9638J . Phys. Chem. 1991, 95, 9638-9647 the stearic acid. This was probably because the weaker alignment of the methyl groups of the hemicyanine were easily disturbed by the interaction between the deposited hemicyanine film and the water or the stearic acid during the deposition processes of the stearic acid overlayer in steps B4 and B5. Therefore, a well-constructed 2-type multilayer is supposed to be produced with the hemicyanine molecule which is modified with a more hydrophobic moiety than methyl groups.Those measurements such as X-ray diffraction method13 and Stark effect spectral0 are known to be employed to characterize the structure of LB films. However, they can be used only to distinguish Y-type structure from those of X-or Z-type, and it seems rather impossible to determine the pointing direction of the specific molecules in a submerged layer by this method. Contact angle measurement has also been utilized to determine whether the outermost layer of a given multilayered LB sample is hy-( I 3) Matsuda, A.; Sugi, M.; Fukui, T.: Iizima, S.; Miyahara, M.: Otsubo, Y . J . Appl. Phys. 1977, 48, 771.FEATURE ARTICLE drophilic or hydrophobic, and undoubtedly this method cannot be utilized to analyze the inner structure of a multilayer. On the other hand, the SHG-CI method is applicable to the layer of optically nonlinear heteromolecules which is sandwiched among other nonlinearly inactive molecules as demonstrated in this report, because this method is quite sensitive to the polar structure of a given interface. The present study is based on the phase inversion of SH waves and this property is characteristic to an even-ordered nonlinear optical phenomenon such as SHG. Therefore, the phase inversion in SH radiation induced by a certain molecular configurational change at a given interface should be emphasized as another advantage of the SHG method besides its surface specificity and simplicity.In conclusion, the SHG-CI method was applied to analyze the molecular configuration of hemicyanine layer installed in multilayered LB films by the Y -and the Z-type deposition. It was demonstrated for the first time to clarify which direction the axis of the hemicyanine molecule pointed in a given layer sandwiched among other nonlinearly inactive layers.A variety of fitting and scaling laws have been developed for the purpose of modeling rotational energy transfer (RET) in diatomic molecules. These include exponential energy gap (EGL), statistical power gap (SPG), and dynamically based angular-momentum scaling laws (e.g., the energy-corrected sudden approximation, ECS). These scaling laws are tested against state-to-state energy-transfer data for diatomic halogens, and stimulated Raman Q-branch band shapes in nitrogen. For state-testate RET in halogens, an ECS scaling law, modified to account for restrictions on angular-momentum transfer, is found to be superior to the EGL. When all available data on Raman band shapes in N2, particularly including the collision-induced Raman line shifts, are taken into account, the ang...

No abstract

Kerr spatial solitons are observed in slab chalcogenide waveguides at near-IR wavelengths. Waveguides are realized either by electron-beam evaporation or rf sputtering of a Ge-Sb-S compound deposited on oxidized silicon wafer. The Kerr coefficient of the thin film is evaluated to be 5 x 10(-18) m(2)/W from the experimentally required soliton power at 1.5 mum. Limitations due to material photosensitivity are revealed.

We numerically and experimentally show the existence of multicolor vector spatial solitons in a Kerr planar waveguide through the combined effects of cross-phase modulation, four-wave mixing, and stimulated Raman scattering. Mutual spatial guiding of the Raman-Stokes, anti-Stokes, and pump waves is achieved in the high-conversion regime mainly by cross-phase modulation and phase-matched four-wave mixing induced by a power imbalance between Stokes and anti-Stokes components, leading to the generation of a clear-cut sech-shape three-frequency spatial soliton.

We numerically and experimentally report the observation of slow-light spatial solitons in a Kerr medium owing to light amplification by stimulated Raman scattering. This was achieved in a CS2 nonlinear planar waveguide that possesses both a strong self-focusing nonlinearity to generate the spatial Raman soliton and a Raman susceptibility sharp enough to induce the slow-light process simultaneously. We show that the Raman Stokes component is optically delayed by more than 120 ps for a 140 ps Raman pulse duration and only 3 cm of propagation length, while propagating as a spatial soliton beam.