title: Continuous control of the nonlinearity phase for harmonic generations.
abstract: 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.
authors: 1] School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK [2] Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
authors: Guixin
authors: G
authors: Li
authors: 1] School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK [2] Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
authors: Shumei
authors: S
authors: Chen
authors: 1] Department of Physics, University of Paderborn, Warburger Straße 100 D-33098 Paderborn, Germany [2] Department of Industrial Physics and Medical Instrumentation, King Mongkut's University of Technology North Bangkok, 1518 Pibulsongkram Road, Bangkok 10800, Thailand [3] Lasers and Optics Research Group, King Mongkut's University of Technology North Bangkok, 1518 Pibulsongkram Road Bangkok 10800, Thailand.
authors: Nitipat
authors: N
authors: Pholchai
authors: Department of Physics, University of Paderborn, Warburger Straße 100 D-33098 Paderborn, Germany.
authors: Bernhard
authors: B
authors: Reineke
authors: Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong.
authors: Polis Wing Han
authors: PW
authors: Wong
authors: 1] Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong [2] State Key Laboratory of Millimeter Waves, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong.
authors: Edwin Yue Bun
authors: EY
authors: Pun
authors: Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
authors: Kok Wai
authors: KW
authors: Cheah
authors: Department of Physics, University of Paderborn, Warburger Straße 100 D-33098 Paderborn, Germany.
authors: Thomas
authors: T
authors: Zentgraf
authors: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors: Shuang
authors: S
authors: Zhang