Photoinduced dynamic tailoring of near-field coupled terahertz metasurfaces and its effect on Coulomb parameters
Deepak Kumar, Manoj Gupta, Yogesh Kumar Srivastava, Koijam Monika Devi, Ranjan Kumar, Dibakar Roy Chowdhury
Abstract
Abstract In modern-day photonic integrated circuits, near-field Coulomb interaction plays an important role in device performance. In fact, harvesting the Coulomb effect intelligently can immensely help to realize advanced photonic devices on micro and nano length scales. In this context, electrically coupled terahertz metasurfaces are investigated for weak and strong near-field coupling regimes under the influence of variable photoexcitation. Our study demonstrates active tuning of metasurface resonances at relatively low pump powers (up to 10 mW (pump fluence of 12.7 µ J cm −2 ) and 20 mW (pump fluence of 25.4 µ J cm −2 ) for strong and weak near-field coupling regimes, respectively). We attribute photoinduced modifications of substrate electronic properties along with modifications of near-field interactions to be responsible for the resonance modulations. Furthermore, we demonstrate that the Coulomb effect parameter can be dynamically tunable with variable pump power. Our study reveals that the change in Coulomb parameter is more pronounced for the weak near-field coupling regime (more than six times enhancement in Coulomb parameter) in comparison to the strong near-field coupling regime. In addition, the optical switching of the fundamental resonance is validated utilizing numerically simulated patterns of surface current and electric field. We envisage that such active modulation of Coulomb effects in near-field coupled metasurfaces can lead to the realization of dynamically tunable terahertz metaphotonic devices.