First experimental results with the free electron laser coupled to a scanning near-field optical microscope

First experiments of coupling a free electron laser to a scanning near-fiel d optical microscope (SNOM) are presented. To address the question of how i mportant such spectroscopy can be for near-field infrared microscopy, we ac quired images of the same region of the sample under investigation at sever al photon wavelengths. SNOM reflectivity images revealed features that were not present in the corresponding shear-force (topology) ones and which wer e due to localized changes in the bulk properties of the sample. Optical da ta in the infrared (near 3.5 mu m), using the probe tips in collection mode , indicates an optical spatial resolution well below the classical limit of lambda/2.