Wide-range control of surface plasmon dephasing time by the strong coupling between surface lattice and gap modes

In applications such as plasmonic sensors and plasmonic nanolasers, constructing metal nanostructures with a wide range of tunability of plasmonic dephasing times is becoming increasingly important. However, the manipulation range of the dephasing time is still limited from only a few femtoseconds to tens of femtoseconds. Here, we propose what we believe to be a novel method to greatly extend the tunable range of plasmonic dephasing time by leveraging the strong coupling between the plasmonic gap mode and the surface lattice resonance mode. The results demonstrate a tunable range of plasmonic dephasing times from about 23 fs to 166 fs, which is more than one order magnitude longer than those for traditional modulation methods. Moreover, the local near-field intensity of the strong coupling modes can increase up to about 2-fold of the intrinsic gap mode. This investigation opens up new opportunities for applications requiring control plasmon dephasing times over a large range and provides an effective approach for better understanding light-matter interactions.