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Ultrasensitive plano-concave optical microresonators for ultrasound sensing


Highly sensitive broadband ultrasound detectors are needed to expand the capabilities of biomedical ultrasound, photoacoustic imaging and industrial ultrasonic non-destructive testing techniques. Here, a generic optical ultrasound sensing concept based on a novel plano-concave polymer microresonator is described. This achieves strong optical confinement (Q-factors > 105) resulting in very high sensitivity with excellent broadband acoustic frequency response and wide directivity. The concept is highly scalable in terms of bandwidth and sensitivity. To illustrate this, a family of microresonator sensors with broadband acoustic responses up to 40 MHz and noise-equivalent pressures as low as 1.6 mPa per √Hz have been fabricated and comprehensively characterized in terms of their acoustic performance. In addition, their practical application to high-resolution photoacoustic and ultrasound imaging is demonstrated. The favourable acoustic performance and design flexibility of the technology offers new opportunities to advance biomedical and industrial ultrasound-based techniques.

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Fig. 1: Plano-concave optical microresonator ultrasound sensor.
Fig. 2: Plano-concave microresonator sensor sensitivity.
Fig. 3: Acoustic frequency response and directivity.
Fig. 4: Optical fibre microresonator sensor.
Fig. 5: Imaging demonstrations.


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This work was supported by the Engineering and Physical Sciences Research Council (EPSRC), the European Union project FAMOS (FP7 ICT, Contract 317744), a Ramsay Trust Memorial Fellowship, the European Research Council through European Starting Grant 310970 MOPHIM, an Innovative Engineering for Health award by the Wellcome Trust (WT101957) and King’s College London and University College London Comprehensive Cancer Imaging Centre, Cancer Research UK and Engineering and Physical Sciences Research Council, in association with the Medical Research Council and Department of Health, UK.

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J.A.G. and P.C.B. wrote the paper. J.A.G. and E.Z.Z. fabricated the sensors. J.A.G., E.Z.Z., I.P., J.L. and P.C.B. developed the fabrication process. J.A.G. and E.Z.Z. performed the sensor characterisations. J.A.G., J.L., E.Z.Z. and P.C.B. developed the characterization methods. T.J.A. and O.O. performed ORPAM experiments. T.J.A., O.O., E.Z.Z. and P.C.B. designed the ORPAM experiments. T.J.A. and J.A.G. analysed the ORPAM data. S.N. and R.J.C. performed the pulse-echo experiment. S.N., R.J.C., E.Z.Z. and A.E.D. designed the pulse-echo experiment. S.N., R.J.C., I.P.P. and A.E.D. developed the ultrasound source used in the pulse-echo experiment. J.A.G. performed tomographic photoacoustic imaging experiments. J.A.G., E.Z.Z. and P.C.B. designed the tomographic imaging experiments. E.Z.Z. and P.C.B. originally conceived the microresonator sensor concept.

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Correspondence to Paul C. Beard.

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Guggenheim, J.A., Li, J., Allen, T.J. et al. Ultrasensitive plano-concave optical microresonators for ultrasound sensing. Nature Photon 11, 714–719 (2017).

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