Module 8 : Laser- II
Lecture   : Rate equations for Lasers
 

The radius increases with distance $ z$as

$\displaystyle w(z) = w_0\sqrt{1+\left(\frac{z}{z_0}\right)^2}= w_0\sqrt{ 1+ \left(\frac{z\theta}{w_0}\right)^2} = 6.4 \ \ {\rm mm}$

Area of the spot is $ \pi w^2= 20.1$(mm) $ ^2$. The intensity of the spot = $ 10^{-2}/20\times 10^{-6}= 500$W/m $ ^2$.
   
   
   
   
   
   
   
   
   
   
   
   
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