Multichannel Optical Add-Drop Processes in Symmetrical Waveguide-Resonator Systems

Multichannel optical add-drop processes are studied in a class of symmetric waveguide-resonator systems. With insight gained from group theory, we analyze these systems and show that they can add or drop multiple wavelengths simultaneously, with 100% efficiency. A new mechanism is presented to reduce the remnant light at the dropped wavelengths in the pass-through port. High-order Butterworth filters can also be achieved in these systems. Built upon conventional or photonic-crystal based structures, these systems can be used in optical communication applications.

Figure 1

A sketch of the case $n=3$. Each waveguide is accompanied by a pair of cavities. Multiple wavelengths of light come in from the input port. Two wavelengths are dropped to the drop1 and drop2 ports, respectively. Light of the corresponding wavelengths is coupled in through the add1 and add2 ports, then merges with the undropped light, and reaches the output port altogether.

Figure 2

The solved ${\tilde{\omega }}_{\alpha c}$, ${\sigma }_{\alpha c}$, and ${\gamma }_{\alpha c}$ are plotted in (a)–(c). Dash-dotted, solid, and dotted lines correspond to $\alpha =0$, 1, and 2, respectively. Reconstructed spectra are shown in (d) on a linear scale, where $I_0^{\prime }$ (dotted line) is a reference lossless spectrum. Each intensity reaches maximum 1 and minimum 0, except the total intensity.

Figure 3

Reconstructed spectra for the third-order Butterworth case, ${\varphi }_a\equiv 0$ for appreciable $|a_1|$.