Fig. 1. Dominant physical processes during intense femtosecond laser nonlinear filamentation. (a) Beam self-focusing induced by optical Kerr effect; (b) beam self-defocusing induced by laser ionized plasma^[7]

Fig. 2. Schematic setup for remote femtosecond laser filament induced breakdown spectroscopy

Fig. 3. R-FIBS experiments by Teramobile at a distance up 90 m. (a) Experimental schematic setup for R-FIBS and beam cross section containing 30 filaments; (b) fluorescence signal of metallic target of Fe at the remote distance of 90 m^[33]

Fig. 4. Experimental setups for spatio-temporally chirped femtosecond laser filamentation. (a) Principal demonstration; (b) application on R-FIBS^[53]

Fig. 5. Fluorescence spectra of neutral (a) Fe and (b) Al induced by spatio-temporally chirped femtosecond laser filamentation at a distance of 22 m (solid lines), and fluorescence spectra excited by normal 50 fs laser filamentation under same focusing condition (dashed lines)^[53]

Fig. 6. R-FIBS measurements of radioactive uranium. (a) Intensity of atomic line (U I 591.54 nm) and molecular spectral band (UO 593.55 nm) as a function of second-order dispersion of incident laser pulse (inset is the initial laser beam profile); (b) beam cross-sections under different second-order dispersion pulse widths recorded by interaction between beam and optical disc (accumulated 40 laser pulses)^[57]

Fig. 7. Supercontinuum spectrum of 200 nm‒14 μm produced by terawatt femtosecond laser filamentation in air^[26]

Fig. 8. Polarization dependent supercontinuum generation by filamentation. (a) Supercontinuum spectra from air filamentation under different laser polarizations (laser pulse energy is 4.75 mJ); (b) laser filament induced supercontinuum spectral intensity as a function of angle of quarter wave plate^[24]

Fig. 9. White light laser generation by tuning the incident angle between different laser incident directions and normal direction of focusing filament lens. (a) Side fluorescence images of femtosecond laser filaments in air; (b)‒(e) corresponding real color images of forward white light lasers^[60]

Fig. 10. Atmospheric sensing of filament induced supercontinuum Lidar. (a) Schematically experimental setup of femtosecond laser filament based supercontinuum Lidar; (b) range-corrected Lidar signals at 270 nm, 300 nm, and 600 nm as a function of vertical distance to the ground; (c) high resolution atmospheric absorption spectra at the vertical distance of 4.5 km to the ground recorded by filament induced supercontinuum Lidar^[4]

Fig. 11. Single pulse signal of filament induced supercontinuum Lidar in the spectral range of 300‒470 nm^[65]

Fig. 12. Schematic model of atmospheric sensing based on spaceborne filament induced supercontinuum Lidar^[71]

Table 1. Comparison of the advantages and application scenario of FIBS at different central wavelengths