Near-field optical and atomic-force microscopy by use of the laser trapping technique of a probe

我们研制了一种扫描摩擦力显微镜，它使用一个小球体捕获和激光束扫描。在样品扫描期间，力可以被检测为球体的位置偏移。该系统由倒置显微镜、扫描台、近红外激光器（Nd：YAG，2 W）、照明光学系统、位置检测器和计算机控制组成。该系统的摩擦力检测极限为1.0（±）SY。在系统中增加了近场光信号检测光学系统，实现了近场光学显微镜。由于该显微镜采用激光捕获探针，探针在水中受到皮牛顿量级的力捕获，因此该系统具有以下优点：1）对样品损伤小; 2）样品表面与探针之间的距离恒定; 3）通过选择合适的探针尺寸可以控制空间分辨率。通过使用这个系统，我们捕获了n ...更多信息 不仅是电介质球，而且还有金属球。金属球具有高散射效率，并提供高信噪比。此外，小球体（φ 40 nm）获得了高的空间分辨率。我们发展了三维微加工技术，利用双光子吸收。双光子吸收过程使聚焦点附近的小光斑成为可能。通过优化锁模钛宝石激光器（790 nm）的脉宽和真实的功率，我们估计横向和轴向分辨率分别为0.6 μ m和1.0 μ m。该系统提供比常规系统高一阶的分辨率。因此，这种方法可以用来制作一种能被激光束稳定、精确捕获的探针。我们还证明了时域有限差分法（FDTD）是分析近场光子力的有效方法。成功地计算了倏逝光场或传播光场对任意形状或材料探针的辐照力（即俘获力）。我们研究了适合我们开发的显微镜的探针的尺寸，材料和形状。少

We developed a scanning friction-force microscope which uses a small sphere trapped and scanned by laser beam. The force can be detected as position shift of the sphere, during the sample scanning. The system consists of an inverted microscope, a scanning stage, a near-infrared laser (Nd : YAG,2W), illumination optics, a position detector, and a computer for control. The detection limit of the friction-force with the system was 1.0(]SY.+-。[)0.2pN when we observed the surface of glass or PMMA.We added detection optics for near-field optical signal to the system in order to realize a near-field optical microscope. Since the microscope uses a laser trapped probe, which is trapped by pico-Newton-order force in water, the system has advantages as follows : 1) it gives little damage to the sample, 2) the distance between the sample surface and the probe is constant, and 3) the spatial resolution can be controlled by choosing an appropriate size of the probe. By using this system we trapped n … More ot only dielectric spheres but also metallic spheres. The metallic sphere has high scattering efficiency and provides high signal-to-noise ratio. Moreover small sphere (phi40nm) attains high spatial resolution.We developed three-dimensional microfabrication technique using two-photon absorption. Two-photon absorption process makes it possible to stiffen only small spot near the focal point. We estimated that lateral and axial resolutions are 0.6mum and 1.0mum respectively, by optimizing pulse-width and real power of mode-locked Ti : Sapphire laser (790nm). This system provides one-order higher resolution than conventional systems. Therefore this technique is available to make a probe, that can be stably and precisely trapped by a laser beam.We also showed that finite-difference time-domain (FDTD) method is effective to amalyze the photon force in near-field. We succeeded in calculation of the irradiation forces (=trapping forces) of evanescent or propagation light field to any shapes or materials probes. We investigated the size, the material, and the shape of the probe which is suitable for the microscope we developed. Less