Figure 1

Illustration of the NRI slow-light heterostructure considered in the analyses. Also shown is a characteristic snapshot (from the FDTD simulations) of the propagation of the excited (dominant) slow-light mode. See also Ref. 10.Reuse & Permissions

Figure 2

Snapshots of slow-light pulse propagation along the central axis of the considered waveguides for (a) case I (neither loss nor gain); (b) case II (loss but no gain); (c) case III (both, loss and gain); and (d) case IV (gain but no loss). In all cases propagation is from left to right.Reuse & Permissions

Figure 3

Comparison between FDTD (symbols) and TMM (lines) calculations of the absorption coefficient $\alpha$ (spatial losses) versus frequency for the TM${}_2^b$ mode in case I (red line, downward triangles), case II (blue line, right triangles), case III (green line, squares), and case IV (orange line, circles). The inset depicts the frequency dispersion of Re$\left\{{\mathit{\text{n}}}_{\mathit{eff}}\right\}$ in all four cases.Reuse & Permissions

Figure 4

Comparison between FDTD (symbols) and TMM (lines) calculations of the temporal losses/gain and group velocity of the complex-$\omega$ and complex-$k$ solutions with varying core thickness (case III). Shown are the group velocity ($v_g$) of the complex-$\omega$ solutions (black solid line, black squares), the group velocity of the complex-$k$ solutions (red dashed line), the imaginary part of the complex-$\omega$ solutions (blue solid line, blue squares), and the imaginary part of the complex-$k$ solutions multiplied by $v_g$ (green dashed line, green circles). The inset shows the rate of energy loss (or gain) for the whole wave packet (purple triangles) with varying core thickness as calculated by the discrete Poynting’s theorem within the FDTD method.Reuse & Permissions