Chromophores for nonlinear

Figure 9. Tetraethynylethene (TEE) and diethynylethene (DEE) molecular scaffoldings, a) Donor-acceptor substituted chromophores for nonlinear optical studies, b) A three-way...

Table 6.1. Some Examples of Chromophores for Nonlinear Optics ...

F. Steybe, F. Effenberger, U. Gubler, C. Bosshard and P. Gunter, Highly polarizable chromophores for nonlinear optics syntheses, structures and properties of donor-acceptor substituted thiophenes and oligothiophenes. 

In guest/host PR polymers the macroscopic nonlinear optical properties result from the molecular constants of the dopant molecule (also called dinmiophore). Chromophores for nonlinear optical properties are usually based upon aromatic ra-electron systems unsymmetrically eiid-capped with electncm donat and electron accepting groups, as shown in Fig. 3. The molecular polarization of such molecules is a nonlinear fonction of the electric field and can be simplified to (4,5) ... 

Zhang Y, Wang L, Wada T, Sasabe H (1996) One-pot synthesis of a new hyperbranched polyester containing 3,6-di-acceptor-substituted carbazole chromophores for nonlinear optics. Macromol Chem Phys 197 667-676... 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

Fig. 8. Examples of some of the donor-acceptor substituted TEEs prepared for the exploration of structure-property relationships in the second- and third-order nonlinear optical effects of fully two-dimensionally-conjugated chromophores. For all compounds, the second hyperpolarizability y [10 esu], measured by third harmonic generation experiments in CHCI3 solution at a laser frequency of either A = 1.9 or 2.1 (second value if shown) pm is given in parentheses. n.o. not obtained...

Polymers and supermolecules modified using electron push-pull chro-mophores are also of particular interest for nonlinear optics (NLO) [10-15]. NLO material has attracted much interest over the past 20 years and has been widely applied in various field (telecommunications, optical data storage, information processing, microfabrication, etc.). Chemists have developed ways to introduce NLO chromophores into many type of polymers, such as Hnear polymers, cross-linked polymers, and branched polymers, and have demonstrated their performance in NLO appHcations. 

The 2PA research in our group began in 1996, involving a number of facets, from fundamental to applications. This review summarizes about 10 years of research efforts on 2PA materials and appHcations in our group. The first section includes the design and synthesis of novel 2 PA chromophores and the chemistry involved in their preparation. The second section is concerned with the linear and nonlinear optical properties of these chromophores as well as their photodynamic behavior. In the last section, further optimization of the chromophores for several intriguing applications is discussed, as are the principles of these applications. 

The theoretical models discussed above indicate that the sulfonyl group, although slightly weaker in electron acceptor strength, is indeed a viable alternative to the nitro group. In particular, sulfonyl derivatives of stilbene and azobenzene display large molecular hyperpolarizabilities and can be used as bifunctional chromophores for the construction of materials with nonlinear optical properties. 

Chromophore—Polymer Assemblies for Nonlinear Optical Materials... 

Bosch M, Fischer C, Cai C, Liakatas I, Jager M, Bosshard Ch, Gunter P (1999) Photochemical stability of highly nonlinear optical chromophores for electro-optic applications. In Organic thin films for photonics applications. Optical Society of America, Washington DC, p 75... 

There have also been reports on the preparation of polar materials by a photo-electro-poling technique that combines the optically induced quadrupolar depletion of chromophores in the direction of the light electric vector with an additional field-induced orientation of dipolar chro-mophores. The latter allows the preparation of cold electrets, which are interesting for nonlinear optical applications, such as optical harmonic generation, wave mixing, etc. ... 

A typical example for a z-scan is shown for compound 96 (compare Section III.C.2) in Figure 3.17. The normalized transmittance is a function of the sample position (z). It is almost negligible in the pure solvent (DMSO dimethylsulfox-ide) compared to the chromophore 96. This compound shows a sharp signal for the loss of transmittance, which is typical for nonlinear absorption. 

Polyphosphazenes are suitable materials to be used as carriers for nonlinear optical (NLO) chromophores. Second order NLO properties have been studied for the polymer (128) and blends of (129) with the free chromophore (130) or the cyclophosphazene (131). All systems have glass transition temperatures higher than 135°C and a wide transparency window. The system (129)-(130) appears to exhibit the highest second-harmonic generation (SHG) response. For possible applications the SHG capability has to be enhanced. ... 

---