Fig. 2. Schematic lay out of a near-field scanning optical microscope. The NSOM probe is a tapered optical fiber (Fig. 3A). Laser light is coupled into the fiber and is used to excite fluorophores as the probe scans the sample surface. The probe-sample distance is maintained constant at <10 nm during scanning by shear-force-based distance detection in combination with an electronic feedback system controlling the piezoelectric scan stage. Fluorescence is collected by a conventional inverted microscope. Dual-channel optical detection allows wavelength and/or polarization discrimination.
