Compact InGaAsP/InP 3 × 3 multimode-interference coupler-based electro-optic switch.

Optical switches are key components in data links for optical communication networks requiring low crosstalk and insertion loss, high switching speed, and power efficiency. A multimode-interference (MMI)-coupler-based switch with multiple inputs and outputs serving as a switching unit is desired toward forming a large-scale switch matrix. Here we demonstrate a compact 3×3 MMI coupler electro-optic switch based on the carrier injection effect on InGaAsP/InP substrates. This switch device is 2780 µm long by 18 µm wide. The switching states can be controlled by two index-modulation regions through applied bias voltages. Our simulation results show that the device exhibits low crosstalk of <-22 dB, high extinction ratio of ≳23 dB, low electrical switching energy of ∼2.0 pJ/bit, maximum operational frequency of ∼1.0 GHz, and optical bandwidth of ∼20 nm in the C band. We experimentally validated one of the switching states on a fabricated device with maximum current injections of ∼25 mA under combined bias voltages of ∼2.5 and ∼3.0 V. Such monolithic integration schemes make them an ideal candidate for future on-chip photonic integrated circuits.