Fig. 1. Mechanisms, phenomena and applications of ultrafast laser processing of transparent dielectrics

Fig. 2. Interaction between ultrafast laser and transparent dielectrics. (a) Diagram of ultrafast laser irradiation inside transparent dielectrics; (b) electron ionization process in transparent dielectrics; (c) structural changes in transparent dielectrics induced by ultra-fast laser with different fluxes

Fig. 3. Three structural changes in transparent dielectrics induced by ultrafast laser. (a) Schematic of refractive index change induced by ultrafast laser; (b) waveguide structure directly written via ultrafast laser induced refractive index change^[19]; (c) diagram of nanograting structures induced by ultrafast laser; (d) back-scattered electron images of nanograting structures^[20]; (e) diagram of nanovo

Fig. 4. Mechanism of ultrafast laser induced structural changes in transparent dielectrics. (a) Structural change of SiO₂ induced by laser irradiation; (b) simple model of nanograting structure; (c) dual plasmon decay model^[39]; (d) self-trapping exciton and semi-permanent point defect formation process^[40]

Fig. 5. Waveguide devices directly written by ultrafast laser. (a) Embedded waveguide structure directly written by femtosecond laser pulse ^[57]; (b) depressed cladding waveguide structure processed by femtosecond laser^[58]

Fig. 6. Diffraction optical elements prepared by ultrafast laser. (a) Microlens prepared by femtosecond laser pulse train irradiating of fused silica substrate^[60]; (b) geometric phase prisms and lens prepared by femtosecond laser^[62]

Fig. 7. Method for preparing micro-hole and microchannel with ultrafast laser. (a) Direct laser ablation; (b) laser induced backside wet etching; (c) laser assisted chemical wet etching

Fig. 8. Micro-holes and microchannels processed by ultrafast laser. (a) Micro-channel processing results by Bessel-like beam(length scale bar is 100μm, and diameter scale bar is 2μm)^[55]; (b) micro-hole processing results by temporal Airy beam and temporally broadened beam^[63]; (c) annular micro-channel structures processed by femtosecond laser before and after compensation of spherical aberration effect<

Fig. 9. Micro-holes and microchannels processed by ultrafast laser in our research group. (a) Enhancement of ablation depth by femtosecond laser double pulses (scale bar is 100μm); (b) micro-channel processed by single Bessel pulse (scale bar is 10μm); (c) micro-channel processed by laser induced backside wet etching in borosilica glass (scale bar is 40μm)

Fig. 10. Distributions of micro-channel diameter and length ^[66-78]