Spectroscopy II/VI

The group is interested in the optical properties of low dimensional II-VI semiconductors. II-VI quantum dots embedded in a II-VI barrier are especially promising for semiconductor based quantum electrodynamics due to the large biexciton binding energy and high potential barriers. We investigate the light emission of single quantum dots applying mesa techniques. Central issues of our research are engaged with spin dynamics in semimagnetic quantum dots, light-matter interaction and single photon sources.

 

Our investigations are based on several optical equipments like:

  • Far field and micro photoluminescence/reflectance spectroscopy
  • Time resolved spectroscopy (ps resolution)
  • Kerr/Hanle spectroscopy
  • Magnetooptics (+/- 8T)

 

Research topics
 

Microcavities with quantum dots

Three dimensionally confined light in microdisk can be tuned to the energy of quantum dot excitons. We have realized high quality microdisks (Q>10000) with whispering gallery modes in resonance with electronic excitations of single quantum dots. Topics of interest are related to

  • Weak/strong exciton-photon coupling
  • Lasing of quantum dots

 

 

Left part: Cross section scheme of a II-VI based heterostructure with embedded CdSe quantum dots. Centre part: Electron microscope image of a microdisk fabricated by electron beam lithography and dry etching. Right part: Emission spectra of a II-VI microdisk with quantum dots (QD). Right part: The QD luminescence forms a broad peak centred at about 2.4 eV. Narrow lines are whispering gallery modes.

 

Semimagnetic quantum dots

The possibility to incorporate Mn ions isoelectronically into II-VI semiconductors allows the control of electronic and magnetic properties of semiconductor quantum dots. As a result, pronounced magneto-optical effects, like giant Zeeman splitting, pronounced Faraday rotation or the formation of magnetic polarons can be observed. In this regard we focus on

  • Light controlled spin polarization
  • Superradiance of quantum dots
  • Tuning of g factors, symmetry and exciton confinement

 

To find out more about our research areas, explore the following links: