Near-Field Coherent Spectroscopy and Microscopy of a Quantum Dot System

We combined coherent nonlinear optical spectroscopy with nano-electron volt energy resolution and low-temperature near-field microscopy with subwavelength resolution (<lambda/2) to provide direct and local access to the excitonic dipole in a semiconductor nanostructure quantum system. Our technique allows the ability to address, excite, and probe single eigenstates of solid-state quantum systems with spectral and spatial selectivity while simultaneously providing a measurement of all the various time scales of the excitation including state relaxation and decoherence rates. In analogy to scanning tunneling microscopy measurements, we can now map the optical local density of states of a disordered nanostructure. These measurements lay the groundwork for studying and exploiting spatial and temporal coherence in the nanoscopic regime of solid-state systems.