InGaAs/InAlAs Multiple Quantum Well Mach–Zehnder Modulator with Single Microring Resonator

We propose and a novel InGaAs/InAlAs multiple quantum well (MQW) Mach–Zehnder (MZ) modulator with a single microring resonator, and a significant reduction of driving voltage is demonstrated for the first time. The modulator is driven by the quantum-confined Stark effect (QCSE) in the MQW and the driving voltage of the proposed modulator is expected to be significantly reduced by the phase-shift-enhancement effect in the microring. A waveguide structure was grown by solid-source molecular beam epitaxy and fabricated by inductively coupled plasma etching. A directional coupler with a shallow gap is employed to control the coupling parameters between a busline and the microring waveguide. An asymmetrical splitter was used as an input coupler to prevent the degradation of the extinction ratio of the MZ modulator. The extinction ratio of the fabricated microring MZ modulator was approximately 17.5 dB. The product of half-wave voltage and phase shifter length V π L was 2.0 Vmm in static modulation. This value was one-third that of a conventional MZ modulator with the same waveguide structure.