Nanometer films of polymethine dyes in optical memory and nonlinear optics

We present a review of experimental investigations in the synthesis and characterization of thin solid films of polymethine dyes in monomer and aggregate forms, which have been performed at the Institute of Organic Chemistry and the Institute of Automation and Electrometry (Siberian Branch of the Russian Academy of Sciences, Novosibirsk) for the past 15 years. The films, obtained by spin-coating technique on glass substrates, were intended for use in optical memory disks of the WORM (write once read many) type and as nonlinear optical media with cubic nonlinearity. The synthesized symmetric thioflavylium dyes with tert-butyl substituents form non-crystallized films of optical quality, which are suited for the creation of recording layers of WORM disks. Thermal, optical, and nonlinear optical properties of thin films based on J-aggregates of pseudoisocyanine derivatives with long alkyl substituents, the films of such dyes doped with cluster anions of higher boron hydrides, and the films of an aggregated thiocarbocyanine dye are considered. Nanometer films of stable J-aggregates of pseudoisocyanine derivatives exhibit the absolute values of the cubic optical nonlinear susceptibility on the order of 10−5 esu at room temperature and 10−4 esu at liquid nitrogen temperature. Thin films of J-aggregates of organic dyes can also be used as saturable absorbers of laser radiation.