Investigation on an ultra-compact $$1\times 2$$ polymer electro-optic switch using cross-coupling $$2N+1$$2N+1 vertical-turning serial-coupled microrings

Generic model and thorough investigation are proposed for a novel \(1\times 2\) polymer electro-optic (EO) switch based on one-group \(2N+1\) vertical-turning serial-coupled microrings. For realizing boxlike flat spectrum as well as low crosstalk and insertion loss, resonance order and coupling gaps are optimized. The MRR switches with \(N \ge 1\) reveal favorable boxlike spectrum as when compared with the simple device with only one microring (\(N = 0\)). For obtaining \(<-30\,\text{ dB }\) crosstalk under through-state, the dependency of switching voltage on \(N\) is determined as \(7.19 \times \text{ exp }(-N/0.72) + 1.72\,(\text{ V })\). Under the operation voltages of 0 V (drop state) and the predicted switching voltages (through state), the device performances are analyzed, and \(1 \le N \le 10\) is required for dropping the insertion loss (drop state) below 10 dB. The crosstalk of the ten devices (\(N = 1-10\)) are \(< -19.5\,\text{ dB }\) under drop state and \(< -28.7\,\text{ dB }\) under through state, and the insertion losses of the devices (\(N = 1-10\)) are \(< 9.715\,\text{ dB }\) under drop state and \(< 1.573\,\text{ dB }\) under through state. The device also has ultra-compact footprint size of only 0.33–1.06 mm, which is only 1/10–1/3 of those of our previously reported polymer EO switches based on directional coupler or Mach–Zehnder interferometer structures. Therefore, the proposed device is capable of highly integration onto optical networks-on-chip.