Third-order Harmonic Generation Research Articles

Nonlinear optical properties of poly(fluorophenyl-diacetylene) evaporated films

A new insoluble polydiacetylene with fluoro-aromatic units directly bound to the π-conjugated main backbone has been obtained via solid-state polymerization induced by UV light, daylight and γ-rays. Third-order harmonic generation has been measured on poly(fluorophenyl-diacetylene) films prepared by the vacuum deposition method. The third-order nonlinear optical susceptibility of this poly(fluorophenyl-diacetylene) film was evaluated as χ (3) = 7.3 × 10 −11 esu.

Synthesis of intelligent materials using ion beams

In order to synthesize intelligent materials which possess characteristics responding to environmental changes, newly synthesized polymeric materials were irradiated with ion beams. Two examples are presented in this report. The first trial was to synthesize temperature-responsive particle track membranes. The monomer of a rigid and radiation-sensitive poly(diethyleneglycol-bis-allylcarbonate) and an amino acid containing acryloyl monomer giving a temperature-sensitive hydrogel were combined either by copolymerization or by graft copolymerization. The membrane, which was irradiated with a heavy ion such as gold, indicated a cyclic change of pore diameter according to the temperature change of the environment. Even a complete on-off of the pore was realized. The second trial concerned the effect of low energy ion beams on the molecular arrangement. A multi-layer of LB membrane composed of a diacetylene-group-containing acid monomer was irradiated with a 60 keV Fe + beam, a 1 keV Ar + beam, a 250 keV electron beam and UV light. The X-ray diffraction pattern indicated that the stretched arrangement of the polymer was obtained by ion beam irradiation. A nonlinear optical material with third-order harmonic generation was obtained by this technique.

Nonresonant third-order nonlinear optical susceptibility of CdS clusters encapsulated in zeolite A and X

Nonresonant third-order harmonic generation from CdS clusters encapsulated in zeolite A and X was observed at a fundamental wavelength of 1900 nm. To avoid scattering from the surfaces of the small zeolite crystals, the powder samples were dispersed in a liquid with nearly the same refractive index as that of the samples. The third-order optical susceptibilities of CdS-encapsulated zeolite A and X estimated from the intensity of their Maker fringe patterns were 4.1×10−12 and 1.1×10−11 esu, respectively. These values were slightly smaller than those reported for the 1.5 nm surface-capped CdS cluster. The hyperpolarizabilities of CdS clusters encapsulated in zeolite A and X were estimated by assuming the Lorentz local field to be in the range of 380–480×10−36 and 270–390×10−36 esu, respectively.

Third-Order Nonlinear Optical Properties of Substituted Polyphenylacetylenes

Abstract Third-order harmonic generation (THG) and electroabsorption (EA) in substituted polyphenylacetylenes (PPAs) which are examples of onedimensional π-conjugated polymeric systems have been studied. The values of x (3)(-3ω;ω,ω,ω) obtained from THG measurement for substituted PPAs increase with increasing λmax of absorption. The dispersion of x (3) (-ω;ω,0,0) for PPA film derived from Kramers-Kronig transformation of optical absorption change under the electric field (EA spectra) has been observed, and it shows the similar shape of the second derivative of the optical absorption spectra. The typical value of x (3)(-ω;ω,0,0) for o-substituted PPA was determined to be ca. 10−11 esu.

Third-order harmonic generation spectra of polymerized 10,12-pentacosadiynoic acid LB films

Etude de la polymerisation de couches de Langmuir-Blodgett d'acide pentacosadiyne-10,12oique par irradiation

Nonlinear optical properties of highly oriented polydiacetylene evaporated films

Third-order harmonic generation has been measured on highly oriented polydiacetylene (PDA) films prepared by the vacuum deposition method. Experimental values of the third-order electric susceptibility χ(3) measured for pumping laser polarized parallel to the polymer chain show a sharp three-photon resonance to the 1Bu exciton in PDA. Potential usefulness of these highly oriented PDA evaporated films in nonlinear optical applications is suggested.