Magneto-photonic ring circulator in Bismuth Iron Garnet thin film: design and fabrication
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Magneto-photonic ring circulator in Bismuth Iron Garnet thin film: design and fabrication L. Magdenko1, E. Popova2, W. Smigaj3, P. Beauvillain1, N. Keller2, B. Gralak3, P. Gogol1, R. Megy1, M. Vanwolleghem1, B. Dagens1 1 Institut d’Electronique Fondamentale, bâtiment 220, Université Paris Sud, 91405 Orsay cedex, France 2 Groupe d’Etude de la Matière Condensée, CNRS – UVSQ, Bâtiment Fermat, 45 avenue des Etats-Unis, 78035 Versailles, France 3 Institut Fresnel, CNRS, Aix-Marseille Université, Ecole Centrale Marseille, Campus de St Jérôme, 13397 Marseille Cedex 20, France
ABSTRACT Magneto-optical garnet based optical circulator was designed and fabricated with waferscale technology. Modeling and simulation strategy is established for the optimization of a new design of circulator based on ring cavity. Wafer-scale technological process is developed and demonstrated allowing fabrication of the optimized BIG/GGG buried ring circulator. INTRODUCTION Non-reciprocal functions like optical isolation or circulation are expected to significantly increase the integration capabilities and the number of integrated elements in photonic circuits. For example, the use of such functions in optical circuits allows inserting emitting sources like laser or amplifiers without risk of performance degradation due to internal feedback. For integrated optic, the most promising isolator or circulator principle consists in using transverse magneto-optical Kerr effect (MOKE), in garnet based devices [1] or in ferromagnetic metal based semiconductor amplifier [2]. Garnet based waveguide presents the advantage of low optical losses at telecom wavelength. But the relatively low magneto-optical strength has led to large devices like a several millimeters long interferometer [1]. Here we have focused our work on resonant circulator in order to obtain non-reciprocal behavior in a compact cavity [3]. Respect to [3], we have considered ring cavity instead of photonic crystal cavity, because, as it will be shown, ring cavity allows better optimization of magneto-optical interaction. We have simultaneously considered device design and fabrication in order to establish the best compromise between performance and technology. In this paper we first present the studied optical circulator, including operation principle and material structure. Then we describe the different steps of device designing. The third part is dedicated to technological waver-scale fabrication of the BIG (Bismuth Iron Garnet) circulator. In the last part we will conclude and discuss on the perspectives of this work. GARNET BASED OPTICAL CIRCULATOR Optical circulator can be described as a magneto-optical ring cavity with additional input waveguides. In a nonmagnetic ring cavity two degenerate orthogonal eigenmodes can be excited. In an external magnetic field perpendicular to the plane of the rings, these degenerate modes
non-reciprocally couple and split into left and right rotating modes with different eigenfrequencies ω- and ω+. When such a non-reciprocal cavity is coupled to 120°
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