Ultralow‐Crosstalk Silicon Electro‐Optic MZI Switch Based on Cascaded Phase Shifters with Arm Loss Equivalence

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Abstract
In silicon electro‐optic (EO) Mach–Zehnder interferometer (MZI) switches, crosstalk is limited by the beam imbalance between the MZI arms, primarily caused by the free carrier absorption loss of the phase‐shift arms, thereby hindering switch scalability. To address this issue, this study proposes a low‐crosstalk push–pull EO MZI switch by cascading a lightly doped, long phase shifter (PSLL) and a heavily doped, short phase shifter (PSHS) to construct phase‐shift arms. In both BAR and CROSS states, the PSLL in one arm and PSHS in the other arm are simultaneously forward‐biased; the phase‐shift difference between them is π/2 to enable switching, while their losses are similar to minimize crosstalk. Simulations indicate that the proposed switch achieves crosstalk below −51 dB at a 1310 nm wavelength. The fabricated 2 × 2 silicon EO MZI switch exhibits crosstalk ranging from −33 to −44.2 dB at 1316 nm across all routing paths, and maintained crosstalk below −30 dB over an impressive optical bandwidth of 61 nm, with response times under 119 ns. Featuring single‐pair electrode control, consistent two‐state performance, and a compact footprint, this approach can enable high‐radix switch fabrics in data centers and artificial intelligence compute clusters.
Funding Information
  • National Key Research and Development Program of China (2023YFB2806600)

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