Ultrafast Optical Switching by using Nanocrystals of a Halogen‐Bridged Nickel‐Chain Compound Dispersed in an Optical Polymer

Nanocrystals of a 1D Mott insulator of a Br-bridged Ni-chain compound (see figure) are dispersed in poly(methyl methacrylate) to form an optical thin film. Using this film, the third-order nonlinear susceptibility χ(3) of the Ni-chain compound at the optical communication wavelength (1.55 μm) is evaluated: the χ(3) real and imaginary parts are very large. Optical switching on the terahertz scale by two-photon absorption processes is demonstrated in the film.