Hyperspectral Molecular Orientation Mapping in Metamaterials

The four polarisation method is adopted for measurement of molecular orientation in dielectric nanolayers of metal-insulator-metal (MIM) metamaterials composed of gold nanodisks on polyimide and gold films. Hyperspectral mapping at the chemical finger printing spectral range of 4-20 mu m was carried out for MIM patterns of 1-2.5 mu m period (sub-wavelength). Overlay images taken at 0, pi/4, pi/2, 3 pi/4 orientation angles and subsequent baseline compensation are shown to be critically important for the interpretation of chemical mapping results and reduction of spurious artefacts. Light field enhancement in the 60-nm-thick polyimide (I in MIM) was responsible for strong absorption at the characteristic polyimide bands. Strong absorbance A at narrow IR bands can be used as a thermal emitter (emittance E = 1 - R), where R is the reflectance and A = 1 - R - T, where for optically thick samples the transmittance is T = 0.

Automated summary

The study utilized a four polarisation method to measure molecular orientation in metal-insulator-metal (MIM) metamaterials, and conducted hyperspectral mapping in the chemical finger printing spectral range. Overlay images and subsequent baseline compensation were crucial for interpreting chemical mapping results and reducing spurious artefacts. The light field enhancement in the polyimide layer within the MIM structure led to strong absorption at characteristic polyimide bands.