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In the paper, a type of phase change metamaterial for tunable infrared stealth and camouflage is proposed and numerically studied. The metamaterial combines high temperature resistant metal Mo with phase-changing material GST and can be switched between the infrared “stealthy” and “non-stealthy” states through the phase change process of the GST. At the amorphous state of GST, there is a high absorption peak at the atmospheric absorption spectral range, which can achieve infrared stealth in the atmospheric window together with good radiative heat dissipation in the non-atmospheric window. While at the crystalline state of GST, the absorption peak becomes broader and exhibits high absorption in the long-wave infrared atmospheric window, leading to a “non-stealthy” state. The relationship between the infrared stealth performance of the structure with the polarization and incident angle of the incident light is also studied in detail. The proposed infrared stealth metamaterial employs a simple multilayer structure and could be fabricated in large scale. Our work will promote the research of dynamically tunable, large scale phase change metamaterials for infrared stealth as well as energy and other applications.

We theoretically present a high-efficiency switchable reflective terahertz polarization converter composed of a periodic array of rectangular-shaped metal-dielectric-graphene sandwich structure on a dielectric substrate supported by a thick metallic film. Graphene sheet together with the rectangular-shaped metal patch provides tunable anisotropic hybrid magnetic plasmon resonance to obtain tunable phase delay of 90° and 180°, corresponding to a quarter-wave plate (QWP) and half-wave plate (HWP), respectively. Results of numerical simulations indicate that the proposed structure can switch functions between a QWP and HWP at a certain frequency simply by adjusting the Fermi energy of graphene. Both the QWP and HWP have high energy conversion efficiency, respectively 83% and 90% at 15.96THz, and high polarization conversion ratio closed to 1.

Enhance light absorption in two-dimensional (2D) materials are of great importance for the development of many optoelectronic devices such as photodetectors, modulators and thermal emitters. In this paper, a resonant nanostructure based on subwavelength gratings of monolayer molybdenum disulphide (MoS

The p-n junction is one of the most important basic structures in the semiconductor field, with vast applications in photodetectors, transistors, light emitting diodes, and solar cells. Here, an new in-plane intramolecular WSe2 p-n junction is realized, in which the n-type region and p-type region are chemically doped by polyethyleneimine and electrically doped by the back-gate, respectively. An ideal factor of 1.66 is achieved, proving the high quality of the p-n junction realized by this method. As a photovoltaic detector, the device possesses a responsivity of 80 mAW-1 (≈20% external quantum efficiency), a specific detectivity of over 1011 Jones and fast response features (200 μs rising time and 16 μs falling time) at zero bias, simultaneously. Moreover, a large open-circuit voltage of 0.38 V and an external power conversion efficiency of ≈1.4% realized by the device also promises its potential in microcell applications.

We theoretically and numerically study visible to near-infrared coherent perfect absorption of ultra-thin materials with a thickness of one-atom to about ten nanometers such as graphene and meta-films.

We show theoretically and numerically that artificially engineered nanometer metal/semiconductor composite films provide a versatile platform for coherent perfect absorption (CPA) of light. By engineering the effective permittivity of the composite nanofilms and tailoring the angle of incidence, CPA can be realized freely in a wide range from visible to infrared. A proof-of-principle demonstration using Au/Ge composite nanofilms is implemented. The results show that CPA can be achieved at any wavelength within the studied range. By contrast, CPA cannot be achieved for single layer of Au or Ge with the same thickness. The simple approach to obtain CPA provides a great deal of flexibility in selecting absorption materials, preparation technology, illumination configuration, and wavelength range.

Engineering light absorption in graphene has been the focus of intensive research in the past few years. In this paper, we show numerically that coherent perfect absorption can be realized in monolayer graphene in the near infrared range by harnessing resonances of dielectric nanostructures. The asymmetry of the structure results in different optical responses for light illuminated from the top side and the substrate side and enables asymmetric interferometric light-light control. The absorbed and scattered light exhibit interesting nonlinear behavior, allowing switching a strong optical signal output with a weak light. This work may stimulate potential applications including new types of sensors, coherent photodetectors and all-optical logical devices.

Electrically biased graphene has been studied experimentally as a novel emitter of thermal radiation. However, there is as yet no systematic theory that quantifies the thermal radiation, heat transfer, and electrical properties of electrically biased graphene. To study the thermal transport properties systematically, a heat conduction model is developed and exploited in this paper. The temperature distribution and heat conduction coefficient of graphene under different bias voltages are obtained using our theoretical model. The I–V curve and the relationship between the radiant power and input voltage of graphene are then obtained. This work could help design a novel efficient wavelength-adjustable thermal radiation source.