Local-field enhancement of optical nonlinearities in the AGZO nano-triangle array

Enhancement of the third order optical nonlinearities in Ga and Al co-doped ZnO (AGZO) nano-triangle array was investigated by performing a Z-scan method with a femtosecond laser (800 nm, 40 fs). The AGZO nano-triangle array was fabricated on silica substrates by nanosphere lithography (NSL) method, showing a surface plasmon resonance (SPR) peak around 3 μm. The two photon absorption (TPA) coefficient and nonlinear refractive index of the AGZO nano-triangle array were determined to be 340 cm/GW and 3.22 × 10−2 cm2/GW under an excitation intensity of 26 GW/cm2. It shows a 3.4-fold enhancement of the nonlinear refraction in the AGZO array with respect to that in the AGZO film, which attributes to the local field enhancement effect. The finite-difference time-domain (FDTD) simulation was in agreement with the experimental results. It indicates that the AGZO nano-triangle arrays have potential applications for nonlinear optical devices like all-optical switching, optical limiting and other types of signal processing.