Development of time-resolved near-field fluorescence spectroscopy and optical control of photodynamics in mesoscopic domains

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The purpose of the project is to develop a near-field time-resolved fluorescence spectroscopic system with a picosecond temporal and a few tens of nm-spatial resolutions and to investigate a possibility of the control of photochemical reactions in mesoscopic domains. Using this system, photochemical dynamics characteristic in mesoscopic domains can be elucidated as a function of spatial position.1. Picosecond evanescent wave-induced fluorescence spectroscopic system. Single-photon timing system with a excitation of evanescent wave was developed. This system has a temporal resolution of -30 ps and a depth resolution of -20 nm by using a total internal reflection element such as a sapphire. Phase transition of a water-soluble polymer in the solid/aqueous solution interface layr has been achieved reversibly by an evanescent wave of near IR laser, indicating the possibility of the optical control of the physical properties in the interface layr.2. Picosecond scanning near field optical mic … More roscopy (SNOM). A tapered aluminized fiber with a 50-100 nm aperture was coupled with a picosecond mode-locked Nd : YLF laser and scanned by piezoelectric transducers with -nm resoluton. The induced fluorescence and scattered intensity in a transmission mode were detected by a combination of a inverted microscope and a single-photon timing method, which resulted in a temporal resolution of 20-30 ps and a spatial resoluton of 200-300 nm.3. Photodynamics in mesoscopic domains. Fluorescence dynamics of polymer latex particles with well defined seizes (100-300nm diameter) were investigated by picosecond SNOM as a function of position. It was found that the fluorescence decays are almost the same irrespective of particles, whereas position dependence was strongly observed in dye adsorbates on glass plates.In conclusion, we have developed a time-resolved near-field fluorescence spectroscopy system, which allows us to investigate the picosecond dynamics in mesoscopic domains as well as to control the photochemical reactions. Less