Kerr-nonlinearity-assisted NIR nonreciprocal absorption in a VO2-based core-shell composite integrated with 1D nonlinear multilayers.

We theoretically investigate the nonreciprocal optical response of a one-dimensional multilayer possessing nonlinear (NL) Kerr dielectrics hybridized with a VO2-based core-shell structure. As a consequence of parameter optimization, it is found that semiconductor-to-metallic reconfiguring of relatively thin VO2 nanoinclusions with a core-shell radius ratio of 0.95 is accompanied by enhanced multispectral near-infrared absorption of the system for both forward and backward incidences of light. However, increasing intensity of the incident wave bends the resonant wavelengths due to the NL response of Kerr dielectrics. When the incident light is well set up for an appropriate non-resonant wavelength, the absorption contrast between two directions of incidence enhances in some ranges of intensities due to the NL Kerr effect. There is also the possibility of reaching S-shaped bistable absorption. These features make the modeled system suitable for designing near-infrared absorptive diodes or isolators.

Tunable terahertz absorption in Si/SiO2-graphene multilayers: disorder and magneto-optical effects.

In this work we theoretically investigate the influence of disorder and external perpendicular magnetic field on terahertz (THz) absorption in graphene/SiC cap layers on top of one-dimensional photonic structures. We show that left-handed circularly polarized light absorption can be achieved up to 0.9 and even nearly perfect absorption at magnetic fields over 4 T. It is also demonstrated that multichannel absorption can be obtained, in a broad frequency range, by increasing the disorder strength in the layer thicknesses, outperforming the corresponding periodic structures. Altogether, our results reveal the potentialities of introducing disorder to not only enhance but also to tune absorption in photonic superlattices with graphene under the influence of an external magnetic field, allowing for applications such as THz circular polarization selective sensors and photodetectors.

Tunable multispectral near-infrared absorption with a phase transition of VO2 nanoparticles hybridized with 1D photonic crystals.

We theoretically demonstrate a switchable multichannel near-infrared absorber in a composite structure based on vanadium dioxide nanoparticles embedded between two and one-dimensional photonic crystal mirrors. A switching of absorption behavior is induced through the reversible semiconductor-to-metal phase transition of vanadium dioxide nanoparticles via its temperature-dependent permittivity-thermo-optical effect. This behavior leads to a multi-wavelength reconfigurable optical response of the proposed structure from poorly absorbing to highly absorbing. For example, there is the possibility of enhancement of absorption from ∼0.14 to ∼0.75 at normal incidence of light by increasing the temperature beyond the critical value of ∼341 K when the vanadium dioxide nanoparticles transform from a semiconducting state into a metallic one. These properties make the considered structure applicable for use in multiband absorbers, light detectors, and optical switching devices.

Magnetically tunable enhanced absorption of circularly polarized light in graphene-based 1D photonic crystals.

We theoretically investigate the magnetic-field-induced terahertz absorption enhancement of a graphene-based one-dimensional photonic crystal using the 4×4 transfer matrix method for the circular polarization of light. The results show that the magnetically tunable absorption of the structure depends on the circular polarization state, magnetic circular dichroism, and, interestingly, absorption behaviors of right-handed and left-handed circularly polarized light interchange by changing the direction of the magnetic field. These properties can be used to design the circular-polarization-based sensors.