The Magneto-optical Coupling With The Saint-Venant Principle Of Layered Composites

More than100years have passed since the magneto-birefringence (MBR) effect was found in gas and liquid. Later, MBR effect was also found in some semiconductors at low temperature and strong magnetic field. But all of those materials were not utilized in reality due to inconvenience. So it is meaningful to seek solids that can show MBR effect at room temperature and low magnetic field. Recently laminate magneto-electric composites have been developed rapidly, which brings inspiration to fabricate laminate magneto-optical composites.In this paper, combining magnetostrictive material with elasto-optical medium, laminate magneto-optical composites were suggested and fabricated, which can show great MBR effect at room temperature. The MBR effect is based upon the product effect of magnetostriction and stress-birefringence. It provides a new idea to develop magneto-optical materials with high performance.Ferroalloy of rare-earth terbium dysprosium iron (TDF) and polycarbonate were selected as magnetostrictive phase material and elasto-optical phase material respectively. First, the properties of each phase materials were characterised and the relevant parameters were measured. Then, the magnetooptical effects of the laminate composites were observed. Second, combined the constitutive equation of magnetostrictive phase with the stress-strain equation of the elasto-optical phase, the formulation of the normalized intensity of emergent light (NIEL) was derived. Analysis showed that the theoretical results were in agreement with the experimental ones. Third, starting from the basic equations of elasticity, a elastic mechanical model was proposed and a set of appropriate boundary conditions were chosen to analyze the effect of Saint-Venant’s principle on the stress distribution in the elastic material under the condition of interfacial elastic coupling, then the formulation of NIEL was modified. At last, the applications of the laminate composites were explored, used the laminate composites as the magneto-optical modulator to implement modulation of low frequency signal (not higher than5kHz) successfully, and then used them as the core component of a micro-displacement measuring system. Experiments showed that the precision of the system can reach1μm.