Advanced polyimide materials: Syntheses, physical properties and applications

The ability of nonlinear optical materials to transmit, process and store information forms the basis of emerging optoelectronic and photonic technologies. Organic chromophore-containing polymers, in which the refractive index can be controlled by light or an electric field, are expected to play an important role.

Design and synthesis of chromophores and polymers for electro-optic and photorefractive applications

Electric field poled organic electro-optic materials: state of the art and future prospects.

This paper deals with recent and important developments in the field of organic materials for second-order nonlinear optics. Attention is drawn to current trends in chromophore design with a discussion of current progress and problems in this field. A number of important classes of chromophores, such as one-dimensional charge-transfer molecules, octopolar compounds, ionic materials, multichromophore systems and organometallics, are discussed.

Second-order nonlinear optical materials: recent advances in chromophore design

This paper reviews the tools to manipulate and minimize the band gap of conjugated (co)polymers. The effects of minimization of the bond length alternation and of the incorporation of donor-π-acceptor units are discussed in particular. A systematic study of a series of alternating donor–acceptor oligomers has revealed the achievable limits and allowed for a prognosis of the performance of corresponding copolymers. The decisive influence of the LUMO eigenvectors of the acceptors on the band gap is highlighted. A new synthesis of benzo[1,2-c:4,5-c]bis[1,2,5]thiadiazole containing donor–acceptor monomers and their acid-catalyzed polymerization are described. Finally, band gap tuning by appropriate substitution, conformational adjustment and mesoscopic ordering is discussed.

Developments in the chemistry and band gap engineering of donor-acceptor substituted conjugated polymers

Novel push-pull thiophenes for second order nonlinear optical applications

It is shown experimentally that the complete replacement of benzene rings with thiophene rings in a donor–acceptor substituted stilbene significantly enhances its second-order nonlinear optical hyperpolarizability (β); results obtained with a series of thiophene-substituted donor–acceptor compounds with different conjugation lengths reveal a power law dependence of βµ on the molecular conjugation length.

Functionalized thiophenes: second-order nonlinear optical materials

Experimentally measured second-order nonlinear hyperpolarizability (βµ) data for a new series of donor-acceptor conjugated compounds containing tricyanovinyl acceptors and thiophene conjugating units, reveal that this combination results in a dramatic enhancement (αµ= 6000–9000 × 10–48 esu) of their molecular nonlinearity.

Dramatically enhanced second-order nonlinear optical susceptibilities in tricyanovinylthiophene derivatives

We present theoretical and experimental studies of the molecular second order nonlinear optical responses of donor–acceptor substituted conjugated compounds which consist of heteroaromatic moieties in place of the traditional benzenoid moieties. Electric‐field‐induced second harmonic generation measurement at a fundamental wavelength of 1.907 μm demonstrated a twofold increase of the off‐resonant molecular hyperpolarizability of a heteroaromatic compound compared to its benzenoid counterpart. Results of theoretical calculations based on ab initio scheme are in good agreement with the experimental results.

Theoretical and experimental studies of the molecular second order nonlinear optical responses of heteroaromatic compounds

A facile synthetic method has been developed to incorporate efficient nonlinear optical chromophores as side-chains into high temperature polyimides resulting in high electro-optic activity and long-term thermal stability at 90 °C for over one month.

V. Pushkara Rao

Papers

Novel push-pull thiophenes for second order nonlinear optical applications

Functionalized thiophenes: second-order nonlinear optical materials

Dramatically enhanced second-order nonlinear optical susceptibilities in tricyanovinylthiophene derivatives

Theoretical and experimental studies of the molecular second order nonlinear optical responses of heteroaromatic compounds

Thermally stable nonlinear optical polyimides: synthesis and electro-optic properties