Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode.

Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement.

High efficiency reflective waveplates in the midwave infrared.

We demonstrate a high efficiency reflective waveplate which exhibits incidence angle dependent phase shift tuning capabilities in the midwave infrared. Using Finite Difference Time Domain (FDTD) modeling, the phase shift and reflection efficiency are simulated for a variety of geometrical parameters, the results of which are then employed to optimize design. Devices were fabricated and both the polarization and efficiency characteristics were measured and compared to FDTD simulations showing excellent agreement.

All-semiconductor negative-index plasmonic absorbers.

We demonstrate epitaxially grown all-semiconductor thin-film midinfrared plasmonic absorbers and show that absorption in these structures is linked to the excitation of highly confined negative-index surface plasmon polaritons. Strong (>98%) absorption is experimentally observed, and the spectral position and intensity of the absorption resonances are studied by reflection and transmission spectroscopy. Numerical models as well as an analytical description of the excited guided modes in our structures are presented, showing agreement with experiment.

Epsilon-near-zero strong coupling in metamaterial-semiconductor hybrid structures.

We present a new type of electrically tunable strong coupling between planar metamaterials and epsilon-near-zero modes that exist in a doped semiconductor nanolayer. The use of doped semiconductors makes this strong coupling tunable over a wide range of wavelengths through the use of different doping densities. We also modulate this coupling by depleting the doped semiconductor layer electrically.

Highly directional thermal emission from two-dimensional silicon structures.

We simulate, fabricate, and characterize near perfectly absorbing two-dimensional grating structures in the thermal infrared using heavily doped silicon (HdSi) that supports long wave infrared surface plasmon polaritons (LWIR SPP's). The devices were designed and optimized using both finite difference time domain (FDTD) and rigorous coupled wave analysis (RCWA) simulation techniques to satisfy stringent requirements for thermal management applications requiring high thermal radiation absorption over a narrow angular range and low visible radiation absorption over a broad angular range. After optimization and fabrication, characterization was performed using reflection spectroscopy and normal incidence emissivity measurements.