Abstract
In common plasmonic structures, absorption and radiation losses are often mutually restricted and can seriously influence the device performance. The current study presents a compound structure composed of multilayer grating stripes and multilayer shallow trenches. A small depth was adopted for the trench configuration to exclude the extra bend loss. These two sections supported Fabry–Perot resonance and cavity modes, respectively, with hybrid modes formed through intercoupling. In addition, the total loss for the entire framework was clearly reduced due to the introduction of the trench geometry, indicating that both absorption and radiation losses were successfully taken into consideration in the compound structure. Significantly, such a low loss realized by the hybridization of surface plasmon polariton modes has rarely been seen before. Moreover, the debatable relationship between the total and partial quality factors was described for the first time based on a hybrid mode analysis to establish a new approach to investigate the different resonance modes. In the detailed calculation process, the relative electric field intensity was first adopted to stipulate the effective areas for the various modes, which is more reasonable than using the common definition that is based on a unit structure. The multilayer trench grating exhibited a relatively low loss without weakening energy localization, which is significant in the design of plasmonic devices.
Highlights
The utilization of surface plasmon polaritons (SPPs) to regulate the optical field and light–matter interaction on a subwavelength scale is a nanophotonics research hotspot[1,2,3,4,5]
Our previous work demonstrated an SPP-mode hybridization phenomenon based on a multilayer trench grating geometry[34], which led to the realization of a large absorption quality factor (Q) in the trench configuration but lacked a quantitative analysis and verification of the entire loss inhibition
Serious absorption loss was evaluated by calculating the relevant quality factor
Summary
The utilization of surface plasmon polaritons (SPPs) to regulate the optical field and light–matter interaction on a subwavelength scale is a nanophotonics research hotspot[1,2,3,4,5]. SPPs are capable of confining energy and enhancing local electromagnetic fields, which can lead to potential applications for surface-enhanced spectroscopy[6,7], spacer[8,9], such a metal–insulator–metal (MIM) structure can show remarkable field localization, significant absorption loss is an inevitable problem due to the presence of the metal, which significantly influences surface wave propagation[24]. Research on low-loss structures based on hybrid SPP modes is rarely reported. Our previous work demonstrated an SPP-mode hybridization phenomenon based on a multilayer trench grating geometry[34], which led to the realization of a large absorption quality factor (Q) in the trench configuration but lacked a quantitative analysis and verification of the entire loss inhibition. The microcavity electrodynamic processes in the hybrid SPP modes, absorption, radiation, and connections between various losses, which are significant to the design of the plasmonic devices, all remain unclear
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