Institute for Biological and Medical Imaging (IBMI), Technical University of Munich and Helmholtz Center Munich, Ingoldstädter Landstrasse 1, 85764 Neuherberg, Germany. amir.rozental@helmholtz‐muenchen.de
Opt Lett. 2011 May 15;36(10):1833-5. doi: 10.1364/OL.36.001833.
A highly sensitive compact hydrophone, based on a pi-phase-shifted fiber Bragg grating, has been developed for the measurement of wideband ultrasonic fields. The grating exhibits a sharp resonance, whose centroid wavelength is pressure sensitive. The resonance is monitored by a continuous-wave (CW) laser to measure ultrasound-induced pressure variations within the grating. In contrast to standard fiber sensors, the high finesse of the resonance--which is the reason for the sensor's high sensitivity--is not associated with a long propagation length. Light localization around the phase shift reduces the effective size of the sensor below that of the grating and is scaled inversely with the resonance spectral width. In our system, an effective sensor length of 270 μm, pressure sensitivity of 440 Pa, and effective bandwidth of 10 MHz were achieved. This performance makes our design attractive for medical imaging applications, such as optoacoustic tomography, in which compact, sensitive, and wideband acoustic detectors are required.
一种基于π相移光纤布拉格光栅的高灵敏度紧凑型水听器已被开发用于宽带超声场的测量。该光栅具有尖锐的共振，其质心波长对压力敏感。共振由连续波（CW）激光监测，以测量光栅内超声引起的压力变化。与标准光纤传感器不同，高精细度的共振——这是传感器高灵敏度的原因——与长传播长度无关。光在相移周围的局域化将传感器的有效尺寸减小到低于光栅的尺寸，并与共振光谱宽度成反比。在我们的系统中，实现了 270μm 的有效传感器长度、440Pa 的压力灵敏度和 10MHz 的有效带宽。这种性能使我们的设计在医学成像应用中具有吸引力，例如光声断层扫描，其中需要紧凑、灵敏和宽带的声学探测器。
