Nonlinear optical and optical power limiting studies of Zn_1-xMn_xO thin films prepared by spray pyrolysis

Zn_1-xMn_xO (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) thin films were deposited at 723 K temperature on glass substrate using a solution of molarity of 0.0125 M through spray pyrolysis method. X-ray diffractogram (XRD) analysis confirmed that all the films have (0 0 2) as a preferential orientation with hexagonal wurtzite structure. The increase of dopant marginally changed the crystallite size and lattice parameters. Surface morphology changes fibrous to spherical structure with an increase in doping. X-ray photoelectron spectroscope (XPS) measurements proved the occurrence of manganese is in the Mn²⁺ transition state along with Oxygen and Zinc content. The films showed ˜90-80% transmittance in the visible region with increasing in Mn concentration. The energy band-gap reduced with increase in dopant, due to sp-d exchange interactions. The nonlinear optical (NLO) properties were studied using z-scan technique under continuous wave (CW) diode pumped solid-state (DPSS) laser operating at 532 nm wavelength. Reverse saturable absorption (RSA) behaviors observed in both undoped and Mn doped films which is attributed to two-photon absorption (TPA) process. The optical limiting properties were also studied, which suggests that the prepared thin films could be used as optical limiters in the visible region.