Quo Vadis, Near-Field Optics?

Scanning near-field optical microscopy (SNOM) has pushed today's optical resolution limit to about 20 nm, with a potential for improvement by another order of magnitude still remaining. SNOM provides chemical specificity based
on spectral (amplitude, phase), polarization, and/or fluorescence contrast; it also allows dynamic studies with femtosecond time resolution and photochemistry on the nanometer scale. In spite of these prospects and considerable ongoing research efforts, progress in near-field optical microscopy has been rather slow in the past
few years.