Characterization of a Fibre Grating Laser-Based Hydrophone for Detection of High Frequency Medical Ultrasound: A Comparison with PVDF Membrane Hydrophone

An ultrasonic hydrophone with a dual polarization distributed Bragg reflector (DBR) fibre laser as the sensing element is described, and its application to the characterization of high frequency ultrasonic field is demonstrated. The principle of the hydrophone is based on the detection of ultrasonically modulated birefringence of the fibre laser output. The generated upper and lower sideband frequency components can be used to determine the frequency and amplitude of the ultrasonic field. It has been found that the performance of the fibre grating laser-based hydrophone, including linearity, sensitivity and frequency response, compares favorably with that of commercial PVDF membrane hydrophone. It suggests that this type of hydrophone can provide a practical alternative to piezoelectric hydrophone technology.

Keywords:

• Ultrasonic hydrophone
• fibre Bragg gratings
• polyvinylidene fluoride

Acknowledgments

The authors are thankful to the Centre for Smart Materials (CSM) of the Hong Kong Polytechnic University, the Hong Kong Research Grant Council (Grant No.: PolyU 5198/03E), and the Hong Kong Polytechnic University Postdoctoral Fellowship Scheme (Project No.: G-YX16) for providing financial supports for this work.

Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005;