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Light is an electromagnetic wave composed of oscillating electric and magnetic fields. In light-matter interactions at terahertz or even optical frequencies, the magnetic component of light generally plays a negligible role. For instance, when we "see" or detect light, only its electric field is perceived; we are practically blind to its magnetic component. This talk deals with exceptions to this rule by considering two examples that involve a sizeable magnetic coupling at highest frequencies. First, we make use of an artificial nano-structure to probe the magnetic component of light inside a waveguide. The probe can be pictured as a slotted hollow metal cylinder with sub-wavelength linear dimensions. It transforms part of the magnetic field components into an electric field, which is then detected. This approach allows for the mapping of magnetic fields at telecom frequencies around 200THz with a resolution of ~200nm [1]. Second, we use sub-picosecond magnetic pulses to launch and stop a terahertz spin precession in the antiferromagnet NiO. Here, the enhanced Zeeman coupling between spins and the driving magnetic pulse at the spin-wave resonance of 1THz is exploited. In contrast to stimulated Raman scattering, this scheme allows for an ultrafast spin control without using spin-orbit coupling and with minimum impact on other degrees of freedom of the solid [2]. References [1] M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, Science 326, 550 (2009). [2] T. Kampfrath, A. Sell, G. Klatt, A. Pashkin, S. Mährlein, T. Dekorsy, M. Wolf, M. Fiebig, A. Leitenstorfer, and R. Huber, (submitted). |