The noise spectra comparison of cavity and population inversion Langevin forces in class-A lasers

We have investigated the single role of cavity Langevin force on the noise spectra of class-A and -B lasers for the first time in 2012. The present aim is to consider the simultaneous effect of cavity and population inversion Langevin forces on the noise spectra of class-A lasers. The Maxwell–Bloch equations of motion are thus solved in the presence of both Langevin forces. The solutions give the fluctuations that are imposed to the cavity electric field and atomic population inversion by the Langevin forces. The noise fluxes of stimulated and spontaneous emission radiations are then calculated by using the notion of correlation function. It is demonstrated that the noise fluxes generated by the cavity Langevin force can be comparable or even larger than those produced by the population inversion Langevin force in some rates of laser pumping. The results are ultimately confirmed by illustrating the flux conservation so that the noise flux entered into laser by pumping is equal to those superimposed on the spontaneous and stimulated emission radiations.