Probing Graphene χ((2)) Using a Gold Photon Sieve

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Graphene exhibits unique optical properties, including nonlinear optical activity.
• Photon sieves, subwavelength nanohole arrays, offer efficient light manipulation.
• Combining graphene with plasmonic nanostructures can enhance optical responses.

Purpose of the Study:

• To determine the nonlinear second harmonic optical activity of graphene.
• To investigate the role of a gold photon sieve in enhancing second harmonic generation (SHG).
• To develop a method for constraining graphene's second-order nonlinear susceptibility (χ((2))) elements.

Main Methods:

• Fabrication of a graphene-coated gold photon sieve on a glass substrate.
• Measurement of nonlinear second harmonic generation (SHG) for varying polarizations.
• Utilizing semianalytical computations to complement experimental data.

Main Results:

• The graphene-coated photon sieve exhibited SHG intensity at least two orders of magnitude higher than a bare gold layer.
• The plasmonic effect of the photon sieve contributed one order of magnitude enhancement.
• The remaining enhancement was attributed to the graphene layer itself, enabling precise determination of χ((2)) elements.

Conclusions:

• The study presents an original method to constrain graphene's second-order nonlinear susceptibility (χ((2))) elements using SHG.
• Obtained values for graphene nonlinear coefficients are |d31 + d33| ≤ 8.1 × 10(3) pm(2)/V and |d15| ≤ 1.4 × 10(6) pm(2)/V.
• This technique is applicable to other two-dimensional materials integrated with plasmonic structures.