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

where $ T_1$and $ T_2$are the transmittance. If the reflectances of both the mirrors are the same, and, using $ T+R=1$, we have

$\displaystyle I$

$\displaystyle =$

$\displaystyle I_0\frac{1}{1+\frac{4R}{(1-R)^2}\sin^2kL}$

 

 

$\displaystyle =$

$\displaystyle I_0 \frac{1}{1+F\sin^2kL}$

 


$ F= 4R/(1-R)^2$is called finesse . $ 1/(1+F\sin^2kL)$is known as Airy function . For non-normal incidence, a similar expression is valid with $ kL$being replaced by $ kL\cos\theta$where $ \theta$is the angle of incidence. The intensity pattern for three values of reflectance is shown.

  \includegraphics{Airy.eps}
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