Generally, the spontaneous emission rate of an emitter is computed via classical electromagnetic simulations, modelling the dipolar source as a point. The quantum and classical simulations usually give identical results, since the size of the quantum emitter (QE) is orders of magnitude smaller than the wavelength. However, close to nanophotonic structures sustaining strongly confined fields, such as graphene and other 2D materials, the approximation is not valid anymore: the dipolar transition is no longer dominant and can be surpassed by the rates of higher-order transitions i.e. transitions beyond the dipolar one, such as two-photon processes, electric and magnetic multipolar transitions. . . The determination of these rates requires the spatial variation of the Green’s function along the spatial extent of the QE, which is not easily accessed by conventional numerical solvers. Here, we compute the high-order transition rates of a hydrogen-like atom close to graphene nanoislands (triangle and crescent geometries), by developing a method valid for any material of any shape, and show, as an example, quadrupolar transition rates becoming 100 times larger than dipolar ones. Engineering the high-order transitions through the complex nanophotonic environment promises new infrared sources, entangled two-photon sources and other novel physical effects.
Personal radiative heat regulation by photonic engineered textiles can help contribute to a more sustainable cooling and heating energy consumption in buildings by expanding the range of comfortable ambient conditions. Here, we propose various dual-mode photonic fabric designs (dynamic and static) that provide thermal regulation in both cold and hot environments. In the first design, we utilize metal-coated monofilaments arranged in a hexagonal geometry within a yarn and stimuli-responsive polymer actuator beads, in this way benefiting from the infrared (IR) photonic effect (or plasmonic gap) to control the wide-band transmission of thermal radiation and to provide for a sharp, dynamic response (Δτ = 0.9). The second design is based on metal microspheres randomly dispersed in a shape memory polymer membrane. The dynamic switching is achieved via a shape memory polymer matrix that responds to environmental changes. This design capitalizes on the strong scattering properties of metallic microspheres, leading to a strong modulation of reflectance (Δρ = 0.55) as a function of the volume fraction. The third design is a Janus-yarn fabric composed of an asymmetric structure, leading to dual emissivity characteristics. The strong emissivity contrast (Δε = 0.72 ) is achieved by utilizing metallic and dielectric fibers within the yarn; here, static switching is achieved via fabric flipping.
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