Investigations of Brillouin scattering at low temperature

Brillouin scattering was first described theoretically 100 years ago and is now one of the strongest and most widely studied forms of optical nonlinearity. It is a three-wave mixing process between two optical fields and one acoustic field that can range from the MHz to GHz in frequency depending on which optical and mechanical modes are addressed. Thus far, most research in Brillouin scattering focusses on room temperature studies in a range of different materials and geometries, and there are some studies that also investigate Brillouin scattering down to 4 K. In this project, we aim to experimentally characterize Brillouin scattering in both amorphous and crystalline materials down to mK temperatures by performing these optical scattering experiments in a dilution refrigerator. These studies will elucidate the properties of the scattering mechanism, including the Brillouin scattering linewidth, with temperature and will allow us to identify important regions of parameter space for both amorphous and crystalline materials.