  Compressing electron pulses is important in many applications of electron
beam systems. In this study, we propose to use optical beat notes to compress
electron pulses. The beat frequency is chosen to match the initial electron
pulse duration, which enables the compression of electron pulses with a wide
range of durations. This functionality extends the optical control of electron
beams, which is important in compact electron beam systems such as dielectric
laser accelerators. We also find that the dominant frequency of the electron
charge density changes continuously along its drift trajectory, which may open
up new opportunities in coherent interaction between free electrons and quantum
or classical systems.
