Electric fields in a Fabry-Pérot resonator.[8] The electric-field mirror reflectivities are 
  
    
      
        
          r
          
            1
          
        
      
    
    {\displaystyle r_{1}}
  
 and 
  
    
      
        
          r
          
            2
          
        
      
    
    {\displaystyle r_{2}}
  
. Indicated are the characteristic electric fields produced by an electric field 
  
    
      
        
          E
          
            
              i
              n
              c
            
          
        
      
    
    {\displaystyle E_{\rm {inc}}}
  
 incident upon mirror 1: 
  
    
      
        
          E
          
            
              r
              e
              f
              l
              ,
              1
            
          
        
      
    
    {\displaystyle E_{\rm {refl,1}}}
  
 initially reflected at mirror 1, 
  
    
      
        
          E
          
            
              l
              a
              u
              n
            
          
        
      
    
    {\displaystyle E_{\rm {laun}}}
  
 launched through mirror 1, 
  
    
      
        
          E
          
            
              c
              i
              r
              c
            
          
        
      
    
    {\displaystyle E_{\rm {circ}}}
  
 and 
  
    
      
        
          E
          
            b-circ
          
        
      
    
    {\displaystyle E_{\text{b-circ}}}
  
 circulating inside the resonator in forward and backward propagation direction, respectively, 
  
    
      
        
          E
          
            
              R
              T
            
          
        
      
    
    {\displaystyle E_{\rm {RT}}}
  
 propagating inside the resonator after one round trip, 
  
    
      
        
          E
          
            
              t
              r
              a
              n
              s
            
          
        
      
    
    {\displaystyle E_{\rm {trans}}}
  
 transmitted through mirror 2, 
  
    
      
        
          E
          
            
              b
              a
              c
              k
            
          
        
      
    
    {\displaystyle E_{\rm {back}}}
  
 transmitted through mirror 1, and the total field 
  
    
      
        
          E
          
            
              r
              e
              f
              l
            
          
        
      
    
    {\displaystyle E_{\rm {refl}}}
  
 propagating backward. Interference occurs at the left- and right-hand sides of mirror 1 between 
  
    
      
        
          E
          
            
              r
              e
              f
              l
              ,
              1
            
          
        
      
    
    {\displaystyle E_{\rm {refl,1}}}
  
 and 
  
    
      
        
          E
          
            
              b
              a
              c
              k
            
          
        
      
    
    {\displaystyle E_{\rm {back}}}
  
, resulting in 
  
    
      
        
          E
          
            
              r
              e
              f
              l
            
          
        
      
    
    {\displaystyle E_{\rm {refl}}}
  
, and between 
  
    
      
        
          E
          
            
              l
              a
              u
              n
            
          
        
      
    
    {\displaystyle E_{\rm {laun}}}
  
 and 
  
    
      
        
          E
          
            
              R
              T
            
          
        
      
    
    {\displaystyle E_{\rm {RT}}}
  
, resulting in 
  
    
      
        
          E
          
            
              c
              i
              r
              c
            
          
        
      
    
    {\displaystyle E_{\rm {circ}}}
  
, respectively.
English: Electric fields in a Fabry-Pérot resonator. [1] The electric-field mirror reflectivities are r 1 {\displaystyle r_{1}} and r 2 {\displaystyle r_{2}} . Indicated are the characteristic electric fields produced by an electric field E i n c {\displaystyle E_{inc}} incident upon mirror 1: E r e f l , 1 {\displaystyle E_{refl,1}} initially reflected at mirror 1, E l a u n {\displaystyle E_{laun}} launched through mirror 1, E c i r c {\displaystyle E_{circ}} and E b − c i r c {\displaystyle E_{b-circ}} circulating inside the resonator in forward and backward propagation direction, respectively, E R T {\displaystyle E_{RT}} propagating inside the resonator after one round trip, E t r a n s {\displaystyle E_{trans}} transmitted through mirror 2, E b a c k {\displaystyle E_{back}} transmitted through mirror 1, and the total field E r e f l {\displaystyle E_{refl}} propagating backward. Interference occurs at the left- and right-hand sides of mirror 1 between E r e f l , 1 {\displaystyle E_{refl,1}} and E b a c k {\displaystyle E_{back}} , resulting in E r e f l {\displaystyle E_{refl}} , and between E l a u n {\displaystyle E_{laun}} and E R T {\displaystyle E_{RT}} , resulting in E c i r c {\displaystyle E_{circ}} , respectively.