Approximate analysis of gain saturation of a distributed feedback laser with end reflectors

An approximate method for the analysis of distributed feedback lasers is presented. An expression for the small-signal gain coefficient α
oN
as a function of the output power P
Nout
normalized to the saturation power P
s
, coupling coefficient
k
, complex reflectivity of the end reflectors
R
, and length of the laser
L
is obtained. The results are found to be in good agreement with published computer solutions.