We theoretically show that a single free electron in circular motion radiates an electromagnetic wave possessing helical phase structure, which is closely related to orbital angular momentum carried by it. We experimentally demonstrate it by interference and double-slit diffraction experiments on radiation from relativistic electrons in spiral motion. Our results indicate that photons carrying orbital angular momentum should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in cosmic space. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.

No abstract

Articles you may be interested in30-kV spin-polarized transmission electron microscope with GaAs-GaAsP strained superlattice photocathode Development of spin polarized electron photocathodes: GaAs-GaAsP superlattice and GaAs-AlGaAs superlattice with DBR AIP Conf.In order to produce a high brightness and high spin polarization electron beam, a pointlike emission mechanism is required for the photocathode of a GaAs polarized electron source. For this purpose, the laser spot size on the photocathode must be minimized, which is realized by changing the direction of the injection laser light from the front side to the back side of the photocathode. Based on this concept, a 20 kV gun was constructed with a transmission photocathode including an active layer of a GaAs-GaAsP superlattice layer. This system produces a laser spot diameter as small as 1.3 m for 760-810 nm laser wavelength. The brightness of the polarized electron beam was ϳ2.0ϫ 10 7 A cm −2 sr −1 , which corresponds to a reduced brightness of ϳ1.0ϫ 10 7 A m −2 sr −1 V −1 . The peak polarization of 77% was achieved up to now. A charge density lifetime of 1.8 ϫ 10 8 C cm −2 was observed for an extracted current of 3 A.

We developed a spin-polarized low energy electron microscopy (SPLEEM) with a highly polarized and high brightness spin electron gun in the present study. Magnetic structures of Co/W(110) were observed with an acquisition time of 0.02 s with a field of view of 6 m. We carried out a dynamic observation of magnetic structures with the SPLEEM during the growth of Co on W(110). #

No abstract