Figure 2.

(a), (b) Real and imaginary parts, respectively, of the relative-permittivity variation profile Δε₁ [cf. Eq. (1)] pertaining to the original waveguide. Loss and gain regions are highlighted with different shadings. (c) Intensity profiles (vertically offset for clarity) of the corresponding three guided modes (with propagation constants given in Table 1), for w = 2λ₀.