A stochastic dilation of master equation for a maser is constructed us
ing the technique of quantum stochastic differential equations with un
bounded operator coefficients. The associated quantum Markov flow is c
haracterized and turns out to extend a classical birth and death proce
ss. Furthermore, the stationary distribution of the aforementioned pro
cess, which is connected to the stationary state of the micromaser, is
obtained in a closed form.