ROOM-TEMPERATURE NEAR-FIELD REFLECTION SPECTROSCOPY OF SINGLE QUANTUM-WELLS

We report on a novel optical near-field technique to measure the local polarizability of a topographically flat sample with a spatial resolu tion better than 100 nm. Using an uncoated fiber probe, we implement a cross-polarization detection of the optical signal at the fiber dithe r frequency. This technique suppresses efficiently the otherwise domin ating far-field background and reduces topographic artifacts. We demon strate its performance on a thin, strained near-surface CdS/ZnS single quantum well at room temperature. The optical structure of these topo graphically flat samples is due to CdS thickness fluctuations, and is observed to be uncorrelated within the spatial resolution of the instr ument.