Optoacoustic microscopy based on pi-FBG ultrasound sensors.

We present an optoacoustic (photoacoustic) microscopy (OAM) imaging system that uses a pi-shifted Fiber Bragg Grating (pi-FBG) as ultrasound (US) sensor. The sensor has an ultra-small footprint and hence allows for the detection of optoacoustic signals in close proximity to their origin. The interrogation of the pi-FBG is performed by a broadband pulsed laser, enabling a high sensitivity of the sensor as well as the elimination of ambient noise. We characterize the pi-FBG in terms of axial and lateral resolution as well as its bandwidth and find that its performance is comparable to US sensors that are based on the piezoelectric effect. We demonstrate the system’s capabilities by images taken from ex vivo zebrafish and mouse ear samples. The results presented herein highlight that pi-FBGs are a promising tool for the comprehensive label-free optoacoustic imaging of biomedical samples