Second and third-order giant non-linear processes in plasmonic metasurfaces

The performance of many applications in non-linear photonics, such as ultrafast sensing, wave generation, or imaging, has usually been hindered by the small response of conventional non-linear materials [see Boyd, R. Nonlinear Optics 3ed Academic Press (2008)]. Even though the advent of metamaterials has alleviated this situation, thanks to their ability to engineer bulk structures able to overcoming phase-mismatches [see A. Rose, et al. Opt. Mater. Express, 1, 1232 (2011)] or to increase the efficiency in non-linear processes [see C. Argyropoulus et al. Phys. Rev. B., 89, 235401 (2014)], their overall non-linear response is still limited. Recently, a new approach based on combining the field enhancement in plasmonic metasurfaces with the intersubband transitions found in engineered quantum-wells has demonstrated second-order susceptibilities orders of magnitude higher than any other nonlinear response measured in flat structures [see J. Lee et al, Nature. 511, 65 (2014)].