Introduction to the Structure and Performance of Thin Film Lithium Niobate Electro optic Modulator
An electro-optic modulator based on different structures, wavelengths, and platforms of thin film lithium niobate, and a comprehensive performance comparison of various types of EOM modulators, as well as an analysis of the research and application of thin film lithium niobate modulators in other fields.
1. Non resonant cavity thin film lithium niobate modulator
This type of modulator is based on the excellent electro-optic effect of lithium niobate crystal and is a key device for achieving high-speed and long-distance optical communication. There are three main structures:
1.1Traveling wave electrode MZI modulator: This is the most typical design. The Lon č ar research group at Harvard University first achieved a high-performance version in 2018, with subsequent improvements including capacitive loading based on quartz substrates (high bandwidth but incompatible with silicon-based) and silicon-based compatible based on substrate hollowing, achieving high bandwidth (>67 GHz) and high-speed signal (such as 112 Gbit/s PAM4) transmission.
1.2Folding MZI modulator: In order to shorten the device size and adapt to compact modules such as QSFP-DD, polarization treatment, cross waveguide or inverted microstructure electrodes are used to reduce the device length by half and achieve a bandwidth of 60 GHz.
1.3Single/Dual Polarization Coherent Orthogonal (IQ) Modulator: Uses high-order modulation format to enhance transmission rate. The Cai research group at Sun Yat sen University achieved the first on-chip single polarization IQ modulator in 2020. The dual polarization IQ modulator developed in the future has better performance, and the version based on quartz substrate has set a single wavelength transmission rate record of 1.96 Tbit/s.
2. Resonant cavity type thin-film lithium niobate modulator
To achieve ultra small and large bandwidth modulators, there are various resonant cavity structures available:
2.1Photonic crystal (PC) and micro ring modulator: Lin’s research group at the University of Rochester has developed the first high-performance photonic crystal modulator. In addition, micro ring modulators based on silicon lithium niobate heterogeneous integration and homogeneous integration have also been proposed, achieving bandwidths of several GHz.
2.2Bragg grating resonant cavity modulator: including Fabry Perot (FP) cavity, waveguide Bragg grating (WBG), and slow light (SL) modulator. These structures are designed to balance size, process tolerances, and performance, for example, a 2 × 2 FP resonant cavity modulator achieves ultra large bandwidth exceeding 110 GHz. The slow light modulator based on coupled Bragg grating expands the working bandwidth range.
3. Heterogeneous integrated thin film lithium niobate modulator
There are three main integration methods to combine the compatibility of CMOS technology on silicon-based platforms with the excellent modulation performance of lithium niobate:
3.1Bond type heterogeneous integration: By directly bonding with benzocyclobutene (BCB) or silicon dioxide, thin film lithium niobate is transferred to a silicon or silicon nitride platform, achieving wafer level, high temperature stable integration. The modulator exhibits high bandwidth (>70 GHz, even exceeding 110 GHz) and high-speed signal transmission capability.
3.2Deposition waveguide material heterogeneous integration: depositing silicon or silicon nitride on thin film lithium niobate as a load waveguide also achieves efficient electro-optic modulation.
3.3Micro transfer printing (μ TP) heterogeneous integration: This is a technology that is expected to be used for large-scale production, which transfers prefabricated functional devices to target chips through high-precision equipment, avoiding complex post-processing. It has been successfully applied to silicon nitride and silicon-based platforms, achieving bandwidths of tens of GHz.
In summary, this article systematically outlines the technological roadmap of electro-optic modulators based on thin film lithium niobate platforms, from pursuing high-performance and large bandwidth non resonant cavity structures, exploring miniaturized resonant cavity structures, and integrating with mature silicon-based photonic platforms. It demonstrates the enormous potential and continuous progress of thin film lithium niobate modulators in breaking through the performance bottleneck of traditional modulators and achieving high-speed optical communication.
Post time: Mar-31-2026