Radiation Lifetime in a Cavity

Laser radiation in a cavity will have a finite lifetime because of losses at the cavity walls. The decay of a radiation mode can be expressed as

For cavity dimension L and reflection coefficient a, the time to make n reflections is

After n reflections, the radiation intensity is

which gives for the lifetime:

Using the series approximation

leads to

For a cavity of length L = cm

and reflectivity a =

the radiation lifetime is tc = x10^ seconds.

This cavity lifetime is one of the parameters which determines the pumping power which must be used to maintain a given level of radiation from a laser.


Laser concepts

Sec. 13-5
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