Publication

We study nonlinear effects due to optical pumping using hot sodium vapour. Beside technical advantages, such as high optical quality, easy variation of parameters over a broad range, high resonant nonlinearity, the benefit of using an atomic vapour is that the equations governing the light-matter interaction can be derived directly from quantum mechanics via the density matrix approach.

The band within the electromagnetic spectrum between about 300 GHz and 3 THz is often referred to as terahertz radiation. Terahertz radiation is considered to be an upcoming technology in material inspection, quality control, gas sensing, surveillance and security applications, and wireless, short-haul communication. We study a method to produce THz radiation by mixing two cw infrared lasers in a special kind of semiconductor (low-temperature grown GaAs).

Semiconductor quantum dots are an exciting new material for photonics and quantum information because their properties can be tailored to a wide extent. In a first approximation, they can be considered as artificial atoms which strongly interact with their environment. This provides challenges as well as opportunities.

Light does not stay confined to small regions in space or time, but wave packets of light have the natural tendency to broaden. For technical applications, it is important to counteract this natural tendency and to confine light to the smallest possible dimensions. Though great partial success was achieved by linear optical element as optical fibres, it was always the dream of researchers to confine light by self-action. This is why the concept of solitary waves received a lot of attraction during the last decades.

Vertical-cavity surface-emitting lasers (VCSELs) are a rather new type of semiconductor laser diode, in which – in contrast to conventional edge emitters – the direction of the light emission is parallel to the epitaxial growth direction. We study the connection between the carrier spin and the polarization of the emitted light of VCSELs.