A design methodology for developing lead-free bulk ceramics with large recoverable energy storage density was proposed in this study.

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The findings in this study could broaden the applications of KNN materials in a new field.

We propose to realize ultra-wideband polarization conversion metasurfaces in microwave regime through multiple plasmon resonances. An ultra-wideband polarization conversion metasurface is designed using a double-head arrow structure and is further demonstrated both numerically and experimentally. Four plasmon resonances are generated by electric and magnetic resonances, which lead to bandwidth expansion of cross-polarization reflection. The simulated results show that the maximum conversion efficiency is nearly 100% at the four plasmon resonance frequencies and a 1:4 3 dB bandwidth can be achieved for both normally incident x- and y-polarized waves. Experimental results agree well with simulation ones.

Metasurfaces provide unprecedented routes to manipulations on electromagnetic waves, which can realize many exotic functionalities. Despite the rapid development of metasurfaces in recent years, the design process of metasurface is still time‐consuming and computational resource‐consuming. Moreover, it is quite complicated for layman users to design metasurfaces as plenty of specialized knowledge is required. In this work, a metasurface design method named REACTIVE is proposed on the basis of deep learning, as deep learning method has shown its natural advantages and superiorities in mining undefined rules automatically in many fields. REACTIVE is capable of calculating metasurface structure directly through a given design target; meanwhile, it also shows the advantage in making the design process automatic, more efficient, less time‐consuming, and less computational resource‐consuming. Besides, it asks for less professional knowledge, so that engineers are required only to pay attention to the design target. Herein, a triple‐band absorber is designed using the REACTIVE method, where a deep learning model computes the metasurface structure automatically through inputting the desired absorption rate. The whole design process is achieved 200 times faster than the conventional one, which convincingly demonstrates the superiority of this design method. REACTIVE is an effective design tool for designers, especially for laymen users and engineers.