Modulation of epsilon-near-zero wavelength and enhancement of third-order optical nonlinearity in ITO/Au multilayer films

We report the modulation of epsilon-near-zero (ENZ) wavelength and enhanced third-order nonlinearity in indium tin oxide (ITO)/Au multilayer films. The samples consisting of five-layer 40 nm ITO films spaced by four-layer ultrathin Au films of different thickness, i.e., ITO(40 nm)/[Au( x)/ ITO(40 nm)](4), were prepared by magnetron sputtering at room temperature. The ENZ wavelength in the multilayer films is theoretically calculated and experimentally confirmed. The nonlinear refractive index and nonlinear absorption coefficient of the samples of x = 0, 2, 3, 4 nm were determined using the Z-scan method at a wavelength of 1.064 mu m. The large nonlinear refractive index n(2) = 1.12 x 10(-13) m(2)/W and nonlinear absorption coefficient beta = -1.78 x 10(-7) m/W in the sample of x = 4 nm are both four times larger than those in the single-layer ITO film. The large optical nonlinearity due to the ENZ enhancement and carrier concentration is discussed. The results indicate that the ITO/Au multilayer films are promising for advanced all-optical devices.

Automated summary

The modulation of epsilon-near-zero (ENZ) wavelength and enhanced third-order nonlinearity in indium tin oxide (ITO)/Au multilayer films is reported. Samples of ITO(40 nm)/[Au(x)/ITO(40 nm)](4) with different thicknesses of ultrathin Au films were prepared using magnetron sputtering. The ENZ wavelength was both theoretically calculated and experimentally confirmed. The results showed that the ITO/Au multilayer films exhibited large nonlinear refractive index and nonlinear absorption coefficient, making them promising for advanced all-optical devices.