Tomoyuki Koike

Degradation of polythiophene film by doping-undoping cycle

Abstract The degradation of polythiophene film was studied by XPS. The degraded sample was prepared as follows: a polythiophene / ITO as a working electrode, a Ni plate as a counter electrode, LiBF 4 (0.5M) / acetonitrile as electrolytic solution. The system was derived by applying the 0.5Hz rectangular pulse in a range of −2 to +4V repeating 1.35×10 5 times. The chemical shift of C(1S) was studied by the peak synthesis. C(1S) shifted by F − was observed at 289.6eV, this peak in the degraded sample is remarkably increased in comparison with the doped sample and the undoped sample. The depth profile was studied. F and B were detected in the doped sample, F was detected, but B was not detected in the degraded sample. Therefore, the degradation of polythiophene film is caused by F − which might be formed by the hydrolysis of BF 4 − . This reaction reaches the inside of polythiophene film.

Merocyanine-p-toluenesulfonic acid complex with large second-order nonlinearity

Merocyanine - p-toluenesulufonic acid complex was investigated for the crystal structure and the optical properties. The molecules are crystallized in the space group P1 so that the crystal exhibits a large optical nonlinearity . The second order nonlinear optical coefficient d11 measured by means of the Maker Fringe ifiethod is 314pm/V as a pristine data and 500pm/V after the correction of scattering and is greater than d11 of 2-inethyl-4-nitroaniline.

Crystal structure and nonlinear optical properties of stilbazolium derivatives having shortened cut-off wavelength

Aiming at the shortening of absorption cut-off wavelength of inerocyanine, we prepared several stilbazoliuni derivatives. Their absorption bands are appreciably shifted to shorter and some of them have large SHG efficiencies. Among them, cyanostilbazolium p-toluenesolfonate complex has an absorption cut-off around 400nm and its nonlinear optical coefficient d33 is four times larger than d14 of POM.

Crystals of stilbazolium p-toluenesulfonate for second-order nonlinear optics

Abstract Crystal growth of 1-methyl-4-(2-(4-methoxyphenyl)vinyl)pyridinium 4-toluenesulfonate (methoxystilbazolium p-toluenesulfonate) was performed by slow evaporation method and two different crystals were found. Crystals grown from methanol solution were second-harmonic generation (SHG) active. On the other hand, crystals grown from water solution were SHG inactive. X-ray crystal structure analysis revealed that in the latter case, the chiral-handle character of p-toluenesulfonate (pTS) anion is obstructed by the hydrogen bonding between two pTS anions and water molecules incorporated during crystallization. The effective d value of SHG active crystals attained on the (010) plane was, as a preliminary result, 190 pm/V at the pumping wavelength of 1064 nm.

Nonlinear optical properties of a fiber with an organic core crystal grown from solution

Single crystals of the nonlinear optical organic materials which cannot be crystallized by the Bridgman-Stockbarger method were grown in cores of glass fibers from solutions. These nonlinear optical fibers were used for the phase-matched secondharmonic generation due to Cerenkov radiation.