Effects of surface deep traps on third- and high-order optical nonlinearities in photopolymerizable semiconductor CdSe quantum dot-polymer nanocomposites

Photopolymerizable nanoparticle-polymer composites are a new class of photonic materials, in which multi-dimensional photonic lattice structures can be constructed optically by holographic assembly of nanoparticles. Multiplexed holographic digital data page storage and cold neutron beam splitter/mirror actions were demonstrated by use of SiO₂ nanoparticles-polymer composite films. We also demonstrated the construction of volume Bragg grating structures in a semiconductor CdSe quantum dots (QDs) dispersed polymer film with diffraction efficiency near 100%. Recently, we reported on the nonlinear optical properties of such semiconductor CdSe QD-polymer composites. We showed that Z-scan and forward degenerate multiwave mixing (DMWM) measurements revealed the occurrence of third- and high-order optical nonlinearities at 532 nm below the quantum-confined electron-hole transition. Nonlinear Bragg diffraction from a fixed volume Bragg grating was also observed. In this work we report on the effect of surface deep traps on optical nonlinearities causing nonlinear transmission and DMWM self-diffraction from CdSe QD-polymer nanocomposites.