Cavity enhanced directional resonance has been experimentally observed in single optically-trapped polystyrene particles, which have a size range from 9 μm down to several hundred nm. The higher resonance peaks correspond to longitudinal modes of the directional laser oscillation in a deformed spherical resonator. The lower peaks are attributed to whispering-gallery modes. For a particle with a diameter of approximately 9 μm, the longitudinal mode numbers of the resonator that is responsible for the observed sharp emission peaks are identified using a ray optics model. It is suggested that both directional and whispering-gallery modes can exist in nanometer-scale size resonators. The potential use of such resonant optical cavities in fiber-based optical sensors for chemical diagnostics is suggested. Considerable additional work is required to completely model and measure the observation of effects briefly summarized here.
Peizoelectric ultrathin composite film comprised of PSS and PDDA was synthesized using the electrostatic self-assembly (ESA) process. The ESA processed PSS/PDDA film is a layer- by-layer laminated structure, which exhibits piezoelectric response directly, with a piezoelectric coefficient d<SUB>33</SUB> = 6.0 pC/N and without poling treatment. It is assumed that the self-assembly process may play a role in molecular alignment resulting in net polarization in the layer-by- layer structured ultrathin film, a process quite different form that used for form conventional piezoelectric films.