Giant nonlinear response from plasmonic metasurfaces coupled to intersubband transitions

• Published in: Nature (London) 2014-07, Vol.511 (7507), p.65-69
• Main Authors: Lee, Jongwon, Tymchenko, Mykhailo, Argyropoulos, Christos, Chen, Pai-Yen, Lu, Feng, Demmerle, Frederic, Boehm, Gerhard, Amann, Markus-Christian, Alù, Andrea, Belkin, Mikhail A.
• Format: Article
• Language: English
• Subjects: 140/125; 142/126; 147/135; 639/624/399/1015; 639/624/400/2797; 639/624/400/385; Asymmetry; Composite materials; Design; Electric properties; Humanities and Social Sciences; letter; Methods; Molecular beam epitaxy; multidisciplinary; Quantum wells; Science; Symmetry
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13455

Multiple-quantum-well semiconductors can provide one of the largest known nonlinear material responses, which is, however, geometrically limited to light beams polarized perpendicular to the semiconductor layers; by coupling a plasmonic metasurface to the semiconductor heterostructure, this limitation can be lifted, opening a new path towards ultrathin planarized components with large nonlinear response. A new angle on nonlinear optics Multiple-quantum-well semiconductor heterostructures have been engineered to generate useful nonlinear optical responses that far exceed those of traditional nonlinear optical materials. But their range of applicability is geometrically limited as they require that the incident light be polarized perpendicular to the semiconductor layers. Jongwon Lee et al . now show that, by coupling a plasmonic metasurface to the semiconductor heterostructure, this geometrical limitation can be removed, thereby lifting the orientation restrictions on the use of these nonlinear optical elements. Intersubband transitions in n-doped multi-quantum-well semiconductor heterostructures make it possible to engineer one of the largest known nonlinear optical responses in condensed matter systems—but this nonlinear response is limited to light with electric field polarized normal to the semiconductor layers 1 , 2 , 3 , 4 , 5 , 6 , 7 . In a different context, plasmonic metasurfaces (thin conductor–dielectric composite materials) have been proposed as a way of strongly enhancing light–matter interaction and realizing ultrathin planarized devices with exotic wave properties 8 , 9 , 10 , 11 . Here we propose and experimentally realize metasurfaces with a record-high nonlinear response based on the coupling of electromagnetic modes in plasmonic metasurfaces with quantum-engineered electronic intersubband transitions in semiconductor heterostructures. We show that it is possible to engineer almost any element of the nonlinear susceptibility tensor of these structures, and we experimentally verify this concept by realizing a 400-nm-thick metasurface with nonlinear susceptibility of greater than 5 × 10 4 picometres per volt for second harmonic generation at a wavelength of about 8 micrometres under normal incidence. This susceptibility is many orders of magnitude larger than any second-order nonlinear response in optical metasurfaces measured so far 12 , 13 , 14 , 15 . The proposed structures can act as ultrathin highly nonlinear optical elements that enabl