Robust thin-film lithium niobate modulator on a silicon substrate with backside holes
Mai Wang, Qi Lu, Haohua Wang, Ziliang Ruan, Gengxin Chen, Bin Chen, Shengqi Gong, Kaixuan Chen, Liu Liu
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 Vcm, 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.