals increase excitation of the phosphors by the light emitted by the LED. 
     
     
         25 . The method of  claim 17 , wherein the photonic crystals are one-dimensional (1D) gratings that diffract differently different components of the light emitted by the LED or the phosphors. 
     
     
         26 . The method of  claim 17 , wherein the photonic crystals are one-dimensional (1D) gratings integrated at different positions on the LED, with different orientations, to diffract the light emitted by the LED or the phosphor in more than one direction. 
     
     
         27 . The method of  claim 17 , wherein the photonic crystals are two-dimensional (2D) gratings that improve extraction of the light emitted by the LED or the phosphors in more than one direction. 
     
     
         28 . The method of  claim 17 , wherein the photonic crystals are fabricated on separate membranes and then are positioned on the LED.