Active tuning of ENZ resonances in a meta-antenna through phase modulation of an optical pulse

Plasmonic nanoantennas provide new avenues to manipulate the propagation of light in materials due to their near-field enhancement and intrinsically ultrafast response time. Here, we investigate the epsilon-near-zero (ENZ) response of an L-shaped nanoantenna structure under the phenomenon of plasmonic analog of enhancement in the index of refraction. Using a quantum mechanical framework, we analyze the modulation in the response of the L-shaped nanoantenna and the emergence of the ENZ frequency region in both the linear and nonlinear plasmonic systems. Active tuning of the ENZ frequency is achieved through phase modulation of a control pulse, enabling coherent and reversible control of the effective permittivity. The analytical and three-dimensional FDTD simulation results show consistent and appreciable spectral shifts of the ENZ modes arising from coupled L-shaped nanoantenna resonances and do not rely on natural ENZ materials or bulk metamaterial layers. Moreover, our method offers a new paradigm for actively tunable plasmonic antennas as metasurfaces. These structures carry strong potential for on-chip photonic integrated circuits, enhanced field localization, slow and fast light manipulation, and emerging quantum photonic technologies.