Lorentzian linewidth and finesse versus Airy linewidth and finesse of a Fabry-Pérot resonator.[8] [Left] Relative Lorentzian linewidth 
  
    
      
        Δ
        
          ν
          
            c
          
        
        
          /
        
        Δ
        
          ν
          
            
              F
              S
              R
            
          
        
      
    
    {\displaystyle \Delta \nu _{c}/\Delta \nu _{\rm {FSR}}}
  
 (blue curve), relative Airy linewidth 
  
    
      
        Δ
        
          ν
          
            
              A
              i
              r
              y
            
          
        
        
          /
        
        Δ
        
          ν
          
            
              F
              S
              R
            
          
        
      
    
    {\displaystyle \Delta \nu _{\rm {Airy}}/\Delta \nu _{\rm {FSR}}}
  
 (green curve), and its approximation (red curve). [Right] Lorentzian finesse 
  
    
      
        
          
            
              F
            
          
          
            c
          
        
      
    
    {\displaystyle {\mathcal {F}}_{c}}
  
 (blue curve), Airy finesse 
  
    
      
        
          
            
              F
            
          
          
            
              A
              i
              r
              y
            
          
        
      
    
    {\displaystyle {\mathcal {F}}_{\rm {Airy}}}
  
 (green curve), and its approximation (red curve) as a function of reflectivity value 
  
    
      
        
          R
          
            1
          
        
        
          R
          
            2
          
        
      
    
    {\displaystyle R_{1}R_{2}}
  
. The exact solutions of the Airy linewidth and finesse (green lines) correctly break down at 
  
    
      
        Δ
        
          ν
          
            
              A
              i
              r
              y
            
          
        
        =
        Δ
        
          ν
          
            
              F
              S
              R
            
          
        
      
    
    {\displaystyle \Delta \nu _{\rm {Airy}}=\Delta \nu _{\rm {FSR}}}
  
, equivalent to 
  
    
      
        
          
            
              F
            
          
          
            
              A
              i
              r
              y
            
          
        
        =
        1
      
    
    {\displaystyle {\mathcal {F}}_{\rm {Airy}}=1}
  
, whereas their approximations (red lines) incorrectly do not break down. Insets: Region 
  
    
      
        
          R
          
            1
          
        
        
          R
          
            2
          
        
        <
        0.1
      
    
    {\displaystyle R_{1}R_{2}<0.1}
  
.
English: Lorentzian linewidth and finesse versus Airy linewidth and finesse of a Fabry-Pérot resonator. [1] (top) Relative Lorentzian linewidth Δ ν c / Δ ν F S R {\displaystyle \Delta \nu _{c}/\Delta \nu _{FSR}} (blue curve), relative Airy linewidth Δ ν A i r y / Δ ν F S R {\displaystyle \Delta \nu _{Airy}/\Delta \nu _{FSR}} (green curve), and its approximation (red curve), and (bottom) Lorentzian finesse F c {\displaystyle {\mathcal {F}}_{c}} (blue curve), Airy finesse F A i r y {\displaystyle {\mathcal {F}}_{Airy}} (green curve), and its approximation (red curve) as a function of reflectivity value R 1 R 2 {\displaystyle R_{1}R_{2}} . The exact solutions of the Airy linewidth and finesse (green lines) correctly break down at Δ ν A i r y = Δ ν F S R {\displaystyle \Delta \nu _{Airy}=\Delta \nu _{FSR}} , equivalent to F A i r y = 1 {\displaystyle {\mathcal {F}}_{Airy}=1} , whereas their approximations (red lines) incorrectly do not break down. Insets: Region R 1 R 2 < 0.1 {\displaystyle R_{1}R_{2}<0.1} .