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The absorption and electroabsorption (EA) spectra of 1-methyl-1'-octadecyl-2,2'-cyanine perchlorate (S120) Langmuir-Blodgett films were measured. From these results, dispersion of the third-order nonlinear optical susceptibility ?(3)(-?; 0,0,?) in the range of 1.8 to 2.7 eV was determined. In addition, the linear-polarizability difference ?? and the permanent dipole-moment difference ?µ between excited and ground states were evaluated. Upon comparison with the results of measurement of the S120 monomer film, it was found that the third-order nonlinear optical susceptibility of the S120 LB film is strongly enhanced by a factor of 1000. It was concluded that this strong enhancement is attributed to the fact that S120 molecules with a short methyne chain that tightly binds two quinoline rings form a rigid J-aggregate with a one-dimensional structure that hardly twists, so as to yield a sharp absorption band with a large transition moment. Finally, we evaluated the average aggregation number of the S120 LB film to be 3-4.

We numerically analyze the group-velocity dispersion (GVD) effect of the nonlinear medium on the femtosecond time-resolved degenerate four-wave mixing (DFWM) signal with the third-order nonlinear delayed response. As a result, we find that material GVD greatly influences not only the magnitude but also the temporal profile of the DFWM signal.

The absorption and electroabsorption (EA) spectra for 4-(N,N-diethylamino)-?-nitrostyrene (DEANST)-doped poly(methyl methacrylate) (PMMA) films in the dopant concentration range of 0.1-40 wt% were measured. Dispersion of the third-order nonlinear optical susceptibility ?(3)(-?; 0,0,?) at each concentration was determined. In addition, the static polarizability change ?? and the static dipole-moment change ?µ were evaluated. Furthermore, the picosecond emission-decay profiles and the time-resolved emission spectra for 0.1-40 wt% DEANST-doped PMMA films were measured. From the experimental results, it was concluded that DEANST molecules in PMMA films aggregate at concentrations over 5 wt%. This aggregation gives rise to two new absorption bands. The intermolecular interaction affected by aggregation causes a decrease in ?µ, in the average effective third-order molecular hyperpolarizability eff, and in the nonproportional behavior in |?(3)(-?;0,0,?)| with increasing dopant concentration. Furthermore, this aggregation explains the absorption spectral change, the EA spectral shift and the existence of two emission-decay constants with concentration. Finally, the average aggregation number of DEANST molecules was evaluated to be two, which suggests that DEANST molecules in the PMMA film form a dimer at concentrations over 5 wt%.

An approach for generation of an ultrabroad-band optical pulse (?550 THz width) is proposed, which is based on mutual induced phase modulation of three synchronized femtosecond pulses in a short fiber. These pulses having equidistant carrier frequencies and constant carrier-phase differences are obtained from the fundamental (?01), the second-harmonic (2?01) and the second-harmonic-pulse pumped parametric (3?01/2) waves. These are generated under the phase-matched, frequency-conserved and gain-maximized conditions by one common femtosecond pulse. Computer analysis shows that chirp of the composite wave at the fiber output can be compensated for by a spatial phase modulator and a 1.76-cycle pulse is generated.

For the crystal and solution of 1-(3-thienyl)-3-(4-chlorophenyl)propene-1-one (TCPP), which is transparent over the whole visible region, the nonresonant third-order nonlinear dynamics is investigated by time-resolved degenerate four-wave mixing spectroscopy. The temporal nonlinear behaviors of both crystal and solution exhibit the instantaneous responses during 80 fs excitation at around 625 nm. The third-order nonlinear susceptibilities are determined to be |?(3)bbbb| = 7.1 ×10-13esu for crystal and |?(3)TC1111| = 7.1 ×10-14esu at 1 mol/l for solution. This suggests that the TCPP crystal has a large value of ?(3)/??= 2.4 ×103esu·cm·s-1under the assumption of the nonlinear response time ?= 30 fs (absorption coefficient ?= 0.01 cm-1), which is a parameter important for ultrafast optical control materials. The obtained |?(3)bbbb| value satisfies an already known relationship between the second- and third-order susceptibilities.

Temporal spectral dynamics of nonlinear propagation of ?80 femtosecond optical pulses is investigated experimentally and analytically for the first time for two single-mode glass fibers of GeO2-doped fused silica and Er:GeO2-doped fused silica. Comparison between experimental and analytical results enables us to determine the nonlinear refractive indices and their response times to be 2.4 ×10-13esu and 1.8 fs, respectively, for the former fiber and 4.0 ×10-13esu and 2.1 fs, respectively, for the latter fiber. This suggests that these fibers are more efficient for compression of extremely short pulses than the conventional fused-silica fiber.

We propose a new femtosecond optical pulse compressor using a CS2liquid-core fiber with negative delayed nonlinear response through induced-phase modulation in a normal-dispersion region. We numerically confirm that, with a 23 kW, 100 fs pump pulse, a 100 fs hyperbolic-secant pulse is compressed to ?30 fs by this compressor without any additional external phase compensation. From the comparison of effective nonlinear refractive index between CS2and silica fibers, it is shown that the efficiency of this compressor is almost the same as that of the conventional silica fiber-grating compressor.

Change in the refractive index at around 630 nm in the femtosecond time region has been measured for the first time for a 75-wt% PbO-doped silica single-mode fiber with a highly sensitive, time-resolved interferometer using a heterodyne pump-probe technique. The result shows that the instantaneous response, nonlinear refractive index is 9.8 times as large as that of a conventional fused-silica fiber. This suggests that the PbO fiber is useful for efficient optical pulse compression and ultrafast optical switching in the visible and near-infrared wavelength region.

A simple semitheoretical relation between ultrafast nonlinear susceptibilities ?(2)and ?(3)due to the electronic polarization in the nonresonant region for noncentrosymmetric materials is derived. This result well explains experimental data.

We investigated time responses of components parallel n2 /\kern-2pt/(t) and perpendicular n2 ?(t) to pump polarization of the nonlinear refractive index in CS2and its dilute solutions using a femtosecond time division interferometer. The temporal profiles of n2 /\kern-2pt/(t) and n2 ?(t) were decomposed into the electronic, fast- and slow-decay nuclear contributions based on the response time. The magnitudes, signs and time constants of these three contributions of n2 /\kern-2pt/(t) and n2 ?(t) were also evaluated with high accuracy. Moreover, the n2 /\kern-2pt/(t) and n2 ?(t) measurements in the dilute CS2solutions showed that the ratio between the fast-decay contributions of time responses of n2 /\kern-2pt/(t) and n2 ?(t) was the same value as that between the slow-decay contributions. This result is explained using a cluster model.

We derived the Berry connection of vector vortex states (VVSs) from the "true" Hamiltonian obtained through the Maxwell-Schrödinger equation for an inhomogeneous anisotropic (IA) medium, and we experimentally demonstrated measurement of the corresponding Pancharatnam-Berry (PB) geometrical phase of VVSs. The PB phase (PBP) of VVSs can be divided into two phases: homogeneous and inhomogeneous PBPs. Homogeneous and inhomogeneous PBPs are related to the conventional PBP and the spatially dependent geometric phase given by an IA medium such as a polarization converter, respectively. We theoretically detected that inhomogeneous PBP accumulation originates from the gauge dependence of the index of the hybrid-order Poincaré sphere, which provides an alternate method for understanding optical spin-orbital angular momentum conversion. The homogeneous PBP, which is explicitly observed, has implications for quantum-state manipulation and information processing. [ABSTRACT FROM AUTHOR]