On-chip Cherenkov radiation tuning in 3.2-14 THz.

Cherenkov radiation has attracted much attention for promoting the free electron radiation sources. Using hyperbolic metamaterial, Cherenkov radiation can be excited using low-energy electrons and thus on-chip free electron radiation source has been realized. However, direct experimental observations of on-chip free-electron-based Cherenkov radiation have been limited to the visible region, and the tunability has not been thoroughly explored.

Free electrons spin-dependent Kapitza-Dirac effect in two-dimensional triangular optical lattice.

The free electron spin dynamics in Kapitza-Dirac (KD) effect had been studied theoretically in one-dimensional standing wave of EUV to X-ray laser with extremely high intensity, which is far beyond experimental realization. Here, we propose to achieve the free electron spin-dependent KD effect in two-dimensional triangular optical lattice with spatial inversion symmetry breaking, and the theoretical results reveal that laser with wavelength in visible or near-IR and five orders of magnitude decreased intensity could lead to obvious spin-dependent KD effect. This work provides the way to realize the free electron spin-dependent KD effect experimentally.