Fig. 1. Physical process of LIPI and corresponding time scale

Fig. 2. Schlieren image of flame kernels for methane/air mixture[4]

Fig. 3. Comparison of plasma shapes after laser energy deposition for 104 μs. (a) Direct breakdown; (b) laser ablation[11]

Fig. 4. Temporal evolution images of CH radicals of premixed methane/air mixture. (a) Laser ablation; (b) direct breakdown[13]

Fig. 5. Principle diagrams of multi-point ignition. (a) Dual-point ignition; (b) three-point ignition[20]

Fig. 6. Shadow graphs of multi-point ignition of H2/air. (a) Dual-point ignition; (b) three-point ignition[19]

Fig. 7. Transmission and development images of flame kernels in single- and dual-point laser plasma ignitions[4]. (a) Single-point, Eab=23.3 mJ, Ein=28.1 mJ; (b) dual-point, d=0 mm, Eab=22.3 mJ, Ein=28.3 mJ; (c) dual-point, d=0.2 mm, Eab=22.7 mJ, Ein=29.6 mJ; (d) dual-point, d=6.5 mm, Eab=28.9 mJ, Ein=35.1 mJ

Fig. 8. Temporal evolution images of OH radicals of propane/air mixture. (a) Laser plasma ignition; (b) pre-ionization laser plasma ignition[25]

Fig. 9. Temporal evolution images of CH radicals[27]. (a) Laser frequency is 100 Hz; (b) laser frequency is 250 Hz

Fig. 10. Absorption of the second laser pulse[28]