Large optical nonlinearity of indium tin oxide in its epsilon-near-zero region

Nonlinear optics: A surprise in store? At ultrafast data rates, the ability to use light to control things could speed information processing. However, photons tend not to interact with each other, and so a nonlinear optical material is needed and the response of such materials is typically weak. Alam et al. report a surprising finding: that indium tin oxide, a commercially available transparent conducting oxide widely used in microelectronics, exhibits a large nonlinear response. They used a wavelength regime where the permittivity of the material is close to zero and observed a large and fast nonlinear optical response. The finding offers the possibility that other, so far unexplored, materials may be out there for nonlinear optical applications. Science , this issue p. 795