Fig. 1. Schematic diagram of ultrashort pulsed laser welding. (a) Welding of fully transparent materials; (b) welding of partial transparent materials

Fig. 2. Microscopic side view images for different focusing depths^[23]. (a) Focus point locates at the interface; (b) focus point locates under the interface

Fig. 3. Microscopic side view images for different focusing depths^[26]. (a) Samples welded by femtosecond laser Bessel beam with different focus positions; (b) samples welded by femtosecond laser Gaussian beam with different focus positions

Fig. 4. Micro-morphology and macro-performance testing of weld^[32]. (a) SEM image of cross section of YSZ ceramics near laser-affected zone; (b) SEM image of cross section of alumina oxide ceramics near laser-affected zone; (c) vacuum pressure versus time (leak-rate measurements); (d) shear test results

Fig. 5. Breaking stress of joint of monocrystalline silicon and glass^[34]

Fig. 6. Microscopic image of cleaved PMMA surface after welding of PMMA substrates^[38]

Fig. 7. Cross sections of weld^[40]. (a) Cross section of weld at laser power of 1700 mW; (b) top view of weld at laser power of 1000 mW

Fig. 8. Optical micrograph of ceramic cavity sealed with glass substrate^[31]

Fig. 9. Schematic of sealed microfluidic devices formed by femtosecond laser welding and top view of sealed microfluidic device^[43]

Fig. 10. Schematics of processes employed in microfluidic device fabrication^[44]. (a) Fabrication channel; (b) cutting inlets; (c) filter screen of 3D fabrication; (d) laser welding

Fig. 11. Photos of microfluidic samples fabricated by femtosecond laser welding^[44]

Fig. 12. Picture of underwater welding parts^[42]