The past decade has seen significant growth in the field of thin film lithium niobate electro-optic modulators, which promise reduced voltage requirements and higher modulation bandwidths on a potentially integrated platform. This article discusses the state-of-the-art in thin film modulator technology and presents a simplified simulation technique for quickly optimizing a hybrid silicon- or silicon nitride-lithium niobate modulator. Also discussed are the feasibility of creating a 1 V half-wave voltage, 100 GHz bandwidth modulator, and the design specifications for a single hybrid silicon-lithium niobate platform optimized to operate across all telecommunication bands (between 1260 and 1675 nm wavelengths).

High bandwidth, low voltage electro-optic modulators with high optical power handling capability are important for improving the performance of analog optical communications and RF photonic links. Here we designed and fabricated a thin-film lithium niobate (LN) Mach-Zehnder modulator (MZM) which can handle high optical power of 110 mW, while having 3-dB bandwidth greater than 110 GHz at 1550 nm. The design does not require etching of thin-film LN, and uses hybrid optical modes formed by bonding LN to planarized silicon photonic waveguide circuits. A high optical power handling capability in the MZM was achieved by carefully tapering the underlying Si waveguide to reduce the impact of optically-generated carriers, while retaining a high modulation efficiency. The MZM has a $$V_\pi L$$ V π L product of 3.1 V.cm and an on-chip optical insertion loss of 1.8 dB.

Broadband integrated thin-film lithium niobate (TFLN) electro-optic modulators (EOM) are desirable for optical communications and signal processing in both the O-band (1310 nm) and C-band (1550 nm). To address these needs, we design and demonstrate Mach-Zehnder (MZ) EOM devices in a hybrid platform based on TFLN bonded to foundry-fabricated silicon photonic waveguides. Using a single silicon lithography step and a single bonding step, we realize MZ EOM devices which cover both wavelength ranges on the same chip. The EOM devices achieve 100 GHz EO bandwidth (referenced to 1 GHz) and about 2-3 V.cm figure-of-merit ( V π L ) with low on-chip optical loss in both the O-band and C-band.

We report advancements in the fabrication of electro-optic Mach-Zehnder modulators made by bonding an unetched thin film of lithium niobate to a second chip with rib waveguides in another material, such as silicon. Devices were fabricated after storing bonded silicon-lithium niobate chips in a common laboratory environment for more than three years. The chips survived the full processing flow and yielded modulators with greater than 50 GHz 3-dB electro-optic bandwidth, and VπL less than 3 V-cm at 1550 nm and equivalent performance to freshly-bonded and processed chips. Furthermore, we demonstrate the co-integration of hybrid bonded thin-film lithium niobate modulators and silicon photonics based high quality-factor ring resonators and higher-order coupled microring optical filters. The silicon microring resonators are used for photon-pair generation at 1550 nm using spontaneous four-wave mixing. These results show the feasibility of a modular modulator fabrication procedure, where the planarization and bonding steps are performed for a batch of chips at one time and smaller sub-batches are customized by end users at a much later time according to their needs and convenience.

Integrated photonics at near-IR (NIR) wavelengths currently lacks high bandwidth and low-voltage modulators, which add electro-optic functionality to passive circuits. Here, integrated hybrid thin-film lithium niobate (TFLN) electro-optic Mach–Zehnder modulators (MZM) are shown, using TFLN bonded to planarized silicon nitride waveguides. The design does not require TFLN etching or patterning. The push–pull MZM achieves a half-wave voltage length product (V π L) of 0.8 V.cm at 784 nm. MZM devices with 0.4 cm and 0.8 cm modulation length show a broadband electro-optic response with a 3 dB bandwidth beyond 100 GHz, with the latter showing a record bandwidth to half-wave voltage ratio of 100 GHz/V and a high extinction ratio exceeding 30 dB. Such fully integrated high-performance NIR electro-optic devices may benefit data communications, analog signal processing, test and measurement instrumentation, quantum information processing and other applications.