A sensitive and compact magnetometer using Faraday effect in YIG waveguide

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Abstract
A new type of sensitive magnetometer with a very small probe is described. It is based on a novel hybrid configuration utilizing the Faraday effect in a ferrimagnetic optical waveguide. A linear polarized light generated by a semiconductor laser operating at 1.3 μm is coupled into a multimode magnetic plane waveguide made of a gadolinium gallium substituted YIG epi-layer. The YIG film is of ‘‘easy in plane magnetization’’ type with a low saturation magnetic field. The Faraday rotation is detected with an infrared photodiode by measuring orthogonal polarization component. A polarization modulation technique at a frequency of 100 kHz is used to provide a high degree of noise rejection. The unknown magnetic field projection on the light propagation direction is measured by a zero magnetic field method based on the cancellation of the output signal at the modulating fundamental frequency. Characteristics of this magnetometer are presented. A sensitivity better than 10−7 Oe/Hz1/2 has been obtained at a frequency of 100 Hz.

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