Optical power limiting

Push-push/pull-pull chromophores 118 and 119 have exhibited material properties to show their prospect for several applications particularly in the fields of two-photon microscopy and optical power limitation <1999CC2055, 2002SM17>. 

A variety of experimental techniques have been used to obtain information about the third-order optical nonlinearities and optical power limiting behavior of materials. This section includes descriptions of those techniques that have been used or have potential use with organometallics. For an excellent source of information about other techniques, the interested reader is directed to Ref. 6. 

Figure 3. Optical power limiting due to self-focusing in bis [1,2-dimethyl-1,2-ethenedithiolato(2-)-S,S ] Nickel (linear polarised light).

The nonlinear absorption of Ptn acetylide chromophores has also continued to retain the interest of many researchers. Malmstrom and coworkers have recently investigated Pt-acetylide chromophores blended with solid-state polymer matrices [94], An example of such a complex is 4.7. They found that the photoluminescence properties of the blends agreed well with that of dilute THF solutions containing the Pt-acetylides. Optical power limiting experiments showed that the clamping levels for dyes nonbonded to the polymer host were about half that for dyes in the highly cross-linked solids at similar concentrations. 

Distinct working mechanisms and different designs of optical power limiters make evaluation of their efficiency difficult and requires comparable experimental... 

Further parameters that are useful to compare the performance of different optical power limiters are the transmission contrast ratio (TCR) Eq. (88), the transmission dynamic range (TDR) Eq. (89), and the transmission cutoff (TCO) Eq. (90). The values 7max and T, are the maximum of transmission and the minimum of transmission, and Igo% and Iio% are the intensity of the 90% and 10% transmission points, respectively [600],... 

This review describes some of the recent developments in materials which exhibit enhanced two-photon absorption that can initiate photopolymerization or up-converted emission. Various optical methods including femtosecond time-resolved pump-probe experiments to characterize the two-photon properties are discussed. Finally, the applications of two-photon processes to optical power limiting, up-converted lasing, 3-D data storage, 3-D micro-fabrication, two-photon fluorescence microscopy and bio-imaging, and two-photon photodynamic therapy are presented. 

Keywords. Two-photon absorption. Non-linear transmission, Z-scan, Optical power limiting. Up-converted lasing... 

Fig. 22. Measured optical power limiting performance of a EHO-OPPE polymer solution. From [22]...

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