LAUSR

Abstract The broadband and strong optical limiting (OL) effects of Tungsten Trioxide-Poly (Vinyl Alcohol) (WO3/PVA) solid-state nanocomposite films are investigated by using the open-aperture (OA) Z-scan technique with 4 ns laser pulses at three laser wavelengths of 355 nm, 532 nm, and 1064 nm, which are located in UV, VIS and IR wavelength region, respectively. Compared with laser wavelengths of 532 nm and 1064 nm, the nanocomposite film exhibits much stronger OL effect at 355 nm. The nonlinear absorption coefficients (β) at 355 nm wavelength are 10.32 cm/GW and 15.44 cm/GW for the WO3/PVA solid-state films with 0.6 wt% and 1 wt% concentration, respectively, which is several times higher than the β values of WO3 nanoparticles or nanorods suspensions reported in other papers. Under the same laser energy and wavelength, the β value increases with the increase of WO3 concentration. At 532 nm wavelength, the sample with 1 wt% concentration has a β value of 5.94 cm/GW, which is obviously larger than those of other reported typical nanocomposite materials, such as graphene oxide nanosheets, multiwalled Carbon nanotubes, CdTe quantum dots, and BDN dye doped matrix. The nonlinear optical (NLO) behaviors of WO3/PVA nanocomposite films are mainly attributable to free carrier absorption (FCA) for 355 and 532 nm wavelength and two-photon absorption (TPA) for 1064 nm. Based on these studies, the WO3/PVA nanocomposite film has potential applications in broadband optical limiters.