High thermal nonlinearity in thin films of Zn doped CuS QDs dispersed into PMMA matrix for NLO applications

Abstract

We report improved thermally stimulated third order nonlinear optical coefficients (nonlinear refraction and nonlinear absorption) in thin films of Zn doped CuS quantum dots (QDs) dispersed into poly (methy methacrylate) (PMMA) matrix. Undoped and Zn doped (1, 2, 3 wt%) CuS QDs were synthesized using co-precipitation method. Powder samples were characterized with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), ultraviolet-visible (UV-vis) spectroscopy, open and closed aperture z-scan technique, etc. XRD spectra confirm the formation of highly pure covellite CuS phase with hexagonal crystal structure in P63/mmc (194) space group. EDS validates the purity of the synthesized samples. HR-TEM micrographs of 1wt% Zn doped CuS QDs clearly show the formation of very narrow sized Zn doped CuS QDs with average size of 2-3nm. Strong blue shift in the maximum absorption wavelength for 3wt% Zn doping with band gap of 2.24 eV is observed. Highly improved third order nonlinear refraction and absorption coefficients have been obtained for 3wt% Zn-CuS-PMMA nanocomposite thin films potentially useful for optical limiters, photonic devices, etc.