Nowadays, the anti-reflective (AR) structures are essential in many applications like display screens, photovoltaic structures and light detection and ranging. Traditionally, the AR surfaces are almost multilayer (ML) structures to minimize the reflection value by producing the destructive interference of reflected light beams at the layers' interfaces. In the new and advanced AR surfaces, nanostructures (NS) are proposed and used for minimizing the reflection. In this paper, we propose a temperature-switchable AR-ML-NS, based on vanadium dioxide (VO2) phase transition from semiconductor to metallic state around the critical temperature of 68 degrees C. Here, a pyramidal NS of VO2 is considered on top surface of a ML which minimizes the light reflection of the structure. While some AR structures may work in some restricted light wavelengths, here our proposed structure's AR wavelength region can be tuned between the visible and near-infrared (NIR) region through the thermal phase transition of VO2. VO2 phase control leads to a temperature-switchable AR structure, which is of great importance for investigating different switchable AR structures.

Nowadays, controlling the light reflection and transmission by metasurface nanostructures opens pathways for efficient energy harvesting in nanophotonics and optoelectronic devices. This paper demonstrates a metasurface broadband absorber in the visible wavelength region of 400–800 nm using two-dimensional titanium carbide (Ti3C2Tx) MXene. A high average absorption of 97.85

The thermally triggered semiconductor-metal phase transition of vanadium dioxide (VO2) is a frequent subject in the study of nanostructure responses due to the high speed of the transition. Here we report on the molecular energy transfer near a hybrid VO2@Au nanoshell during the VO2 phase transition when induced by a continuous-wave (CW) laser. The presence of VO2 causes a bistable and reversible change in the optical response of the nanoshell through the thermo-optical process at the resonance wavelength of the VO2@Au nanoshell. This behavior is achieved by controlling the laser intensity during the heating and cooling processes. In this paper we couple the thermodynamics with the Forster-Dexter theory of energy transfer between molecules which is generalized to use a nearby VO2@Au nanoshell. The bistable and reversible change in the response of the nanoshell causes the molecular energy transfer in the same manner over an intensity range of 1.52 (GW/m(2)). This work also provides general guidelines for designing switchable surface plasmon based biosensors, switchable molecular junction devices and switching the energy exchange between proteins.

Recently, interest in the use of hot electron photodetectors (HEPDs) for energy harvesting has increased. In this paper, we introduce a switchable structure consisting of an absorber and metal/semiconductor Schottky-junction HEPD that incorporates a phase change material in the design. The structure is a purely planer configuration composed of a vanadium dioxide (VO 2 )/molybdenum disulfide (MoS 2 )/photonic crystal-distributed Bragg reflector (PC-DBR). VO 2 is a phase change material that exhibits a reversible semiconductor to metal phase transition at the critical temperature of 68 °C. The nanostructure response relies on the VO 2 phase transition under thermal heating. The transition of the VO 2 phase from the semiconductor to the metal phase causes the formation of the Schottky-junction between the VO 2 /MoS 2 interface, causing the structure to switch from the absorber to the hot electron photodetector in the near infrared region. In addition to, the switchable absorber–HEPD response; the absorption–photoresponsivity shows spectral tunability via the chosen thickness of the VO 2 and MoS 2 layers. This hybrid nanostructure is also sensitive to the light polarization state of both TE and TM modes. The proposed hybrid nanostructure is a promising candidate for switchable absorber–HEPD structures, with applications as switchable hot electron-based photovoltaic and sensing systems.

We theoretically investigate the bistable spontaneous emission behavior of a single emitter in the vicinity of a hybrid V O 2 –Au nanoshell. The hybrid nanoshell is illuminated by a continuous wave pump laser. The incident beam generates heat through light absorption and causes the V O 2 to undergo a phase change from semiconductor to metallic mode. Our calculation shows that for certain values, over a range of incident laser intensity [ 0.25 ( G W / m 2 ) < I < 0.84 ( G W / m 2 )], at the resonance wavelength of the V O 2 (semiconductor)–Au nanoshell ( λ = 630 n m ), there is a reasonable bistable contrast for the two spontaneous emission rate values: the radiative and nonradiative decay rates. Our results provide important general guidelines for enabling platforms for optical switching sources and tunable sensors.