Figure 2. Theoretical and experimental polariton anti-crossing curves.
(a) Simulated transmission obtained from finite-difference time-domain calculations for sample A (λIST: 10 μm, QW-width: 11 nm). For the simulation, we describe the ISTs as single Lorentzian oscillators37; details are given in the Methods section. The anti-crossing observed between 26 and 34 THz is clearly visible. The dashed, white line shows the quantum-mechanically calculated polariton frequencies. (b) Experimental transmission for sample A (λIST: 10 μm, QW-width: 11 nm). The incoming light is polarized along the y-direction. The step-like x axis indicates that only a discrete number of metamaterial cavities has been fabricated and tested experimentally. (c) Detailed transmission plots for three different metamaterial nanocavities corresponding to bare cavity frequencies of 25.8 (black), 28.9 (red) and 31.6 THz (blue), respectively. The individual curves are offset vertically by 0.35 for clarity. (d) Polariton frequencies for all three mid-infrared samples extracted from transmission spectra. The symbols indicate experimental values; the solid lines are the quantum-mechanical predictions. The figure legend gives the designed IST wavelength, with the width of the quantum-well indicated in brackets. (e) Experimental time trace of Ey for sample B (λIST: 8 μm, QW-width: 9.5 nm) measure using TDS (black). The beating with a period of 480 fs corresponds to the energy exchange rate between the electromagnetic field and the quantum-wells. The red line represents the incoming pulse.