Research on photonic signal processing devices for photonic IP-routing by using marine-biopolymer DNA-surfactant complex films

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Recently, DNA-surfactant complexes have attracted much attention due to their functionality produced by the doping of various organic dyes. Especially, the photochromic effect in DNA-surfactant complexes have been expected to add a new functionality, such as ultra-fast optical switching, logic circuits, memory, etc., for next generation lightwave systems.With the aim of clarifying capability of such materials, we have studied optical characteristics, such as refractive indices, absorbance and fluorescence intensity, and photochromic properties, of spiropyran-doped DNA-cetyltrimethilammonium (OTMA) complex films, which have been derived from marine biopolymers. It was found that absorption and fluorescence spectral intensity of those films strongly depend on the DNA concentration, while the refractive index showed very small changes. The change is due to the molecular structure change by the photochromic nature of spiropyran. We have made a preliminary study on switching characteristics of the spiropyran doped DNA-CTMA film. By using the photochromic nature of the spiropyran, an entry data written by 360 nm lights can be readout as a signal of 620 nm lights when a 520 nm light is irradiated on the film. Fundamental operation was confirmed with transition times of several tens millisecond. Although much precise measurement should be necessary, these results indicated potential use of DNA-CTMA films.Furthermore, we tested the reproducibility of the photochromic change of the spiropyran doped DNA-CTMA films for more than 300 times of the on-off cycle, and confirmed no degradation in the fluorescence intensity.