Metal plasmonic filters enable compact multispectral sensing, yet conventional designs are constrained by Ohmic losses. In this work, we designed and fabricated a narrowband long-wave infrared spectral filter based on perforated Au films and nanorings, achieving high-resolution multispectral filtering in the 7.5–14 μm range with a FWHM of only 0.26 μm, approximately one-fifth that of conventional plasmonic filters. Fabrication was accomplished using i-line stepper lithography for large-area patterning, while the self-deposition effect during ion-beam etching was ingeniously leveraged to achieve cost-effective nanoring fabrication. The transmission bandwidth of the fabricated filter was characterized using Fourier-transform infrared spectroscopy, demonstrating excellent agreement between experimental and simulation results. This work holds promise for addressing the long-standing resolution limitations of plasmonic filters.
Wang et al. (Mon,) studied this question.