Highly sensitive time-resolved fluorescence measurements of ultra-thin films upon guided wave mode or surface plasmon resonance excitation and applications

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We have achieved highly sensitive time-resolved fluorescence measurements of ultra-thin films upon guided wave mode or surface plasmon resonance excitation and their applications to chemical sensing, molecular photonics and non-contact evaluation of molecular motion in very thin polymer films. Major achievements are as follows :1.A novel time-resolved fluorescence measurement system was developed by using enhanced evanescent light at surface plasmon resonance (SPR) or guided wave mode (GWM) as an excitation light source.2.We demonstrated that highly sensitive, fast responsive and highly reversible sensing of nitrogen dioxide, nitric oxide, and nitrous oxide at a ppm-to-sub-ppm level has been achieved by fluorescence measurements upon excitation of various dye-doped deoxyribonucleic acid (DNA) and hydrophobic DNA thin films spin-coated on a thin silver film by electric field enhanced evanescent light at SPR.3.Ultrafast and large absorption change in the optical telecommunication wavelen … More gth region was achieved in solid films by making transitory expansion of a π-electronic system with photoinduced electron transfer and reverse reactions between redox-active ion pairs. This polymer film may be applied to terahertz all optical information processing in the telecommunication system.4.Fluorescence lifetimes of dyes dispersed in ultrathin films of poly(vinyl alcohol) or polytricyclodecane were examined by GWM or SPR excitation. The fluorescent behavior of the dyes at interface or surface of ultrathin films was strongly suggested to be different from that in the bulk state.5.Highly sensitive ultrafast all-optical light modulation was proposed on the basis of photoinduced complex refractive-index changes in composite GWM geometry composed of a low-refractive-index polymer and a photoresponsive polymer. The present device can give highly enhanced changes of probe light as compared with simple transmission-type devices or the GWM geometry in a metal thin film. A photoelectrochromic polymer (shown above 3) was employed in this geometry to demonstrate ultrafast reflectance control upon femtosecond laser excitation. Less