Integrated Slow-Light Enhanced Silicon Photonic Modulators for RF Photonic Links

An integrated RF-photonic link that consists of a slow-light enhanced silicon (Si) electro-optic modulator, a single mode Si optical waveguide and a silicon-germanium (SiGe) photodetector was fabricated using a Si photonic standard foundry service. The third-order intermodulation distortion (IMD3) of the RF signals and the link spur-free dynamic range (SFDR) were characterized through a two-tone test method. The Si Mach-Zehnder modulator architecture is designed to have unequal arms to operate on a simplified driving scheme. As a result, on-chip thermal heaters can be omitted, and the modulator can configure near its quadrature point by adjusting the wavelength to the modulator. Owning to enhanced light-matter interaction in the slow-light region, an increased slope efficiency is observed in the modulator. By selecting the optimal DC bias to the grating and the reference arms of the modulator, a SFDR of 96 dB/Hz(2/3) can be obtained in the RF link at the slow light region. The slow-light modulator also displays increased modulation efficiency, allowing for a reduced footprint for large array integration.