Photonic-based laser driven electron beam deflection and focusing structures

We propose a dielectric photonic structure for ultrafast deflection and focusing of relativistic charged particle beams. The structure is designed to transform a free-space laser beam into a deflection force that acts on the free particles with the same optical phase over a distance of travel that is much greater than the laser wavelength. The proposed structure has a two-dimensional geometry and is compatible with existing nanofabrication methods. Deflection fields of $\mathrm{GV}/\mathrm{m}$ magnitude and subfemtosecond switching speeds are expected to be possible from these dielectric structures. With these elements a submeter scale extreme ultraviolet synchrotron source seems feasible.

Figure 1

Top view of a proposed periodic-phase modulation accelerator structure. The grating grooves are parallel to the $\widehat{z}$ axis and the laser beam is traveling parallel to the $\widehat{y}$ axis. The electron beam is traveling in the vacuum channel parallel to the $\widehat{x}$ axis. The pulse-front tilt causes the laser pulse envelope in the vacuum channel to remain overlapped with the relativistic electron bunch. The substrate is a dielectric material transparent to the laser wavelength in question.

Figure 2

Perspective view of the laser-driven dielectric deflection structure. The oblique orientation of the grating grooves with respect to the electron beam is a key aspect of the proposed structure.

Figure 3

Geometry of the incident TM-polarized plane wave on the grating structure and the electron beam trajectory. The side view inset shows the oblique orientation of the electron trajectory with respect to the grating grooves.

Figure 4

(a) Top view of the grating vacuum channel and the orders $W_n$. (b) Magnitude of the diffraction modes as a function of the grating groove depth $g$.

Figure 5

(a) Magnitude of the grating diffraction modes as a function of the grating tile angle satisfying the synchronicity condition for the first diffraction mode. The grating groove depth $g$ is $g=0.2\lambda$. (b) Magnitude of the corresponding deflection force in the $z^{\prime }$ direction.

Figure 6

(a) Cross-sectional view of the deflector structure and the electron beam. (b) Transverse view of the deflector structure, the focusing structure, and the electron beam. The solid arrows indicate the expected force generated by the laser beam pattern on the electron beam.

Figure 7

Transverse beam profile as a function of distance behind the structure shown in Fig. 5. Without further focusing elements the beam comes to a line focus about 13 cm downstream.

Figure 8

(a) Schematic of an electron ring based on dielectric grating manipulation elements. (b) Synchrotron parameters as a function beam energy.