Nonlinear optics of nontoxic nanomaterials

We studied the linear and nonlinear optical properties of halloysite nanotubes using Z-scan technique. Halloysite is alumina silicate clay rolled into 50 nm diameter hollow cylinders, where the silica layer is at the outer surface of the tube and alumina layer is in the inner surface. Optical absorption spectra show an absorption peak around 600 nm. Open aperture Z-scan measurements using 3 ns laser pulses at 532 nm reveal two-photon induced absorption. The closed aperture Z-scan indicates a positive nonlinear refractive index. As these nanotubes are nontoxic and biocompatible, they have advantages over conventional carbon nanotubes for biomedical applications.