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
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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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