Search

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.

An on-chip 64-channel hybrid (de)multiplexer for wavelength-division multiplexing (WDM) and mode-division multiplexing (MDM) is designed and demonstrated on a 220 nm SOI platform for the demands of large capacity optical interconnections. The designed hybrid (de)multiplexer includes a 4-channel mode (de)multiplexer and 16-channel wavelength-division (de)multiplexers. The mode (de)multiplexer is comprised of cascaded asymmetric directional couplers supporting coupling between fundamental TE mode and higher-order modes with low crosstalks in a wide wavelength range. The wavelength-division (de)multiplexers consist of two bi-directional micro-ring resonator arrays for four 16-channel WDM signals. Micro-heaters are placed on the micro-resonators for thermal tuning. According to the experimental results, the excess loss is

In this work, we propose a mode-conversion-based chirped Bragg grating on thin-film lithium niobate (TFLN). The device is mainly composed of a 4.7-mm long chirped asymmetric Bragg grating and an adiabatic directional coupler (ADC). The mode conversion introduced by the ADC allows the chirped Bragg grating operates in reflection without using an off-chip circulator. The proposed device has experimentally achieved a total time delay of 73.4 ps over an operating bandwidth of 15 nm. This mode-conversion-based chirped Bragg grating shows excellent compatibility with other devices on TFLN, making it suitable in monolithically integrated microwave photonics, sensing, and optical communication systems.

Based on two-dimensional elliptical microresonator arrays, we designed and fabricated a compact filter on the silicon-on-insulator platform with potential applications for on-chip optical interconnects. The fabricated optical filter exhibits a wide flat bandwidth of 951 GHz with the shape factor of 0.57 at the through port for the 3×20 arrays. The out-of-band rejection is as high as 50 dB. The crosstalk is also very low (−46 dB). The spectral shows a boxlike response. Although there are sixty rings used in the array, the insertion loss is still very small (≤1.36 dB).

In this work, we report a linearity-enhanced dual-parallel Mach–Zehnder modulator (MZM) on a thin-film lithium niobate platform. By setting the optical and electrical splitting ratios at a specific condition, the third-order intermodulation distortions (IMD3) of the child MZMs cancel with each other, whereas the first-order harmonics (FH) reach the maximum. Passive devices instead of thermo-optical switches are used to control the optical power and phase of the child MZMs, which greatly improve the device stability and simplify the operation complexity. To the best of our knowledge, the experimental results show a record-high spurious-free dynamic range on a thin-film lithium niobate platform (110.7 dB·Hz2/3 at 1 GHz). The E-O response decayed about 1.9 dB from 10 MHz to 40 GHz, and the extrapolated E-O 3 dB bandwidth is expected to be 70 GHz. A half-wave voltage of 2.8 V was also achieved. The proposed modulator provides a promising solution for high-bandwidth and low-voltage analog optical links.