Fig. 4.
2D schematic of tilted laser pulse concept for copropagating standing wave used for attosecond electron compression (thick temporal lens). When θ1 = θ2 = 0, then v0 = c/3 for ω and 2ω beams (14). With frequencies of ω and 2ω the velocity of the copropagating standing wave can be tuned by tilting the 2 laser pulses angles θ1 and θ2. When the 2 angles are chosen according to θ2 = arcsin(2sinθ1), the wells in the standing wave are perpendicular to the electron propagation.