Magneto-optics & femtosecond laser laboratory

The Magneto-Optical Kerr Effect, or MOKE, is a phenomenon widely used to measure the magnetic behavior of magnetic thin films. The phenomenon, first discovered by John Kerr in 1887, demonstrates the change in ellipticity and rotation angle of light after reflection of a magnetic structure. Nowadays a wide range of advanced schemes is available, exploiting the Kerr effect for basic magnetic characterization, but also to spatially resolve domains in micro-magnetic structures and to explore magnetization dynamics down to femtosecond timescales.  In the group Physics of Nanostructures we have several measurement setups relying on this technique.

Room temperature MOKE

For a quick measurement of the magnetic behavior of magnetic thin film structures there is a home build MOKE setup available in the laser laboratory of FNA. The setup is equipped with a Class III/a HeNe CW laser, and uses a lock-in technique in combination with a PEM to increase the sensitivity of the measurement.

Femtosecond time resolved MOKE

In the high power (Class IV) part of the laser laboritory, two femtosecond laser setups are available to measure the magnetic response, at the sub-picosecond timescale, of magnetic structures after femtosecond laser excitation. By using a mechanical delay line the time delay between the pump and probe pulse can be extended up to several nanseconds. A double modulation technique including a PEM and a chopper is used to increase the sensitivity of the measurement

Kerr microscope

The Kerr microscope is used to visually investigate the magnetic behavior of a magnetic structure. Using the magneto-optical Kerr effect a contrast difference is created in the recorded image, representing different orientations of the magnetization. This system can be used to investigate the nucleation/propagation of magnetic domains in magnetic thin films at the micro/nanometer length scale under the influence of a 3D magnetic field or electrical current.