Experiments on the depolarization near-field scanning optical microscope

We demonstrate the operation of an apparatus which we call the depolarization near-field scanning optical microscope. It delivers subwavelength resolution with uncoated optical fiber tips without the need for additional modulation techniques. We show that-in the near field-the edges perpendicular to the incident optical polarization are imaged. This dependence on the orientation of the linear polarization as well as the influence of small ellipticities of the polarization state on the imaging process are measured on a well-defined test sample. The transition from near- to far-field imaging as a function of the tip height is demonstrated. The results are in good agreement with recent theoretical predictions. (C) 1999 American Institute of Physics. [S0003-6951(98)03344-0].