Third-order nonlinearity and two-photon-induced molecular dynamics: Femtosecond time-resolved transient absorption, Kerr gate, and degenerate four-wave mixing studies in poly (p-phenylene vinylene)/sol-gel silica film

Abstract

Femtosecond response and relaxation of the third-order optical nonlinearity in a newly developed poly (p-phenylene vinylene)/sol-gel silica composite are investigated by time-resolved forward wave degenerate four-wave mixing, Kerr gate, and transient absorption techniques using 60 fs pulses at 620 nm. Using a theoretical description of two- and four-wave mixing in optically nonlinear media, it is shown that the results obtained from simultaneous use of these techniques yield valuable information on the real and imaginary components of the third-order susceptibility. In the composite material investigated here, the imaginary component is derived from the presence of a two-photon resonance at the wavelength of 620 nm used for the present study. This two-photon resonance is observed as transient absorption of the probe beam induced by the presence of a strong pump beam. It also provides fifth-order nonlinear response both in transient absorption and in degenerate four-wave mixing. The fifth-order contributions are derived from the two-photon generated excited species which can absorb at the measurement wavelength and therefore modify both the absorption coefficient and the refractive index of the medium.

Linear and nonlinear optical properties of the conjugated polymers PPV and MEH-PPV

“…[1][2][3] This interest is in large part motivated by the demonstration of electroluminescence with high efficiency 3 and the very large, ultrafast, optical nonlinearities that these materials possess. 4 Critical to the existence of such effects is the presence of a delocalized -electron system associated with the conjugated molecular backbone. In order to optimize conjugated polymers for device applications, it is important to know the energies and nature of the excited states of this -electron system as well as how they depend on chemical and physical structure.…”

Novel, Organically Doped, Sol-Gel-Derived Materials for Photonics: Multiphasic Nanostructured Composite Monoliths and Optical Fibers

“…[91][92][93] In the concentration-dependent measurements, the intensity of the signal of the dye solution at zero time-delay is detected and compared with the intensity of the signal at zero time-delay of a reference; (3) was calculated using Eqn [6].…”

Nonlinear Optical Absorption of Organic Molecules for Applications in Optical Devices

“…When a medium is excited to a higher energy level, the linear polarization of material, is the total number of molecules of the system, and e N and g N are the excited and ground state population, respectively. This description of polarization is not linear with the electric field anymore, because the excited state population fraction depends on the light intensity, which is equivalent to the square of the electric field, according to (Pang et al,1991):…”

“…The evolution of the nonlinear effect related to the population of excited states can be monitored by rate equations that describe every electronic transition involved in the absorption. The temporal population evolution of a given excited state can be described by (Pang et al,1991):…”