Multifunctional emitter based on inverse design for infrared stealth, thermal imaging and radiative cooling

In contrast to conventional emitters fashioned from traditional materials, tunable thermal emitters exhibit a distinct propensity to fulfill the demands of diverse scenarios, thereby engendering an array of prospects within the realms of communications, military applications, and control systems. In this paper, a tunable thermal emitter without continuous external excitation is introduced using Ge₂Sb₂Te₅ (GST) and high-temperature-resistant material Mo. It is automatically optimized by inverse design with genetic algorithm (GA) to switch between different functions according to the object temperature to adapt to diverse scenarios. In "off" mode, the emitter orchestrates a blend of infrared (IR) stealth and thermal management. This is evidenced by average absorptivity values of 0.08 for mid-wave infrared (MIR, 3-5 µm), 0.19 for long-wave infrared (LIR, 8-14 µm), and 0.68 for the non-atmospheric window (NAW, 5-8 µm). Conversely, when confronted with high-temperature entities, the emitter seamlessly transitions to "on" mode, instigating a process of radiative cooling. This transformation is reflected in the augmented emissivity of the dual-band atmospheric window including MIR and LIR, attaining peak values of 0.96 and 0.97. This transition yields a cooling potential, quantified at 64 W/m² at the ambient temperature of 25°C. In addition, our design employs a layered structure, which avoids complex patterned resonators and facilitates large-area fabrication. The emitter in this paper evinces robust insensitivity to polarization variations and the angle of incidence. We believe that this work will contribute to the development in the fields of dynamic tunability for IR stealth, dynamic radiative cooling systems, and thermal imaging.