Magneto-optical and Ultrafast Optical Studies

Kerr microscopy is an optical imaging technique based on the magneto-optical Kerr effect (MOKE). It is used to study the magnetic properties of materials at the microscopic level. When polarized light is reflected from a magnetized surface, the plane of polarization is rotated slightly depending on the direction and magnitude of the local magnetization. This phenomenon allows to visualize magnetic domains and their dynamics in ferromagnetic materials.
Our Kerr microscope posesses a finest resolution of 100 nm, a magnetic field application in z-direction up to 0.6 T and arbitrary in-plane direction up to 0.4 T, a temperature range from 10 K using liquid helium to 400 K.
To study Racetrack memory devices, we have developped a bespoke program for automatic measurement of the current-induced dynamics of magnetic domain walls. We can measure domain wall motion with excitations from DC, RF and pulsed current with the finest pulse length of 300 ps.

Advanced optical techniques are essential for probing local structural, lattice, and magnetic properties in functional materials in a non-invasive way, offering powerful complementary insights to conventional transport measurements. Our OptiCool-based optical platform with home-made microscope integrates a suite of state-of-the-art functionalities, including: Raman spectroscopy Photoluminescence (PL), Second harmonic generation (SHG), Reflected magnetic circular dichroism (RMCD), Reflection spectroscopy, Photocurrent (PC) measurements. For each optical technique, this multifunctional platform supports: spatial mapping with 1 µm resolution, polarization-resolved excitation and detection, temperature control from 2 K to 350 K and Out-of-plane magnetic fields up to 7 T. We plan to expand its capabilities to include time-resolved techniques, such as time-resolved photoluminescence (TRPL) and ultrafast pump–probe spectroscopy.
This powerful and versatile setup enables comprehensive exploration of opto-spintronics, offering exceptional opportunities for PhD students and postdoctoral researchers interested in cutting-edge optical studies of quantum materials.

We utilize cryogenic s-SNOM to investigate the nanoscale mid-infrared (MIR) and terahertz (THz) reflectivity of thin films grown in our department. Temperature-dependent scattering scanning near-field optical microscopy (s-SNOM) offers a unique capability for non-contact optical imaging, providing direct spatial visualization at a resolution beyond the diffraction limit. 
For example we study the spatial mapping of metal-to-insulator transitions (MITs) in functional materials to understand the mechanisms behind the transition.

Spatially resolved Raman spectroscopy is essential for probing local structural, vibrational, and magnetic properties in functional materials. Temperature- and magnetic-field-dependent confocal Raman microscopy enables non-invasive optical characterization, providing detailed insight into phonon–magnon coupling, spin–lattice interactions, and symmetry changes with high spatial resolution.
Using an attocube cryogenic Raman system equipped with a vector magnet capable of applying magnetic fields up to 9 T at z axis and 3 T at x axis, we investigate the field- and temperature-dependent Raman spectra of 2D materials and thin films synthesized in our lab. This setup enables comprehensive exploration of magneto-structural correlations and local heterogeneities at cryogenic temperatures.