  From the demonstration of saturable absorption by Vavilow and Levshin in
1926, and with invention of the laser, unavailability of strongly nonlinear
materials was a key obstacle for developing optical signal processing, in
particular in transparent telecommunication networks. Today, most advanced
photonic switching materials exploit gain dynamics and near-band and excitonic
effects in semiconductors, nonlinearities in organic media with
weakly-localized electrons and nonlinearities enhanced by hybridization with
metamaterials. Here we report on a new type of artificial nonlinearity that is
nano-opto-mechanical in nature. It was observed in an artificial metamaterial
array of plasmonic meta-molecules supported by a flexible nano-membrane. Here
nonlinearity is underpinned by the reversible reconfiguration of its structure
induced by light. In a film of only 100 nanometres thickness we demonstrated
modulation of light with light using milliwatt power telecom diode lasers.
