Artificial Coherent Circulation of Electromagnetic Flows in Free-Space

This paper explores the generation of coherent electromagnetic energy flows to form a shock wave in free-space as a linear medium. Flows of energies from several waves need to build up coherently to create the wave. In free-space, energy in the propagation direction flows at speed of light and therefore cannot match the required energy accumulation. Electromagnetic waves carrying orbital angular momentum are suggested instead of ordinary plane waves because they have a controllable energy flow in the transverse direction of propagation. Flows of several waves are managed under certain conditions to accumulate energy and create a shock wave in the transverse direction. These conditions must be maintained to preserve the waveform during propagation. Previous studies on acoustical shock waves in a nonlinear medium explained the effect of nonlinear medium on the wave. Nonlinear effects are implemented to create similar propagation conditions in the linear medium and to preserve the waveform. The wave, however, rotates and expands during propagation due to the evolution of its internal energies. Internal energy flows are studied, and an analogy is drawn with flows in fluids. Numerical simulations are conducted to support the theoretical derivations on wave generation and propagation.