Semiconductor laser element having excellent light confinement effect and method for producing the semiconductor laser element

Abstract

A semiconductor laser element including: a three-dimensional photonic crystal structure which has a light confining effect and includes alternating first and second refractive index changing layers, where refractive index of light periodically changes in a first direction in each first refractive index changing layer and periodically changes in a second direction in each second refractive index changing layer; and an active unit which is disposed in a portion having a predetermined refractive index inside the three-dimensional photonic crystal structure, and generates a laser beam in response to reception of electric power.

What is claimed is:  
     
         1 . A semiconductor laser element comprising: 
 a three-dimensional photonic crystal structure which has a light confining effect and includes alternating first and second refractive index changing layers, wherein refractive index of light periodically changes in a first direction in each first refractive index changing layer and periodically changes in a second direction in each second refractive index changing layer; and    an active unit which is disposed in a portion having a predetermined refractive index inside the three-dimensional photonic crystal structure, and generates a laser beam in response to reception of electric power.    
     
     
         2 . The semiconductor laser element of  claim 1 , wherein 
 the active unit is disposed substantially at a center of the three-dimensional photonic crystal structure.    
     
     
         3 . The semiconductor laser element of  claim 2  further comprising 
 a light waveguide which extends horizontally from an end of the active unit to at least a vicinity of an end of the three-dimensional photonic crystal structure.  
 
     
     
         4 . The semiconductor laser element of  claim 2 , wherein 
 each first refractive index changing layer is composed of a plurality of optically refractive stripes arranged parallel to each other with a predetermined pitch so that refractive index of light periodically changes in the first direction,    each second refractive index changing layer is composed of a plurality of optically refractive stripes arranged parallel to each other with substantially the same pitch as the predetermined pitch so that refractive index of light periodically changes in the second direction,    phase of period of the plurality of optically refractive stripes constituting one refractive index changing layer is different from a phase of period of the plurality of optically refractive stripes constituting adjacent refractive index changing layer, and    a laser emitting stripe that includes the active unit is disposed in place of one optically refractive stripe.    
     
     
         5 . The semiconductor laser element of  claim 4 , wherein the active unit is disposed substantially at a center of the laser emitting stripe in the direction of length, and two portions ranging from both ends of the active unit to both ends of the laser emitting stripe are a p-type light waveguide and an n-type light waveguide, respectively, the p-type and n-type light waveguides each doubling as a carrier conduction path.  
     
     
         6 . The semiconductor laser element of  claim 5  further comprising: 
 a p-type carrier conduction path formed to overlap the p-type light waveguide;  
 an n-type carrier conduction path formed to overlap the n-type light waveguide;  
 a p-type contact layer formed to overlap the p-type light waveguide;  
 a p-type electrode formed to overlap the p-type light waveguide;  
 an n-type contact layer formed to overlap the n-type light waveguide; and  
 an n-type electrode formed to overlap the n-type light waveguide.  
 
     
     
         7 . The semiconductor laser element of  claim 6  further comprising 
 a high-reflection layer covering a side of the laser emitting stripe at an end in the direction of length.  
 
     
     
         8 . The semiconductor laser element of  claim 7 , wherein 
 the high-reflection layer is composed of a plurality of dielectric layers.    
     
     
         9 . The semiconductor laser element of  claim 8 , wherein 
 the high-reflection layer includes at least a SiO 2  layer and an amorphous Si layer, in the order from an end of the laser emitting stripe.    
     
     
         10 . The semiconductor laser element of  claim 4 , wherein 
 each optically refractive stripe is made of a material selected from the group consisting of InP, GaAs, AlGaInP, MgZnSSe, and AlGaN.    
     
     
         11 . The semiconductor laser element of  claim 2 , wherein 
 each first refractive index changing layer is composed of (a) a plurality of optically refractive stripes arranged parallel to each other with a predetermined pitch and (b) a plurality of dielectric stripes displacing space between the plurality of optically refractive stripes so that refractive index of light periodically changes in the first direction,    each second refractive index changing layer is composed of (c) a plurality of optically refractive stripes arranged parallel to each other with substantially the same pitch as the predetermined pitch and (d) a plurality of dielectric stripes displacing space between the plurality of optically refractive stripes in (c) so that refractive index of light periodically changes in the second direction,    phase of period of the plurality of optically refractive stripes constituting one refractive index changing layer is different from phase of period of the plurality of optically refractive stripes constituting adjacent refractive index changing layer, and    one optically refractive stripe has been replaced with a laser emitting stripe that includes the active unit.    
     
     
         12 . The semiconductor laser element of  claim 11 , wherein 
 the active unit is disposed substantially at a center of the laser emitting stripe in the direction of length, and two portions ranging from both ends of the active unit to both ends of the laser emitting stripe are a p-type light waveguide and an n-type light waveguide, respectively, the p-type and n-type light waveguides each doubling as a carrier conduction path.    
     
     
         13 . The semiconductor laser element of  claim 12  further comprising: 
 a p-type carrier conduction path formed to overlap the p-type light waveguide;  
 an n-type carrier conduction path formed to overlap the n-type light waveguide;  
 a p-type contact layer formed to overlap the p-type light waveguide;  
 a p-type electrode formed to overlap the p-type light waveguide;  
 an n-type contact layer formed to overlap the n-type light waveguide; and  
 an n-type electrode formed to overlap the n-type light waveguide.  
 
     
     
         14 . The semiconductor laser element of  claim 13  further comprising 
 a high-reflection layer covering a side of the laser emitting stripe at an end in the direction of length.  
 
     
     
         15 . The semiconductor laser element of  claim 13 , wherein 
 the high-reflection layer is composed of a plurality of dielectric layers.    
     
     
         16 . The semiconductor laser element of  claim 15 , wherein 
 the high-reflection layer includes at least a SiO 2  layer and an amorphous Si layer, in the order from an end of the laser emitting stripe.    
     
     
         17 . The semiconductor laser element of  claim 11 , wherein 
 each optically refractive stripe is made of a material selected from the group consisting of InP, GaAs, AlGaInP, MgZnSSe, and AlGaN, and    each dielectric stripe is made of a material selected from the group consisting of SiO 2 , SiN, Al 2 O 3 , and AlN.    
     
     
         18 . A method of producing the semiconductor laser element defined in  claim 1 , characterized by 
 an assembling step for systematically arranging and assembling a plurality of optically refractive stripes and a laser emitting stripe including an active unit that generates a laser beam in response to reception of electric power.    
     
     
         19 . The semiconductor laser element production method of  claim 18 , wherein 
 the assembling step includes: 
 a first large step for forming a refractive index changing layer by arranging optically refractive stripes in parallel to each other so that refractive index of light periodically changes in a predetermined direction;  
 a second large step for forming a laser emitting layer in which refractive index of light periodically changes in a predetermined direction, by arranging the laser emitting stripe and optically refractive stripes in parallel to each other; and  
 a third large step for stacking the refractive index changing layer and the laser emitting layer.  
   
     
     
         20 . The semiconductor laser element production method of  claim 19 , wherein 
 in the first large step, the refractive index changing layer is formed by arranging optically refractive stripes in parallel to each other with a predetermined pitch so that refractive index of light periodically changes, the optically refractive stripes having a different refractive index of light from air layers between the optically refractive stripes, and    in the second large step, the laser emitting layer is formed by arranging optically refractive stripes in parallel to each other with the same pitch as the refractive index changing layer, disposing the laser emitting stripe at a center of the optically refractive stripes instead of an optically refractive stripe.    
     
     
         21 . The semiconductor laser element production method of  claim 19 , wherein 
 the second large step includes: 
 a first step for forming an etching stop layer on a surface of a substrate;  
 a second step for forming on a surface of the etching stop layer an active unit area whose shape is similar to that of the active unit;  
 a third step for forming on the surface of the etching stop layer a p-type light waveguide area and an n-type light waveguide area in the vicinity of the active unit area, shapes of the p-type light waveguide area and the n-type light waveguide area being similar to those of a p-type light waveguide and an n-type light waveguide, respectively;  
 a fourth step for forming on the surface of the etching stop layer an optically refractive material layer to enclose the active unit area, the p-type light waveguide area, and the n-type light waveguide area; and  
 a fifth step for forming the laser emitting layer by shaping the optically refractive material layer into a plurality of stripes with the same period as each refractive index changing layer, using a patterning method, wherein  
   the third large step includes 
 a removing step for removing the etching stop layer and the substrate after the refractive index changing layer and the laser emitting layer are stacked.  
   
     
     
         22 . The semiconductor laser element production method of  claim 21 , wherein 
 the second step includes: 
 a first small step for forming on the surface of the etching stop layer a layer of a material of the active unit; and  
 a second small step for forming the active unit area by partially removing the layer using a patterning method.  
   
     
     
         23 . The semiconductor laser element production method of  claim 21 , wherein 
 the second step includes: 
 a first small step for forming on the surface of the etching stop layer a layer of an insulating material;  
 a second small step for forming a pit in the insulating material layer;  
 a third small step for forming the active unit area in the pit by an organometallic vapor deposition method; and  
 a fourth small step for removing the insulating material layer after the active unit area is formed.  
   
     
     
         24 . The semiconductor laser element production method of  claim 19 , wherein 
 the active unit is a quantum well type, and    the second step includes: 
 a first small step for forming an etching stop layer on a surface of a substrate;  
 a second small step for forming on a surface of the etching stop layer a stripe of a material of the active unit having a size enough to include the active unit, a p-type light waveguide, and an n-type light waveguide;  
 a third small step for introducing impurities into the active unit material stripe except for a center portion thereof so that two impurities-introduced portions around the center portion become a p-type light waveguide area and an n-type light waveguide area, and so that the center portion becomes an active unit area;  
 a fourth small step for forming on the surface of the etching stop layer an optically refractive material layer to enclose the active unit area, the p-type light waveguide area, and the n-type light waveguide area; and  
 a fifth step for forming the laser emitting layer by shaping the optically refractive material layer into a plurality of stripes with the same period as the refractive index changing layer, using a patterning method, wherein  
   the third large step includes 
 a removing step for removing the etching stop layer after the refractive index changing layer and the laser emitting layer are stacked.  
   
     
     
         25 . The semiconductor laser element production method of  claim 24 , wherein 
 the second step includes: 
 a first small step for forming on the surface of the etching stop layer a layer of a material of the active unit; and  
 a second small step for forming the active unit material stripe by partially removing the layer using a patterning method.  
   
     
     
         26 . The semiconductor laser element production method of  claim 24 , wherein 
 the second step includes: 
 a first small step for forming on the surface of the etching stop layer a layer of an insulating material;  
 a second small step for forming a channel in the insulating material layer;  
 a third small step for forming the active unit area in the channel by an organometallic vapor deposition method; and  
 a fourth small step for removing the insulating material layer after the active unit area is formed.  
   
     
     
         27 . The semiconductor laser element production method of one of  claims 21  to  26  further comprising 
 a conduction path forming step for forming the p-type carrier conduction path and the n-type carrier conduction path to overlap the p-type light waveguide and the n-type light waveguide, respectively, after a three-dimensional photonic crystal structure is formed by stacking the refractive index changing layer and the laser emitting layer.  
 
     
     
         28 . The semiconductor laser element production method of  claim 18 , wherein 
 the assembling step includes: 
 a first large step for forming a refractive index changing layer by arranging (a) a plurality of optically refractive stripes in parallel to each other and (b) a plurality of dielectric stripes displacing space between the plurality of optically refractive stripes so that refractive index of light periodically changes in a predetermined direction;  
 a second large step for forming a laser emitting layer in which refractive index of light periodically changes in a predetermined direction, by arranging the laser emitting stripe and optically refractive stripes in parallel to each other and arranging a plurality of dielectric stripes to displace space between the laser emitting stripe and the optically refractive stripes so that refractive index of light periodically changes in a predetermined direction; and  
 a third large step for stacking the refractive index changing layer and the laser emitting layer.