Jürgen Kuhl | PubMed Health

PubMed2005

Transition between different coherent light-matter interaction regimes analyzed by phase-resolved pulse propagation.

We present phase-resolved pulse propagation measurements that allow us to fully describe the transition between several light-matter interaction regimes. The complete range from linear excitation to the breakdown of the photonic bandgap on to self-induced transmission and self-phase modulation is studied on a high-quality multiple-quantum-well Bragg structure. An improved fast-scanning cross-correlation frequency-resolved optical gating setup is applied to retrieve the pulse phase with an excellent signal-to-noise ratio. Calculations using the semiconductor Maxwell-Bloch equations show qualitative agreement with the experimental findings.

Journal Article↗

PubMed2003

Tunable subpicosecond optoelectronic transduction in superlattices of self-assembled ErAs nanoislands.

In applications as diverse as fibre-optic communications and time-domain or terahertz spectroscopy, researchers are keen on ultrafast optoelectronic transducers that can be tailored to specific needs. The molecular beam epitaxy of photoconductors composed of equidistant layers of self-assembled ErAs-islands in a III-V semiconductor matrix, which act as efficient non-radiative carrier capture sites, enables this flexibility. Here, photocurrent autocorrelation techniques are applied to metal-semiconductor-metal photodetectors patterned on ErAs:GaAs superlattices. The experiments demonstrate that the electrical response speed can be conveniently tuned over at least two orders of magnitude starting from 190 fs by increasing the thickness of the GaAs spacer separating adjacent ErAs layers. The same concept is applied to the narrower bandgap InGaAs matrix. We demonstrate an electron lifetime of approximately 1 ps for this material. This brings closer the prospect of implementing terahertz technology at the important optical communication wavelengths of 1.3 and 1.55 microm.

Nanotechnology↗