The absorption behaviors of a 35 nm-vanadium dioxide (VO ₂ ) layer grown on top of a 1D photonic crystal (Sio ₂ /Si) ¹⁰ are investigated theoretically in the near infrared spectral range. VO ₂ has an insulator-to-metal phase transition around a critical temperature of 68 °C. The filling fraction (f) is defined as the portion of the VO ₂ in the metallic phase—i.e. f = 0 and f = 1 for semiconductor and metal phase, respectively, and 0 < f < 1 during intermediate stages of the transition. Through the transfer matrix method, the influence of the filling fraction on the absorption of the structure has been inspected. It is shown that near-unity absorption can be achieved through VO ₂ semiconductor-to-metal phase transition. Moreover, the tunability of absorption at oblique incidence reveals higher values of absorption peaks in the metallic phase of VO ₂ than the semiconducting one at each angle of incidence. In addition, there is sensitivity to the state of polarization, so that the absorption peaks for TE mode are higher than the TM case. Finally, adjusting the thickness of the VO ₂ layer indicates the possibility of achieving nearly complete absorption in both the semiconductor and metal phases. We believe that these properties make our structure a suitable basis for designing VO ₂ -based absorbers.

We theoretically investigate the absorption bistability behavior of a nanostructure consisting of a vanadium dioxide (VO₂) layer grown on top of a one-dimensional photonic crystal. The proposed structure is illuminated by a continuous wave pump laser, resulting in heat generation within the VO₂ layer, and a subsequent phase transition which drastically affects the optical response of the nanostructure. We solve a multiphysics problem containing electromagnetism and thermodynamics in order to show that the optically induced transitions in the VO₂ layer can lead to a bistable response in the nanostructure over some ranges of incident intensities during the VO₂ heating and cooling modes. Interestingly, when the laser is well set up for an appropriate wavelength, the high contrast of two absorption values in the hysteresis loop indicates bistability and the possibility of achieving near-unity absorption. For example, considering λ = 1025 nm, we get bistability over 1.182 W/cm² < I < 1.457 W/cm² which leads to absorption values of about 0.47 and 0.999 for the heating and cooling modes, respectively. The corresponding heat generation for I = 1.3 W/cm² is 2.41 × 10⁵ W/cm³ and 3.52 × 10⁵ W/cm³, respectively. These properties make our structure promising for designing tunable VO₂-based absorbers and optical switching devices.

We systematically investigate the optical response of a semiconductor quantum dot (QD) hybridized with a vanadium dioxide nanoparticle (VO ₂ NP) in the infrared (IR) region. The VO ₂ NP features a semiconductor to metal phase change characteristic below and above a critical temperature that leads to an abrupt change in the particle’s optical properties. This feature means that the QD-VO ₂ NP hybrid system can support the coherent coupling of exciton-polaritons and exciton-plasmon polaritons in the semiconductor and metal phases of the VO ₂ NP, respectively. In our calculations, the VO ₂ NP phase transition is modelled with a filling fraction ( f ), representing the fraction of the VO ₂ NP in the metallic phase. The phase transition is driven by the hybrid system’s interaction with a continuous wave (CW) IR laser field. In this paper, we show how control over the filling fraction results in the enhancement or suppression of the QD’s linear absorption. These variations in the QD absorption is due to dramatic changes in the effective local field experienced by the QD and the non-radiative energy transfer from the QD to the VO ₂ NP. The presented results have the potential to be applied to the design of thermal sensors at the nanoscale.

Chalcogenide phase-change materials (PCMs) offer a unique feature that can be used to dynamically control the response of the photonic devices and achieve fast, nonvolatile, reversible, multilevel, and specific optical modulation. The phase-change material ${\rm Ge} _{2}{\rm Sb}_2{\rm Se} _{4}{\rm Te}_1$ (GSST) has recently received a lot of attention due to the large index contrast between its amorphous and crystalline states with significantly low optical loss in the optical to near-IR spectrum. In this paper, we propose a tunable and reconfigurable hybrid PCM plasmonic nanostructure composed of a spacer layer of GSST sandwiched between a Ag back reflector and a 1D Ag Fabry–Perot grating structure. We use the finite element method (FEM) to numerically calculate the light absorption, absorption contrast, and figure of merit of the plasmonic nanostructure for both the amorphous and crystalline state of the GSST. Our calculations show that with constant structural variation the observed multimode absorption is drastically modified when the GSST undergoes a phase change from the amorphous to the crystalline state. The absorption contrast spectrum, which is defined as the absorption difference between the amorphous and crystalline state of GSST, shows four extrema modes between 70% and 89%. The figure of merit spectrum shows two large values of 44.39 and 37.78 at the 1502 nm and 2063 nm wavelengths, respectively. We also address the observed modes in the absorption contrast spectrum through spatial representation of the enhanced electric field distribution at their corresponding wavelengths. We show how the phase change in the GSST spacer can control the coupling between the optical cavity modes and the Ag surface plasmon resonance modes in the cavities and GSST spacer strip boundaries. The findings in this paper may open new avenues toward the design of next-generation photonic systems such as thermal emission controllers, sensors, ranging holograms, modulators and optical detection devices.

In this paper, we investigate the thermodynamic properties of a highly reconfigurable and broadband perfect metamaterial absorber in the near-infrared region. Our model is a periodic nanostructure composed of an array of L-shaped hybrid gold and vanadium dioxide nanostructures on gold and glass substrates. The reconfigurability of the nanostructure is based on the metal–insulator transition of vanadium dioxide. The degree of reconfigurability depends on the temperature of the vanadium dioxide nanostructure. In order to study the photo-thermal effect on the reconfigurability of the nanostructure, we irradiate it with a time-dependent Gaussian pulse laser with a 1.5 ns pulse width. Our main purpose is twofold. On the one hand, we aim to investigate how the laser increases the temperature of the nanostructure, and on the other hand, we intend to explore whether the temperature modifies the absorption and reflection of the array. Our results reveal that the VO₂ fully transitions to its metallic phase when the fluence of the incident laser is adjusted to 17.8 mJ/cm².