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Sensitive, small, broadband and scalable optomechanical ultrasound sensor in silicon photonics


Ultrasonography1 and photoacoustic2,3 (optoacoustic) tomography have recently seen great advances in hardware and algorithms. However, current high-end systems still use a matrix of piezoelectric sensor elements, and new applications require sensors with high sensitivity, broadband detection, small size and scalability to a fine-pitch matrix. This work demonstrates an ultrasound sensor in silicon photonic technology with extreme sensitivity owing to an innovative optomechanical waveguide. This waveguide has a tiny 15 nm air gap between two movable parts, which we fabricated using new CMOS-compatible processing. The 20 μm small sensor has a noise equivalent pressure below 1.3 mPa Hz−1/2 in the measured range of 3–30 MHz, dominated by acoustomechanical noise. This is two orders of magnitude better than for piezoelectric elements of an identical size4. The demonstrated sensor matrix with on-chip photonic multiplexing5,6,7 offers the prospect of miniaturized catheters that have sensor matrices interrogated using just a few optical fibres, unlike piezoelectric sensors that typically use an electrical connection for each element.

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Fig. 1: Concept of new OMUS and innovative split-rib waveguide.
Fig. 2: CMOS fabrication process developed to produce the 15 nm gap.
Fig. 3: Ultrasound sensor characterization.
Fig. 4: Ten OMUSs with photonic WDM .
Fig. 5: Photoacoustic tomography with the OMUS.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

Photonic and mechanical numerical modelling was performed using commercially available Lumerical and COMSOL softwares. The code that analyses the experimentally measured data is available from the corresponding author upon reasonable request.


  1. Szabo, T. L. Diagnostic Ultrasound Imaging: Inside Out 2nd edn (Academic Press, 2014).

  2. Wang, L. V. & Yao, J. A practical guide to photoacoustic tomography in the life sciences. Nat. Methods 13, 627–638 (2016).

    Article  Google Scholar 

  3. Taruttis, A. & Ntziachristos, V. Advances in real-time multispectral optoacoustic imaging and its applications. Nat. Photonics 9, 219–227 (2015).

    Article  ADS  Google Scholar 

  4. Winkler, A. M., Maslov, K. & Wang, L. V. Noise-equivalent sensitivity of photoacoustics. J. Biomed. Opt. 18, 097003 (2013).

    Article  Google Scholar 

  5. Bogaerts, W. et al. Silicon microring resonators. Laser Photon. Rev. 6, 47–73 (2012).

    Article  ADS  Google Scholar 

  6. Bogaerts, W. et al. Silicon-on-insulator spectral filters fabricated with CMOS technology. IEEE J. Sel. Top. Quantum Electron. 16, 33–44 (2010).

    Article  ADS  Google Scholar 

  7. Dong, P. Silicon photonic integrated circuits for wavelength-division multiplexing applications. IEEE J. Sel. Top. Quantum Electron. 22, 370–378 (2016).

    Article  ADS  Google Scholar 

  8. Dizeux, A. et al. Functional ultrasound imaging of the brain reveals propagation of task-related brain activity in behaving primates. Nat. Commun. 10, 1400 (2019).

    Article  ADS  Google Scholar 

  9. Errico, C. et al. Ultrafast ultrasound localization microscopy for deep super-resolution vascular imaging. Nature 527, 499–502 (2015).

    Article  ADS  Google Scholar 

  10. Tan, M. et al. A front-end ASIC with high-voltage transmit switching and receive digitization for 3-D forward-looking intravascular ultrasound imaging. IEEE J. Solid-State Circuits 53, 2284–2297 (2018).

    Article  ADS  Google Scholar 

  11. Wissmeyer, G., Pleitez, M. A., Rosenthal, A. & Ntziachristos, V. Looking at sound: optoacoustics with all-optical ultrasound detection. Light Sci. Appl. 7, 53 (2018).

    Article  ADS  Google Scholar 

  12. Rosenthal, A. et al. Sensitive interferometric detection of ultrasound for minimally invasive clinical imaging applications. Laser Photon. Rev. 8, 450–457 (2014).

    Article  ADS  Google Scholar 

  13. Wissmeyer, G., Soliman, D., Shnaiderman, R., Rosenthal, A. & Ntziachristos, V. All-optical optoacoustic microscope based on wideband pulse interferometry. Opt. Lett. 41, 1953–1956 (2016).

    Article  ADS  Google Scholar 

  14. Shnaiderman, R. et al. Fiber interferometer for hybrid optical and optoacoustic intravital microscopy. Optica 4, 1180–1187 (2017).

    Article  ADS  Google Scholar 

  15. Guggenheim, J. A. et al. Ultrasensitive plano-concave optical microresonators for ultrasound sensing. Nat. Photonics 11, 714–719 (2017).

    Article  ADS  Google Scholar 

  16. Jathoul, A. P. et al. Deep in vivo photoacoustic imaging of mammalian tissues using a tyrosinase-based genetic reporter. Nat. Photonics 9, 239–246 (2015).

    Article  ADS  Google Scholar 

  17. Zhang, C., Ling, T., Chen, S. L. & Guo, L. J. Ultrabroad bandwidth and highly sensitive optical ultrasonic detector for photoacoustic imaging. ACS Photonics 1, 1093–1098 (2014).

    Article  Google Scholar 

  18. Li, H., Dong, B., Zhang, Z., Zhang, H. F. & Sun, C. A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy. Sci. Rep. 4, 4496 (2014).

    Article  ADS  Google Scholar 

  19. Zhang, C., Chen, S.-L., Ling, T. & Guo, L. J. Review of imprinted polymer microrings as ultrasound detectors: design, fabrication, and characterization. IEEE Sens. J. 15, 3241–3248 (2015).

    Article  ADS  Google Scholar 

  20. Shnaiderman, R. et al. A submicrometre silicon-on-insulator resonator for ultrasound detection. Nature 585, 372–378 (2020).

    Article  ADS  Google Scholar 

  21. Rosenthal, A. et al. Embedded ultrasound sensor in a silicon-on-insulator photonic platform. Appl. Phys. Lett. 104, 021116 (2014).

    Article  ADS  Google Scholar 

  22. Zarkos, P., Hsu, O. & Stojanović, V. Ring resonator based ultrasound detection in a zero-change advanced CMOS-SOI process. In Conference on Lasers and Electro-Optics, OSA Technical Digest, JW2A.78 (Optical Society of America, 2019).

  23. Ravi Kumar, R. et al. Enhanced sensitivity of silicon-photonics-based ultrasound detection via BCB coating. IEEE Photonics J. 11, 6601311 (2019).

    Article  Google Scholar 

  24. Chrostowski, L. et al. Silicon photonic resonator sensors and devices. In Proc. Laser Resonators, Microresonators, and Beam Control XIV (Eds. Kudryashov A. V. et al.), 823620 (SPIE, 2012).

  25. Westerveld, W. J. & Urbach, H. P. Silicon Photonics: Electromagnetic Theory (IOP Publishing, 2017).

    Google Scholar 

  26. Leinders, S. M. et al. A sensitive optical micro-machined ultrasound sensor (OMUS) based on a silicon photonic ring resonator on an acoustical membrane. Sci. Rep. 5, 14328 (2015).

    Article  ADS  Google Scholar 

  27. Chason, E., Mayer, T. M. & Howard, A. J. Kinetics of surface roughening and smoothing during ion sputtering. MRS Proc. 317, 91 (1993).

    Article  Google Scholar 

  28. Basiri-Esfahani, S., Armin, A., Forstner, S. & Bowen, W. P. Precision ultrasound sensing on a chip. Nat. Commun. 10, 132 (2019).

    Article  ADS  Google Scholar 

  29. Hazan, Y. & Rosenthal, A. Passive-demodulation pulse interferometry for ultrasound detection with a high dynamic range. Opt. Lett. 43, 1039–1042 (2018).

    Article  ADS  Google Scholar 

  30. Snyder, B. & O’Brien, P. Packaging process for grating-coupled silicon photonic waveguides using angle-polished fibers. IEEE Trans. Compon. Packaging Manuf. Technol. 3, 954–959 (2013).

    Article  Google Scholar 

  31. Welch, P. D. The use of fast Fourier transform for the estimation of power spectra: a method based on time averaging over short, modified periodograms. IEEE Trans. Audio Electroacoust. 15, 70–73 (1967).

    Article  ADS  Google Scholar 

  32. Xu, M. & Wang, L. V. Universal back-projection algorithm for photoacoustic computed tomography. Phys. Rev. E 71, 016706 (2005); erratum 75, 059903 (2007).

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We thank B. Du Bois, M. Dahlem, R. Jansen, C. Pieters and H. Tilmans for fruitful discussions; N. Hosseini for simulations of the directional coupler; P. Coene for the Process Design Kit; R. Demeyer and T. Raes for preparatinon of the CMOS masks; K. Baumans, J. de Coster, J. He and B. Snyder for fibre coupling; Imec’s 200 mm Pilot Line Engineering and FAB teams for fabrication process development; M. Billen, P. Czarnecki, T. D. Kongnyuy and M. Zunic for lab assistance; T. A. La and O. Ülgen for preparing the photoacoustic phantom; P. Absil, J. De Boeck, L. Lagae and H. Osman for support. V.N. acknowledges financial support from the Deutsche Forschungsgemeinschaft (DFG; Gottfried Wilhelm Leibniz Prize 2013; NT 3/10-1).

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Authors and Affiliations



W.J.W., M.M.-U.-H., S.S. and V.R. invented the sensor and fabrication concept. W.J.W. designed the sensor, carried out the ultrasound experiments, analysed the data and wrote the manuscript. W.J.W. and R.S. carried out the photoacoustic experiments and analysed these data. M.M.-U.-H. and S.S. designed and supervised the CMOS-compatible process integration. V.N. supervised the photoacoustic experiments. X.R., S.S. and V.R. and supervised the work.

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Correspondence to Xavier Rottenberg.

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Competing interests

The authors declare the following competing interests: Imec (Leuven, Belgium) has patents pending related to the reported sensor concept.

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Peer review information Nature Photonics thanks the anonymous reviewers for their contribution to the peer review of this work.

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Westerveld, W.J., Mahmud-Ul-Hasan, M., Shnaiderman, R. et al. Sensitive, small, broadband and scalable optomechanical ultrasound sensor in silicon photonics. Nat. Photonics 15, 341–345 (2021).

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