Electrically tunable nonlinear polaritonic metasurface

Nonlinear polaritonic metasurfaces created by the coupling of intersubband nonlinearities in semiconductor heterostructures with optical modes in nanoresonators have recently demonstrated efficient frequency mixings at very low pumping intensities of the order of a few tens of kilowatts per square centimetre. In these subwavelength structures, the efficiency, spectral bandwidth and local nonlinear phase of wave mixing do not depend on phase matching but only on the nonlinear response of the constituent meta-atoms. We exploit this property to demonstrate an electrically tunable nonlinear metasurface that combines a plasmonic nanocavity and a quantum-engineered semiconductor heterostructure, in which the magnitude and phase of the local nonlinear responses are controlled by a bias voltage through the quantum-confined Stark effect. We demonstrate spectral tuning, dynamic intensity modulation and dynamic beam manipulation for second-harmonic generation. Our work suggests a route for electrically reconfigurable flat nonlinear optical elements with versatile functionalities.