Nonlinear optics with quantum-engineered intersubband metamaterials

Abstract

Intersubband transitions in n-doped semiconductor heterostructures provide the possibility to quantum engineer one of the largest known nonlinear optical responses in condensed matter systems, limited however to electric field polarized normal to the semiconductor layers. Here we show that by coupling of electromagnetic modes in plasmonic metasurfaces with quantum-engineered intersubband transitions in semiconductor heterostructures one can create ultra-thin highlynonlinear metasurfaces for normal light incidence. Structures discussed here represent a novel kind of hybrid metalsemiconductor metamaterials in which exotic optical properties are produced by coupling electromagneticallyengineered modes in dielectric and plasmonic nanostructures with quantum-engineered intersubband transitions in semiconductor heterostructures. Record values of effective optical nonlinearities of over 400 nm/V are experimentally measured for metasurfaces optimized for efficient second harmonic generation at 9.7 μm pump wavelength under normal incidence.