Fig. 4

(a) Reflection spectrum (\(R_{total}\)) of the structure with \(P=500\) nm, \(S_1= S_2= 170\) nm, and different values of \(W_1\) and \(W_2\). As a reference, the reflection spectrum of a fully symmetric structure with \(W_1=W_2=80\) nm is inserted with a black solid line. The two red oval shapes marked as 1 and 2 are illustrative for the reflection peaks at \(\lambda =500\) nm and \(\lambda =725\) nm, respectively. (b) \(R_0\), \(R_{\pm 1}\), and \(R_{total}\) and \(T_0\), \(T_{\pm 1}\), and \(T_{total}\) for the structure with \(W_1=W_2=80\) nm. (c)/ (d) \(R_{total}\), \(R_0\), and \(R_{\pm 1}\)/ \(T_{total}\), \(T_0\), and \(T_{\pm 1}\) spectrum of the structure with \(W_1=140\) nm and \(W_2=20\) nm.