Electron beam induced modifications in third harmonic process of spray coated Mn: ZnO nanostructures

Abstract

We report the energetic 8 MeV electron beam induced modification on linear and nonlinear optical process in Mn doped ZnO (MZO) thin films at different irradiation dosage. The modifications incorporated on third order nonlinear optical absorption were studied using Z-Scan technique in both continuous and pulsed laser regime. Open aperture Z-scan measurement indicates that pristine and film treated at 15 kGy electron beam dosages reveals reverse saturable absorption (RSA) mechanism and films treated at 5 kGy, 10 kGy and 20 kGy exhibits saturable absorption (SA) phenomena. The irradiation resulted in a high βeff value of 12.1 ×10-2 cm/W in continuous wave excitation and 5.6×10-4 cm/W for pulsed excitation as compared pristine films. Gaussian deconvolution fitting on room temperature PL spectra shows a quenching of defect centers upon electron beam irradiation. The observed decrement in PL emission intensity for the films treated with energetic electron beam can be probably due to recombination of defect centers and enhanced non radiative defects. The decrease in the energy band gap and increase in the urbach energy of the MZO thin films was observed due to creation of deep energy levels into the band gap. The irradiation treatment resulted in significant changes on the crucial parameters of optical sensing such as limiting threshold and optical clamping. The present study indicates that nonlinear parameters of MZO thin films can be tuned by choosing appropriate electron beam dosage for photonics applications.