Tunable infrared plasmonic absorption by metallic nanoparticles

We exploit unique infrared plasmonic absorption properties of gold (Au) nanoparticles in the range of 2.5 to 20 μm. Fabrication of Au nanoplasmon particles with variable nanometer (nm) scale size and thickness gave us full control of tuning the absorption wavelength in the above infrared (IR) spectral regions. We did not observe polarization dependence for square size plasmon particles. However, by using plateau crescent (metal crescent structure with flat instead of rounded side on the top) metal particles we observed significant polarization effects in IR absorption spectra. We observed that the position of the absorption peak has linear dependence on the size of nanoparticles, and the absorption quantity depends on the density of the nanoparticles per unit area. The proposed nanoplasmon structure can be used to improve the performance of detector and light emitting diode (LED) devices operating in the IR region.