Reflection-mode scattering-type scanning near-field optical microscope using a laser trapped gold colloidal particle as a scattering probe

We have developed a reflection-mode scattering-type scanning near-field optical microscope using a laser trapped gold colloidal particle as a scattering probe and succeeded in observing the reflectance change of an opaque semiconductor sample with the alternating layers of GaAs and Al0.55Ga0.45As. The spatial resolution became as high as 200 nm when using a 200 nm gold colloidal particle. The results indicated that the resolution obtained in the experiment is in good agreement with the trapped particle size and overcame the diffraction limit (420 nm) of the lens system.