Develoment of a Ultra-Minute Laser Scanning Microscope and Novel Optical Properties

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We have developed an ultra-minute simple scanning laser microscope which is of basically confocal type and operates at cryogenic temperature with high efficiency and resolution without laborious adjustment. A gradient index rod-type micro lens with suitable length can operate as an objective lens with no working distance because an incident parallel beam passed through one side of the rod lens focuses on the other side plane. Due to the solid immersion lens (SIL) effect, this rod lens enhances the resolution of microscope and also collect efficiently the fluorescence emitted by a sample directly attached on the focal plane. This is the reason why we proposed the gradient index solid immersion lens scanning microscope (grin-SBL microscope) for the study of optical properties of condensed matter.In spite of high efficiency, traditional optical microscope has a limit of resolution due to the diffraction of light. On the other side, near field scanning optical microscope(NSOM) beyond this … More limit in principle must operate instead at very low signal intensities and has not been put into practical use sufficiently. The grin-SBL microscope we have developed here fills up these deficiencies and proved to be very useful for specified purposes.The performance was demonstrated on single molecules of terrylene in a dodecane crystal at 1.6 K and on molecular J aggregates by halogenated pseudoisocyanine in poly (vinylsulfate) thin film. In the latter system, while spectral characteristics of sharp and intense J-band shifted to the red from that of the monomers due to the formation of quasi-1D Frenkel exciton is most notable, a relation to its microscopic structures is not clear yet. To get insight into this issue, we have tried to observe local reflection spectra of the J-aggregates fibril-shape structures provided in thin PVS polymer films, preliminary results of which is presented in connection with their microscopic morphological observations and exciton-polariton model is proposed.We have also started a preparation of organic-inorganic nano-composite nanocrystals of semiconductor CdSe with synthetic chemical ways, whose optical properties are characterized with quasi zero dimensional Wannier excitons. To improve optical properties of CdSe nanocrystals, passivation with a wider gap material ZnS was performed. Although the nanocrystal sizes are limited to the range of 2〜5nm in diameter, the quantum efficiency of fluorescence greater than 50% is obtained. Less