Higher-Order Nonlinear Chirality In AlGaAs Metasurfaces

High harmonics generation finds an increasing number of applications: it is the only source of atto-second pulses - currently shortest accessible time intervals. It is also the only table-top sources of light in extreme ultraviolet and soft X-ray spectral regions. Chiral high-harmonics generation established itself as a tool to study the ultrafast response of chiral properties of matter as well as to amplify chiro-optical effects. Traditionally, chiral high harmonics were associated with gases of enantiomer molecules [1] or, more recently, solids with helicity in their crystalline structure [2]. Here we bring the concept of chiral high-harmonics generation to nanophotonics, specifically to metasurfaces consisting of arrays of nanoresonators. The generation of high harmonics benefits from the engineered resonant response of our nanostructures [3,4]. Our system is achiral at the material level as well as at the level of an individual nanoresonator. Chirality rises and falls in a controlled manner via an interplay of the nanoresonators symmetry and the symmetry of the metasurface lattice.