Fig. 1. Diagram of femtosecond laser processing cavity inside calcium-sodium glass and the cavity structure. (a) Schematic of processing cavity inside calcium-sodium glass using femtosecond laser; (b) cavity structure machined at 4.1 μJ observed under bright-field microscope

Fig. 2. Experimental setup of Mach-Zehnder quantitative phase imaging

Fig. 3. Quantitative phase imaging analysis of the interior of calcium-sodium glass processed by femtosecond laser. (a) Quantitative phase image of the processed cavity with the single pulse energy of 4.1 μJ; (b) phase average curve of the cross-section of the processed cavity with the single pulse energy of 4.1 μJ; (c) diameter of the semicircle refractive-index modified region and the cavity width change with the pulse energy

Fig. 4. Schematic of femtosecond laser processing K9 glass cube and the results analysis. (a) Schematic of femtosecond laser processing K9 glass cube; (b) a photo of the four-sided polished K9 glass cube; (c) top-view of the cavity processed at different pulse energies captured by a microscope; (d) side-view of the cavity processed at different pulses of energies captured by a microscope

Fig. 5. Physical model of femtosecond laser processing in K9 glass cube

Fig. 6. Imaging of cavity processed by femtosecond laser in fused quartz. (a)-(c) Phase diagram, phase curve, and bright-field microscopy image of quartz cube interior in overlooking direction after femtosecond laser machining; (d)-(f) phase diagram, phase curve, and bright-field microscopy image of quartz cube interior in side-view direction after femtosecond laser machining