Magneto-electric Rectification: A New Universal Second-order Nonlinearity

Ultrafast magneto-electric (M-E) interactions have attracted a great deal of attention because they potentially enable novel ultrafast all-optical switching, sensing technology, and terahertz emission. Most M-E effects have been observed in multiferroic materials or in metamaterials. Very interestingly, it has been reported recently that magnetic properties of homogeneous dielectric media can be controlled by optical nonlinearities driven jointly by electric and magnetic field components of light. Through the action of optical torque at the atomic scale, magneto-electric (M-E) interactions drive the bound electrons to move in curved trajectories even under non-relativistic conditions, breaking temporal and spatial inversion symmetry. As a result, several unforeseen physical phenomena take place, such as longitudinally polarized second harmonic radiation, induced transverse magnetization at the optical frequency, and forward optical rectification. Interestingly, no special crystal symmetry is necessary for M-E rectification. In this work, we report the first observation of the transient forward magneto-electric rectification in a pentacene thin-film using an electric-field-induced second harmonic generation (EFISH) technique.