Sub-three-cycle pulses at 2 µm from a degenerate optical parametric amplifier.

In this work we present a compact two-stage optical parametric amplifier (OPA) pumped at degeneracy by the fundamental of a Yb:KGW laser system. The output pulses span from 1.7 to 2.

Switchable dissociation of excitons bound at strained CdTe/CdS interfaces.

Charge carrier dynamics of semiconductor nano-heterostructures are determined by band alignment and lattice mismatch of the adjacent materials. However, quantum efficiencies for the separation of excited charge carriers at such an interface are hard to predict and cannot yet be easily controlled. In this work we examine nanorods with a severely strained, axial CdTe/CdS interface using femtosecond transient absorption spectroscopy.

Incoherent Pathways of Charge Separation in Organic and Hybrid Solar Cells.

In this work, we investigate the exciton dissociation dynamics occurring at the donor:acceptor interface in organic and hybrid blends employed in the realization of photovoltaic cells. Fundamental differences in the charge separation process are studied with the organic semiconductor polymer poly(3-hexylthiophene) (P3HT) and either [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or titanium dioxide (TiO) acting as the acceptor. By using ultrafast broad-band transient absorption spectroscopy with few-fs temporal resolution, we observe that in both cases the incoherent formation of free charges dominates the charge generation process.

Below-gap excitation of semiconducting single-wall carbon nanotubes.

We investigate the optoelectronic properties of the semiconducting (6,5) species of single-walled carbon nanotubes by measuring ultrafast transient transmission changes with 20 fs time resolution. We demonstrate that photons with energy below the lowest exciton resonance efficiently lead to linear excitation of electronic states. This finding challenges the established picture of a vanishing optical absorption below the fundamental excitonic resonance.

Stable single-photon emission by quantum dot/polymer hybrid particles.

Colloidal quantum dots are well-established probes for quantum optical experiments. However, they possess a limited stability toward their environment. Herein, the generation of hybrid particles composed of a high optical quality quantum dot centered in a polymer particle by means of a miniemulsion polymerization procedure is reported.