title: High sensitivity differential magneto-optical imaging with a compact Faraday-modulator.
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 noise level of 50 mG Hz(-1/2) at a full frame rate of 1 fps (frame per second) with each frame being of size 512 × 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 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.
authors.affiliation: Department of Physics, Indian Institute of Technology, Kanpur 208016, India.
authors.forename: Pabitra
authors.initials: P
authors.lastname: Mandal
authors.forename: Debanjan
authors.initials: D
authors.lastname: Chowdhury
authors.forename: S S
authors.initials: SS
authors.lastname: Banerjee
authors.forename: T
authors.initials: T
authors.lastname: Tamegai