Abstract
The rapid expansion of cloud computing and artificial intelligence has driven the demand for faster optical components in data centres to unprecedented levels. A key advancement in this field is the integration of multiple photonic components onto a single chip, enhancing the performance of optical transceivers. Here silicon photonics, benefiting from mature fabrication processes, has gained prominence in both academic research and industrial applications. The platform combines modulators, switches, photodetectors and low-loss waveguides on a single chip. However, emerging telecommunication standards require modulation speeds that exceed the capabilities of silicon-based modulators. To address these limitations, thin-film lithium niobate has been proposed as an alternative to silicon photonics, offering a low voltage–length product and exceptional high-speed modulation properties. More recently, the first demonstrations of thin-film lithium tantalate circuits have emerged, potentially addressing some of the disadvantages of lithium niobate, enabling a reduced bias drift and enhanced resistance to optical damage. As such, this material arises as a promising candidate for next-generation photonic platforms. However, a persistent drawback of such platforms is the lithium contamination, which complicates integration with CMOS fabrication processes. Here we present for the first time the integration of lithium tantalate onto a silicon photonics chip. This integration is achieved without modifying the standard silicon photonics process design kit. Our device achieves low half-wave voltage (3.5 V), low insertion loss (2.9 dB) and high-speed operation (>70 GHz), paving the way for next-generation applications. By minimizing lithium tantalate material use, our approach reduces costs while leveraging existing silicon photonics technology advancements, in particular supporting ultra-fast monolithic germanium photodetectors and established process design kits.
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The datasets generated during and/or analysed during the current study are available from the corresponding authors on reasonable request.
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Acknowledgements
We would like to acknowledge the contribution of imec’s 200 mm pilot line for silicon photonics wafer fabrication and imec’s PDK team for the mask tape-out. We also would like to acknowledge the contribution from P. Eswaran and S. Culhaoglu for the help in Si-PIC process development; S. Verstuyft, P. Geerinck, E. Özçeri and L. Van Landschoot for the help during the lithium tantalate device fabrication; and C. Krückel and J. Van Kerrebrouck for measurement support. Micro-transfer printing (μTP) is a technology under licence from X-Celeprint. We want to thank the European Space Agency for funding under the E/0365-70—NAVISP, LEO Project and the Research Foundation Flanders (FWO) for projects 3G035722 and 3F025420 and the FWO and F.R.S.-FNRS under the Excellence of Science (EOS) programme (40007560).
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S.B., P.A., J.V.C., S.J., P.V., Neha Singh, D.B., M.D. and F.F. developed and fabricated the silicon nitride, silicon platform on 200 mm. M.N., T.Z. and M.B. fabricated the hybrid LiTaO3/SiN devices and realized the heterogeneous integration. E.V., A.M., P.N. and O.C. performed the numerical simulations. E.V., A.M. and T.V. designed the devices. M.N. and T.V. performed the characterization (optical and quasi-DC). M.N., T.V., Nishant Singh, J.D., C.B. and S.N. performed the high-speed characterization and data communication experiment. M.N., T.V., B.K. and M.B. prepared the figures, data and the paper with input from other authors. P.A., S.L., X.Y., G.R., B.K. and M.B. supervised the project.
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Extended data
Extended Data Fig. 1 Description of the successive steps for the fabrication and printing of suspended LiTaO3 membranes with a schematic representation as well as a microscope picture.
(a) LiTaO3 (300 nm) / oxide (2 μm) / Si wafer (substrate) starting point. (b) Patterning of the LiTaO3 membranes. (c) Patterning of the oxide release layer. (d) Photoresist mechanical encapsulation of the structures. (e) Undercutting (releasing) of the oxide layer, making the structures suspended. (f) Top view of the sample with suspended LiTaO3. (g) picking of the suspended LiTaO3. (h) Printing of the LiTaO3 on a pre-processed external chip. (i) Encapsulation removal. (j) Top view of a few successfully printed LiTaO3 membranes.
Extended Data Fig. 2 Transmission measurements for four fabricated MZMs.
Transmission (T) measurements for four fabricated MZMs. The losses from the grating couplers and external routing are removed. The insertion loss contribution from the Si-PIC components (C1 and C2 from Extended Data Table 2) and the contribution of the back-end integration process (C3, C4 and C5 from Extended Data Table 2) are described on top of the graphs.
Extended Data Fig. 3 Transition from the Si waveguide to a LiTaO3 ridge waveguide.
Transition from the Si waveguide to a LiTaO3-on-insulator ridge waveguide. (a) Schematic of the tri-layer adiabatic transition. Mode profiles in the regions of interest are added. (b) Expected transmission from a Si waveguide to a ridge LiTaO3 waveguide as a function of the lateral misalignment. (inset) Mode in the LiTaO3-on-insulator waveguide.
Extended Data Fig. 4 Data transmission link characterisation.
(a) Amplitude and (b) phase characteristic of the data transmission link, used to generate eye diagrams.
Extended Data Fig. 5 Impact of micro-transfer printing on an optical filter.
(a) Schematic representation of the optical filter (b) Spectrum before heterogeneous integration of LiTaO3. (c) Spectrum after heterogeneous integration of LiTaO3, showing very little influence of the micro-transfer printed LiTaO3 membranes.
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Niels, M., Vanackere, T., Vissers, E. et al. A high-speed heterogeneous lithium tantalate silicon photonics platform. Nat. Photon. (2026). https://doi.org/10.1038/s41566-025-01832-9
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DOI: https://doi.org/10.1038/s41566-025-01832-9
