Sub-picosecond terahertz generation by a non-relativistic electron beam in field-poled lithium niobate

We present a novel, to our knowledge, scheme for terahertz generation based on the interaction of a nonrelativistic electron beam with surface plasmon polaritons in a conductor-electret structure. A spatially periodic frozen-in electric field in a lithium niobate electret acts as an electrostatic wiggler, modulating the beam velocity. As the beam traverses the vacuum gap between the electret and a conducting sheet, it resonantly excites SPP modes, driving a THz instability. The resulting radiation amplifies on sub-picosecond timescales and is tunable near 1 THz, enabling a compact, efficient, and chip-integrable THz source.