Fig. 1. Supercontinuum generation induced by femtosecond laser filamentation. (a) Generation of supercontinuum spectra by filament induced self-phase modulation in calcite^[28]; (b) photograph of weakly diverging conical emission recorded at distance of 30 m from filamentation position^[29]; (c) angularly resolved spectra produced by filamentation in air with laser pulse with energy of 60 mJ and pulse duration of 42 fs^[30]; (d) supercontinuum spectra generated in atmosphere by mid-infrared driving light source (3.9 μm)^[31]; (e) ion transition wavelength versus 1580 nm pump laser intensity^[32]; (f) evolution of supercontinuum spectra under 1580 nm pump laser intensity^[32]

Fig. 2. Supercontinuum radiation optimized by micro lens array induced filament array. (a) Supercontinuum spectra generated at 320 mm from microlens array and 40 mm from single lens with filament array and cross-section of its far-field supercontinuum radiation shown in inset^[41]; (b) filament arrays generated using microlens array modulation and corresponding supercontinuum spectra^[41]; (c) filament arrays generated by 800 nm and 400 nm light source excitation^[40]; (d) side fluorescence images of filaments formed by Gaussian beam and flattened beam in fused silica and cross-section intensity distributions of Gaussian beam and flattened beam^[42]

Fig. 3. Optimized supercontinuum radiation generated by phase plate induced filament arrays. (a) Semi-circular phase plate and central half-wavelength phase plate and resulting filament arrays^[45]; (b) side fluorescence images of filaments and corresponding far-field laser spots without (upper) and with (lower) phase plate^[46]; (c) side fluorescence images and far-field laser spots of filament arrays generated by quarter-phase plate at different focal lengths^[47]

Fig. 4. Optimized supercontinuum radiation generated by axicon induced multifilaments. (a) Supercontinuum spectra generated using convex and conical lenses^[48]; (b) supercontinuum spectra produced with and without axicon and side fluorescence images of filaments generated under input laser energies of 80 μJ and 1.5 mJ shown in inset^[49]; (c) initial beam profile in nonlinear propagation (upper) and simulated longitudinal filament intensity distribution using axicon (lower)^[50]

Fig. 5. Influence of axicon focusing condition adjustment on supercontinuum radiation. (a) Side fluorescence images of filaments in K108 glass generated by lens (left) and axicon (right)^[51]; (b) far-field conical radiation patterns when focusing with lens (left) and axicon (right)^[51]; (c) side fluorescence imagers of filaments in BaF₂ at different cone angles and different incident laser energies^[52]; (d) supercontinuum spectra generated in BaF₂ under different incident laser energies^[52]

Fig. 6. Regulating filament and supercontinuum radiation by spatial light modulator. (a) Regulating filament position by spatial light modulator^[56]; (b) multi-filament arrays with different focal lengths generated by spatial light modulators in quartz crystals and their corresponding spectra^[57]; (c) widths and peak positions of supercontinuum spectra modulated by spatial light modulator^[58]; (d) incident laser spectrum and supercontinuum spectra produced under multi-focal-length mechanism and single lens mechanism^[59]

Fig. 7. Regulating filament distribution mode and supercontinuum spectra by pulse shaping. (a) Manipulating position, length, and energy of filament by adjusting phase of incident laser^[65]; (b) supercontinuum spectra produced by patterned light fields composed of multiple individual light fields^[66]

Fig. 8. Regulating supercontinuum spectrum distribution and intensity by pulse shaping. (a) Optimized supercontinuum spectra in range of 355-365 nm^[68]; (b) supercontinuum spectra under different phase masks^[69]; (c) evolution of supercontinuum radiation under spatiotemporal modulation^[70]; (d) supercontinuum spectra under typical numbers of iterations^[70]; (e) spectral integral of supercontinuum radiation (400-700 nm band) versus number of iterations^[70]

Fig. 9. Regulating supercontinuum spectrum distribution and intensity by polarization. (a) Supercontinuum spectra produced by circularly polarized incident light and linearly polarized incident light^[71]; (b) far-field spectral distributions of filaments produced by linear and circular polarized lasers^[72]; (c) plasma density of polarized filament corresponding to Fig. 9(b)^[72]; (d) on-axis filament intensity distribution corresponding to Fig. 9(b)^[72]; (e) supercontinuum spectra produced by single filament in nitrogen and oxygen versus ellipticity of incident light^[73]

Fig. 10. Regulating supercontinuum spectrum distribution and intensity by polarization. (a) Supercontinuum spectra generated by linear (0°), elliptical (15° and 30°), and circular (45°) polarized lasers^[75]; (b) supercontinuum intensity versus rotation angle of quarter plate^[75]; (c) ellipticity of incident laser versus clamping intensity of filament^[77]; (d) supercontinuum spectra generated by circularly polarized and linearly polarized light at different focal lengths^[77]; (e) effect of BaF₂ crystal orientation on supercontinuum spectrum^[78]; (f) relationship between supercontinuum spectra in BaF₂ crystal measured by two spectrometers and driving laser energy when crystal orientation is fixed^[78]

Fig. 11. Regulating supercontinuum spectrum distribution and intensity by vortex. (a) Far-field vortex intensity of supercontinuum radiation of filaments^[79]; (b) spectrum corresponding to Fig. 11(a)^[79]; (c) near-field vortex intensity of supercontinuum radiation of filaments^[79]; (d) spectrum corresponding to Fig. 11(c)^[79]; (e) comparison of supercontinuum spectrum and input laser spectrum^[80]; (f) supercontinuum spectrum versus topological charge of vortex beam at different incident laser energies^[81]

Fig. 12. Regulating spatial distribution of filament and supercontinuum spectrum distribution by focusing condition. Evolutions of supercontinuum intensity and plasma density when water surface is (a) behind and (b) in front of focal plane^[84]; (c) side fluorescence images of filaments at different lens deviations^[85]; (d) supercontinuum spectra at different lens deviations^[85]

Fig. 13. Regulating supercontinuum spectra by materials and focusing elements. (a) Supercontinuum spectrum and (b) corresponding far-field conical radiation generated in lanthanum glass under 0.44 GW incident laser^[86]; (c) supercontinuum spectrum generated in CaF₂ crystal^[87]; (d) side fluorescence images of filaments under different exposure time^[87]; (e) spatial distributions of filaments in thin lens, thick bi-convex lens, and thick plano convex lens^[88]

Fig. 14. Enhancing supercontinuum radiation by optimizing multistage quartz slices^[91]. (a) Schematic of experiment setup; (b) supercontinuum spectra produced by femtosecond laser interaction with different numbers of quartz slices