Silicon mode-loop Mach-Zehnder modulator with L-shaped PN junction for 0.37 V·cm VπL high-efficiency modulation

Optical signaling without a high voltage driver for electric-optic modulation is in high demand to reduce power consumption,packaging complexity,and cost.In this work,we propose and experimentally demonstrate a silicon mode-loop Mach-Zehnder modulator(ML-MZM)with record-high modulation efficiency.We used a mode-loop structure to recycle light twice in the phase shifter.With an L-shaped PN junction,a comparably large overlap between the PN junction and optical modes of both TE0 and TE1 was achieved to lower the driving voltage or decrease the photonic device size.Proof-of-concept high-efficiency modulation with low VπL of 0.37 V·cm was obtained.Subvoltage Vπ can be realized with a millimeter's length phase shifter by this scheme,which makes the realization of CMOS-compatible driverless modulation highly possible.40 Gb/s signal-ing with a bit error rate below the 7％forward-error-correction threshold was then demonstrated with the fabricated ML-MZM,indicating great potential for high-speed optical communication.