Utilization of photon orbital angular momentum in the low-frequency radio domain.

We show numerically that vector antenna arrays can generate radio beams that exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies (< or = 1 GHz), digital techniques can be used to coherently measure the instantaneous, local field vectors and to manipulate them in software. This enables new types of experiments that go beyond what is possible in optics. It allows information-rich radio astronomy and paves the way for novel wireless communication concepts.

Competition between Langmuir and upper-hybrid turbulence in a high-frequency-pumped ionosphere.

We show how the secondary escaping radiation, also known as stimulated electromagnetic emission (SEE), from the ionosphere irradiated by a high-intensity radio beam, can be used to study both reflection altitude ponderomotive parametric instabilities and upper-hybrid altitude thermal parametric instabilities. This has allowed us to observe the transfer of energy from smaller to higher sideband frequency offsets and to identify a new transient SEE feature.