PhD Defence by Simon Lehnskov Lange

Title: Terahertz-Enabled Ultrafast Electron Field Emission

Principal supervisor: Prof. Peter Uhd Jepsen, DTU Fotonik
Co Supervisor: Prof. Jes Broeng, DTU Entrepreneurship

Evaluation Board
Prof. Franz X Kärtner,  CFEL, University of Hamburg, Germany
Prof. Frank Hegmann, University of Alberta, Edmonton, Canada

Senior Researcher Stela Canulecsu, DTU Fotonik

Master of the Ceremony
Assistant Prof.: Edmund Kelleher, DTU Fotonik

This PhD work explores ways to use ultrafast electron field emission (FE) as an enabling phenomenon for the development of new technologies. The work has been carried out as a research project of both fundamental science and innovation.

Ultrafast electron FE is a phenomenon that occurs in physics when a strong electric field from a short laser pulse is applied to a subject like an atom, a molecule or solid state material. As a result, electrons residing inside the subject can undergo quantum mechanical tunneling to emit into the surrounding environment. The FE phenomenon is mostly accessible if the laser pulse consists of infrared light. In this work, we rely on the particular part of infrared light that is called terahertz (THz).

We find that it is possible to enable FE when illuminating an artificial surface – called a metasurface - with THz light. The metasurface is designed with computer simulations and fabricated in a cleanroom. As a result of the interaction between THz light and the metasurface, we observe that we can emit electrons in ultrashort bunches and thus make an ultrafast electron gun. We demonstrate how this electron gun can be used to emit electrons directly into a polymer as a basis for initiating and observing chemical reactions on an ultrafast time scale. This technique can potentially enable a broader scientific audience to conduct a range of time-resolved experiments that were previously impossible on normal lab scales.

We also demonstrate how to use the metasurface as a detector for infrared light, which is of great practical importance for many fields of science and applications. This detector is sensitive to the electric field of the light and can hence resolve a range of properties of the light that are commonly hard to access. We expand this detection principle to a vacuum electronic platform, where we embed our metasurfaces into very sensitive light detectors called photomultiplier tubes (PMT). This work is done in collaboration with the Japanese company Hamamatsu Photonics. The results show great promise to make a novel class of detectors for all infrared light. In the coming years, DTU and Hamamatsu Photonics will continue the joint development of this technology, thus showing that fundamental research and innovation can go hand in hand.


Mon 10 Feb 20
13:30 - 16:30


Lyngby Campus
Building 341, auditorium 22