This article is a review of the advances and progresses in the field of heat cloaking which is being realized using metamaterials. Heat cloaking has been a particularly important subject of study due to its potential multidimensional applications. The process which manipulates the heat flux in such a way that it can neither enter into the cloaked region nor be distorted outside is called thermal cloaking. Transformation optics has made the hitherto inconceivable advancements in the field of thermodynamics possible with the remarkable assistance of metamaterials. In this article we present a review of the work done in the field of heat cloaking, its progress and outlook. We discuss the theoretical and experimental studies, models, design managements, implementations and behaviors of thermal invisibility cloaking and related devices. This review is intended to help further develop practical and applicable concepts, examine fabrication techniques for a variety of different invisibility cloaking devices and systems, and to pave a way for the new avenues leading to new future technologies.

We propose a high-efficiency plasmonic metamaterial selective emitter based on a tungsten (W) spherical core-shell nanostructure for potential applications in planar solar thermophotovoltaics. This structure consists of silicon dioxide (SiO 2 )-coated W nanospheres periodically distributed on a W substrate and a thin W layer deposited on top. Using a new definition of spectral efficiency, numerical optimization is performed and its optical behaviors are systematically investigated. The numerical results show that our selective emitter has a high emissivity in the short wavelength range below the wavelength corresponding to the bandgap of the back photovoltaic cell and a low emissivity in the long wavelength range beyond it. Its spectral efficiency of 0.39 is much higher than those of other cases without the top W cover layer or the W nanospheres. Such excellent emission selectivity is attributed to the strong photonic interaction within the gaps between the adjacent core-shell nanospheres, the tightly confined optical fields in both the Ω-shaped W-SiO 2 -W nanocavities, and the bottom nanocavities formed by the W nanospheres and the W substrate. It is also very tolerant toward the thicknesses of the SiO 2 layer and the top W cover layer.

We propose a polarization-insensitive and high-efficiency plasmonic silicon Schottky diode for detection of sub-bandgap photons in the optical communication wavelength range through internal photoemission. Our photodiode is based on a hybrid plasmonic silicon waveguide. It has a gold film covering both the top and the sidewalls of a dielectric silicon waveguide with the Schottky contact formed at the gold-silicon interface. An extensive physical model is presented in detail and applied to calculate and analyze the performance of our detector. By comparison with a diode with only top contact of gold, the polarization sensitivity of responsivity is greatly minimized in our photodetector with sidewall coverage of gold.Much higher responsivities for both polarizations are also achieved in a very broad wavelength range of 1.2-1.5 μm. Moreover, the Schottky contact is only 4 μm long, leading to a very small dark current. Our design is very promising for practical applications in high-density silicon photonic integration.Internal photoemission (IPE) is an intrinsic property of a Schottky diode, occurring at a metal-semiconductor interface [1]. In IPE, three processes are involved.Firstly, an electron (hole) in the metal is excited to a higher level after absorbing a photon, becoming a hot electron (hot hole). Secondly, the hot carrier (electron or hole) travels to the metal-semiconductor interface. During its travel, the hot carrier may lose some energy due to scattering by cold carriers or by thermal relaxation. Finally, upon