Silicon photonic modulators with a 2 × 1 Fabry–Perot cavity

Silicon photonics modulators based on a 2 × 1 Fabry–Perot (FP) cavity, which is circulator-free, are proposed and demonstrated by introducing two asymmetric multimode-waveguide grating (AMWG) reflectors and a short straight modulation section with interleaved PN junctions. In particular, the straight modulation section in the FP cavity is broadened to be far beyond the single-mode regime, alleviating the inherent sensitivity to the variations of waveguide dimensions and thus reducing stochastic resonance-wavelength variations. The Q factor of the FP cavity is manipulated by optimally manipulating the reflection of the AMWGs, and the modulation bandwidth is enhanced to be over 40 GHz by utilizing the optical peaking enhancement effect, which happens when operating at the wavelength slightly detuning to its resonance wavelength. Eye diagrams for high-speed modulation with 50 Gbps are also demonstrated in experiments. Finally, wafer-level measurement is conducted by characterizing the silicon photonic modulators based on the 2 × 1 FP cavity and a conventional microring fabricated on the same chip, experimentally revealing an average improvement of 43 % in minimizing the random resonance-wavelength variation, which is attributed to the implementation of broadening the straight modulation section in the FP cavity.