Ultralinear heterogeneously integrated ring-assisted Mach–Zehnder interferometer modulator on silicon

A linear modulator is indispensable for radio frequency photonics or analog photonic link applications where high dynamic range is required. There is also great interest to integrate the modulator with other photonic components, to create a photonic integrated circuit for these applications, with particular focus on silicon photonics integration in order to take advantage of complementary metal–oxide–semiconductor compatible foundries for high-volume, low-cost devices. However, all silicon modulators, including the highest performing Mach–Zehnder interferometer (MZI) type, have poor linearity, partially due to the inherent nonlinearity of the MZI transfer characteristic, but mostly due to the nonlinearity of silicon’s electro-optic phase shift response. In this work, we demonstrate ultralinear ring-assisted MZI (RAMZI) modulators, incorporating heterogeneously integrated III–V multiple quantum wells on silicon phase modulation sections to eliminate the nonlinear silicon phase modulation response. The heterogeneously integrated III–V/Si RAMZI modulators achieve record-high spurious free dynamic range (SFDR) for silicon-based modulators, as high as 117.5  dB·Hz2/3 at 10 GHz for a weakly coupled ring design, and 117  dB·Hz2/3 for a strongly coupled ring design with higher output power. This is a higher SFDR than typically obtained with commercial lithium niobate modulators. This approach advances integrated modulator designs on silicon for applications in compact and high-performance analog optical systems.