Wavelength-selective thermal emitters (WS-EMs) hold considerable appeal due to the scarcity of cost-effective, narrow-band sources in the mid-to-long-wave infrared spectrum. WS-EMs achieved via dielectric materials typically exhibit thermal emission peaks with high quality factors ({Q}${Q}$ factors), but their optical responses are prone to temperature fluctuations. Metallic EMs, on the other hand, show negligible drifts with temperature changes, but their {Q}${Q}$ factors usually hover around 10. In this study, we introduce and experimentally verify an EM grounded in plasmonic quasi-bound states in the continuum (BICs) within a mirror-coupled system. Our design numerically delivers an ultra-narrowband single peak with a {Q}${Q}$ factor of approximately 64 and near-unity absorptance that can be freely tuned within an expansive band of more than 10 µm. By introducing air slots symmetrically, the {Q}${Q}$ factor can be further augmented to around 100. Multipolar analysis and phase diagrams are presented to elucidate the operational principle. Importantly, our infrared spectral measurements affirm the remarkable resilience of our designs’ resonance frequency in the face of temperature fluctuations over 300°C. Additionally, we develop an effective impedance model based on the optical nanoantenna theory to understand how further tuning of the emission properties is achieved through precise engineering of the slot. This research thus heralds the potential of applying plasmonic quasi-BICs in designing ultra-narrowband, temperature-stable thermal emitters in the mid-infrared. Moreover, such a concept may be adaptable to other frequency ranges, such as near-infrared, terahertz, and gigahertz.

中文翻译：

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由镜面耦合等离子体准BIC超表面驱动的单峰窄带中红外热发射器

由于中长波红外光谱中经济高效的窄带源的稀缺，波长选择性热发射器 (WS-EM) 具有相当大的吸引力。通过介电材料实现的WS-EM通常表现出具有高质量因子（{Q}${Q}$因子）的热发射峰，但它们的光学响应容易受到温度波动的影响。另一方面，金属电磁场随温度变化而表现出的漂移可以忽略不计，但它们的{Q}${Q}$因子通常徘徊在 10 左右。在这项研究中，我们引入并通过实验验证了一种基于连续体中等离子体准束缚态 (BIC) 的电磁场在镜面耦合系统内。我们的设计在数值上提供了超窄带单峰，其{Q}${Q}$因子约为 64，吸收率接近统一，可以在超过 10 µm 的宽频带内自由调节。通过对称地引入空气槽，{Q}${Q}$因子可以进一步增大到 100 左右。多极分析和相图阐明了工作原理。重要的是，我们的红外光谱测量证实了我们设计的谐振频率在面对超过 300°C 的温度波动时具有卓越的弹性。此外，我们还开发了一种基于光学纳米天线理论的有效阻抗模型，以了解如何通过精确的缝隙设计来实现发射特性的进一步调整。因此，这项研究预示着应用等离子体准 BIC 在设计中红外超窄带、温度稳定的热发射器方面的潜力。此外，这样的概念可以适用于其他频率范围，例如近红外、太赫兹和千兆赫兹。