BRILLOUIN LIGHT SCATTERING
Brillouin Light Scattering is a powerful technique for the investigation of spin waves in magnetic thin films (transparent or opaque) and patterned magnetic structures. This optical technique probes the intensity of the dynamic magnetization and allows frequency-, wavevector-, time-, phase- and space-resolved measurements of the spin waves.
This technique relies on inelastic scattering process due to interaction between incident photons and magnons. Magnons are created or annihilated during the interaction with photons. A frequency shift is observed along with the laser frequency taking into account energy and momentum conservation. The cross section of the inelastic process is very weak compared to the elastic one and it requires a very high contrast to detect these spin waves. This is achieved using Sandercock type multi-pass Tandem-Fabry-Perot-Interferometer (TFPI) which has a frequency resolution better than 100 MHz. This TFPI allows a wide range of frequency analysis from 1-500GHz. Due to very high sensitivity of the TFPI thermally excited spin waves at room temperature can also be detected which means no external excitation mechanism is required.