Broadband third-order nonlinear optical response of indium tin oxide in the near infrared spectrum

Abstract

We reported the broadband optical nonlinearity of indium tin oxide (ITO) films with different thickness in the near-infrared spectrum region. The maximum nonlinear response is obtained at its epsilon-near-zero (ENZ) wavelength, and the measured maximum nonlinear refractive index n2 and nonlinear absorption coefficient β at the ENZ wavelength are 47 times and 28 times larger than the corresponding values at the 1000 nm wavelength, respectively. Meanwhile, a large modulation depth of 9.8% hinted that the ITO has good nonlinear modulation characteristics. In addition, the numerical simulation analysis illustrates the large nonlinear enhancement effect of ITO films, which is attributed to the significant enhancement of electric field due to the ENZ conditions. Our results highlight that ITO is a competitive nonlinear material and has great potential applications in the field of nonlinear optics and all-optical modulators.