Nonlinear optical properties of organic and polymeric materials
29 Sep 1983-
About: The article was published on 1983-09-29 and is currently open access. It has received 762 citations till now.
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TL;DR: In this article, the second harmonic generation (SHG) and very weak two-photon emission were observed for the alkylated ruthenium-bipyridine compexes with two long alkyl chains attached via amide bonds.
Abstract: Quadratic nonlinear optical properties for the crystalline powders of two types of ruthenium-bipyridine [Ru(bipy)3] complexes were investigated. The nonlinear optical processes markedly depended on the molecular structures of the ruthenium complexes. Second harmonic generation (SHG) and very weak two-photon emission were observed for the alkylated ruthenium-bipyridine compexes with two long alkyl chains attached via amide bonds (RuCnB), whereas only two-photon emission was observed for Ru(bipy)3. The existence of two amide bonds in one bipyridine ligand for RuCnB complexes most probably enhanced the molecular hyperpolarizability as compared with Ru(bipy)3. The SHG intensity from RuCnB complexes increased in the order RuC18B < RuC12B < RuC16B. The order of SHG intensity from RuCnB was ascribed to the difference in size of each crystalline powder estimated by X-ray diffraction methods.
5 citations
TL;DR: In this paper, conjugated oligomer and polymer chains are considered as promising materials for devices based on third-order nonlinear effects for optoelectronics, which can combine properties such as proper organization at the molecular level with possible symmetry constraints, chemical stability, etc.
Abstract: Materials which exhibit high nonlinear responses are currently subject of large research activities. The interest in organics [1–5] not only lies in their enhanced NLO responses over a wide frequency range and ultrafast response times, but also in the inherent adaptability of their molecular structures, the possibility of film forming and processing, and higher laser damage thresholds. In particular, conjugated oligomer and polymer chains are currently considered as very promising for devices based on third-order nonlinear effects. To be useful as materials, these compounds must combine, in addition to high electric susceptibilities, other properties such as proper organisation at the molecular level with possible symmetry constraints, chemical stability, etc. Moreover it is expected that the compounds used to form materials will depend on the particular application and therefore it is likely that there will be a continuous need for designing new molecules for optoelectronics.
5 citations
01 Jun 1991
TL;DR: The third-order (pi) -electron polarizability of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold as discussed by the authors.
Abstract: The third-order (pi) -electron polarizability, (gamma) (pi), of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold. The following selected values of (gamma) (pi) (units of 10-36 esu) are observed: (gamma) (0;0,0,0) equals 2482 +/- 327; (gamma) (-3(omega) ;(omega) ,(omega) ,(omega) ) equals 2976 +/- 385 ((omega) equals 0.25 eV), 5867 +/- 704 ((omega) = 0.5 eV), 14863 +/- 1614 ((omega) = 0.66 eV), 15817 +/- 2314 ((omega) equals 1.0 eV), 10755 +/- 1733 ((omega) equals 1.17 eV). The third-order polarizability of this protein which contains an all-trans retinyl protonated Schiff base chromophore with six double bonds, is comparable to that observed for much longer chain polyenes (for example, dodecapreno (beta) -carotene, a polyene with 19 double bonds, exhibits a third-order (pi) -electron polarizability at 0.66 eV of 17000 +/- 6000 X 10-36 esu. The authors attribute the enhanced third-order nonlinearity associated with the protein bound chromophore of bacteriorhodopsin to two mutually enhancing origins. First, the chromophore is protonated, and the resultant charge reorganization enhances the polarizability in a fashion that is similar to that known to occur for polaronic and bipolaronic chromophores. It is estimated that protonation generates a five-fold enhancement in (gamma) (pi). Second, the protein bound chromophore exhibits a large change in dipole moment upon excitation into the lowest-lying, strongly-allowed 1B*u+-like state ((Delta) (mu) = 13.5 D). The latter property is responsible for a Type III enhancement of the third-order polarizability, and yields at least a 20-fold increase in (gamma) (pi).
5 citations
TL;DR: In this paper, the authors proposed to optimize nonlinear optical activity in centrosymmetric polymers by control of conformation to maximize n-orbital overlap between adjacent sp2 centers and to minimize interruptions of delocalization by minimizing sp3 defects.
Abstract: It is well-known that electron delocalization associated with π-orbital overlap contributes to third order susceptibility (1–6). It is thus reasonable to attempt to optimize nonlinear optical activity in centrosymmetric polymers by control of conformation to maximize n-orbital overlap between adjacent sp2 centers and to minimize interruptions of delocalization by minimizing sp3 defects. Steric interactions frequently force nonplanar conformations in linear-chain polymers and many systems such as polyacetylene have yet to be prepared in a form free of sp3 defects such as cross bridges. Ladder polymers, such as shown in Fig. 1, represent structures which should lead to extensive electron delocalization and interesting nonlinear optical activity. Some theoretical evidence exists (6,7) to support this contention. Clearly, orbital overlap is optimized in ladder polymers with a zero dihedral angle between adjacent phenyl rings and for systems where nitrogen atoms exist in the deprotonated (imine) form.
5 citations
TL;DR: In this paper, the authors proposed the new polymeric systems with polar side chains which are expected to utilize both the through-bond and through-space interactions, and employed the coupled-Hartree-Fock (CHF) method to calculate the third-order hyperpolarizabilities for these systems.
5 citations