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The authors experimentally demonstrate a magnetically tunable optical negative refraction (NR) in nematic liquid crystals (NLCs), arising from the variation of optical anisotropy in the NLCs induced by external magnetic field. By measuring the refraction angle of the transmitted beam through the prism-shaped NLC device, the tunable extraordinary refractions for different molecular directions using magnetic field are observed. It shows that NR in NLCs occurs at certain inclination angle and can be tuned by changing the direction of the magnetic field, which is in good agreement with the established theory. [ABSTRACT FROM AUTHOR]

An electrically tunable negative permeability metamaterial consisting of a periodic array of split ring resonators infiltrated with nematic liquid crystals is demonstrated. It shows that the transmitted resonance dip of the metamaterial can be continuously and reversibly adjusted by an applied electric field, and the maximum shift is about 210 MHz with respect to the resonance frequency around 11.08 GHz. Numerical simulation shows that the permeability is negative near the resonance frequency, and the frequency range with negative permeability can be dynamically adjusted and widened by about 200 MHz by the electric field. It provides a convenient means to design adaptive metamaterials. [ABSTRACT FROM AUTHOR]