Fig. 1. Principle diagram of ideal optical limiter

Fig. 2. Research status of optical limiting^[4]

Fig. 3. Optical limiting properties of graphene. (a)(b) Nonlinear transmittance and scattering signal of graphene dispersions versus incident laser energy density^[22]; (c)(d) open aperture Z-scan curves of graphene NMP dispersions under action of nanosecond pulse laser ^[23]; high-magnification (e) SEM and (f) TEM images of etched graphene^[24]; (g) open aperture Z-scan curves of different materials^[24]; (h) normalized transmittance versus incident laser fluence ^[24]

Fig. 4. Optical limiting properties of different nanostructured graphene dispersions under action of 532 nm and 1064 nm nanosecond lasers^[25]. (a)(b) Normalized transmittance; (c)(d) scattering signals

Fig. 5. Nonlinear optical properties and mechanisms of MoX₂ dispersions. (a)(b) open aperture Z-scan results of MoX₂ dispersions under action of femtosecond laser^[33] ; (c)(d) normalized transmittance (solid circles) and scattering signals (open circles) of TMDCs suspensions^[34]; (e) mechanism diagram of all-optical modulation^[35]; (f) mechanism diagram of SA and NLS of nanosheet dispersions^[35]

Fig. 6. Nonlinear optical properties of TMDCs. (a) Two-photon absorption property of monolayer MoS₂ under action of near-infrared femtosecond laser^[36]; (b) SA property of multilayer MoS₂^[36] ; (c) two-photon absorption coefficients of cm-scaled few-layered WS₂ under 1030 nm laser irradiation^[37]; (d) four two-photon absorption saturation models^[38]; (e)(f) self-focusing and defocusing behaviors of monolayer and bulk WS₂ ^[39]

Fig. 7. Optical limiting properties of MoS₂ composite materials under 532 nm and 1064 nm laser irradiation. (a)(b) Output fluence versus input fluence for MoS₂/PMMA composite materials ^[40]; (c)(d) normalized transmittance versus input laser intensity for MoS₂ composite materials^[41]

Fig. 8. Nonlinear optical properties of BP nanosheets. (a)--(c) Z scan results under action of 1064, 532, 355 nm lasers^[48]; (d) normalized transmittance versus input laser intensity for each wavelength^[48]; (e) optical modulation properties of BP dispersions^[49]; (f) modulation depths under different pump fluences^[49]; (g) open aperture Z-scan results and corresponding (h) scattering signals^[49]

Table 1. Summarization of several laser protection technologies