Light emitting devices

Abstract

A new light emitting device is disclosed. The device includes a reflector, a surface layer, and a light emitting layer located there-between. The light emitting layer emits light at a wavelength λ. An optical thickness from the light emitting layer to the reflector is approximately m*λ/4, where m is a positive integer. Furthermore, the said device may, in addition, include an optical transform layer adjoining to the light emitting layer. Thus, the light emitted by the device can be not only collimated but also polarized.

1 . A light emitting device, at least comprising:
 a surface layer;   a light emitting layer which the emitted light has a wavelength; and   a reflective layer,   wherein the light emitting layer is disposed between the reflective layer and the surface layer, and an optical thickness between the light emitting layer and the reflective layer is about a value of integer times of a quarter of the wavelength.   
   
   
       2 . The light emitting device as claimed in  claim 1 , wherein the optical thickness between the light emitting layer and the reflective layer is about a value between integer m−1 and m+1 times of a quarter of the wavelength. 
   
   
       3 . The light emitting device as claimed in  claim 1 , wherein the optical thickness between the light emitting layer and the reflective layer is about a value of m times of a quarter of the wavelength, where m is a positive integer, and is satisfied 1≦m≦12. 
   
   
       4 . The light emitting device as claimed in  claim 1 , wherein the surface layer is a light polarizing layer. 
   
   
       5 . The light emitting device as claimed in  claim 1 , wherein the structure of the light emitting layer is a quantum well structure or a quantum dot structure. 
   
   
       6 . The light emitting device as claimed in  claim 1 , wherein the material of the light emitting layer is a fluorescent inorganic material, a phosphorescent inorganic material, a fluorescent organic material, or a phosphorescent organic material. 
   
   
       7 . The light emitting device as claimed in  claim 1 , wherein the reflective layer at least comprises a metallic layer. 
   
   
       8 . The light emitting device as claimed in  claim 4 , wherein the light polarizing layer is a metal layer, a periodic parallel stripe interval arranged metal layer, a plurality of dielectric stack of light polarizing thin films or an organic light polarizing layer. 
   
   
       9 . The light emitting device as claimed in  claim 1 , wherein a material of the light emitting layer comprises a III-V group semiconductor material. 
   
   
       10 . The light emitting device as claimed in  claim 9 , wherein the III-V group semiconductor material is a nitrided base material, an eptiaxial GaAs or InP base grown material. 
   
   
       11 . The light emitting device as claimed in  claim 1 , wherein the optical thickness between the surface layer and the reflective layer is about equal to or less than 20 times of the wavelength, but greater than or equal to a half of the wavelength. 
   
   
       12 . The light emitting device as claimed in  claim 1 , further comprising a conductive layer interposed between the light emitting layer and the reflective layer. 
   
   
       13 . The light emitting device as claimed in  claim 1 , further at least comprising:
 a light transformation layer, wherein the light transformation layer is adjacent to the light emitting layer.   
   
   
       14 . The light emitting device as claimed in  claim 13 , wherein the light transformation layer is an interface layer with a plurality of structures, the structures is distributed on an interface of the transformation in patterned forms, and a dielectric function of the interface is a spatial function of pattern variations such that the emitted light of the light emitting device is collimated. 
   
   
       15 . The light emitting device as claimed in  claim 1 , wherein the optical thickness between the light emitting layer and the reflective layer is about a value of m times of a quarter of the wavelength, where m is a positive integer, and is satisfied 1≦m≦40. 
   
   
       16 . The light emitting device as claimed in  claim 13 , wherein the light transformation layer is interposed between the light emitting layer and the reflective layer. 
   
   
       17 . The light emitting device as claimed in  claim 13 , wherein the transformation layer is interposed between the light emitting layer and the surface layer. 
   
   
       18 . The light emitting device as claimed in  claim 13 , wherein the optical thickness between the surface layer and the reflective layer is about equal to or less than 20 times of the wavelength. 
   
   
       19 . The light emitting device as claimed in  claim 14 , wherein the plurality of structures at least comprise an opening, a pillar, a pore, or a stripe grating. 
   
   
       20 . The light emitting device as claimed in  claim 14 , wherein the plurality of structures have a periodic or a non-periodic pattern. 
   
   
       21 . The light emitting device as claimed in  claim 20 , wherein the periodic pattern is a honeycomb, a non-equilateral parallelogram, an equilateral parallelogram, an annular, a ID grating or a quasi photonic crystal. 
   
   
       22 . The light emitting device as claimed in  claim 13 , wherein a material of the light transformation layer at least comprises a transparent conductive material or a carrier conductive layer.