into the two linear defects at the output. The input linear defect consists of an empty row and the second linear defect consists of cylinders that change their radius from $r_{dL}=2.25\,\rm{mm}$ (the size of the cylinders in the SC) to $r_{dL}=0$. The two linear defects are separated by one row of the SC.

Considering $P_{U,out}$ and $P_{L,out}$ as the power integrated over the width of the upper and the lower linear defects ($5\,\rm{mm}$), respectively, [Fig. \[sc\_figsplitrange\]]{}(a) plots the normalized power at the two outputs, $\tilde{P}_{U,out}=P_{U,out}/P_{out}$ and $\tilde{P}_{L,out}=P_{L,out}/P_{out}$ as a function of the frequency, where $P_{out}=P_{U,out}+P_{L,out}$. On the other hand, [Fig. \[sc\_figsplitrange\]]{}(b) shows the normalized total power reaching the outputs relative to the maximum power at the two outputs, i.e., $\tilde{P}_{out}=P_{out}/\max(P_{out})$. We can observe that the adiabatic splitting works for a significantly broad range of frequencies from $1.71\times 10^5\,\rm{Hz}$ to $1.95\times 10^5\,\rm{Hz}$, in agreement with the available frequencies for the S supermode in the band diagrams for the different positions along the propagation, see Figs. \[sc\_fig2\](a) and (b). Thus, this structure constitutes a coherent multifrequency adiabatic splitter. The splitting process works for different frequencies as long as it is possible to follow adiabatically the S supermode. If the supermode is not 