Electronic Metamaterials with Tunable Second-order Optical Nonlinearities

Abstract

The ability to engineer metamaterials with tunable nonlinear optical properties is crucial for nonlinear optics. Traditionally, metals have been employed to enhance nonlinear optical interactions through field localization. Here, inspired by the electronic properties of materials, we introduce and demonstrate experimentally an asymmetric metal-semiconductor-metal (MSM) metamaterial that exhibits a large and electronically tunable effective second-order optical susceptibility (χ(2)). The induced χ(2) originates from the interaction between the third-order optical susceptibility of the semiconductor (χ(3)) with the engineered internal electric field resulting from the two metals possessing dissimilar work function at its interfaces. We demonstrate a five times larger second-harmonic intensity from the MSM metamaterial, compared to contributions from its constituents with electrically tunable nonlinear coefficient ranging from 2.8 to 15.6 pm/V. Spatial patterning of one of the metals on the semiconductor demonstrates tunable nonlinear diffraction, paving the way for all-optical spatial signal processing with space-invariant and -variant nonlinear impulse response.

On the observation of dispersion in tunable second-order nonlinearities of silicon-rich nitride thin films

“…1b. The revised Maker fringes analysis was then employed to carry out the tensorial analysis of the second-order nonlinearity [7,[11][12][13]. As is evident from the figure, the generated second-harmonic signal from the film with the highest silicon content (S3) is up to 20 times larger compared to that generated from the film with a stoichiometric composition (S1).…”

Linear electro-optic effect in ferroelectric HfO2-based epitaxial thin films

“…the Pockels effect, due to centrosymmetry unless they are under high gradient stress. [13][14][15][16] However, in 2011, Böscke et al reported that some doped HfO 2 -based thin films have noncentrosymmetric lattices and thus show ferroelectricity. 17) In addition, it was found that their ferroelectricity is stable over a broad range of film thicknesses, normally less than 100 nm.…”