Meta-Mirror with Giant Nonlinear Response

Our group, in collaboration with the group of M. Belkin in our department and TU Munich, has created a new nonlinear metasurface, or meta mirror with giant nonlinear response, that could one day enable the miniaturization of laser systems. The metamaterial has a nonlinear optical response a million times as strong as traditional nonlinear materials, and demonstrated frequency conversion in films 100 times as thin as human hair using light intensity comparable with that of a laser pointer.

Nonlinear optical effects are widely used by engineers and scientists to generate new light frequencies, perform laser diagnostics and advance quantum computing. Due to the small extent of optical nonlinearity in naturally occurring materials, high light intensities and long propagation distances in nonlinear crystals are typically required to produce detectable nonlinear optical effects.

This work opens a new paradigm in nonlinear optics by exploiting the unique combination of exotic wave interaction in metamaterials and of quantum engineering in semiconductors. The metamaterial at the basis of this unusual optical response consists of a sequence of thin layers made of indium, gallium and arsenic on the one hand and aluminum, indium and arsenic on the other. Our team stacked approximately 100 of these layers, each between 1 nanometer and 12 nanometers thick, and sandwiched them between a layer of gold at the bottom and a pattern of asymmetric gold nanocrosses on top. The thin semiconductor layers confine electrons into desired quantum states, and gold nanocrosses resonate at input and output frequencies to enable the the nonlinear optical response of the mirror. The realized mirror converts light from a wavelength of 8 micrometers to 4 micrometers; however, the structures can be tailored to work at other wavelengths, from near-infrared to mid-infrared to terahertz.

Alongside frequency doubling, our structures may be designed for sum- or difference-frequency generation, as well as a variety of four-wave mixing processes, and our work unveils a pathway towards the development of ultrathin, highly nonlinear optical elements for efficient frequency conversion that will operate without stringent phase-matching constraints of bulk nonlinear crystals.

To learn more:

J. Lee, M. Tymchenko, C. Argyropoulos, P. Y. Chen, F. Lu, F. Demmerle, G. Boehm, M. C. Amann, A. Alù, and M. A. Belkin, “Giant Nonlinear Response from Plasmonic Metasurfaces Coupled to Intersubband Transitions,” Nature, Vol. 511, No. 7507, pp. 65-69, July 2, 2014. (web)

S. Zaragoza, “Researchers Invent ‘Meta Mirror’ to Help Advance Nonlinear Optical Systems”, UT Austin Press Release, July 2, 2014.”Highly non-linear metamaterials for laser technology – a million times better”, Nanowerk.com, July 2, 2014