We are continuously looking for talented people to join our group. We offer a cutting-edge research program on ultrafast spectroscopy of nanosystems as well as comprehensive training in several spectroscopic techniques. At the moment, we are especially interested to find candidates for the following projects, but are also open for proposal of the prospective co-workers.
Bachelor and Master Theses
Most of these topics are suitable as both a bachelor's and master's thesis.
Angle-resolved radiation of plasmonic waveguides
Plasmonic waveguides have different optical modes with different effective refractive indices. The aim of this work is to measure this ‘mode index' by exploiting the conservation of momentum in the direction of propagation when diffracted at a grating: different modes are deflected in different directions. For this purpose, different waveguides and gratings are to be produced and tested and the measurements compared with simulations.
Single-crystalline gold and silver flakes for plasmonics
Thin single crystals of gold and silver are the ideal starting point for plasmonic circuits. In this work, the chemical synthesis of these crystal flakes will be further optimized to produce large and smooth flakes. The crystals are characterized in an optical microscope and in a scanning force microscope.
Direct measurement of the absorption of very small particles in the near-infrared
A single nanoparticle absorbs only about 10-5 of the light in one focus. In order to still detect this small signal, the position of the particle should be modulated and then this modulated signal should be measured with a lock-in detector. In particular, we are interested in the absorption in the near infrared between 1000 and 2000 nm wavelength. An appropriate setup should be designed, constructed and characterized in order to finally measure the absorption of individual particles.
Dye molecules as single photon sources
Dye molecules are quantum optical single-photon sources, but unfortunately also very sensitive to photo-induced chemical reactions that destroy the molecule. In this work the photostability of a promising molecule should be investigated and optimized in order to couple it with plasmonic nanostructures.
Planarization of nanostructures
We would like to go into the third dimension with our plasmonic structures. For this, however, already existing structures in one level must be planarized by applying a suitable coating, on which then the next layer is fabricated. The aim of this work is to investigate this planarization: how well can we control the thickness? How high can the structure be that is covered? Test structures are produced, planarized and measured, for example, in a scanning force microscope.
Quantum optical circuits based on plasmonic waveguides
Semiconductor quantum dots serve as single photon sources. To build a photonic quantum computer from them, it is necessary to combine many single photon sources with a network of waveguides. Plasmonic waveguides promise efficient coupling and truly nanoscale footprint. We achieved already the first step of coupling to the waveguide (NanoLetters 2017), now we want to design and manufacture plasmonic circuits. Plasmonics and spectroscopy are done by us, the production and structuring of semiconductor samples together with cooperation partners.
Nonlinear near-field microscopy
Plasmonic nanostructures locally increase the electric field and are also themselves highly optically nonlinear, so that processes such as the generation of the second (SHG) or third harmonic (THG) are very efficient. The interaction of fundamental field distribution, plasmonic resonance, nonlinear polarization and finally nonlinear emission is quite complex. In special cases, this can be observed despite the limited resolution of a far-field microscope (NatComm 2016). Within the framework of a DFG project, however, we are looking for structures that enable well-controlled plasmonic near fields, for example, in order to excite molecules at specific positions on the nanometer scale. Therefore, we want to image non-linear plasmonic near fields in a near-field microscope consisting essentially of a scattering AFM tip as a probe. In an iterative process of simulation, production and measurement, a light source is to be developed that works below the diffraction limit.
For further information please contact Markus Lippitz.