Two-dimensional photonic crystal surface-emitting laser

Abstract

Two-dimensional photonic crystal surface-emitting laser comprising a two-dimensional photonic crystal, having media different in refractive index arrayed in a two-dimensional cycle, disposed in the vicinity of an active layer that emits light by the injection of carriers, wherein the two-dimensional photonic crystal consists of square lattices having equal lattice constants in perpendicular directions, and a basic lattice consisting of a square with one medium as a vertex has an asymmetric refractive index distribution with respect to either one of the two diagonals of the basic lattice to thereby emit light in a constant polarizing direction.

1 . A two-dimensional photonic crystal surface-emitting laser having a two-dimensional photonic crystal placed near an active layer that emits light when carriers are injected thereinto, the two-dimensional photonic crystal having media having different refractive indices arrayed with a two-dimensional period, 
 wherein the two-dimensional photonic crystal is formed as a square lattice having patches of one medium arrayed periodically at equal intervals in two mutually perpendicular directions, and at least part of fundamental lattices, of which each has a shape of a square that has vertices thereof at patches of the one medium and of which a length of each side equals a minimum period of equally sized patches of the one medium, has an asymmetric refractive index distribution with respect to one of two diagonal lines of those fundamental lattices.    
     
     
         2 . A two-dimensional photonic crystal surface-emitting laser having a two-dimensional photonic crystal placed near an active layer that emits light when carriers are injected thereinto, the two-dimensional photonic crystal having media having different refractive indices arrayed with a two-dimensional period, 
 wherein mode degeneration at a Γ point of the two-dimensional photonic crystal is resolved.    
     
     
         3 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 1  or  2 , 
 wherein a frequency at which the active layer exhibits a maximum gain is coincident with a frequency at which the two-dimensional photonic crystal resonates.  
 
     
     
         4 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 1  or  2 , 
 wherein the two-dimensional photonic crystal has a first medium that has a predetermined refractive index and a second medium that has a refractive index different from the refractive index of the first medium and of which equally sized patches are arrayed at equal intervals in mutually perpendicular first and second directions within the first medium, and  
 at least part of fundamental lattices that have vertices thereof at patches of the second medium have a third medium of which patches are arrayed asymmetrically with respect to one of two diagonal lines of those fundamental lattices.  
 
     
     
         5 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 4 , 
 wherein, assuming that a length of each side of the fundamental lattices is “a,” the patches of the third medium are arrayed within a width of “0.1a” of one side of the fundamental lattices or within a width of “0.1a” of a bisecting normal to one side of the fundamental lattices.    
     
     
         6 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 4 , 
 wherein, assuming that a length of each side of the fundamental lattices is “a,” and that the first and second directions are, with an origin set at patches of the second medium, X- and Y-axes, the patches of the third medium are arrayed within a radius of “0.1a” of a point having X- and Y-coordinates of    ( na/ 4,  ma/ 4), where  n= 0, 2, and 4, and  m= 1 and 3 or ( na/ 4,  ma/ 4), where  n= 1 and 3, and  m= 0, 2, and 4.    
     
     
         7 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 4 , 
 wherein the patches of the second medium and the patches of the third medium are differently sized.    
     
     
         8 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 4 , 
 wherein the second medium and the third medium are formed of a same material.    
     
     
         9 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 1  or  2 , 
 wherein the two-dimensional photonic crystal has a first medium that has a predetermined refractive index and a second medium that has a refractive index different from the refractive index of the first medium and of which patches are arrayed at equal intervals in mutually perpendicular first and second directions within the first medium, and  
 at least in part of fundamental lattices that have vertices thereof at patches of the second medium, the patches of the second medium have, as seen in a plan view, an asymmetrical shape with respect to one of two diagonal lines of those fundamental lattices.  
 
     
     
         10 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 1  or  2 , 
 wherein the two-dimensional photonic crystal has patches of different media, each rectangular in shape as seen in a plan view, arrayed in close contact with one another, and, with respect to the patches of at least one medium, the patches of two other media adjacent thereto in two mutually perpendicular directions have different refractive indices.  
 
     
     
         11 . A two-dimensional photonic crystal surface-emitting laser as claimed in  claim 10 , 
 wherein the two-dimensional photonic crystal is formed by cementing together two one-dimensional diffraction gratings having equal periods in such a way that directions of the periods thereof are perpendicular to each other.