Helical-wavefront laser beams produced with a spiral phaseplate

Is Orbital Angular Momentum (OAM) Based Radio Communication an Unexploited Area?

“…By changing the value on φ we can obtain all possible relative rotations between the two antenna arrays. Using the angles between two elements on each array as described in (16), while introducing a relative array rotation φ, the angle between transmit element n TX and receive element n RX becomes…”

“…Radio OAM can be seen as a development of techniques used in laser optics, where Laguerre-Gaussian (LG) mode laser beams are created using spiral phase plates [16]. The phase fronts of the created LG beams are helical in the sense that the phase front varies linearly with azimuthal angle, as illustrated in Fig.…”

Coherent optical vortices from relativistic electron beams

“…Promising applications include expanded x-ray magnetic circular dichroism [9] where angle-resolved energy loss spectrometry distinguishes spin-polarized atomic transitions subject to different photon OAM and polarization states [10]. Traditionally, these "optical vortices" are created by shaping of the phase front of a laser as it passes through different optical media [11][12][13], such as spiral phase plates [14] or computer generated holograms [15]. Analogous techniques have also been used to transform x-rays into vortices at synchrotron light sources [16,17], and alternate methods suggest vortex beams can be created through Compton back-scattering [18] or harmonic emission in undulators [19].…”

Circular Polarized Patch Antenna Generating Orbital Angular Momentum

“…As an example, the higher order laser modes of a laser cavity, also known as Laguerre-Gauss (LG) laser modes, have a non-zero OAM and can be either directly generated [10] or obtained by properly combining two Hermite-Gauss (HG) laser modes [11]. This means that, for instance, a LG 1 0 laser mode can be generated combining two orthogonal HG 10 and HG 01 modes with a π/2 phase delay between them [1].…”