Diffraction effects in directed radiation beams

摘要

1467_37A number of proposed applications of electromagnetic waves require that the radiation beam maintain a high intensity over an appreciable propagation distance. An example of this is the possibility of a power satellite providing electrical energy to a host of other satellites by means of directed radiation beams. This is referred to as power beaming. Another example is the possibility of accelerating particles to ultra-high energies by utilizing high-power laser beams. Other applications include advanced radar and directed-energy sources. The quest to achieve these objectives has led to a resurgence of research on propagation of radiation beams and diffraction theory. Diffraction causes a beam of radiation to spread out in the lateral direction and, from energy conservation, the intensity drops off correspondingly. Briefly, the objective of much of the research being carried out is: 'Can diffraction be overcome?' The authors present a survey and critique of the analyses and experimental tests of solutions of the wave equation in connection with so-called diffractionless and other directed radiation beams. The examples discussed include electromagnetic missiles, Bessel beams, electromagnetic directed energy pulse trains, and electromagnetic bullets.