High sensitivity differential Magneto-Optical Imaging with a compact Faradaymodulator

TL;DR

This paper introduces a compact Faraday-modulator based optical magnetometer that significantly improves sensitivity for imaging weak magnetic fields in magnetic and superconducting materials, especially useful in space-constrained environments.

Contribution

The paper presents a novel, scalable design of a compact Faraday-modulator magnetometer with enhanced sensitivity and noise performance for imaging weak magnetic fields.

Findings

Achieved an rms noise level of 50 mG.Hz-1/2 at 1 fps

Provided an order of magnitude improvement in S/N ratio over traditional methods

Enabled imaging of weak magnetization near superconducting transitions

Abstract

We present here the design of a sensitive Compact Faraday-modulator (CFM) based optical magnetometer for imaging the distribution of weak local magnetic fields inside hysteretic magnetic materials. The system developed has a root mean square (rms) noise level of 50 mG.Hz-1/2 at a full frame rate of 1 frame per second with each frame being of size 512 x 512 pixels. By measuring the local magnetic field distribution in different superconducting samples we show that our magnetometer provides an order of magnitude improvement in the signal to noise (S/N) ratio at low fields as compared to ordinary magneto-optical imaging technique. Moreover, it provides the required sensitivity for imaging the weak magnetization response near a superconducting transition where a number of other imaging techniques are practically unviable. An advantage of our CFM design is that it can be scaled in size to fit into situations with tight space constraints.