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

我们研制了一种超微小的简单扫描激光显微镜，它基本上是共聚焦型，在低温下工作，效率高，分辨率高，无需费力调节。具有合适长度的梯度折射率棒型微透镜由于入射平行光束经过棒透镜的一侧聚焦在另一侧平面上，可以作为无工作距离的物镜工作。由于固体浸没透镜（SIL）效应，该棒透镜提高了显微镜的分辨率，并能有效地收集直接附着在焦平面上的样品发出的荧光。这就是为什么我们提出了梯度折射率固体浸没透镜扫描显微镜（grin-SBL显微镜）来研究凝聚态物质的光学性质。传统的光学显微镜虽然效率很高，但由于光的衍射，分辨率有一定的限制。另一方面，近场扫描光学显微镜（NSOM）在原理上有很大的限制，只能在非常低的信号强度下工作，尚未充分投入实际应用。我们在这里开发的grin-SBL显微镜填补了这些不足，并被证明是非常有用的特定目的。在1.6 K的温度下，对十二烷晶体中涤纶的单分子和聚硫酸乙烯基薄膜中卤化假异氰胺的分子J聚集体进行了表征。在后一种体系中，由于准一维Frenkel激子的形成，单体的j波段明显且强烈地向红色偏移的光谱特征最为显著，但其与微观结构的关系尚不清楚。为了深入了解这一问题，我们尝试观察了PVS聚合物薄膜中j聚集体纤维状结构的局部反射光谱，并结合其微观形态观察给出了初步结果，并提出了激子-极化子模型。我们也开始用合成化学方法制备半导体CdSe的有机-无机纳米复合纳米晶体，其光学性质以准零维万尼尔激子为特征。为了改善CdSe纳米晶体的光学性能，采用宽间隙材料ZnS进行钝化。虽然纳米晶体的尺寸限制在2 ~ 5nm的直径范围内，但荧光的量子效率大于50%。少

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