Detection of magneto-optical Kerr signals via weak measurement with frequency pointer.

Detection of the magneto-optical Kerr effect with high precision is of great significance but has challenges in the field of magnetic physics and spintronic devices. Kerr rotation angle and Kerr ellipticity always coexist and are difficult to distinguish, which jointly determines the light intensity received by the detector and limits the improvement of measurement precision. In this Letter, a nonlinear weak measurement scheme for magneto-optical Kerr signals with a frequency pointer is proposed. The Kerr rotation and Kerr ellipticity can be separately detected by constructing different pre-selections and choosing the appropriate coupling strength. Moreover, two signals obtained through the weak measurement scheme have higher precision and signal-to-noise ratio compared with the standard polarimetry scheme. Our method may have important applications in the field of magneto-optic parameters measurement or magnetic sensors.