Nonvolatile Tunable Wavelength‐Selective Emitter with Phase‐Changing Material Ge₂Sb₂Te₅ Designed by Bayesian Optimization Method

The ability to tune the emission wavelength of infrared emitter while maintaining wavelength‐selectivity remains a challenge. By incorporating the nonvolatile phase‐changing material Ge₂Sb₂Te₅ (GST), a nonvolatile tunable wavelength‐selective emitter (gold (Au)‐GST‐Au structure) based on Fabry–Perot (FP) resonance theory is demonstrated. An algorithm based on Bayesian optimization (BO) and transfer matrix method (TMM) for optimal design is proposed. First, the influence of amorphous proportion on tunability is investigated. It is found that the peak emission wavelength shifts from 5.3 to 3.8 μm and peak emissivity increases from 0.75 to 0.98 with an increase of the amorphous proportion. Second, the influence of the thickness of the top and middle layer on the emission spectrum is studied. It is illustrated that the thickness of each layer has a significant impact on the emission spectrum. Finally, an objective function considering wavelength‐selectivity in atmospheric and nonatmospheric windows as well as tunability is proposed. The optimal structure can be realized within calculations for less than 0.027% of total candidate structures. When the weight w = 0, the optimal structural parameters are d_Au = 0.0018 μm and d_GST = 0.4318 μm; and the effect of the weight factor in objective function is also investigated.