In transformation optics and transformation thermodynamics, many structures capable of regulating a single physical field have been proposed, such as electromagnetic/thermal cloaking structures, electromagnetic/thermal focusing structures, electromagnetic/thermal beam expansion structures, electromagnetic/thermal bending structures, and electromagnetic/thermal beam splitting structures. Among these structures, beam/field splitting structures can divide an incident wave into two or more outgoing waves. For instance, electromagnetic wave splitters can divide an incident wave into two or more outgoing waves, which can be employed for power distribution, power tracking, and electromagnetic signal routing. Thermal flux splitters can divide the incident heat flux into two or more outgoing heat fluxes and play a key role in fields such as thermal management, energy-saving technology, and thermal sensing, thus providing new pathways and solutions for heat flux control and utilization. With the continuous improvement in on-chip system integration, there is an increasing demand for yielding splitting effects for both electromagnetic waves and heat fluxes by a single structure. However, to date, there is still no structure that is effective for both electromagnetic waves and heat fluxes simultaneously. Meanwhile, the design of structures using transformation optics and transformation thermodynamics is always complex with precise requirements for the materials of the structure, which increases the implementation difficulty. To this end, we design an electromagnetic?thermal splitter that can simultaneously split transverse magnetic (TM) polarized electromagnetic waves and heat fluxes by staggered aluminum plates and expanded polystyrene boards. Additionally, both numerical simulations and experimental results have verified the double-physical-field splitting effect of the proposed electromagnetic?thermal splitter. By adjusting the arrangement of the two materials, a tunable splitting ratio can be achieved. Finally, we provide a new method for electromagnetic?thermal regulation in applications that require the consideration of both electromagnetic compatibility and thermal management, such as double-physical-field detection, highly integrated on-chip systems, and electronic devices.

We propose an electromagnetic?thermal splitter based on staggered aluminum plates and expanded polystyrene boards, which performs as a reduced double-physical-field null space medium. The effective dielectric constant, magnetic permeability, and thermal conductivity of the staggered aluminum plates and expanded polystyrene boards are derived by adopting the effective medium theory. Meanwhile, they are very large along the interface direction of the aluminum plates and expanded polystyrene boards, and they tend towards zero in all other orthogonal directions. Theoretical analyses indicate that the staggered aluminum plates and expanded polystyrene boards act as a reduced double-physical-field null space medium, capable of guiding both electromagnetic waves and heat fluxes along the interface between two materials. Consequently, the staggered aluminum plates and expanded polystyrene boards are utilized as a building block for designing an electromagnetic?thermal splitter in our study. Subsequently, numerical simulations are conducted to verify the double-physical-field splitting effect of the electromagnetic?thermal splitter. Then, the double-physical-field splitter is fabricated, with the double-physical-field splitting effect verified via experimental validation.

The proposed electromagnetic?thermal splitter can yield the same splitting effect for both electromagnetic waves and heat fluxes. To quantitatively describe the splitting effect of the electromagnetic?thermal splitter, we define two parameters of the energy transmission rate and the beam splitting ratio. Meanwhile, numerical simulation is initially performed to bring simulation outcomes for electromagnetic waves and heat fluxes [Figs. 2(a) and 2(b)], with the z-component of the magnetic field strength and the temperature field distribution depicted respectively. The simulation results show that after the incidence of TM plane waves and heat fluxes both bifurcating into two beams of plane waves or two flows of heat fluxes on the splitter’s output port, the electromagnetic?thermal splitter possesses sound splitting effect for both electromagnetic waves and heat fluxes. To study the influence of the number of aluminum alloy plates and expanded polystyrene boards (denoted as M and N) on the beam splitting ratio, we conduct additional simulations to observe the variations in splitting effects of the electromagnetic?thermal splitter for electromagnetic waves and heat fluxes when M and N are altered (Figs. 3 and 4). The results indicate that by appropriately adjusting the proportion of M and N in the upper and lower routes of the electromagnetic?thermal splitter, the beam splitting ratio for both electromagnetic waves and heat fluxes can be simultaneously controlled. Further experimental splitting performance validation of the electromagnetic?thermal splitter is conducted. For the electromagnetic experiment (Fig. 6), the measured results show that two distinct peaks in the magnetic field amplitude at the exit surface are observed to verify the expected electromagnetic splitting effect. For the thermal experiment (Fig. 7), the measured results demonstrate that the incident heat flux can be divided into two output heat fluxes after passing through the fabricated electromagnetic?thermal splitter. Both the numerical simulations and experimental results confirm the excellent beam splitting performance of the proposed electromagnetic?thermal splitter.

We propose a novel electromagnetic?thermal splitter capable of producing identical splitting effects for both electromagnetic waves and heat fluxes by employing staggered aluminum alloy plates and expanded polystyrene boards. By simply altering the quantity of aluminum alloy plates and expanded polystyrene boards, the beam splitting ratio of the splitter can be tuned. Then, the electromagnetic?thermal splitter is fabricated, and its double-physical-field splitting effect is verified by both numerical simulations and experimental measurements. The proposed electromagnetic?thermal splitter can be applied to fields that require simultaneous regulation of electromagnetic waves and heat fluxes, such as double-physical-field sensing, double-physical-field detection, and on-chip electromagnetic/thermal compatibility.