Giant Efficiency of Visible Second-Harmonic Light by an All-Dielectric Multiple-Quantum-Well Metasurface

Developing a high-efficiency coherent nonlinear light source is a critical step for photonic quantum technologies in signal processing, imaging, and switching. A promising approach is second-harmonic generation (SHG) via intersub-band transitions in a semiconductor quantum-well structure with a specific plasmon resonant mode of metal structures. There are, however, two significant challenges with this approach. First, limited by the conduction-band offset, the SHG wavelength based on intersub-band transitions is unlikely to extend into the visible region. Second, the high dissipative losses of plasmonic metal nanostructures could severely limit their applicability. Here we demonstrate an alternative configuration using interband excitonic transitions in an all-dielectric multiple-quantum-well metasurface capable of achieving high SHG conversion efficiency in the visible region. Taking advantage of the magnetic resonance of the multiple-quantum-well metasurface, the tightly concentrated optical field that is induced in the metasurface is responsible for boosting the conversion efficiency to about 2 x 10(-7) . This demonstration opens a viable path toward a coherent light source using SHG that is extended to the visible region and beyond with high conversion efficiency, enabling nanophotonic quantum-information applications.