Internal and external field fluctuations of a laser oscillator. II - Electrical circuit theory

The amplitude and phase-noise spectra of the internal and external fields of a negative resistance oscillator are derived using electrical circuit theory. It is shown that the difference between internal and external fluctuations becomes important in the quantum domain where external noise sources are not negligible, as they often are in the classical domain. Using established methods to describe quantum fluctuations in electrical circuits, the results are obtained which are in full agreement with the more exact but less general direct quantum mechanical analysis of a Fabry-Perot laser by Yamamoto and Imoto (1986).