Microspherical upconversion laser for near field microscopy

我们初步制备了稀土离子掺杂的玻璃微球，并在近红外光的多光子激发下，成功地诱导了可见光和紫外波段的微球激光振荡。这些微球激光器具有独特的特点：(1)与有机染料掺杂聚合物微球相比，在长时间范围内具有极高的激光器稳定性；(2)由于上转换过程产生了较宽的波长差，因此易于将抽运光与发射光分离；(3)近红外激光器对激光微球进行非接触和非破坏性操作，可以同时用于抽运。在这项研究中，我们利用我们最初开发的三维空间分辨和皮秒时间分辨光谱系统分析了上转换发射动力学。然后，我们设计了适合微球激光器的稀有离子和玻璃材料，并开发了一种形成数十微米尺寸的表面光滑球体的新技术。我们不仅成功地获得了蓝色和红色的上转换发射，而且还获得了对生物应用有用的绿色激光发射。我们分析了这些玻璃微球激光器的各种特性，并讨论了它们在近场显微镜探针上的适用性。

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.