A compact design for realizing narrowband optical absorbers at deep subwavelength is proposed, the physical regime of which is based on the excitation of quasi-surface plasmon polariton (quasi-SPP) mode at metal–substrate interface. Due to its small intrinsic loss balanced with the radiation loss, peak absorbance exceeding 99.9% with full width at half-maximum (FWHM) 2.6nm is achieved at normal incidence. The spatially resolved feature at fixed wavelength, with narrower angular width and high peak absorbance at larger angle of incidence for TE polarization, makes the design more suitable for potential applications in optical filters, optical measurement, biosensors, and thermal emitters.

提出了一种在深亚波长下实现窄带光吸收器的紧凑设计，其物理机制基于金属-衬底界面处准表面等离子体激元（quasi-SPP）模式的激发。由于其较小的固有损耗与辐射损耗相平衡，在垂直入射时实现了超过 99.9% 的半峰全宽 (FWHM) 2.6nm 的峰值吸光度。固定波长的空间分辨特征、更窄的角宽度和更大的 TE 偏振入射角处的高峰值吸光度，使该设计更适合在光学滤波器、光学测量、生物传感器和热发射器中的潜在应用。