Orientational optical nonlinearity of nematic liquid crystals integrated with THz metamaterials

Abstract

We report on orientational, optical nonlinearity of nematic liquid crystals (NLCs), observed when integrated with THz metallic metamaterial (MM) resonators. Our findings show that the bulk NLCs orientation breaks down close to the MM-NLC interface. The THz MMs exhibit extreme electric field ‘hotspots’, when on resonance, that strongly alter the NLCs local orientation. We model numerically the distribution of the refractive index of NLCs molecules close to the MM interface which demonstrates that the resonantly induced electric fields of the MMs are able to drive the birefringence of the NLC device. We experimentally verified our theoretical predictions with THz-Time Domain Spectroscopy (THz-TDS) in the 0.1-1.4 THz range and showed that, even a relatively thin layer of NLCs (20μm) integrated with MMs, can manipulate long wavelengths (such as 300 μm), beyond the limitations imposed by the NLC anisotropy.