Magnetic field and electric field effect on magnetostrictive and electrostrictive photonic resonators

Abstract

The goal of this work is to investigate the effect of electric and magnetic field on the optical resonances of electrostrictive and magnetorheological optical resonators. The optical resonances, also known as whispering gallery modes (WGM) or morphology dependent resonances (MDR) experience a shift in the transmission spectrum whenever the resonator changes its size and/or index of refraction. Their small size, the elimination of electrical cabling, and the high optical quality factor, Q, make them attractive for a large number of applications. In these studies, we investigate the magnetostrictive and the electrostrictive effect of fiber coupled photonic spherical resonators. The electrostrictive and the magnetostrictive effect are the elastic deformation of a solid when subject to an electric or magnetic field respectively. In these studies, three different configurations were investigated to tune the optical modes of the spherical optical resonator. In the first configuration, the resonator was fabricated by embedding magnetic micro particles in a polymeric matrix of PVC plastisol (commercial name super soft plastic, SSP). For these configurations we studied the WGM shift that was induced when the sphere was immersed in a static and a harmonic magnetic field. These results lead to the development of a magnetic flied sensor and a non-contact transduction mechanism for displacement measurements. The sphere showed a sensitivity to the magnetic field of 0.285 pm/mT and to the displacement of 0.402 pm/?m. These values lead to a resolution of 350 ?T and 248 nm respectively. The second configuration was a microsphere that was made of pure super soft plastic and was subject to a static and harmonic electric field. The results lead to the development of a non-contact displacement sensor whose sensitivity is 0.642 pm/?m and the resolution is 155 nm. Both studies also indicate for the first time that it is possible to couple light into a PVC compound and achieve high optical quality factor of the order of 106. The third configuration was a metglas film that was mechanically coupled to a PDMS microsphere. The results of these studies lead to the development of a magnetic field sensor with sensitivity and resolution of 0.6 pm/?T and 166 nT respectively. In conclusion, these studies lead to a fundamental understanding of the dynamical behavior of electrostrictive and magnetorheological optical resonators and its potential for sensing applications. In addition, these devices could be embedded into polymeric matrix for the development of materials with actuation and sensing capabilities.