2×2 Mach–Zehnder interferometric switch based on hetero‐n‐i‐p‐i quantum wells

A 2×2 Mach–Zehnder interferometric switch has been developed employing 3 dB multimode interference (MMI) couplers and laterally contacted hetero‐n‐i‐p‐i quantum wells as the active material providing refractive index changes. Switching over a 4π range between the cross state and the bar state with an on/off ratio of 17:1 has been observed. A record voltage‐length product for switching is observed of less than 1 V mm. By exploiting the quadratic nature of the quantum confined Stark effect, a differential switching voltage as low as 0.2 V mm is observed in the push–pull configuration.