Mid-wave infrared multi-order SPPs resonance by exciting multi-order diffractions in 1D Dammann gratings

Mid-wave infrared photodetectors offer significant potential for a wide range of important applications. Due to their unique sub-wavelength localization properties, infrared photodetectors based on surface plasmon polaritons (SPPs) have garnered considerable research interest. Many of these applications require bandwidth response from the infrared photodetectors. In this paper, Dammann gratings (DGs) with a one-dimensional (1D) metal/dielectric layer structure were designed to achieve a diffraction field distribution modulated by a non-sinc function, which in turn was used to excite SPPs resonance. These gratings are capable of supporting multi-order SPPs resonance, facilitating enhanced bandwidth absorption across multiple resonant orders. By varying the combinations of diffraction slit spacings within a single period, the DGs could achieve distinct phase difference distributions. Specifically, DGs with a lattice constant of <i>d</i> = 27.3 μm demonstrated the ability to generate two to four orders of strong diffraction intensity distribution within 4-5 μm range, thereby enabling multi-order resonance-enhanced absorption of SPPs. Furthermore, the SPPs response of the DGs exhibited improved tolerance to variations in polarization angles across a broadband spectrum. This multi-order SPPs resonance-enhanced structure presents significant potential for applications in infrared detection, including the development of large-scale infrared photodetector units.