Abstract

Recently, Mach–Zehnder modulators based on thin-film lithium niobate have attracted broad interest for their potential for high modulation bandwidth, low insertion loss, high extinction ratio, and high modulation efficiency. The periodic capacitively loaded traveling-wave electrode is optimally adopted for ultimate high-performances in this type of modulator. However, such an electrode structure on a silicon substrate still suffers from the velocity mismatch and substrate leakage loss for microwave signals. Here, we introduce a thin-film lithium niobate modulator structure using this periodic capacitively loaded electrode on a silicon substrate. Backside holes in the silicon substrate are prepared to solve robustly the above difficulties. The fabricated device exhibits an insertion loss of 0.9 dB, a halfwave-voltage–length product of 2.18 V·cm, and an ultra-wide bandwidth well exceeding 67 GHz for a 10-mm-long device. Data transmissions with rates up to 112 Gb/s are demonstrated. The proposed structure and fabrication strategy are compatible for other types of monolithic and heterogeneous integrated thin-film lithium niobate modulators on a silicon substrate.

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