Microspherical upconversion laser for near field microscopy

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We have originally prepared rare-earth ion-dope glass micropheres, and succeeded in inducing microspherical laser oscillation in visible and ultraviolet wavelength regions, which was based on multiphoton excitation with near-infrared light. These microspherical lasers have unique characteristics: (1) extremely stable lasing in the long time range, compared with organic dye doped polymer microspheres, (2) easiness in separation between pumping and emission light, because of wide wavelength difference due to upconversion processes, and (3) noncontact and nondestructive manipulation of the lasing microspheres with a near infrared laser, which can be simultaneously used for pumping. In this research, we have analyzed upconversion emission dynamics by use of three-dimensional space-resolved and picosecond time-resolved spectroscopy system we originally developed. Then, we designed the rare-ions and glass materials suitable for microspherical lasers, and developed a new technique for forming tens of micrometers sized spheres with smooth surfaces. We have succeeded in obtaining not only blue and red upconvesion emissions but also green lasing emission that is useful for biological applications. We have analyzed various properties of these glass microspherical lasing and discussed on the applicability to a probe of near field microscopy.