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Development of magneto-optic effect measurement device using dual-comb spectroscopy

16 December 2019 | News
by Ian Michael

Professor Kaoru Minoshima from the University of Electro-Communications and NEOARK Corporation have succeeded in prototyping a greatly improved magneto-optic effect measurement device using dual-comb spectroscopy.

Dual-comb spectroscopy uses two precisely controlled ultrashort pulse lasers, known as optical frequency combs (optical combs). Dual-comb spectroscopy offers major improvements over conventional Fourier spectroscopy in areas including resolution, sensitivity and measuring time. So far, dual-comb spectroscopy has primarily been used for gas spectroscopy. The project that is the first in the world to develop a solid physical property evaluation technology using dual-comb spectroscopy, has demonstrated the principles in various physical property measurements.

As a first step in developing practical applications of the technique, Professor Minoshima and her colleagues developed a magneto-optic effect measurement device capable of evaluating the characteristics of magnetic materials. The optical system and signal detection system of the prototype were improved to achieve measurement performance that greatly exceeds conventional measurement methods.

The prototype achieved major progress towards practical application, featuring a magneto-optic effect measurement resolution of 0.01°, a wavelength resolution of 0.01 nm, capable of high-speed measurement through batch measurements of all wavelength components. The prototype is a desktop system, consisting of a measurement unit, a dual-comb light source and a controller. The generated magnetic field is a maximum of ±10 kilo-Oersted.

Furthermore, based on the above-mentioned solid physical property evaluation technology, the research team also developed a prototype device for measuring the complex refractive index of solids. A major feature of the prototype is its capability to measure the phase difference of light in addition to its intensity ratio.

Measurement devices leveraging dual-comb spectroscopy for magneto-optic effect measurement and complex refractive index measurement are expected to become important new tools for the precise measurement of polarisation and spectroscopy, and for material development. They will proceed with development targeting commercialisation in the near future.

Details are reported in Optics Letters.


Prototype of the dual-comb magneto-optical effect measurement system. (a) Dual-comb light source with a width of 470 mm, a length of 600 mm, a height of 180 mm and a weight of 12 kg. (b) Measurement unit with a width of 260 mm, a length of 360 mm, a height of 400 mm and a weight of 35 kg. Maximum induced magnetic field is ±10 kOe. ©The University of Electro-Communications, Kaoru Minoshima and NEOARK.

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