Authors

Reina Aydé, Gwenaël Gaborit, Jean Dahdah, Lionel Duvillaret, Nadège Courjal, Clément Guyot, Raphaël Sablong, Anne-Laure Perrier, and Olivier Beuf

Abstract

A pigtailed Ti:LiNbO3 waveguide is here associated to a specific nuclear magnetic resonant coil to perform a low invasive magnetic field measurement. The developed device exploits a passive electro-optic transduction between the measured magnetic field and polarization state modulation of a laser probe beam. Because of the use of integrated optics, the coil electromotive force induces a dramatically enhanced electric field, thus leading to sensitivity improvement. A minimum detectable magnetic field lower than 60 fT · Hz−½ is achieved at the resonant frequency of 128 MHz. A dynamic range exceeding 100 dB is experimentally demonstrated.

Introduction

Magnetic Resonance Imaging (MRI) constitutes a non invasive technique which provides information related to the anatomy of a living being and allows to diagnosis certain diseases thanks to the analysis of soft tissues. Based on nuclear magnetic resonance (NMR), MRI consists in the study of magnetic modification properties of a nuclei which reflects its interaction with the environment (other nuclei and lattice) [1]. In order to extract this information, it is necessary to modify the magnetization from its equilibrium state, and then to detect its return to this equilibrium state driven by magnetic resonance frequency and different relaxations processes. Conventionally, an inductive loop is used to characterize the magnetization variations via the induced electromotive force (EMF). The measurement is usually performed with an external coil to image the biological media [2]. However, despite technical MRI improvements, spatial resolution and
achievable image quality with external coil are still limited for the examination of deep regions. It has been demonstrated that an endoluminal (internal) coil provides an important increase in local signal to noise ratio (SNR), and enables very high resolution images [3]…

Reference

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 26, NO. 12, JUNE 15, 2014

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