Nano-Composites: New Materials for Photonics?

Molecular sieves are inorganic nano-porous crystals with a structure-specific inner pore system. The ordering of guest molecules by the channels of molecular sieves has attracted considerable interest because of the optical effects resulting from the alignment of the molecules. It is found that para-nitroaniline (pNA) molecules in the channel of the molecular sieve AlPO-5 can form solid-like dipole chains, in which the orientation of the length axis of the incorporated pNA molecules differs from the channel axis by less than 9°. The occurrence of nonlinear optical effects of second order (second harmonic generation) does furthermore prove that the dipolar molecules have a preferred direction in all channels additionally to the alignment of the molecules. Therefore, modified molecular sieve crystals are very promising for all χ(²)-applications. The advantages are the high nonlinearities of organic guest molecules and the tunability of the material by varying both host and guest in this nm-scale composite. This material could be used for micro-optical devices in waveguide structures