Multicolor femtosecond pump-probe system with single-electron sensitivity at low temperatures and high magnetic fields.

We present an ultrafast spectroscopy system designed for temporal and spectral resolution of transient transmission changes after excitation of single electrons in solid-state quantum structures. The system is designed for optimum long-term stability, offering the option of hands-off operation over several days. Pump and probe pulses are generated in a versatile Er:fiber laser system where visible photon energies may be tuned independently from 1.

Efficient Emission Enhancement of Single CdSe/CdS/PMMA Quantum Dots through Controlled Near-Field Coupling to Plasmonic Bullseye Resonators.

A strong increase of spontaneous radiative emission from colloidally synthesized CdSe/CdS/PMMA hybrid particles is achieved when manipulated into plasmonic bullseye resonators with the tip of an atomic force microscope (AFM). This type of antenna provides a broadband resonance, which may be precisely matched to the exciton ground state energy in the inorganic cores. Statistically analyzing the spectral photoluminescence (PL) of a large number of individual coupled and uncoupled CdSe/CdS/PMMA quantum dots, we find an order of magnitude of intensity enhancement due to the Purcell effect.

Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters.

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic luminescence. In isolated colloidal quantum dots, spatial confinement of the vibrational motion is expected to give rise to an interplay between the quantized electronic and phononic degrees of freedom.