Department of Physics
The capability of locally engineering the nonlinear optical properties of media is crucial in nonlinear optics. Although poling is the most widely employed technique for achieving locally controlled nonlinearity, it leads only to a binary nonlinear state, which is equivalent to a discrete phase change of π in the nonlinear polarizability. Here, inspired by the concept of spin-rotation coupling, we experimentally demonstrate nonlinear metasurfaces with homogeneous linear optical properties but spatially varying effective nonlinear polarizability with continuously controllable phase. The continuous phase control over the local nonlinearity is demonstrated for second and third harmonic generation by using nonlinear metasurfaces consisting of nanoantennas of C3 and C4 rotational symmetries, respectively. The continuous phase engineering of the effective nonlinear polarizability enables complete control over the propagation of harmonic generation signals. Therefore, this method seamlessly combines the generation and manipulation of harmonic waves, paving the way for highly compact nonlinear nanophotonic devices.
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This work was partly supported by EPSRC (EP/J018473/1). T.Z. and S.Z. acknowledge financial support by the European Commission under the Marie Curie Career Integration Program. N.P., B.R. and T.Z. acknowledge the financial support by the DFG Research Center TRR142 ‘Tailored nonlinear photonics’. K.W.C. and E.Y.B.P. acknowledge the support by the Research Grant Council of Hong Kong under Projects HKUST2/CRF/11G and AoE/P-02/12. G.L. acknowledges support from the High Performance Cluster Computing Centre, Hong Kong Baptist University. S.Z. acknowledges financial support from the National Science Foundation of China (grant no. 61328503) and Leverhulme Trust (grant no. RPG-2012-674).
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Li, Guixin, Shumei Chen, Pholchai Nitipat, Bernhard Reineke, Polis Wing Han Wong, Edwin Yue Bun Pun, Kok Wai Cheah, Thomas Zentgraf, and Shuang Zhang. "Continuous control of the nonlinearity phase for harmonic generations." Nature Materials 14.6 (2015): 607-612.