Surface-emission laser diode operable in the wavelength band of 1.1-1.7 um and optical telecommunication system using such a laser diode

Abstract

A surface-emission laser diode includes a distributed Bragg reflector tuned to a wavelength of 1.1 μm or longer, wherein the distributed Bragg reflector includes an alternate repetition of a low-refractive index layer and a high-refractive index layer, with a heterospike buffer layer having an intermediate refractive index interposed therebetween with a thickness in the range of 5-50 nm

1 - 8 . (canceled)  
     
     
         9 . A distributed Bragg reflector, comprising: 
 a first semiconductor layer having a first bandgap;    a second semiconductor layer having a second bandgap, said first bandgap smaller than said second bandgap, said first and second semiconductor layers being stacked alternately; and    a material layer, having a third bandgap intermediate between said first and second bandgaps, provided between said first and second semiconductor layer,    said material layer changing a valence band energy thereof in a thickness direction from said first semiconductor layer to said second semiconductor layer,    said material layer comprising a first layer adjacent to said first semiconductor layer and a second layer adjacent to said second semiconductor layer, and    said first layer and second layer having first and second rates of compositional change such that said first rate being larger than said second rate.    
     
     
         10 . A distributed Bragg reflector as claimed in  claim 9 , wherein said intermediate layer changes said valence band energy continuously and gradually from said first semiconductor layer to said second semiconductor layer.  
     
     
         11 . A distributed Bragg reflector as claimed in  claim 9 , wherein said intermediate layer changes said valence band energy stepwise from said first semiconductor layer to said second semiconductor layer.  
     
     
         12 . A distributed Bragg reflector as claimed in  claim 9 , wherein said intermediate layer comprises a layer in which said valence band energy changes continuously and a layer in which said valence band energy changes stepwise.  
     
     
         13 . A distributed Bragg reflector as claimed in  claim 9 , wherein said first and second layers have respective first and second thicknesses, such that said first thickness is smaller than said second thickness.  
     
     
         14 . A distributed Bragg reflector as claimed in  claim 9 , wherein there is a stepped change of valence band energy at an interface between said first semiconductor layer and said material layer.  
     
     
         15 . A distributed Bragg reflector as claimed in  claim 9 , wherein said first and second semiconductor layers comprise a material of AlGaAs system.  
     
     
         16 . A distributed Bragg reflector as claimed in  claim 9 , wherein said first and second semiconductor layers comprise a material of AlGaInP system.  
     
     
         17 . A distributed Bragg reflector as claimed in  claim 9 , wherein 
 said first and second semiconductor layers and said intermediate layer have a carrier density of 5×10 17  cm −3 -2×10 18  cm −3 ,    said intermediate layer has a thickness in the rage of 5-40 nm, and    said intermediate layer is characterized by an average change rate of Al content in the range of 0.02-0.15 nm −1 .    
     
     
         18 - 62 . (canceled)