Contact
Prof. Dr. Sebastian Frederick Mährlein
Head of High-Field THz-driven Phenomena
s.maehrlein
hzdr.de
Phone: +49 351 260 2240
Dr. Jan-Christoph Deinert
Coordinator TELBE user facility
High-field THz driven Phenomena
j.deinerthzdr.de
Phone: +49 351 260 3626
THz Cavity Electrodynamics
Cavity Electrodynamics is a promising avenue for studying fundamental light-matter interactions, providing a pathway to steer excited-state dynamics and encourage collective behavior. In the context of THz radiation science, there is growing interest in using cavities to modify low-energy resonances in the THz spectral region, in large part due to their relationship to fundamental material properties. Such efforts include, for example, the modification of correlated electron transitions, as well as growing evidence of cavity control over superconductivity.
Intracavity Sampling
We investigate cavity light-matter interactions from a fundamental perspective and explore how cavities offer a route to control material excitations. To explore these possibilities, we develop new experimental techniques that reveal cavity dynamics on ultrafast timescales, measuring observables inside cavities, in contrast to conventional techniques that measure transmitted radiation. We therefore employ all-optical THz methodologies to reveal excited-state dynamics of cavity-coupled THz quasiparticles on sub-cycle timescales, enabling a detailed view of intra-cavity excitation dynamics.
Cavity Electro-Optic Sampling
We perform electro-optic sampling inside an electromagnetic cavity to gain direct access to the cavity electric fields [1]. This technique, called Cavity Electro-Optic Sampling, benefits from higher sensitivity than conventional cavity transmission, and is free from substrate effects. Furthermore, we use z-cut α-Quartz, which enables straightforward measurement of vectorial driving fields [2]. This technique is not restricted to a single electro-optic crystal – in fact, with two crystals, a tunable cavity can be created, exhibiting a rich mode structure even before including an active material.
Cavity Electro-Optic Sampling: This all-optical technique uses the Pockels effect of an ultrafast probe pulse to measure the local THz electric field inside of a cavity, thereby reflecting all cavity modes excited within the THz spectrum.
Cavity electro-optic sampling is furthermore capable of simultaneously measuring phonon amplitudes in addition to electric fields, with a particular emphasis lying on strongly-coupled cavity modes. Cavity electro-optic sampling therefore offers a unique opportunity to measure the full time-domain response of a polaritonic excitation, rather than just the electric field component, as is typically measured, thereby revealing new details of excited-state material dynamics.
Related publications
- [1] M. S. Spencer, J. M. Urban, M. Frenzel. N. S. Mueller, O. Minakova, M. Wolf, A. Paarmann, S. F. Maehrlein, “Electro-optic cavities for in-situ measurement of cavity fields,” npg Light: Science & Applications, 14, 69 (2025). [press release]
- [2] M. Frenzel, J. M. Urban, L. Nest, T. Kampfrath, M. S. Spencer, S. F. Maehrlein, "Quartz as an accurate high-field low-cost THz helicity detector," Optica 11, 362-370 (2024).
