Near-Field Spectroscopy of Disordered Nanostructures

Abstract

For many years, Roland Zimmermann and his research group have devoted much of their attention to the effects of disorder and exciton localization on the optical properties of semiconductor nanostructures. With the recent development of spectroscopic techniques providing subwavelength spatial resolution, new experiments became possible to reveal some of the rich physics linked to exciton localization. This paper briefly reviews recent work of the authors' group using near-field nano-spectroscopy. Specifically, it is shown that near-field autocorrelation spectra give strong evidence for quantum mechanical level repulsion of localized exciton states and allow for a quantitative estimate of the underlying microscopic disorder features. Femtosecond non-linear near-field spectroscopy allows to probe the transient optical nonlinearity from a single localized exciton in a thin quantum film on ultrashort time scales.