Abstract
We demonstrate a side-polished fiber-optic ultrasound sensor (SPFS) with a broad frequency bandwidth (dc–46 MHz at 6-dB reduction) and a wide amplitude detection range from several kPa to 4.8 MPa. It also exhibits a high acoustic sensitivity of 426 mV/MPa with a signal-to-noise ratio of 35 dB and a noise-equivalent pressure of 6.6 kPa (over 1–50 MHz bandwidth) measured at 7-MHz frequency. The SPFS does not require multi-layer-coated structures that are used in other high-sensitivity optical detectors. Without any coating, this uses a microscale-roughened structure for evanescent-field interaction with an external medium acoustically modulated. Such unique structure allows significantly high sensitivity despite having a small detection area of only 0.016 mm2 as a narrow line sensor with a width of 8 μm. The SPFS performance is characterized in terms of acoustic frequency, amplitude responses, and sensitivities that are compared with those of a 1-mm diameter piezoelectric hydrophone used as a reference.
Highlights
Optical ultrasound sensors have been actively studied to achieve high sensitivity and broad acoustic frequency bandwidth
SPF1 can lead to stronger modulation of evanescent region I is initially guided with a propagation angle of 85
II, itthan couples back the SPF1 nononly for the following characterization
Summary
Optical ultrasound sensors have been actively studied to achieve high sensitivity and broad acoustic frequency bandwidth. The Fabry-Perot sensors have particular advantages in terms of fabrication flexibility Their multi-layer structures can be produced on a glass substrate [5,10,11], as well as on a tiny microscale tip of optical fibers to realize miniature ultrasound devices [12]. These structures have been utilized for all-optical transducers with not just a single element [12,13] and with an optically addressable multi-channel configuration [14].
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