Nonlinear optical characteristics and optical limiting performance of copper nanoparticles embedded polystyrene nanocomposite foils for photonic application

Abstract

Copper (Cu) nanoparticles (< 50 nm) embedded PS/Cu composite foils were prepared via solution casting (ex-situ) technique for nonlinear optical (NLO) characterization. The crystalline nature of the nanocomposite foils was confirmed by XRD. Surface morphology, purity, and elemental composition were studied using FESEM micrographs with EDX and EDS mapping, respectively. The presence of vibrational modes of the functional groups is established by FTIR spectroscopy. Third-order NLO properties of PS/Cu nanocomposite foils were studied using a single beam Z-scan technique with a continuous diode laser of power ~ 200 mW at a wavelength of ~ 532 nm. The nonlinear optical parameters were obtained using Z-scan data in open and close aperture geometry that reveal two-photon-assisted reverse saturable absorption, and self-defocusing nonlinear refraction. Third-order nonlinear susceptibility (${\chi }^{3}$) were found to increase, by two orders of magnitude, from 5.205 × 10^–7 to 2.25 × 10^–5 (e.s.u), with the increase in nonlinear absorption coefficient (β), and nonlinear refraction coefficient (${n}_{2}$) from 0.82 × 10^–3 to18.8 × 10^–1 (cm/W), and −9.16 × 10^–9 to −3.86 × 10^–7 (cm²/W), respectively and also increases with the increase in wt % of CuNPs from 0 to 8 wt %. The second-order hyper-polarizability (${\upgamma }_{\mathrm{h}}$) lies in the range 1.525 × 10^–26 to 9.284 × 10^–25 (e.s.u). Optical limiting studies were also carried out by measuring the limiting threshold of these foils that reduced from 4.44 to 2.17 kJ/cm² with increasing wt % CuNPs from 0 to 8 wt % CuNPs. The NLO properties of PS/Cu nanocomposite foils confirm to serve as a potential candidate for optical power limiting applications with continuous laser excitations at ~ 532 nm.