Fig. 1. Schematic comparison of data-transmitting set-ups. (a) Integrated LN modulator^[18]; (b) traditional LN modulator^[19]; (c) normalized optical transmission of a 20 mm device as a function of the applied voltage, showing a low half-wave voltage of 1.4 V and a measured extinction ratio of 30 dB^[18]; (d) microscopy image of the fabricated chip consisting of three Mach‒Zehnder modulators with various microwave signal line widths and device lengths, where the inset shows the cross-sectional schematic of the nanophotonic LN modulator^[18]

Fig. 2. Processing and fabrication diagrams of advanced high-efficiency LN electro-optic modulators. (a) Schematic of cross-section of the hybrid waveguide^[20]; (b) schematic of the multifunctional photonic integrated chip and its characterization^[21]; (c) schematic of small-sized LN photonic-crystal electro-optic modulator (EOM)^[22]; (d) schematic of an thin-film lithium niobate (TFLN) based in-phase/IQ EOM^[23]

Fig. 3. LN modulators with micro-structured electrode designs and advanced fabrication techniques. (a) Artistic top view of integrated LN modulator with segmented electrodes^[25]; (b) schematic diagram of a TFLN modulator^[27]; (c) static electro-optical (EO) response of the TFLN modulator^[27]; (d) S₂₁ curve of the TFLN EO modulator^[27]

Fig. 4. Modulators based on a periodic CLTW (capacitively loaded traveling-wave) electrode and slow-light (SL) effect. (a)(b) Structure and cross-section of an MZI modulator with a periodic CLTW electrode^[29]; (c) top view of the coupled Bragg resonator based SL waveguide^[30]; (d) schematic view of the proposed traveling-wave SL-MZM^[30]; (e) top view of the modulation region including multiple cascaded-coupled Bragg resonators^[30]

Fig. 5. Architecture of a typical hybrid photonic neural network (PNN)^[31]

Fig. 6. A schematic of proposed IPTC^[32] (The IPTC consists of four physical components: a laser, two thin-film lithium niobate Mach‒Zehnder modulators (MZMs), and a charge-integration photoreceiver)

Fig. 7. Integrated photonic convolution accelerator (IPCA)^[35]. (a) Optical micrograph of the IPCA chip; (b) V_π of LN phase modulator (PM); (c) conceptual schematic of the fully integrated optical convolutional neural networks (OCNN) using the integrated photonic convolution accelerator (IPCA) fabricated on LNOI platform and the micro-ring resonator (MRR) filter

Fig. 8. Schematic diagram of LN-based microwave photonics (MWP) processing engine, consisting of a high-speed electro-optic modulation block and a low-loss, multipurpose photonic processing section

Fig. 9. Implementation of PRTC on TFLN platform. The PRTC consists of four high-speed push-pull Mach‒Zehnder modulators (MZMs) for parameter encoding, followed by coherent optical processing and detection components for binary result generation

Fig. 10. Poled thin-film lithium niobate waveguide^[39]. (a) Optical image of the waveguide with a poled region; (b) high-resolution confocal second-harmonic microscopy of the poled domains

Fig. 11. Spontaneous parametric down-conversion (SPDC) based on layer-poled lithium niobate (LPLN) and dual-layer LNOI. (a) Schematic of cascaded SHG-SPDC processes for photon-pair generation^[40]; (b) coincidence spectrum measured from 1486 nm to 1625 nm, covering telecom S, C, and L bands^[40]; (c) experimental setup to characterize the generated photon pairs from LNOI waveguide^[41]; (d) count rates of signal photon, idler photon and two-photon under different pump powers^[41]; (e) pair generation rate (PGR) under different pump powers^[41]

Fig. 12. Photonic chip with dimensions of 50 mm×5 mm×0.5 mm^[42]

Fig. 13. Optical quantum computing platform and full-chip integration fabricated on thin film lithium niobate. (a) Schematic of an experimental setup for measurement of on-chip quantum interference^[44]; (b) a top-view schematic layout of a microchip^[45]