N-step linear phase-shifting algorithms with optimum signal to noise phase demodulation

The wave side of wave–photon duality, describing light as an electromagnetic field (EMF), is used in this article. The EMF of spontaneous light emission (SE) of a laser-excited atom is calculated from first principles for the first time. This calculation is done using the simple method of atomic quantum electrodynamics. The EMF of SE is also calculated for three types of polyatomic light sources excited by a laser. It is shown that light radiated by such sources can be coherent, which explains recent experiments on SE of laser-excited atoms. Small sources of SE can be superradiant, which also conforms to experiment. Thus, SE is shown not to be a random event itself. Random properties of natural light are simply explained as a result of thermal excitation randomness without additional hypotheses. The EMF of SE is described by simple complex functions, but not real ones.