Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

An integrated optical modulator operating at cryogenic temperatures


Photonic integrated circuits (PICs) operating at cryogenic temperatures are fundamental building blocks required to achieve scalable quantum computing and cryogenic computing technologies1,2. Silicon PICs have matured for room-temperature applications, but their cryogenic performance is limited by the absence of efficient low-temperature electro-optic modulation. Here we demonstrate electro-optic switching and modulation from room temperature down to 4 K by using the Pockels effect in integrated barium titanate (BaTiO3) devices3. We investigate the temperature dependence of the nonlinear optical properties of BaTiO3, showing an effective Pockels coefficient of 200 pm V−1 at 4 K. The fabricated devices show an electro-optic bandwidth of 30 GHz, ultralow-power tuning that is 109 times more efficient than thermal tuning, and high-speed data modulation at 20 Gbps. Our results demonstrate a missing component for cryogenic PICs, removing major roadblocks for the realization of cryogenic-compatible systems in the field of quantum computing, supercomputing and sensing, and for interfacing those systems with instrumentation at room temperature.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Fig. 1: BaTiO3 EO device concept.
Fig. 2: EO and electrical response of BaTiO3-based optical switches at 4 K.
Fig. 3: Temperature dependence of the Pockels effect in BaTiO3.
Fig. 4: Demonstration of low-power switching and high-speed data modulation with BaTiO3-based devices at 4 K.

Data availability

The data from the electro-optic measurements analysed and presented in Figs. 2a–c, 3 and 4 are available in an online repository with the digital object identifier: The remaining data supporting the findings of this study are available from the corresponding author upon reasonable request.


  1. Silverstone, J. W., Bonneau, D., O’Brien, J. L. & Thompson, M. G. Silicon quantum photonics. IEEE J. Sel. Top. Quantum Electron. 22, 6700113 (2016).

    Article  Google Scholar 

  2. O’Brien, J. L., Furusawa, A. & Vučković, J. Photonic quantum technologies. Nat. Photon. 3, 687–695 (2009).

    Article  Google Scholar 

  3. Abel, S. et al. Large Pockels effect in micro- and nanostructured barium titanate integrated on silicon. Nat. Mater. 18, 42–47 (2019).

    Article  CAS  Google Scholar 

  4. Mukhanov, O. A. Energy-efficient single flux quantum technology. IEEE Trans. Appl. Supercond. 21, 760–769 (2011).

    Article  CAS  Google Scholar 

  5. Ladd, T. D. et al. Quantum computing. Nature 464, 45–53 (2010).

    Article  CAS  Google Scholar 

  6. Zeghbroeck, B. Van Optical data communication between Josephson-junction circuits and room-temperature electronics. IEEE Trans. Appl. Supercond. 3, 2881–2884 (1993).

    Article  Google Scholar 

  7. Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008).

    Article  CAS  Google Scholar 

  8. Javerzac-Galy, C. et al. On-chip microwave-to-optical quantum coherent converter based on a superconducting resonator coupled to an electro-optic microresonator. Phys. Rev. A 94, 053815 (2016).

    Article  Google Scholar 

  9. Greganti, C., Roehsner, M. C., Barz, S., Morimae, T. & Walther, P. Demonstration of measurement-only blind quantum computing. New J. Phys. 18, 303–309 (2016).

    Article  Google Scholar 

  10. Mehta, K. K. et al. Integrated optical addressing of an ion qubit. Nat. Nanotechnol. 11, 1066–1070 (2016).

    Article  CAS  Google Scholar 

  11. Johnston, A. R. et al. Optical links for cryogenic focal plane array readout. Opt. Eng. 33, 2013–2019 (1994).

    Article  CAS  Google Scholar 

  12. Dowell, J. D. et al. Optoelectronic Analogue Signal Transfer for LHC Detectors CERN/DRDC-91-41 (CERN, 1991).

  13. Benea-Chelmus, I.-C., Settembrini, F. F., Scalari, G. & Faist, J. Electric field correlation measurements on the electromagnetic vacuum state. Nature 568, 202–206 (2019).

    Article  CAS  Google Scholar 

  14. Elshaari, A. W., Zadeh, I. E., Jöns, K. D. & Zwiller, V. Thermo-optic characterization of silicon nitride resonators for cryogenic photonic circuits. IEEE Photon. J. 8, 2701009 (2016).

    Article  Google Scholar 

  15. Gehl, M. et al. Operation of high-speed silicon photonic micro-disk modulators at cryogenic temperatures. Optica 4, 374–382 (2017).

    Article  CAS  Google Scholar 

  16. Harris, N. C. et al. Efficient, compact and low loss thermo-optic phase shifter in silicon. Opt. Express 22, 83–85 (2014).

    Article  Google Scholar 

  17. Li, Y., Humphreys, P. C., Mendoza, G. J. & Benjamin, S. C. Resource costs for fault-tolerant linear optical quantum computing. Phys. Rev. X 5, 41007 (2015).

    Google Scholar 

  18. Pintus, P. et al. Characterization of heterogeneous InP-on-Si optical modulators operating between 77 K and room temperature. APL Photon. 4, 100805 (2019).

    Article  Google Scholar 

  19. Alexander, K. et al. Nanophotonic Pockels modulators on a silicon nitride platform. Nat. Commun. 9, 3444 (2018).

    Article  Google Scholar 

  20. Wang, C. et al. Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages. Nature 562, 101–104 (2018).

    Article  CAS  Google Scholar 

  21. Eltes, F. et al. Low-loss BaTiO3-Si waveguides for nonlinear integrated photonics. ACS Photon. 3, 1698–1703 (2016).

    Article  CAS  Google Scholar 

  22. Herzog, C., Poberaj, G. & Günter, P. Electro-optic behavior of lithium niobate at cryogenic temperatures. Opt. Commun. 281, 793–796 (2008).

    Article  CAS  Google Scholar 

  23. Lauermann, M. et al. 40 GBd 16QAM signaling at 160 Gb/s in a silicon-organic hybrid modulator. J. Light. Technol. 33, 1210–1216 (2015).

    Article  CAS  Google Scholar 

  24. Eltes, F. et al. A BaTiO3-based electro-optic Pockels modulator monolithically integrated on an advanced silicon photonics platform. J. Lightwave Technol. 37, 1456–1462 (2019).

    Article  CAS  Google Scholar 

  25. Kay, H. F. & Vousden, P. XCV. Symmetry changes in barium titanate at low temperatures and their relation to its ferroelectric properties. Lond. Edinb. Dublin Phil. Mag. J. Sci. 40, 1019–1040 (1949).

    Article  CAS  Google Scholar 

  26. He, F. & Wells, B. O. Lattice strain in epitaxial BaTiO3 thin films. Appl. Phys. Lett. 88, 152908 (2006).

    Article  Google Scholar 

  27. Tenne, D. A. et al. Absence of low-temperature phase transitions in epitaxial BaTiO3 thin films. Phys. Rev. B 69, 2–6 (2004).

    Article  Google Scholar 

  28. Bernasconi, P., Zgonik, M. & Gunter, P. Temperature dependence and dispersion of electro-optic and elasto-optic effect in perovskite crystals. J. Appl. Phys. 78, 2651–2658 (1995).

    Article  CAS  Google Scholar 

  29. Acosta, M. et al. BaTiO3-based piezoelectrics: fundamentals, current status, and perspectives. Appl. Phys. Rev. 4, 041305 (2017).

    Article  Google Scholar 

  30. Pfeiffer, M. H. P. et al. Ultra-smooth silicon nitride waveguides based on the Damascene reflow process: fabrication and loss origins. Optica 5, 884–892 (2018).

    Article  CAS  Google Scholar 

Download references


This work has received funding from the European Commission under grant agreement numbers H2020-ICT-2015-25- 688579 (PHRESCO) and H2020-ICT-2017-1-780997 (plaCMOS), from the Swiss State Secretariat for Education, Research and Innovation under contract numbers 15.0285 and 16.0001, from the Swiss National Foundation project number 200021_159565 PADOMO, from EPSRC grants EP/L024020/1, EP/M013472/1 and EP/K033085/1, the UK EPSRC grant QuPIC (EP/N015126/1), and ERC grant 2014- STG 640079. J.B. thanks D. Sahin for her assistance with the experimental setup.

Author information

Authors and Affiliations



F.E. and J.F. fabricated and structurally characterized the epitaxial BaTiO3/SrTiO3 layer stack with support from H.S. F.E. designed all photonic circuits and fabricated them with support from D.C. F.E., P.S. and S.A. performed optical simulations for the device design. G.E.V.-G., F.E., A.A.G., A.H., G.D.M. and J.B. characterized the electro-optic performance at different temperatures, including low-speed and radiofrequency measurements. The electro-optic data were analysed by F.E. and A.A.G. F.E. and P.S. performed all electrical measurements. The concept for this work was defined by S.A., G.D.M. and M.G.T. and implemented by F.E. with support of S.A. and J.B. F.E., J.F. and S.A. wrote the manuscript with contributions from all authors.

Corresponding authors

Correspondence to Felix Eltes or Stefan Abel.

Ethics declarations

Competing interests

F.E., J.F. and S.A. are involved in commercially developing barium titanate technologies at Lumiphase AG. M.G.T. is involved in developing photonic quantum technologies at PsiQuantum Corporation.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Notes 1–9, Figs. 1–12, Table 1 and refs 1–14.

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Eltes, F., Villarreal-Garcia, G.E., Caimi, D. et al. An integrated optical modulator operating at cryogenic temperatures. Nat. Mater. 19, 1164–1168 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing