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Electro-optic modulators with large bandwidth and low voltage are crucial for the high-baud-rate digital communication and high-carrier-frequency analog links. Recently, thin-film lithium niobate (TFLN) modulators with sub-1 V voltage and 140 GHz bandwidth have been emerged on the low permittivity substrates, such as quartz. However, on the high permittivity environment, such as silicon substrates, the bandwidth dramatically reduced to below 100 GHz even if the voltage was raised to around 3 V. We break the voltage–bandwidth trade-off limit in TFLN modulators on silicon substrates using low inductance thick metal traveling wave electrodes, which reduce RF phase index and microwave losses while preserving high EO modulation efficiency. We demonstrate a TFLN EO modulator on silicon substrate with 3 dB EO bandwidth $>$ 120 GHz and half-wave voltage $(V_\pi) < $ 2 V. Bandwidth/$V_\pi$ reach 60, which is significantly larger than traditional TFLN modulators. The proposed thin-film lithium niobate modulators offers a practical solution for the hybrid integration of silicon and lithium niobate.

A 32-channel hybrid (de)multiplexer on silicon is designed and experimentally demonstrated to enable polarization division multiplexing (PDM) and wavelength division multiplexing (WDM) for improving the capacity of optical communication links. The hybrid (de)multiplexer is realized by monolithically integrating a polarization rotator and splitter (PRS) and two 16-channel microring resonators (MRRs) arrays. The through and cross ports of the PRS are connected to the bus waveguide of the MRR arrays, respectively. In order to ensure a larger free spectrum range (FSR) to cover all wavelength channels, the radius of the microring is about 3 $\mu$m and the wavelength-channel spacing is 1.6 nm. For the hybrid (de)multiplexer, the crosstalk between the adjacent channels and the non-adjacent channels are −20 dB and −25 dB, respectively. When TE$_{0}$ mode input, the insertion loss is 1.5 dB–3.8 dB, the crosstalk between the through and cross port is less than −24 dB. When TM$_{0}$ mode inputs, the insertion loss is 1.9 dB–4.5 dB and the polarization crosstalk is less than −22 dB. In order to eliminate the influence of the fabrication errors and temperature on resonance wavelength, a TiN thermal tuning electrode is added to calibrate the deviation of the wavelength.