title: Air-coupled ultrasound detection using capillary-based optical ring resonators.
abstract: We experimentally demonstrate and theoretically analyze high Q-factor (~107) capillary-based optical ring resonators for non-contact detection of air-coupled ultrasound. Noise equivalent pressures in air as low as 215 mPa/√Hz and 41 mPa/√Hz at 50 kHz and 800 kHz in air, respectively, are achieved. Furthermore, non-contact detection of air-coupled photoacoustic pulses optically generated from a 200 nm thick Chromium film is demonstrated. The interaction of an acoustic pulse and the mechanical mode of the ring resonator is also studied. Significant improvement in detection bandwidth is demonstrated by encapsulating the ring resonator in a damping medium. Our work will enable compact and sensitive ultrasound detection in many applications, such as air-coupled non-destructive ultrasound testing, photoacoustic imaging, and remote sensing. It will also provide a model system for fundamental study of the mechanical modes in the ring resonator.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave., Ann Arbor, MI, 48109, USA.|Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, MI, 48109, USA.
authors.forename: Kyu Hyun
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, MI, 48109, USA.|School of Optical and Electrical Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, 430074, Wuhan, Hubei, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Luo
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, MI, 48109, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave., Ann Arbor, MI, 48109, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Tian
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, MI, 48109, USA.
authors.forename: L Jay
authors.identifier: 0000-0002-0347-6309
authors.initials: LJ
authors.lastname: Guo
authors.affiliation: Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave., Ann Arbor, MI, 48109, USA.
authors.forename: Xueding
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, University of Michigan, 1101 Beal Ave., Ann Arbor, MI, 48109, USA. xsfan@umich.edu.
authors.forename: Xudong
authors.initials: X
authors.lastname: Fan
mesh_terms: D002196:Capillaries; D004867:Equipment Design; D019544:Equipment Failure Analysis; D055620:Optical Phenomena; D061088:Photoacoustic Techniques / Q000295:instrumentation*; D014463:Ultrasonography / Q000295:instrumentation*