Fig. 1. Influence of pulse-front distortion on focused pulsed-beam^[13]. (a) Without distortion; (b) pulse-front tilt; (c) pulse-front curvature

Fig. 2. Pulse-front tilt. (a) Prism induced pulse-front tilt; (b) grating induced pulse-front tilt

Fig. 3. Pulse-front curvature. (a) Lens induced pulse-front curvature^[43]; (b) Fresnel zone plate induced pulse-front curvature^[43]

Fig. 4. Optical wave superposition and pulse-front distortion. (a) Angular dispersion induced pulse-front tilt; (b) axial dispersion induced pulse-front curvature

Fig. 5. Adaptive optics control of pulse-front^[66]

Fig. 6. Experimental generation and measurement of optical Bessel-X wave packet^[54]. (a) Setup for generation and measurement; (b) simulation result; (c) experimental result

Fig. 7. Pulse-front tilt to realize superluminal and subluminal X-shape optical wave-packets^[59]. (a) Method; (b) propagation dynamics of superluminal X-shape optical wave-packet; (c) propagation dynamics of subluminal X-shape optical wave-packet; (d) propagation dynamics of gap Δz between group-velocity and phase-velocity of X-shape optical wave-packet

Fig. 8. Pulse-front curvature to realize accelerating and decelerating X-shape optical wave-packets^[59]. (a) Schematic; (b) propagation dynamics of accelerating X-shape optical wave-packet; (c) propagation dynamics of decelerating X-shape optical wave-packet; (d) propagation dynamics of gap Δz between group-velocity and phase-velocity of X-shape optical wave-packet

Fig. 9. Complex pulse-front to realize variable-group-velocity X-shape optical wave-packet^[60]. (a) Propagation dynamics of X-shape optical wave-packet; (b) 3D spatiotemporal profiles of X-shape optical wave-packet at different times; (c) propagation dynamics of gap Δz between group-velocity and phase-velocity, group-velocity v_g, and group-acceleration a of X-shape optical wave-packet

Fig. 10. X-shape optical wave-packet, variation of angular dispersion along radial axis, and spatiotemporal spectrum in the Fourier space^[76]. (a) No pulse-front control; (b) concave conical pulse-front tilt; (c) convex conical pulse-front tilt; (d) concave pulse-front curvature; (e) convex pulse-front curvature; (f) cosine-function pulse-front