New tests and clarification of some conceptual issues in the superposition of monochromatic light fields

摘要

The linear mathematics of Fourier composition and decomposition of monochromatic electromagnetic fields is supposed to have a direct realization in the physical world in the sense that we assume complete equivalence of reality as well as of physical effects when an arbitrary electromagnetic field is substituted physically with its Fourier components, and vice versa, in the same spatial region. In the simplest cases, two superposed light fields at frequencies ω_1 and ω_2 are supposed to be identical in their physical effects to a single field at the average frequency, amplitude modulated at half the difference frequency, in spite of the significant differences in the experimental arrangements needed to produce the two cases. This equivalence has been questioned and recently Lee and Roychoudhury cited experimental results on atomic resonance and Fabry-Perot filters to assert that there is no such equivalence. Considering the importance of such assertions for the foundations of physics in general, we have conducted a detailed analysis of the issue, and have conducted tests in which amplitude modulated field at resonant frequency, corresponding mathematically to a superposition of two monochromatic fields detuned equally away from the resonance, is applied to Rb atomic vapor, and also passed through a Fabry-Perot cavity. We conclude from the results of these experiments that there is complete physical equivalence, corresponding to the mathematical equivalence. We clarify several conceptual issues that have been raised about the superposition of light in this context.