Figure 4

The cavity refractive indices versus relative channel spacings and continuous tuning of the edge channels. ( a) The cavity refractive indices $n_{\text{def}}^{(\mathbf{2}\mathbf{,}\mathbf{4}\mathbf{,}\mathbf{6})}$ versus the ratio of the channel spacings, λ_{s 12}/λ_{s 23}. (b) Continuous blue shift of the edge channels with a linear decrease in the central cavity refractive index, $n_{\text{def}}^{\left(\mathbf{4}\right)}\text{,}$ by ∆n = 0.02 (thin black line), ∆n = 0.052 (dashed blue line) and ∆n = 0.11 (dashed dotted blue line). The triple transmission channels, for ∆n = 0, are also demonstrated (thick black line). ( c) Continuous red shift of the edge transmission channels with a linear increase in the central cavity refractive index, $n_{\text{def}}^{\left(\mathbf{4}\right)}\text{,}$ by ∆n = 0.02 (thin black line), ∆n = 0.052 (red dashed line) and ∆n = 0.11 (red dashed dotted line).