Plasmonic coupling effect on dephasing time of asymmetric gold nanodimers in capacitive, conductive and overlapping regimes

Revealing the spectral and temporal dynamics of hybrid plasmonic modes in strongly interacting plasmonic nanodimers, including capacitively coupled dimer (CaCD), conductively coupled dimer (CoCD), and overlapping dimer (OLD) nanostructure is important for such applications as sensing, enhanced spectroscopy and plasmonic lasers. We theoretically present near field spectral signatures in three asymmetric nanodisk-nanorod (ND-NR) dimers configurations via Finite difference time domain (FDTD) simulation, and investigate the corresponding dephasing time of coupled plasmon modes supported by these nanoparticle dimers using Quasi-Normal mode (QNM). In our results from near-field spectrum fitting across three regimes, we found dephasing times of Fano resonance mode in CaCD is 4.94fs, CTP mode in CoCD is 5.26 fs and BDP mode in OLD is 3.50 fs respectively. This implies that CTP mode in conductively connected nanoparticle exhibit longer dephasing time compared to those in capacitive coupling and overlapping dimers. Moreover, the dephasing time can be further manipulated by varying nanoparticle and connecting junction parameters. Thus, our investigation opens up alternative opportunities for the application of plasmon based sensing, enhanced spectroscopy, non-linear optics and plasmon lasers.