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Large optical nonlinearity of ITO/Ag/ITO sandwiches based on Z-scan measurement.

Indium tin oxide (ITO)-based sandwich structures with the insertion of silver (ITO/Ag/ITO) show large nonlinear optical enhancement of both nonlinear refraction and saturable absorption. Here optical nonlinearity is measured using a Z-scan experiment with a 1310 nm pulsed laser at normal incidence. The nonlinear refractive index (n2=15.43×10-16  m2/W) for an ITO/Ag/ITO sandwich with a 14 nm silver interlayer and the nonlinear absorption coefficient (β=-648×10-11  m/W) for an ITO/Ag/ITO sandwich with a 10 nm silver interlayer are about 18 and 16 times greater than that of a single-layer ITO, respectively. Meanwhile, a large figure of merit and modulation depth values hinted that ITO/Ag/ITO sandwiches are promising saturable absorber materials to switch continuous laser waves into laser pulses. These novel nonlinear optical properties make ITO/Ag/ITO sandwiches a promising candidate for all-optical modulation devices at optical communication wavelengths.