Enhancement in Verdet Constant of an e-field oriented polymer nanocomposite

Magneto-optical (MO) materials based on the Faraday effect have a variety of applications in current sensing, magneto-optic current transformers, optical modulation, lasers and magneto-optical imagery due to their wide operation bandwidth, immunity to electromagnetic interference (EMI), tunability for high measurement accuracy and inexpensive development costs. Magneto-optic current transformers (MOCT) are potential replacements for conventional current transformers due to the MOCT's almost linear response, accurate output and the absence of core saturation which is lacking in the latter. Rare earth element based garnets used to design the sensors in an MOCT still suffer from saturated response for high values of current, despite expensive development. Contemporary advancements in nanotechnology have been sought to tackle this issue to yield relatively inexpensive and accurate sensors. Optical glasses and polymers doped with nanoparticles and quantum dots have proven to be highly responsive and suitable as MO current sensors. This research describes an effort to use an optical quality polymer, phenyl methyl vinyl siloxane doped with hematite and maghemite nanoparticles for the development of an optical current sensor with enhanced MO sensitivity or Verdet Constant by orienting the doped nanoparticles using externally applied DC electric fields. E-field based orientation of nanoparticles in a polymer creates dipole moments on the nanoparticles, producing a torque that tends to align them with the applied field. From a boundary value formulation of this torque, it was observed that optimal orientation could be achieved when the nanoparticle major axis is at 45° to the applied electric fields. The samples of doped polymers were experimentally characterized using small angle x-ray scattering, electron microscopy, Faraday rotation and evaluation of Verdet constant. The Verdet constants were measured with respect to the applied electric field strength and field duration, wavelength based dispersion of Verdet constant and effect of surface plasmons in enhancing magneto-optic capabilities.;The results demonstrated an improvement in the SNR of the sensors, showed a linear increase in Faraday rotation angle due to applied e-fields and enhancements in Verdet constants from 1.419 °/T-cm for the undoped polymer to 2.9 °/T-cm and 4 °/T-cm for the e-field oriented hematite and maghemite doped PMVS samples. The effect of applied e-field durations and surface plasmons also showed enhancement in the magneto-optic sensitivities. Future studies may include development of other magneto-optical nanocomposites with tuned morphologies and the effect of AC electric fields on those materials to build highly enhanced MO current sensors.