Silicon mode-loop Mach-Zehnder modulator with L-shaped PN junction for 0.37 V·cm V<sub>π</sub>L high-efficiency modulation
Jiacheng Liu, Gangqiang Zhou, Jiangbing Du, Weihong Shen, Linjie Zhou, Zuyuan He
Abstract
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>TE</mml:mi> </mml:mrow> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>TE</mml:mi> </mml:mrow> <mml:mn>1</mml:mn> </mml:msub> </mml:mrow> </mml:math> was achieved to lower the driving voltage or decrease the photonic device size. Proof-of-concept high-efficiency modulation with low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">π</mml:mi> </mml:mrow> </mml:msub> <mml:mi mathvariant="italic">L</mml:mi> </mml:mrow> </mml:math> of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mn>0.37</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">V</mml:mi> <mml:mo>·</mml:mo> <mml:mi>cm</mml:mi> </mml:mrow> </mml:math> was obtained. Subvoltage <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>π</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> 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 signaling 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.