Materials with a tunable optical response that can be controllably tailored using external stimuli excitation have undergone considerable research effort for the development of active optical devices, such as thermo‐optical modulators. Although bismuth (Bi) nanodots, embedded into glass matrices, have been proven to have a thermo‐optical response, the recyclability of the structure in solid–liquid phase transitions is a major challenge. Herein, a facile and lithography‐free fabrication method is proposed to realize densely packed stand‐alone Bi nanorods (NRs), with deep subwavelength gaps and a resonance at the midinfrared range (λ ≅ 4.462 μm). Owing to these ultrasmall gaps that support lossy Mie‐like resonances, strong field confinement is achieved, and the resonance wavelength exhibits great sensitivity to temperature, as the thermal sensitivity reaches as high as 1.0316 nm °C⁻¹. This operation is conducted in the moderate temperature interval of 25–85 °C, which is far from the melting point of Bi. Overall, our simple, robust, and high‐performance device is highly promising for realizing optical switches, thermo‐optic modulators, and infrared camouflage.

中文翻译：

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铋纳米棒作为线性热可调超材料的深亚波长光限制。

可以使用外部刺激激发来控制可调谐光学响应的​​材料，在开发有源光学器件（如热光调制器）方面已经进行了相当多的研究。尽管已证明嵌入玻璃基质中的铋（Bi）纳米点具有热光学响应，但结构在固-液相转变中的可回收性仍是一个重大挑战。在此，提出了一种简便且无光刻的制造方法，以实现密集包装的独立Bi纳米棒（NRs），具有深的亚波长间隙和在中红外范围（λ≅4.462μm）的共振。由于这些微小的间隙支持有损耗的Mie共振，因此可以实现强的场约束，并且共振波长对温度表现出极大的敏感性，^-1。该操作在25-85°C的中等温度区间内进行，该温度区间距离Bi的熔点较远。总体而言，我们的简单，耐用且高性能的设备在实现光学开关，热光调制器和红外伪装方面非常有前途。