Magneto-optic Effect - Wavelength Parallel Measurement of Magneto-optical Effect

Wavelength Parallel Measurement of Magneto-optical Effect

Because the MO activity is usually very small, normally less than 1°,in conventional systems, the monochromator produces quasi-monochromatic light in a narrow wavelength window since the amplitude of modulation is wavelength dependent. Therefore, to measure the spectroscopic MO activity, a large number of measurements over the full spectra is required to obtain satisfactory wavelength resolution and thus is very time consuming. To obtain the spectroscopic information of the MO activity, light wavelength is varied by the monochromator. Therefore, these methods cost huge amount of time though provide high sensitivity to small MO activities. Fast spectroscopic characterization of the MO activity is thus desirable. Can we use white light source and perform wavelength-parallel measurement such as that in the state-of-art ellipsometry for the characterization of refractive index?

It is well established that when this linear polarized light passes through another polarizer, also called analyzer, the transmitted light intensity could be varied depending on their relative angle θ governed by a cos^{2}θ law. Based on this simple idea, now researcher has developed a fast spectroscopic MO system, they can get full spectral range MO activity in a single magnetic field scan. The system requires only stable continuous spectral light source, two polarizers, an achromatic quarter-wave plate and a spectrometer.

It is low cost and flexible for application in full spectral range from UV to IR, or even in THz applications.This new system would booster the exploration to the MO characteristics of a large variety of materials in the full spectral range. The minimum resolvable angle depends on the full scale signal of light source and is limited by the instability and dark noise of the spectrometer. A minimum resolvable angle of 0.004° has been demonstrated in the their configuration.