Temporal Dynamics of Strongly Coupled Epsilon Near-Zero Plasmonic Systems

Deeply sub-wavelength epsilon near-zero (ENZ) films feature strong optical nonlinearities such as a giant Kerr effect and high four-wave mixing efficiency [1] , [2] . The enhanced nonlinear response is largely owed to the the slow-light effect consequent of the flat dispersion of the ENZ mode [3] . Here, we numerically investigate the hybridisation of this mode with plasmonic antennas decorated on top of the ENZ film. In this new regime, slow-light propagation can contribute significantly to the strong nonlinear response. However, unveiling the temporal dynam-ics necessitates use of time-resolved approaches which have not yet been undertaken. Therefore, we employed a finite-difference time-domain approach to study two representative ENZ media, namely Indium Tin Oxide (ITO) and Silicon Carbide (SiC) and with ENZ frequency ν ε0 = 211 × 10 12 Hz and ν ε0 = 29.1 × 10 12 Hz, respectively. In both cases, we quantify the slow-light effect by focusing on the group delay, δt (computed from the difference of electric field envelope centres of mass t in and t out at the input and output, respectively). As depicted in Fig. 1 , the delay depends on the excited mode (field polarisation) and shows maxima where strong coupling occurs.