> Abstract
Strongly correlated electron materials, which show interesting transport and magnetic properties such as high-Tc superconductivity or colossal magnetoresistance, are also promissing for optoelectronics materials. Large third order optical nonlinearity (χ(3) 〜10-5-10-8 esu) and ultrafast ground state recovery (〜2 ps) are observed in one-dimensional copper oxides and halogen-bridged nickel compounds. In these materials, existence of nearly degenerate and spatially overlapped excited states enhances optical nonlinearity. In a layered manganite La0.5Sr1.5MnO4, on the other hand, optical anisotropy, which is induced by orbital ordering, is drastically changed upon photo-irradiation. Photo-irradication melts the orbital ordering within 200 fs. The phenomenon may also be applied to ultrafast optical memory and switching.
