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.
We have determined the longitudinal optical conductivity of (TaSe4),I in the energy range from 50 meV to 2 eV at different temperatures between 15 K and 420 K. We find a clear evidence that the free carriers are condensed into a charge density wave ground state not only below the transition temperature of 263 K but also at higher temperature up to the limits of the chemical stability of this compound.
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