Semiconductor laser

Abstract

A semiconductor laser comprises: a first cladding layer of a first conduction type; an active layer stacked on the first cladding layer; and a second cladding layer of a second conduction type stacked on the active layer. The first cladding layer, the active layer and the second cladding layer are made of II-VI compound semiconductors. Pulse oscillation occurs with characteristics of a threshold current Ith(A), a threshold voltage Vth(V) of the diode composed of the first cladding layer, the active layer and the second cladding layer, a differential resistance RS(Q) of the diode after the rising, a thermal resistance Rt(K/W) and a characteristic temperature T0(K). When two amounts alpha and beta are defined by:the point (alpha,beta) exists in an area on the alpha-beta plane surrounded by the straight line alpha=0, the straight line beta=0, and the curve ((2ln t-1)/t, (1-ln t)/t2) having t as a parameter. The semiconductor laser may include a first optical waveguide layer between the first cladding layer and the active layer and include a second optical waveguide layer between the second cladding layer and the active layer, the first optical waveguide layer and the second optical waveguide layer being made of II-VI compound semiconductors. II-VI compound semiconductors making the first cladding layer and the second cladding layer may be a ZnMgSSe compound semiconductor. A semiconductor laser using II-VI compound semiconductors and having the capability of continuous oscillation at high temperatures including the room temperature is provided.

What is claimed is:  
     
       1. A semiconductor laser comprising: 
       a first cladding layer of a first conduction type;  
       an active layer stacked on said first cladding layer; and  
       a second cladding layer of a second conduction type stacked on said active layer, wherein:  
       said first cladding layer, said active layer and said second cladding layer are made of II-VI compound semiconductors, and  
       pulse oscillation occurs with characteristics of a threshold current I th (A), a threshold voltage V th (V) of a diode composed of said first cladding layer, said active layer and said second cladding layer, a differential resistance R s (Ω) of said diode after the rising, a thermal resistance R t (K/W) and a characteristic temperature T 0 (K), and wherein:  
       when two amounts α and β are defined by:  
       
         
           α≡(R t /T 0 )I th V th    
         
       
       
         
           β≡(R t /T 0 )R s I th   2    
         
       
       continuous oscillation occurs at room temperature when the operating point (α,β) exists in an area on the α-β plane surrounded by the straight line α=O, the straight line β= 0 , and the curve ((2ln t−1)/t, (1−ln t)/t 2 ) having t as a parameter. 
     
     
       2. The semiconductor laser according to claim  1  including a first optical waveguide layer between said first cladding layer and said active layer and including a second optical waveguide layer between said second cladding layer and said active layer, said first optical waveguide layer and said second optical waveguide layer being made of a II-VI compound semiconductor. 
     
     
       3. The semiconductor laser according to claim  1  wherein said II-VI compound semiconductor forming said first cladding layer and said second cladding layer is a ZnMgSSe compound semiconductor. 
     
     
       4. A semiconductor laser comprising: 
       
         a first cladding layer of a first conduction type;  
       
       
         an active layer stacked on said first cladding layer; and  
       
       
         a second cladding layer of a second conduction type stacked on said active layer, wherein:  
       
       
         said first cladding layer, said active layer and said second cladding layer are made of III-V GaN type compound semiconductor, and  
       
         pulse oscillation occurs with characteristics of a threshold current I   th ( A ),  a threshold voltage V   th ( V )  of a diode composed of said first cladding layer, said active layer and said second cladding layer, a differential resistance R   s (Ω)  of said diode after the rising, a thermal resistance R   t ( K/W )  and a characteristic temperature T   0 ( K ),  and wherein:    
       
         when two amounts α and β are defined by:  
       
       
         
           α≡( R   t   /T   0 ) I   th   V   th    
         
       
       
         
           β≡( R   t   /T   0 ) R   s   I   th   2    
         
       
         continuous oscillation occurs at room temperature when the operating point  (α,β)  exists in an area on the α - β plane surrounded by the straight line α= 0 , the straight line β= 0 , and the curve  ((   2 ln t− 1   )/ t,  (   1 −ln t )/ t   2 )  having t as a parameter.   
     
     
       5. The semiconductor laser according to claim  4  including a first optical waveguide layer between said first cladding layer and said active layer and including a second optical waveguide layer between said second cladding layer and said active layer, said first optical waveguide layer and said second optical waveguide layer being made of a III-V compound semiconductor. 
     
     
       6. A method of fabricating a laser, said method comprising the steps of: 
       
         forming a semiconductor laser structure by:  
       
       
         selecting first, second and third compositions of II-VI compound semiconductors for a first cladding layer, an active layer and second cladding layer, respectively, such that  
       
         pulse oscillating occurs with characteristics of a threshold current I   th ( A ),  a threshold voltage V   th ( V )  of a diode composed of said first cladding layer, said active layer and said second cladding layer, a differential resistance R   s (Ω)  of said diode, a thermal resistance R   t ( K/W )  and a characteristic temperature T   0 ( K ),  and wherein    
       
         when two amounts α and β are defined by:  
       
       
         
           α≡( R   t   /T   0 ) I   th   V   th    
         
       
       
         
           β≡( R   t   /T   0 ) R   s   I   th   2    
         
       
         the point  (α,β)  exists in an area on the α-β plane surrounded by the straight line β= 0 , the straight line β= 0 , and the curve  ((   2 ln t− 1   )/ t,  (   1 −ln t )/ t   2 )  having t as a parameter; and then:    
       
         forming the first cladding layer of a first conduction type from said first composition of II-VI compound semiconductors;  
       
       
         forming the active layer stacked on said first cladding layer from said second composition of II-VI compound semiconductors; and  
       
       
         forming the second cladding layer of a second conduction type stacked on said active layer from said third composition of II-VI compound semiconductors. 
       
     
     
       7. The method of fabricating a laser as claimed in claim  6 , wherein said step of forming a semiconductor laser structure further comprises the steps of: 
       
         forming a first optical wave guide layer between said first cladding layer and said active layer; and  
       
       
         forming a second optical wave guide layer between said second cladding layer and said active layer, said first optical wave guide layer and said second optical wave guide layer being made of a II-VI compound semiconductor. 
       
     
     
       8. The method of fabricating a laser as claimed in claim  6 , wherein said II-VI compound semiconductor forming said first cladding layer and said second cladding layer is a ZnMgSSe compound semiconductor. 
     
     
       9. A method of fabricating a laser, said method comprising the steps of: 
       
         forming a semiconductor laser structure by:  
       
       
         selecting first, second and third compositions of III-V compound semiconductors for a first cladding layer, an active layer and a second cladding layer, respectively, such that  
       
         pulse oscillation occurs with characteristics of a threshold current I   th ( A ),  a threshold voltage V   th ( V )  of a diode composed of said first cladding layer, said active layer and said second cladding layer, a differential resistance R   s (Ω)  of said diode, a thermal resistance R   t ( K/W )  and a characteristic temperature T   0 ( K ),  and wherein    
       
         when two amounts α and β are defined by:  
       
       
         
           α≡( R   t   /T   0 ) I   th   V   th    
         
       
       
         
           β≡( R   1   /T   0 ) R   s   I   th   2    
         
       
         the point  (α,β)  exists in an area on the α - β plane surrounded by the straight line α= 0 , the straight line β= 0 , and the curve  ((   2 ln t− 1   )/ t,  (   1 −ln t )/ t   2 )  having t as a parameter; and then:    
       
         forming the first cladding layer of a first conduction type from said first composition of III-V compound semiconductors;  
       
       
         forming the active layer stacked on said first cladding layer from said second composition of III-V compound semiconductors; and  
       
       
         forming the second cladding layer of a second conduction type stacked on said active layer from said third composition of III-V compound semiconductors. 
       
     
     
       10. The method of fabricating a laser as claimed in claim  9 , wherein said step of forming a semiconductor laser structure further comprises the steps of: 
       
         forming a first optical wave guide layer between said first cladding layer and said active layer; and  
       
       
         forming a second optical wave guide layer between said second cladding layer and said active layer, said first optical wave guide layer and said second optical wave guide layer being made of a III-V compound semiconductor.