Metasurface plays a key role in various terahertz metadevices, while the designed terahertz metasurface still lacks flexibility and variety. On the other hand, inverse design has drawn plenty of attention due to its flexibility and robustness in the application of photonics. This provides an excellent opportunity for metasurface design as well as the development of multifunctional, high-performance terahertz devices. In this work, we demonstrate that, for the first time, a terahertz metasurface supported by the electromagnetically induced transparency (EIT) effect can be constructed by inverse design, which combines the particle swarm optimization algorithm with the finite-difference time-domain method. Incorporating germanium (Ge) film with inverse-designed metasurface, an ultrafast EIT modulation on the picosecond scale has been experimentally verified. The experimental results suggest a feasibility to build the terahertz EIT effect in the metasurface through an optimization algorithm of inverse design. Furthermore, this method can be further utilized to design multifunctional and high-performance terahertz devices, which is hard to accomplish in a traditional metamaterial structure. In a word, our method not only provides a novel way to design an ultrafast all-optical terahertz modulator based on artificial metamaterials but also shows the potential applications of inverse design on the terahertz devices.

中文翻译：

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基于逆向设计的超表面的超快全光太赫兹调制

超表面在各种太赫兹超器件中起着关键作用，而设计的太赫兹超表面仍然缺乏灵活性和多样性。另一方面，逆向设计因其在光子学应用中的灵活性和鲁棒性而引起了广泛关注。这为超表面设计以及多功能、高性能太赫兹设备的开发提供了绝佳机会。在这项工作中，我们首次证明了可以通过逆向设计构建由电磁感应透明 (EIT) 效应支持的太赫兹超表面，它将粒子群优化算法与有限差分时域方法相结合。将锗 (Ge) 薄膜与逆向设计的超表面相结合，皮秒级的超快 EIT 调制已经过实验验证。实验结果表明，通过逆向设计的优化算法在超表面中构建太赫兹 EIT 效应是可行的。此外，该方法还可以进一步用于设计多功能、高性能的太赫兹器件，这在传统的超材料结构中是难以实现的。总之，我们的方法不仅提供了一种设计基于人造超材料的超快全光太赫兹调制器的新方法，而且展示了逆向设计在太赫兹器件上的潜在应用。该方法可进一步用于设计多功能、高性能的太赫兹器件，这是传统超材料结构难以实现的。总之，我们的方法不仅提供了一种设计基于人造超材料的超快全光太赫兹调制器的新方法，而且展示了逆向设计在太赫兹器件上的潜在应用。该方法可进一步用于设计多功能、高性能的太赫兹器件，这是传统超材料结构难以实现的。总之，我们的方法不仅提供了一种设计基于人造超材料的超快全光太赫兹调制器的新方法，而且展示了逆向设计在太赫兹器件上的潜在应用。