Fig. 1. Confinement effect of magnetic field on plasma^[9]. (a) Schematic of binding effect of transverse magnetic field on laser-induced plasma; (b) schematic of binding effect of electromagnetic force on plasma

Fig. 2. Longitudinal magnetic field generated relative to the sample^[10]

Fig. 3. Schematic of different stages of water-based transverse magnetic field-assisted femtosecond laser drilling^[11]. (a) Blind hole; (b) through hole; (c) schematic after laser irradiation

Fig. 4. Schematic for a single charge motion in laser-induced plasma within a transverse magnetic field^[12]

Fig. 5. Water-based longitudinal magnetic field-assisted laser drilling^[10]

Fig. 6. Experimental equipment and devices. (a) Magnetic field-assisted laser drilling device^[13]; (b) water-based magnetic field-assisted laser drilling device^[11]; (c) rotating magnetic field-assisted laser drilling device^[14]; (d) real-time monitoring system of ultrasonic vibration-magnetic field-assisted laser drilling^[15]

Fig. 7. Surface morphologies of microholes under different single pulse energies (I‒VI correspond to pulse energies of 20‒140 μJ, respectively)^[12]. (a) 0 mT; (b) 70 mT; (c) 110 mT

Fig. 8. Effect of current on laser-induced plasma^[19]. (a) Without current; (b) with current

Fig. 9. SEM photos and EDS elemental analysis diagrams of copper laser drilling with or without current assistance^[19]. (a) Without current; (b) with 0.5 A current

Fig. 10. Cross sections of holes drilled at the laser power 2200 W^[20]. (a) No electromagnetic field; (b) static magnetic field; (c) rotating magnetic field; (d) static electromagnetic field; (e) rotating electromagnetic field

Fig. 11. SEM images of splashing at microhole entrance with different processing methods^[22]. (a) Laser direct processing; (b) rotating magnetic field-assisted processing with speed of 50 r/min; (c) rotating magnetic field-assisted processing with speed of 150 r/min; (d) rotating magnetic field-assisted processing with speed of 250 r/min

Fig. 12. Effect of a rotating magnetic field on hole entrances and exits obtained by femtosecond laser layered spiral hole-cutting operations^［14］. （a） Without assistance； （b） assisted by rotating magnetic field

Fig. 13. Schematic of magnetic field-assisted laser-induced plasma micromachining^[23]. (a) Transverse magnetic field; (b) vertical magnetic field

Fig. 14. Ellipse fitting of plasma images and plasma edge profiles in water with or without transverse magnetic field^[23]. (a) 0 T; (b) 0.05 T; (c) 0.10 T; (d) 0.15 T; (e) 0.20 T; (f) 0.30 T

Fig. 15. Ellipse fitting of plasma images and plasma edge profiles in water with or without longitudinal magnetic field^[23]. （a） 0 T； （b） 0.05 T； （c） 0.10 T； （d） 0.15 T； （e） 0.20 T； （f） 0.30 T

Fig. 16. Hole section images and surface roughness under different drilling conditions^[10]

Fig. 17. SEM images of the cross-section for four laser drilling modes^[25]. (a) Unassisted laser drilling in air; (b) magnetic field-assisted laser drilling; (c) ultrasonic-assisted laser drilling; (d) ultrasonic-magnetic field-assisted laser drilling