Polarized electroabsorption spectra of the 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) microcrystal, which is well-known as an organic nonlinear optical material, were measured in decalin liquid using electric-field modulation spectroscopy. On the basis of the results, the magnitude of the electric dipole moment in the ground state of DAST microcrystals whose size was about 0.35 μm was determined to be as large as ∼4.5 × 104 D, and the magnitude of the difference in the dipole moment between the ground state and excited state was estimated to be ∼2.5 × 103 D, though the local field correction was not made. The transition moment of the DAST crystal was also found to be a little affected by application of electric fields.

We have investigated silver nanoparticles (AgNPs)-accelerated photopolymerization of a diacetylene derivative, 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD), which undergoes a phase transformation of the crystal structure from monomer to polymer during the photopolymerization. We have successfully fabricated nanocomposites of AgNPs and DCHD monomer nanocrystals by means of the modified reprecipitation method, and we monitored its photopolymerization process with Raman spectroscopy upon 532 nm excitation. Although the localized surface plasmon resonance (LSPR) wavelength of AgNPs in an aqueous dispersion was located around 400 nm, that of AgNPs in the present nanocomposites was shifted to longer wavelength region. The extinction of the nanocomposites at 532 nm became significant because of the red-shift and broadening of the LSPR, and, thus, surface plasmon-enhanced photoelectric fields on the AgNP surfaces could generate upon 532 nm excitation. As compared to the Raman spectra of bare DCHD monomer nanocrystals, the nanocomposites exhibited strongly enhanced Raman intensities and 20–40 times faster photopolymerization. Because the excitation power used in the present experiments is considered to be insufficient for the thermal process, two- or multiphoton polymerization was assumed to be dominant. We have also observed a unique power dependence of the polymerization rate derived from the phase transformation behavior.

Photopolymerization of SU-8 was performed on gold films over microspheres (AuFOMs) that can provide plasmon-enhanced fields on their surfaces. Strong dependence of the photopolymerization reactivity on the surface roughness of AuFOMs was observed; the photopolymerization was enhanced significantly on rough gold surfaces rather than flat surfaces. The results also suggested that photoexcitation of the photoinitiator via a multiphoton process was induced on AuFOM surfaces even with an incoherent light source.

Polydiacetylene (PDA) nanocrystals were successfully encapsulated by soap-free copolymerization of styrene monomer and hydrophilic styrene derivative. The resulting polystyrene-encapsulated PDA nanocrystals became almost uniform and spherical and could be arranged conveniently on a patterned substrate using the tapered cell method. These basic processes to fabricate ordered array structure on a substrate are very important toward photonic devices application made up of PDA nanocrystals in the near future. In addition, the formation mechanisms for encapsulation were discussed in detail.