Micro-/Nanotechnology - Optics

Broadband Plasmonic Response of Semiconductor Disks

The plasmonic behavior of touching semiconductor disks shows a highly efficient broadband response in the terahertz regime as predicted by theoretical studies.

Recently, there has been a strong interest in tailoring of the spectral characteristics of localized surface plasmons resonances due to potential applications in sensing, imaging, and photovoltaics. Fano-like resonances can be used to control the optical properties only within an extremely narrow frequency window. In contrast, the concept of transformation optics has been proposed to transfer the broad bandwidth behavior of plasmonic waveguides to nanoantennas using geometric singularities. Although efforts have been made to reduce the geometric requirements for these nanostructures, theoretical designs are still largely beyond current nanofabrication capabilities.

For the first time Stefan Maier, Steven Hanham (Imperial College London) and co-workers were able to realize such a broadband plasmonic response experimentally by employing a simple strategy. By replacing the usual plasmonic materials with a semiconductor, indium antimonide (InSb), the wavelength of operation shifts from the optical to the terahertz regime. This shift in length scale greatly facilitates the device fabrication. They could show that a touching disk geometry results in a broadband absorption response consistent with the theoretical predictions of transformation optics for gold nanostructures at visible frequencies.

This study proves that semiconductors are extremely useful materials to test plasmonic devices whose fabrication requirements are still out of reach in the optical regime. The presented efficient broadband  terahertz harvesting properties of touching InSb disks will definitely find applications in technological areas such as spectroscopy, biosensing, and security.

The research was reported in Advanced Optical Materials, a new section in Advanced Materials dedicated to breakthrough discoveries and fundamental research in photonics, plasmonics, metamaterials, and more, covering all aspects of light-matter interactions. To get Advanced Optical Materials email alerts, click here.


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