A Further Discussion of Stimulated Emission of Bremsstrahlung

In an earlier paper1 we showed that stimulated emission of bremsstrahlung exists. This statement has the following meaning. Bremsstrahlung is the radiation which an electron emits by passing in the vicinity of a nucleus. We demonstrated that the emitted power into a specific mode of the radiation field is proportional to the energy density in that mode, which shows that we have indeed stimulated emission of radiation. It has to be expected that the emitted power can not be strictly proportional to the energy density, but that it must depend on the energy density in some nonlinear fashion. If this were not the case, the oscillation would not reach saturation and the energy density in the cavity of the oscillator would build up indefinitely. If we knew the nonlinear dependence of the emitted power on the energy density, we could predict the power output of a practical device. Since it is very hard to find an exact solution of the problem, we will give an approximation by finding the next higher approximation of the perturbation theory, which will give us a term proportional to the square 415