Index and gain coupled distributed feedback laser

Abstract

A method of forming a laser involves forming, on a substrate, a first epitaxial part of the laser that includes at least an active region layer surrounded by first and second waveguide layers. A dielectric layer is formed over the first epitaxial part. Two or more mask openings are patterned within the dielectric layer. The mask openings extend normal to a light-propagation direction of the laser and are spaced apart in the light-propagation direction of the laser. A second epitaxial part of the laser is formed in the mask openings using selective area epitaxy. The second epitaxial part includes a refractive grating with three-dimensional grating features.

1 . A method of forming a laser, comprising:
 forming, on a substrate, a first epitaxial part of the laser comprising at least an active region layer surrounded by first and second waveguide layers;   forming a dielectric layer over the first epitaxial part;   patterning two or more mask openings within the dielectric layer, the mask openings extending normal to a light-propagation direction of the laser and are spaced apart in the light-propagation direction of the laser; and   forming, in the mask openings using selective area epitaxy, a second epitaxial part of the laser comprising a refractive grating comprising three-dimensional nano-stripes.   
     
     
         2 . The method of  claim 1 , wherein the three-dimensional nano-stripes comprise trapezoidal cross-sections. 
     
     
         3 . The method of  claim 1 , wherein the three-dimensional nano-stripes comprise rectangular cross-sections. 
     
     
         4 . The method of  claim 1 , wherein the three-dimensional nano-stripes comprise triangular cross-sections. 
     
     
         5 . The method of  claim 1 , wherein the mask openings align with a center of the nano-stripes. 
     
     
         6 . The method of  claim 1 , wherein the active layer region, first and second waveguide layers, and three-dimensional refractive grating are formed of III-V semiconductors. 
     
     
         7 . The method of  claim 6 , wherein the III-V semiconductors are selected from a group consisting of AlGaInN, AlGaInAs, AlGaInP, and AlGaInSb. 
     
     
         8 . The method of  claim 1 , wherein the dielectric layer is formed of SiO 2 . 
     
     
         9 . The method of  claim 1 , further comprising forming an electron blocking layer between one of the first and second waveguide layers and the dielectric layer. 
     
     
         10 . The method of  claim 1 , further comprising forming a conductive cover layer over the nano-stripes, the cover having a different refractive index than the refractive grating and filling in gaps between the nano-stripes. 
     
     
         11 . The method of  claim 10 , wherein the conductive cover layer has a lower refractive index than that of the refractive grating. 
     
     
         12 . The method of  claim 10 , wherein the conductive cover layer is in contact with the dielectric layer. 
     
     
         13 . The method of  claim 10 , wherein the conductive cover layer is formed of ITO. 
     
     
         14 . The method of  claim 1 , wherein the nano-stripes extend beyond the edges of the mask openings in the light propagation direction. 
     
     
         15 . The method of  claim 1 , wherein the nano-stripes comprise surfaces facing away from the active region that are atomically smooth. 
     
     
         16 . The method of  claim 1 , wherein using selective area epitaxy comprises using metalorganic vapor-phase epitaxy. 
     
     
         17 . The method of  claim 1 , wherein using selective area epitaxy comprises using molecular beam epitaxy. 
     
     
         18 . The method of  claim 1 , wherein the use of selective area epitaxy forms the nano-stripes without etching or milling, resulting in atomically smooth surfaces on the nano-stripes. 
     
     
         19 . A method of forming a laser heterostructure, comprising:
 performing a first epitaxial run in which a first part of the laser heterostructure is grown in an unpatterned manner, the first part comprising an active region layer surrounded by first and second waveguide layers;   interrupting the first epitaxial run to deposit a dielectric mask over an upper layer of the first part, the mask comprising openings extending normal to a light-propagation direction of the laser heterostructure and are spaced apart in the light-propagation direction of the laser heterostructure; and   performing a second epitaxial run in which selective area epitaxy is used to form a second part of the laser heterostructure, the second part comprising three-dimensional nano-stripes formed in the openings.   
     
     
         20 . The method of  claim 19 , wherein the first and second parts of the laser heterostructure are formed of III-V semiconductors.