Third order optical nonlinear properties of gold (Au) nanoparticles synthesized by green laser ablation in bio-based Poly (?-caprolactone) solution

Abstract

In this work, Poly(epsilon-caprolactone) (PCL) and gold(Au) nanocomposite has been fabricated by pulsed laser ablation (PLA) of gold target dipped in PCL solution performed by aid of Ti: Sapphire femtosecond (fs) laser to form nanoparticles (NPs). The prepared sample have been investigated by various analyses techniques to evaluate their elemental composition, optical and morphological properties. UV-Vis absorbance spectrum was recorded over a range of wavelength from 300 nm to 900 nm and it has shown a typical Au surface plasmon effect in visible region and PCL:Au nanocomposite absorbed more photons in UV region compared with that in infrared region. Photon energy band gap value has been calculated as 3.5 eV by means of absorbance spectrum. Transmission Electron Microscopy (TEM) and TEM-Energy dispersive X-Ray (TEM-EDX) images proved that the size of Au NPs appears to vary from 5 nm to 50 nm range produced using fs laser ablation in liquid medium. Fourier Transform Infrared Spectroscopy (FT-IR) analysis have been carried out for PCL and PCL:Au composite which they were characterized in over a frequency region from 400 to 4000 cm- 1 and characteristic peaks were seen at 2905, 2805, 1755 and 1205 cm- 1. Furthermore, nonlinear optical properties of PCL:Au composite was investigated using fs laser z-scan technique changing laser intensity between 9.50 x 1011 W/cm2 and 2.37 x 1012 W/cm2. The nonlinear absorption coefficient (beta), nonlinear refractive indexes (n2) have been computed to be -10-10 - 10-11 cm2/W and -10-16 - 10-19 cm/W, respectively. Third-order susceptibilities have also revealed for PCL:Au nanocomposite as 10- 13-10- 14 esu. The obtained green synthesized PCL:Au composite material can be applicable in the optoelectronic field as optical limiting materials.