Polarization-dependent ponderomotive gradient force in a standing wave

Abstract

The ponderomotive force is derived for a relativistic charged particle entering an electromagnetic standing wave with a general three-dimensional field distribution and a nonrelativistic intensity, using a perturbation expansion method. It is shown that the well-known ponderomotive gradient force expression does not hold for this situation. The modified expression is still of simple gradient form but contains additional polarization-dependent terms. These terms arise because the relativistic translational velocity induces a quiver motion in the direction of the magnetic force, which is the direction of large field gradients. Consistent perturbation expansion of the equation of motion leads to an effective doubling of this magnetic contribution. The derived ponderomotive force generalizes the polarization-dependent electron motion in a standing wave obtained earlier [A. E. Kaplan and A. L. Pokrovsky, Phys. Rev. Lett. 95, 053601 (2005)]. Comparison with simulations in the case of a realistic, nonidealized, three-dimensional field configuration confirms the general validity of the analytical results.

Electron round lenses with negative spherical aberration by a tightly focused cylindrically polarized light beam

“…When free electrons interact with photons in an optical standing wave, electron scattering tends to be highly directed because one type of photons acts as an incident beam, whereas counter-propagating photons serve as a stimulating beam. This phenomenon corresponds to stimulating Compton scattering in the quantum systems and is known as the Kapitza-Dirac effect (KDE), which has been the subject of theoretical [1][2][3][4][5][6][7][8] and experimental [9][10][11][12][13][14] research since it was proposed in 1933. Those efforts have brought a variety of electron optical applications, including the electron bunch-length measurement [15,16], energy modulation of nonrelativistic electrons [17], attosecond electron bunching [18,19], wavefront manipulation of an electron beam [20], electron phasecontrast imaging [21], and a proposal of a spin-polarizing beam splitter [22].…”

Observation of the Relativistic Reversal of the Ponderomotive Potential

“…A significant theoretical effort has been dedicated to generalizing the ponderomotive potential for particles with relativistic initial velocities [12][13][14][15][16][17]. In this case, the interaction depends on both the particle velocity and EM wave polarization.…”

“…While non-relativistic particles are always pushed away from the high electric field amplitude regions of the wave, relativistic particles can be deflected towards them, in an effect called relativistic reversal [14]. This effect enables polarization-based control of the coherent manipulation of relativistic electron beams using laser light, with applications including rapidly-switchable electron beamsplitters, Kapitza-Dirac diffraction-free phase shifters, and ponderomotive free-electron laser wigglers [12,18].…”