High Resolution Magneto-Optic Measurements in GaAs using a Sagnac Interferometer

The Sagnac Interferometer is a tool which measures the Polar Kerr effect--a direct indicator of magnetism. Using 820 nm light from a superluminescent diode, we probe GaAs structures and measure the Kerr angle with sub-microradian resolution. ~By utilizing diffraction limited optics and a piezoelectric scanner, we also achieve high spatial resolution. Our measurements are performed at cryogenic temperatures and offer a way to measure the Spin Hall Effect in the DC regime along with other forms of magnetic order.