Transition from two-photon absorption to saturable absorption in gold patterned ruby thin film

Abstract Nonlinear behaviour of gold micro disks patterned Ruby film has been investigated via Z-scan technique. Open Z-scan was performed for Ruby and Ruby/gold thin film using 532 nm Laser source. Two-photon absorption (TPA) and Saturable absorption (SA) have been observed in pure Ruby and Ruby/gold thin film respectively. The expression for normalized transmittance in open Z-scan was obtained by Gaussian decomposition method for fitting. The values for nonlinear absorption coefficient (β) for Ruby/gold ( 7.41 × 10 - 7 m / W ) was two orders of magnitude higher than that of Ruby ( 1.41 × 10 - 9 m / W ). Further, TPA and SA were confirmed by open Z-scan on these films, performed using 633 nm Laser source.