Figure: (a) A 3D volumetric contour plot with a 2D projection onto the bottom plane, depicting the radial component of emitted electric field at t =2.6 ps. The plasma density increases linearly from 0 to 0.004 nc over the range x=0 to 140 μm, then remains flat to 160 μm (represented by the solid black line on the front plane); vacuum region ranges from x =−60 to 0 μm. (b) Angular distribution of radiated field Er (GV/m) in vacuum (x =−23.3 μm). (c),(d) Temporal profile of radiated field and its corresponding power spectrum determined at the vacuum side.