There are no official vacancies at the moment, but we will be advertising again soon. Please contact us directly to find out the latest status. A lab tour is always possible without obligation.

Students who would like to write their thesis with us are of course very welcome.

There are many smaller and larger projects that can be carried out in our attosecond laboratory in room W2 0-025 with the shortest laser pulses and our own electron microscope. Previous experience is not necessary, but an interest in learning new things and mastering somewhat more complex measurement setups is certainly beneficial. From femtosecond laser systems to vacuum systems, from attosecond pulses in the ultraviolet to time-resolved electron microscopy on nanostructures, a wide variety of techniques can be tried out.

Just get in touch with us. We will be happy to show you around the lab without obligation and talk about current opportunities for theses. If you already have a concrete idea of what you would like to study, we will of course also take your wishes into account. And since the question comes up often: As an independent junior research group, we can supervise Bachelor's, Master's and doctoral theses in the same way as other groups whose leaders already have the title of professor. However, a second examiner with a title can of course be chosen.

Below is a (by no means exhaustive) list of potential topics to give you a better idea of what you can learn with us.

We are about to generate attosecond pulses in our laboratory for the first time. We offer you the opportunity to join us from day 1 and to characterise the generated pulses in a self-built spectrometer and to investigate them with time resolution for the first time.

This includes first of all the construction and adjustment of a number of optical elements that belong to the spectrometer. In addition, an interferometer has to be set up, which is necessary for the temporal characterisation of the pulses. This is then done with the help of an argon gas jet and an electron spectrometer.

If you are interested, please contact us to find out about the current status and the possibility of a thesis. Depending on whether it is a Bachelor's or Master's project, we would of course adapt the scope.

Photoemission electron microscopy (PEEM) differs somewhat from conventional microscopy techniques. In this case, the sample is also the electron source, in that electrons are triggered from it - by illumination with short laser pulses. If first a laser pulse is used for optical excitation and then a second one to interrogate the dynamics after a variable waiting period, the electrons carry valuable information about the charge carrier dynamics at the time of triggering after emission.

The trigger locations of the electrons are imaged in the microscope with high spatial resolution. At the same time, the time of flight of the electrons is recorded, so that their kinetic energy spectrum is also measured. This allows us to gain detailed insights into the charge carrier dynamics near the surface of a nanostructure after optical excitation.

We have recently commissioned our PEEM and are now offering various projects on different samples as final theses. Techniques used include sample preparation, nanopositioning systems, ultra-high vacuum, electron microscopy, time-of-flight electron spectroscopy and excitation-interrogation experiments with short laser pulses. Please contact us if you would like to do something at PEEM and we will tell you what particularly exciting samples are currently available. You can then prepare them yourself, investigate them in PEEM in a time-resolved manner and evaluate the data for your thesis.

We have recently built a laser system that uses non-linear processes to generate ultrashort laser pulses in the infrared spectral range around a central wavelength of 2µm. However, these pulses are not (quite) short enough for the planned experiments. There are various approaches to shorten light pulses by spectral broadening and subsequent temporal compression so much that they last only a few oscillations of the electric field. The aim of this project is to further compress laser pulses at a central wavelength of 2 µm and a pulse duration of about 30 fs by focusing them into thin glass plates and to characterise them with regard to their pulse duration, beam quality and power stability. Intensive on-site supervision is guaranteed (don't worry!), and an exchange with colleagues in Lund (Sweden) is possible at the same time. Your tasks would be to set up the optical experiment, perform the spectral broadening and characterisation by means of a spectrometer, as well as the final temporal compression and measurement of the pulses.

Shao, B. et al. 1.9 μm Few-Cycle Pulses Based on Multi-Thin-Plate Spectral Broadening and Nonlinear Self-Compression. IEEE Photonics Journal 13, 1-8 (2021).

Short laser pulses are characterised by a briefly oscillating electromagnetic field with high amplitude. For applications, however, usually only the envelope of the field is relevant, not its instantaneous oscillation itself. It is also this that is measured in most pulse-quenching methods. However, we would like to go a step further in our experiments and also use the electric field itself to control ultrafast processes such as the generation of high harmonics. This requires measuring and controlling the phase between the envelope and the carrier frequency, the so-called CEP (carrier envelope phase).

In this project, this phase of our short laser pulses is to be measured with the help of an interferometer and, in addition, our laser is to be extended so that the CEP of each pulse remains the same over a longer period of time. To do this, you will set up such an interferometer and use the signal generated from it to control a piezo stage. Does this sound confusing? Hopefully not after a lab visit with us. :)

Feel free to contact us if there is something for you in the proposed projects. And feel free to contact us if no project appeals to you directly. Sometimes we come up with spontaneous project ideas or a project seems different after we've done a little lab tour.

With us there is

• Intensive supervision, support for the whole group
• the opportunity to try out many new devices and techniques
• first own research results
• an exciting final project

Please contact Katrin or Jan.