Optical Sensor of Magnetic Dynamics: A Balanced-Detection MOKE Magnetometer
Team Members
LI Junxiang E1127462@u.nus.edu
Patricia Breanne Tan Sy pb.sy82@u.nus.edu
Idea
We will use a laser-based magneto-optical Kerr effect setup featuring a high-sensitivity differential photodiode array to measure the Kerr rotation angle induced by surface magnetism. This system serves as a versatile optical platform to investigate how external perturbations such as magnetic fields or radiation source alter the magnetic ordering of materials, allowing for the quantitative extraction of the magneto-optical coupling coefficients of various thin films.
Introduction
Experimental Setup
We utilize a 658 nm HL6501 red Continuous Wave (CW) laser. The beam passes through an ND filter to attenuate its intensity. To achieve continuous intensity control while maintaining a pure linear polarization (S or P), a combination of a fixed Polarizer, a rotating Half-Wave Plate (HWP), and a second Polarizer is used. The beam is then directed via a Non-Polarizing Beam Splitter (NPBS) and focused onto the sample by an objective lens. The reflected light, carrying the Kerr rotation signal, is collected and directed into a Wollaston prism. The prism splits the beam into two orthogonal components ((<math>I_1<math> and <math>I_2<math>), which are then captured by a Balanced Detector. The micro-Kerr rotation (<math>theta_K<math>), induced by the material's magnetic properties, is extracted from the normalized difference of the two intensities, effectively cancelling out laser intensity noise
Methods
Results
Conclusion and Discussion
Reference
1. McCord, J. Progress in magnetic domain observation by advanced magneto-optical microscopy. J. Phys. D: Appl. Phys. 48, 333001 (2015).
